Text mode and graphics mode

If you are running in a virtual console, rather than an xterm on your graphical desktop, you will need to have the gpm daemon running in order to be able to use the mouse. However the text mode in Links functions perfectly well without the mouse.

To enter graphics mode you have to use the -g option . Type on the command line:

Links will try to autodetect the graphic systems which you have installed on your computer. If it finds one, it will switch into graphics mode. Graphics systems will be searched for in this sequence: pmshell , x , svgalib , atheos . If you want to choose a graphics system manually, use the option -driver with one of the arguments: pmshell , x or svgalib .

If you are using the X-Window system and detection fails, you will need to set up the environmental variable DISPLAY to point to your display.

The -mode option is used to pass parameters to the graphics driver. For SVGAlib systems, it is used to determine screen resolution. For the X-Window system it selects the display.

X-Window graphics system

Grayscale modes are not supported, and nor are so-called «StaticColor» modes which do not allow the setting up of private colour palettes. If your display has several colour depths, the browser will choose the highest one. If you have a display with only paletted mode, the program will create its own colour palette, which will be set up on activation of the window and unset after deactivation.

In the X-Window system the -mode option sets the display for the output from Links web browser. The display is written down in the form In the majority of cases the display number and screen number are zero. If it is a local computer, the computer address is an empty string. If you do not select the display using this option, the environment variable DISPLAY will be read. If it is not set, the browser will open on the display :0.0 .

Examples, what the command line may look like during running under the X-Window system:

In the first example the output of the browser will be displayed on the remote computer delta.ether.net . In the second case you explicitly say that the X-Window graphics driver should be used and the output should be displayed on the computer you run the browser on. The third case is equivalent to the second one. In the last example the output will be displayed on computer micron in local network, on display number 1.

Other graphics systems: SVGAlib and framebuffer

In this case you use the -mode option to set the graphics resolution. To list all possible resolutions write:

Graphics resolution is specified in the form: where width and height are dimensions of the screen in pixels and colour depth determines the number of colours. Possible colour depths are: 16 , 256 , 32K , 64K , 16M , 16M32 .

Example of graphics modes:

If you want for example to run Links in graphics resolution 1024×768 and 16 million colours, write:

If you are using Links under the Linux operating system, you can also run it graphically in the framebuffer. There is a limitation that only systems with linear memory mapping are supported. Another limitation is the mouse driver, which is implemented using the gpm library, in the interests of portability. As the gpm library was created for text mode, and graphics mode has much higher resolution, this would make the mouse too slow. Therefore the mouse pointer doesn’t move smoothly but in steps of several pixels. In exceptional cases it is possible that a particular place on the screen will not be possible to click on. In this case you can use the F5 , F6 , F7 , and F8 keys for fine movement control of the mouse pointer.

This is not a bug in Links, but in the gpm library, which is character oriented. There is no other option for reading the mouse on the framebuffer. If you do not like this solution, please write to the authors of gpm and ask them to add graphics support to gpm .

If you have administrator rights, it is possible to change the source code of gpm for the mouse pointer to move smoothly, and then recompile gpm . Patch gpm with the patch included with Links, which you find in the same directory as the program; it is named PATCH-gpm-1.20.0-smooth-cursor . The patch has been created for source codes of gpm version 1.20.0. It will probably work for other versions of gpm too.

Virtual consoles versus windows

Links has the capacity to create so called virtual consoles on graphics systems such as the Linux framebuffer, where new browser windows cannot be created. After launching the browser, it is possible to create up to 10 virtual consoles which correspond to browser windows on a windowing system. You can switch between virtual consoles using the key combinations ALT +1 , ALT +2 to ALT +0 . If you create a new browser window (for example by using the function «New window»), a new virtual console will be allocated with lowest number available (after running the browser you are therefore on virtual console number 1) and the requested page will be displayed on it. If you close this window, the corresponding virtual console will disappear and the remaining consoles will remain as they are — they won’t be renumbered as one might expect.

This technique allows users to view several pages in parallel even on systems where windows can’t be created.

The Links user interface

After launching, the web browser window is displayed. If you entered a URL on the command line, the requested page will be displayed directly. Otherwise you will see a plain gray screen. At the bottom edge of the window a status line is visible, where information about progress of the connection is displayed. The link address is also displayed here, when you point to a link with the cursor, as well as image titles and similar things. In the upper left corner there is a left-pointing arrow that allows you to move back to previous pages.

Basic terms

Before describing the interface in detail,we will clarify some terms that will later occur in the text: mouse buttons: The basic mouse has either two or three buttons on it: in this manual they will be referred to as left, right, and middle.

Some mice have a scroll wheel instead of the middle button (we will talk about scrolling later). This wheel works as a middle button when you press it. When you roll the wheel, you scroll up and down. Mice with two wheels occur too — one instead of the middle button and one instead of the right button. The middle wheel (wheel 1) is used for vertical scrolling and the right wheel (wheel 2) for scrolling in the horizontal direction. clicking: In Links, this always means a single click with a mouse button. Usually you will be told which button should be clicked; for example «click right button on the OK button» which means placing the cursor over the button with the label «OK» and pressing and releasing the right button. If you are not told which button should be clicked, the left button is meant.

Warning: in some programs, clicking means double-clicking. In Links, the button always is pressed and released only once. If you press the button twice, it will be treated as two clicks.

cursor This can refer to the mouse pointer in graphical mode or to the rectangular box that covers the current character position in text mode. arrow keys / cursor keys: The quartet of keys in the central section of the keyboard. These keys are marked with arrows: up, down, left, and right and are used to control the cursor in text mode. main menu: This is situated on the horizontal bar at the upper edge of the screen, but is hidden until you click on the bar or press the escape key. It provides groups of browser functions («Setup», «View», «File», and so on). Each main menu entry leads to a pull-down menu containing individual functions. URL: Abbreviation for «Uniform Resource Locator», which means the address of a document on the network. The basic form of the URL (some parts are not mandatory) is:

Using URLs, HTTP documents (web pages) can be accessed as well as FTP directories and files on local disks. Examples of URLs:

Frames and scrolling

As is well known, HTML pages can contain separate frames. It is possible to switch between individual frames in text mode by using the TAB key and in graphics mode by clicking inside the frame.

Scrolling a page is simple too. In graphics mode you can scroll using the scrollbar situated on the right side of the frame. You can also scroll by using the arrow keys. The up arrow moves you up to the previous page and the down arrow to the next page. The PAGE UP and PAGE DOWN keys also take you to the previous or next page of the document. You can also scroll forward by one page by pressing the space bar. The HOME and END keys move you to the beginning or end of document, respectively. If you have a mouse with a wheel, you can scroll vertically in graphics mode by using this wheel. If you have a mouse with two wheels, the first wheel (usually in place of middle button) scrolls vertically and second wheel (usually in place of the right button) scrolls horizontally.

Even if you do not have a wheel mouse, you can scroll at any time by using the middle button: hold the middle button down and move the mouse as if you wanted to grab and slide the paper page by hand. This method works for shifting in both directions — horizontally and vertically. So if you hold the middle button and move the mouse to the right, the view will being moved towards the left edge of the whole page. With the mouse you therefore move in the opposite direction than with the scrollbar.

You can also move the page using the right mouse button but only when you do not hit an image, link, form element or similar. If you hit one of these with the right button, a menu of actions appears that can be performed with the image, link, or element.

In text mode the keys PAGE UP , PAGE DOWN , HOME , END and space work analogously. As the arrow keys are used for movement across links, the page is moved to the left and right by the [ and ] keys , and up and down by the INSERT and DELETE keys (or by CTRL +p a CTRL +n .

Note: If a page contains several frames, these methods move you within the current frame only.

Links and the status line

Links are followed in graphics mode simply by clicking the link. In text mode, you first have to select the link using the up/down arrows. The currently selected link is highlighted in inverse video. If you want to follow the link, press the right arrow key or the ENTER key. Links are shown in blue, unless the page defines a different colour for the links.

When you click on a link, Links first looks up the address (sends a query to the DNS server). Then it starts establishing a connection with the remote server. After the connection is established, a request for the page is transmitted and Links then waits for the reply. The whole course of the communication is displayed in the status line at the bottom of the screen. As soon as the whole page is downloaded, «OK» will be displayed. If the page has not been completely downloaded, you can terminate the connection by using the «back» function in the File menu, by hitting the Z key (or, in text mode, the left arrow key), and also by clicking the left arrow in the top left corner.

Adter loading the page, the status line shows informations about links, images and other elements of page. If you move over a link, the address of the target is displayed (you can easily determine if something is a link by this method). If you move over an image, its title (alt attribute or URL of the image in case it doesn’t have an alt) is displayed. After moving over a form element (text area, checkbox, radio button etc.) information about that particular form element is displayed (for example its name, value, address where the form will be sent to, . ).

If javascript is running on the page, it can also write into the status line. In this case the status line doesn’t show the information described above but instead shows the text that javascript set.

What a status line at the bottom edge of the screen looks like.

During downloading, an image not yet decoded is displayed as an empty frame the size of the image (as specified in the HTML code). After downloading and decoding the image, it will be displayed instead of this frame. If an error occurs such that the image cannot be downloaded (the image is damaged or it can’t be displayed for another reason) a broken frame will be shown instead of the image. A frame has the dimensions of the image, where these are known. If they are not known, the frame has the basic dimensions 32×32 pixels.

The upper part of the image shows what a broken image looks like. In the lower part you see the empty frame for an image not yet downloaded.

Objects on the page

Links only partially supports certain HTML tags, which can occur on a page. As some of these can contain important information, Links displays the following tags as links:

• EMBED: This tag can insert some additional documents into the page (such as flash images or text). Links can insert only images in obedience to this tag. The image is then displayed as an ordinary image. If a different document type is required to be embedded, a button labelled EMBED will be displayed at the corresponding place on the page. If you click on this button, the embedded document will be displayed separately. For example, you can hook up an external flash animation player and, after clicking on the EMBED button for a flash animation, the program displaying flash animations will be run. For details on specifying external viewer programs see the association function.
• OBJECT: This behaves in the same way as EMBED . The difference is that an image cannot be inserted this way; therefore a button labelled OBJ will always be created. This button behaves similarly to an EMBED button.
• IFrame: Inserted frame. As Links does not support inserted frames, an IFrame link will be displayed instead. After clicking, the inserted frame will appear.
• Link: This tag serves for creating a link in the document header. At its place (at the top of the page) a Links link will be displayed. Again it is possible to click on this link to reach the target of the link.

In text mode you can also encounter USEMAP or IMAP buttons, which are displayed instead of a clickable map image. After clicking on the button a list of links (which are in graphics mode under individual images) is displayed, from which you can choose the link you want to follow.

On some pages you can encounter a link Refresh linking to a different page. «Refresh» is redirection to a different page, which is performed automatically by some browsers. Links does not perform redirection automatically, because it can be very frustrating for the user who wishes to go back to the previous page; after pressing «Go back» she hits the redirect instruction and this will automatically direct her forward again. To avoid this, redirection is displayed as «Refresh» in Links. After clicking the link, redirection to the target page will be performed.

If some characters occur on a web page which Links doesn’t have in its built-in font, a «blotch» character will be displayed instead of them. If there are too many blotches in the page and you think that the page should display correctly, try in «HTML options» menu in «View» to change the value of «Default codepage». It is possible that the server doesn’t send information about code page and you just have a different encoding set as default. It is also possible that the server is sending wrong information about the code page of the document. In this case you can tick the entry «Ignore charset info sent by the server» in the same menu.

Instead of a missing character, a blotch symbol is displayed:

If foreground and background colours have luminances which are too similar, then a foreground colour will be selected with as much contrast to the background colour as possible. This function is built into Links to increase the legibility of text on pages that have unsuitable colours which make the text difficult for the user to read.

Warning:
On some web pages it can happen that the text colour will not be displayed in the way the authors intended, but rather in such a way that the text is as legible as possible. This is not a bug in the browser; this feature is intentional. If the colours were displayed in the way that the authors intended, the text would be very poorly legible.

Links menus

The whole Links program is controlled using interactive menus; control is therefore very easy and intuitive. All functions can be reached from the main menu, and additionally most can be launched by a so-called hot key.

You can invoke the main menu by pressing the ESC key or by clicking the mouse on the bar along the top edge of the window. You can close the menu by pressing the ESC again or by clicking underneath the bar. You select individual entries in the menu either by a direct mouse click, or by using the cursor keys — in the main menu the left and right arrow keys, and in pull-down menus the up and down arrow keys.

Activate your chosen function by pressing ENTER or the space bar.

Some menu entries have one character of the name highlighted in inverse video. If you press this letter when in the menu, a direct choice of this entry will be performed, which is usually faster than moving onto the entry with the text cursor or the mouse.

To the right of some entries a so called hot key is listed. If you press this hot key anywhere in the browser, the corresponding function will be directly called, which is again faster than looking for the function in menu. However, you don’t have to remember hot keys — all the available functions can be reached through the menu.

Dialog windows

Links dialogs are designed for functionality, not beauty. Memory and processor cycles are not wasted on pretty 3D effects such as buttons that move when you press them. The dialogs are designed to be equally easy to use with both keyboard and mouse.

Dialog windows are controlled in a way very similar to menus: up and down arrows select individual fields of the dialog, the spacebar activates the selected field (button, checkbox, etc). You can also of course use the mouse. Dialogs can be cancelled by using the ESC key. The dialog is closed and all changes are forgotten. On the other the ENTER key closes the dialogue and all changes will be accepted.

Dialogs often contain fields for entering text. Before doing so, you must activate the field (by either clicking it with mouse or selecting it using the cursor keys) — a text cursor will then appear in the field. After this you can normally insert text, numbers and so on. The left and right arrow keys move the cursor within the text field. The BACKSPACE and DELETE keys delete the text. CTRL +x erases the whole line and puts it into the clipboard (OS/2 only). Keys CTRL +v insert the clipboard contents (again only on OS/2). CTRL +u erases text from the cursor to the beginning of the line.

The up and down arrow keys allow you to browse the history of previously entered values. while the CTRL +w key combination activates a text autocompletion function. If you want to enter text that you have already entered previously, just a few leading characters can be typed and a previously used continuation will be filled in, or a dialogue is presented if there is more than one possible choice. The up and down arrow keys leave the text field and therefore end the edit.

All Links dialogs have two buttons at the bottom labeled OK and Cancel

By clicking on the OK key you confirm your entries. By clicking on Cancel you cancel them.

Functions accessible through the menu

Now we are going to show all functions of the browser in detail, as they are listed in the menu.

File Menu

In the File menu you will find functions for working with URLs: changing the current URL, history, bookmarks, then functions for downloading documents, system information, an operating system command line and exiting the browser.

Goto URL

Go back

History

Reload

During the first invocation of this function, this page will be requested again from the network. If there is a proxy server between you and the Internet, it can hapen that this proxy replies immediately from its own cache and will not download the document from network. Therefore second and further «Reload» invocations force downloading from the network even with a proxy cache. During second and subsequent «Reload», a «Pragma: no-cache» is actually present in the HTTP request.

Bookmarks

Bookmarks allow you easy storage of a pointer to an interesting page. They are used in the same way as bookmarks in a book.

The bookmark consist of a name (bookmark label) and a URL. Bookmarks are arranged in directories, which makes navigation easier and more comfortable. After invoking the «Bookmarks» function, a bookmark manager window appears on the screen. The upper part of the window contains a list of bookmarks and directories (or their names). Below this are buttons for managing the bookmarks.

Within the list in the upper part of the window, the cursor keys, and the PAGE UP , PAGE DOWN , HOME and END keys move the current selection (indicated by an inverse video bar). You can select an entry in this list as in a menu: use the up and down arrow keys, or click the left mouse button on the entry you want. PAGE UP or HOME move you to the top of the list, PAGE DOWN or END to the bottom.

Scrolling is performed by holding the middle mouse button and dragging the mouse up and down or by using the scrollbar at the right edge of the window.

To the left of every entry there is a graphics symbol that indicates whether it is a bookmark, an open directory, or a closed directory. A minus sign in a square means a closed directory, a plus sign in a square means an open directory and a longer horizontal line means a bookmark. Vertical lines show which directory the bookmark belongs to. You can open or close a directory by clicking the directory symbol or moving on to directory and pressing the space bar. Alternatively, the + key opens a directory, the — key closes it.

Now we will describe individual actions that can be performed using the buttons at the bottom of the window. These buttons work with the entry (bookmark or directory) that currently has the cursor bar. We will call this the current entry.

Goto: Shows the web page that the bookmark points to. If the cursor bar is over a directory, nothing will be performed.

Directory: Creates a new directory. After pressing this button a dialogue will appear into which you enter the name of the new directory. A new directory will be created. If the current entry is an open directory, the new directory will be made within this directory. Otherwise it will be created in the same directory as the current entry.

Add: Works similarly to the «directory» button, but creates a new bookmark. Again a dialogue will appear into which you enter a name and URL for the bookmark. If you have some page displayed, both these entries will already be filled in with title and URL of this page. After pressing OK a new bookmark will be created below the current entry. As with directories, if the current entry is an open directory, the new bookmark will be placed in it.

Delete: Deletes the current entry. If it is a directory, this also deletes all entries within it. Before deletion you will be asked to confirm that you wish to delete the entry.

Entries in the list can also be moved. This function is performed by the Move button . First it is necessary to mark the entry you wish to move. An entry can be marked by the INSERT or * keys (these are toggle keys that mark an unmarked entry and unmark a marked one), or by clicking the right mouse button on the corresponding entry. The marked entry has an asterisk before its name (in text mode) or a little square (in graphics mode). Using the Unselect all button, you can deselect all entries. When a directory is closed, all entries inside the directory are automatically deselected.

When you have marked all the entries that you want to move, place the cursor bar over the entry behind which you want to move the selected entries, and click the Move button . The selected entries will be moved behind the current entry; if the current entry is an open directory, the entries will be placed into that directory. Moved entries will be in the same order as they were before the movement so that the sequence of selected entries will not change. Directories will be moved with their contents.

Note:
Only one copy of the bookmark manager can be open at any one time. If you have more than one browser window open and you have the bookmark manager already open in one, then it is not possible to open it again in a different window.

Bookmarks are stored in the file bookmarks.html in the .links sub-directory in your home directory. The format of the file is compatible with that used in Netscape, therefore it is possible to have common bookmarks for the Links and Netscape browsers. The path and name of the file where bookmarks will be stored can be selected in the «Setup->Miscellaneous Options» menu. In this menu you can also set up encoding of the bookmarks file. If you change the file or encoding of the bookmarks, the changes that you have made in bookmarks, will be automatically stored and a file with new bookmarks will be loaded.

Changes in bookmarks (for example addition or deletion) are automatically stored at exit of the browser. Therefore it is not necessary to save the bookmarks explicitly with the menu function. After the first run of the browser (when the bookmark file doesn’t yet exist), a basic bookmark file will be created for you. This file will contain the Links home page and calibration page.

New window

In svgalib and framebuffer graphics environments, instead of opening a new window, the lowest available free virtual console number will be assigned to a newly created virtual console. The requested page will be displayed on this console. You can switch between virtual consoles by using the keys ALT+0 to ALT +9 . If you close a console, it will disappear and the remaining consoles will remain as they are. They will not be renumbered.

Save as

Save URL as

Kill background connections

Flush all caches

Resource info

OS Shell

View Menu

The View menu contains functions for processing the currently displayed page: searching the document, switching between formatted and unformatted views, information about the document, and HTML settings.

Search

During searches, case is usually ignored. This however is not the case with letters that carry accents. Accented letters will be searched for exactly as. written. Therefore don’t forget this behaviour during entering the text.

For explanation we’ll show couple of examples:

1. looking for a word «tree»: «Tree» and «TREE» will also be found.
2. looking for the Czech word «laviиka»: «Laviиka» will also be found. «LAVIИKA» won’t be found, because we entered a lower case «и». Word «LAVIиKA» will be found if it occurs in the text.
3. looking for «№uplнk»: Only the word «№uplнk» will be found. Neither «©uplнk» nor «©UPLНK» will be found, because we entered the accented letters «№» and «н» in lower case.

Search backwards

Find next

Find previous

Toggle html/plain

Document info

Header info

Frame at full-screen

HTML options

In this menu, various options for page display can be set. The menu contains the following entries:

• Display tables: toggles whether tables will be displayed as tables or just as a dump of their contents.
• Display frames: toggles the display of frames. If frames are turned off, usually a version without frames is displayed, i.e. the «noframes» section in the original HMTL.
• Display links to images: if this option is enabled and images are not being displayed (you are in a text mode or you have image display turned off in graphics mode), then a link is shown instead of each image.
• Move by columns in table: this option is available only in text mode; it determines how links are numbered in tables. If this option is on, table links are numbered vertically, if off, horizontally.
• Links are numbered: Again available in text mode only. After ticking this option, a number for each link will be displayed.
• Display images: This setting is available only in graphics mode. It serves to toggle the display of images.
• Text margin: Sets the space between text and the edge of the screen or browser window. Possible values are 0 to 9, default is 3. The unit of the numbers is not specified.
• Default codepage: After pressing this button, a menu with possible codepages will appear. Select the codepage for the currently displayed web page. Links is able to negotiate the page encoding with most servers; therefore it isn’t usually necessary to set up the codepage manually. Some badly configured servers don’t specify the code page and in this case, this default setting will be used.
• Ignore information about code page: is closely related to the previous setting. This option is used when the page is in a different encoding than the server says. In such cases tick up this field and set up the correct encoding in «Default codepage».
• User font size: This setting is avilable in graphics mode only. Using this you can enlarge the letters on the page. The letter size is entered in points. It doesn’t enlarge the letters in menus — there is a separate option for this under Setup -> Miscellaneous options.
• Scale all images: Again available only in graphics mode. This allows you to enlarge or shrink pictures and conveniently view fine details which are not visible at normal size, or to fit large pictures onto the screen. Enter value in per cent (100 per cent is original size).

Warning:
If you set up an image scaling other than 100% or a font size other than 16 pixels, some pages may display in a strange way (for example «fallen apart»), because they assume a certain size for images and text.

Save HTML options

Link menu

The link menu contains actions that can be carried out on the currently selected link — for example download, display image, and follow link. In graphics mode, this menu can also be displayed as a context menu by right-clicking on the link.

Downloads menu

Contains an overview of files that are currently being downloaded in the background. After clicking one of the items, a window with detailed information and the option to interrupt is presented. In the following picture you can see the menu with selection of individual files being downloaded.

The following information is displayed in the window displayed for each file:

• size of the file
• amount of data already received
• average speed of download
• current speed of the download
• percent of the file size downloaded

Thus a window with detailed information about a particular file looks like:

Clicking the Background button puts the download into the background again. The Abort button aborts the download. Abort and delete file aborts the download and also deletes the partially downloaded file.

Warning! The browser won’t ask you for confirmation when you press these buttons — it will immediately abort. Therefore if you press this button in error, the download will be aborted and you will have to download the file again.

Help menu

The Help menu contains helpful information on the program: a list of keyboard functions, an online manual and program licence information. The Keys entry displays a window with a list of hotkeys. After pressing the User’s manual entry an online manual will be displayed (this works only if you are connected to the Internet). You can also visit the Links homepage by clicking the Home page . By clicking Calibration you get into the browser calibration procedure, which needs to be performed after first launching the browser. This function also requires you to be connected to the Internet.

Customising Links: the Setup Menu

In this menu you will find all the global settings for the browser, for example language, character set (for text terminal only), network, terminal, cache, and similar. If you change any of these settings, don’t forget to click the entry Save options , which saves the change into the configuration file. If you don’t save the changes, they will be forgotten when the program closes down, and the old values will be used when the browser is started up next time.

Language

This menu allows you to select a language for the user interface. Up and down arrows select language, enter confirms the selection, the key ESC cancels the selection menu.

Terminal options

Video settings

The «Video Settings» entry is available only in graphics mode. After clicking on it, the video setting window will appear. It is possible to set the gamma for your monitor, turn image and text dithering on or off, turn on aspect ratio correction or optimize for LCD displays.

The dialog contains fields for entering gamma correction value for individual colour channels (red, green, blue) and then user gamma for correction of ambient lighting. A description of correct gamma setting follows.

Setting the gamma correction
First it is necessary for you to set up contrast and brightness correctly for your monitor according to the following instructions:

1. Set the monitor contrast as low as possible.
2. Darken the room or shade the edge of the screen with one hand.
3. Set the brightness as low as possible, then increase it to the point at which the black edge of the screen just starts to brighten.
4. Now set the contrast according to your preference.

Now, having correctly set up your monitor, you can set the gamma correction:

1. Set the user gamma to 1.0
2. Display the page gamma.html in the browser. You can find this page in the doc directory .
3. Look at the red field. If the right part is lighter than the left part, reduce the value of the red gamma. If the right part is darker, then increase the value of the red gamma.
4. Repeat this procedure until both parts look the same.
5. Do the same for blue and green gamma.
6. Check the white field. Both parts should be the same brightness. If they are not, then you probably did something wrong; repeat the procedure.
7. If the white field is displayed correctly, set up the user gamma according to the table below.
8. Save the settings.

Table of gamma corrections for various lighting intensities:

Warning:
If the recommended instructions are not carried out, images and letters will be displayed distorted, due to either bad brightness or bad gamma settings. This will show up as incorrect colour tones, parts of the picture appearing too dark or too pale, jagged edges on letters, too dense or too pale colours, or coloured garlands or stripes in fine transitions between colour tones. On devices which perform upsampling or downsampling of the image incorrectly (some LCD monitors and projectors at certain resolutions) , the image will be displayed incorrectly at lower colour depths. If you use Links on the X-Window platform, we recommend turning off the gamma correction performed by the X-Window system, if possible. This produces the finest colour reproduction. If you turn it off, then do so before doing the gamma setting in links.

The Aspect ratio fields are for aspect ratio correction in graphics modes with non-square pixels. The usual ratio for cathode ray tube monitors is 4:3 (800×600, 1024×768, 640×480 etc.) With these resolutions, the pixels on the screen are square. With other resolutions (e. g. 640×400, 320×200) the pixels are elongated in one direction. So if you try to draw a square on the screen, you will see an oblong. The Aspect ratio option corrects this problem.

Fill in the field Aspect ratio with the ratio of monitor pixel width divided by monitor pixel height. So if the image is too narrow and tall, insert a number greater than 1, if too wide and low, set a number lower than 1.

In typical cases the default setting of 1 should be sufficient, because the graphics driver automatically determines the resolution and calculates a correction coefficient according to this, for a screen with 4:3 side ratio. If this is not enough (for example you have an atypical monitor), the coefficient has to be set manually.

By ticking up the field Aspect correction on you turn on the aspect correction. If the aspect correction is off, the pixels on screen are mapped 1:1 to pixels on the CRT/LCD.

To summarize: turn on the aspect ration correction, leave the value at 1 and try out with the calibration picture; if the circle is displayed as an ellipse, correct the shape by chaging the value. Increase if the picture is too tall and narrow, decrease if too low and wide.

Furthemore you can use this menu to set the output device for which the picture should be optimized. Tick up one of the following possibilities:

• Optimize for CRT — if you have a monitor with a classical glass cathode ray tube
• Optimize for LCD (RGB) — if you are using an LCD monitor with pixel sequence Red, Green, Blue (from left to right).
• Optimize for LCD (BGR) — if you are using an LCD monitor or display (for example on a notebook) with pixel sequence Blue, Green, Red (from left to right).

You can find the pixel sequence for your LCD in the technical manual or you can look with a magnifying glass or try out the options to find the best sharpness for small letters.

The LCD display correction is necessary because on an LCD display the picture elements are side by side so that the three separate images are shifted by 1/3 pixel. On a CRT this is adjusted so that the images fit exactly over each other.

Network options

In this dialogue you set parameters for network access.

HTTP and FTP proxy cache: if your network is behind a proxy server, it is necessary to set the address of your HTTP or FTP proxy server. If you don’t know it, ask your network administrator. The address is inserted either as address or address:port . For example: If an HTTP proxy cache is configured, all HTTP requests will be set to the configured proxy using the given address and port. Similarly for FTP.

Furthermore various network connection parameters can be set:

Max connections: Determines the maximum number of open connections (overall). Max connections to one host: Determines the maximum number of open connections to a single host (server). Retries (0-unlimited): Number of attempts to reopen a broken connection. Receive timeout (sec): Time (in seconds) to wait when no more data is coming in, before the connection is deemed dead and the browser tries to reconnect. Timeout when unrestartable: Elapsed time in seconds with no successful restart attempt before the connection is closed. Async DNS lookup: Whether aynchronous DNS lookup should be performed. If this option is on, several DNS translations can be performed while downloading data. This speeds up download of files.

Set time of downloaded files: If this is checked, downloaded files will have the time of last modification set to the current time on the server from which they were downloaded.

The FTP options button invokes a dialog where you can enter a password for anonymous access to FTP servers. Some FTP servers require a password for anonymous access, usually your email address.

Warning:
We do not recommend entering your own email address for an anonymous FTP password, because it can be misused by the FTP server operator for sending spam.

The button HTTP options invokes a dialogue for setting the properties of HTTP connections. In this dialogue you can set:

• Use HTTP/1.0: Some servers still can’t properly communicate with the HTTP/1.1 protocol; therefore it is sometimes necessary to enforce the older 1.0 version.
• Allow blacklist of buggy servers: If a server claims to support the HTTP/1.1 protocol, but its use of the protocol is faulty, the connection will be closed, the request will be resubmitted in HTTP/1.0 and the address of the server will be remembered so that any subsequent requests will be sent directly in HTTP/1.0
• Broken redirect 302: If an HTTP server sends a «302 redirect» reply to a POST request, the browser according to the HTTP specification should send a POST request with the same data to the new server. However Netscape and IE browsers violate this specification and, instead of a POST request, they send a GET request. If you check this option, Links will behave like Netscape or IE and will send a GET request. Some badly configured server require this behaviour.

The Header options button allows you to set the refer information to one of the following possibilities. HTTP refer means that the browser sends information to the server telling from which page you got to the currently loaded page. However this is not secure, as you may wish to keep this information undisclosed. The following are your options:

• No referer: The information is not sent at all (default setting). Some servers however require the referer and for these you can select from the options below.
• Send requested URL as referer: Send the address of the page itself as the referer.
• Fixed referer: You can fill in your own text into the text field below. This will be sent as the referer if you check this option.
• Send real referer: Sends the page from which you got to the page being currently loaded. This is the correct behaviour (according to the HTTP specification), but we repeat once more, this is not secure .

You have the option to enter a text string into the Fake User-Agent field. This text will be sent to the server as user-agent. User-agent is a string giving information about your browser and operating system. By default true information about your operating system and the Links browser is sent. If you insert any text into this field, then this text will be sent instead and the server will never know your real operating system and browser. If you leave the field empty, the true user-agent will be reported.

Miscellaneous options

In the «Miscellaneous options» dialog in graphics mode you can set the menu letter size. You can also set the file where bookmarks are stored and character encoding of the bookmarks.

Menu font size determines how big letters should be in the menu. The size is counted in screen pixels.

You can set colours for various parts of the menu: foreground , background , scrollbar , scrollbox , and scrollbar frame . All colours should be entered as hexadecimal triplets for the red, green and blue bytes. That is six characters, two for each component, chosen from the characters 0-9 , a-F . For example 00ff00 is bright green, 000000 is black, 444400 is dark yellow, a700a7 is light violet, ffffff is white and so on.

Bookmarks file is a file into which the bookmarks will be saved (see the section on bookmarks). The default is bookmarks.html in the .links directory in your home directory. This dialog allows you to change the bookmark file, for example when you want to share bookmarks with other browsers. When you are changing the bookmarks file the changes you have already made will be saved into the old file and the new file will be automatically loaded.

After clicking on Bookmarks encoding you will have an option to select the encoding in which the bookmarks file will be stored. Like changing the filename, a change in the encoding causes the pending changes to be saved into the old file in the old encoding and a new file in new encoding will be loaded.

If it is not possible to determine keyboard input encoding in graphics mode from the environment variables, this menu contains one more entry. The entry is a button marked Keyboard encoding . After pressing this button you will be presented with a choice of encoding in which your keyboard sends the characters. This setting is different for each graphics driver. For example you can have a different encoding for SVGAlib than for X-Window system. The encoding selection is always related to the graphics driver you are currently using.

Cache

In this dialogue you can set the cache size for document cache (in kilobytes) and number of formatted documents that can be stored in the cache. Maximum number of documents in the cache is 256.

Mail and telnet

In this dialog you can set programs for mail and telnet. They are used for links like «mailto:», «telnet:», and «tn3270:». The dialog contains three text fields: program for mail, program for telnet and program for tn3270. Write commands which should be executed into these fields, the character «\» will be replaced by the address (for mail) or the name of machine and port (for telnet).

Associations and extensions

These two functions allow you to request execution of external programs for unknown file types. Each file received over the network has a so-called MIME type. This is a text string consisting of two parts separated by a slash (/). The part before the slash is the so-called main type (text, image, audio etc.). The part after slash defines the file format. For example when the main type is audio, the format could be MP3. In the table below you can find an overview of some widely used MIME types.

The Links browser can display only text and images; however it allows you to choose external programs to be executed for other MIME types, for example for audio files. For this there are two functions. With «associations» you can specify an external program and the MIME types for which this program should be executed. With «extensions» you can assign MIME types to file extensions for cases where the MIME type is not known to Links or cannot be acquired from the server, but can be derived from the filename extension.

Both associations and extensions are managed using a dialog very similar to the «Bookmark manager» dialog. After invoking the «Associations» or «File extensions» function, a dialog labeled «Associations manager» or «Extension manager» appears.

Working with the Associations manager and the Extensions manager is the same. Therefore we first describe the common elements, and then the dialogs for editing and addition, which differ between associations and extensions.

As in the bookmark manager, there is a list of extensions or associations in the top window. There are Add , Delete , Edit , Move , Unselect all and Close buttons at the bottom. Each extension or association shows a label and a mime-type after a colon which belongs to the association or extension.

It is possible to select an entry in the upper part of the window as you do in a menu. The selected entry is highlighted by an inverse video bar. You can move the bar with cursor keys and PAGE UP , PAGE DOWN , HOME , and END keys. Left and right cursor keys select the button (at the bottom of the window), pressing ENTER activates the button. Alternatively click on a button to activate it. You can scroll through the list by holding the middle mouse button and moving the mouse up and down. It is also possible to scroll with the scrollbar at the right part of the window.

Now we will describe individual actions that can be performed using the buttons. The buttons always have effect on the entry (extension or association) which is selected by the cursor. We will call this entry the current entry.

• Add: Creates a new entry. After pressing this button, you are presented with a dialogue, in which you enter information about the new entry. Pressing OK creates a new entry right after the current entry. Cancel revokes the current edit.
• Delete: Deletes the current entry. You will be asked first if you really want to delete this entry.
• Edit: Invokes a dialog in which it is possible to change the current entry. By pressing OK you confirm the changes, by Cancel you cancel them.

It is also possible to rearrange the entries in the list. This is what the Move button is for. First it is necessary to mark the entries we want to move. An entry can be marked by the INSERT key or * . These are toggle keys which unmark a marked entry and mark an unmarked one. It is also possible to mark entries by clicking the right mouse button on the entry. A marked entry has an asterisk in front (in text mode) or a square (graphics mode). If you press the Unselect all button, all entries will be unmarked.

When you have all the entries marked that you want to move, move the cursor bar to the entry behind which you want to move the entries. Then press the Move button. The marked entries will be moved to just after the current entry. The marked entries will be in the same sequence as they were before the move (this means the relative sequence of the marked entries is unchanged).

Note:
Both extension and association managers can be opened only once. If you have multiple windows and there is an associations manager (or extensions manage) already open in one window, it is not possible to open the same manager in the other windows. A message will be displayed in that case.

Warning:
If you perform any change in associations or extensions you have to save the browser settings. If you don’t save them, they will be treated as temporary and will be forgotten when the browser is terminated.

Associations
The dialogue for editing and adding new associations looks like this:

• Fill the Label field with the name of the association (can be an arbitrary text).
• Fill the Content Type(s) field with a comma-separate list of MIME types (or just one MIME type. Do not insert spaces next to the commas.
• Fill the Program field with commandline (including possible parameters) that should be executed on the entered MIME types. The «\» character will be replaced with a filename.
• Block terminal while program running: Blocks the terminal while the given program is running, i. e. you will be returned into the Links browser only after the program exits.
• Run on terminal: That means whether the program is allowed to be excuted on a terminal. For example some programs run only on a windowing system and it doesn’t make sense to run them on a terminal.
• Run in X-Window: It has a similar meaning like the previous one with the difference that it’s about running in a window of an X-Window system.
• Ask before opening: If you tick up this field you will be asked on each encounter whether you want to download the file, view, run the external program or it, or cancel.

Here are example of MIME type settings:

Of course you can set more programs for a single MIME type (for example multiple PDF viewers). If you set more program, a dialog will be presented before executing the external program, where you can select which of the programs should be executed.

File extensions
This function allows certain file extensions to be bound together with a concrete MIME type. The extension is used in the case when it is not possible to determine the MIME type from a server. The type is then determined from the filename extension. Editation and addition of a new extension invokes a dialogue into which you enter a list of extensions (without the dot) separated by commas, and a MIME type on which these extensions should be mapped. So for example:

If you are running the browser for the first time, extensions for basic file types (images, graphics formats, documents, music files, animations etc.) will be automatically created.

Save settings

Saves the settings into the configuration file. If you change some setting and don’t save the settings later, then the change will be forgotten when the browser is exited. Therefore do not forget to save the setting if you change something and want it to be kept for the next execution of the browser.

Examples

Displaying the www.linux.cz page
Run the browser and press the g key . A dialog for entering a URL will appear. Enter «www.linux.cz» into the dialog. Click «OK» and wait until the page is displayed.

How to change the page encoding to win-1250
Invoke the menu by pressing ESC , click on «View», click on «HTML options», click on «Default codepage», select «Windows 1250» from the menu, press ENTER , tick the «Ignore charset info sent by server» field and click «OK».

Setting proxy server proxy.local.net and port 8000
Invoke the menu by pressing ESC , click «Setup», click «Network options». Enter «proxy.local.net:8000» into the «HTTP proxy» and «FTP proxy» fields and click on «OK».

We want to search for the word «cemetery» on a page
Press / : a dialogue for entering search text will appear. Enter «cemetery» and click «OK». If the text occurs anywhere in the page, it will be shown in inverse video.

Adding a bookmark on www.praha-mesto.cz into the «Cities» bookmark directory
Display the page «www.praha-mesto.cz», press s . A window labeled «Bookmark manager» will be displayed. Click «Folder», a dialogue will pop up, enter «Cities» and click «OK». A directory labeled «Cities» will be created. Move over the «Cities» directory and press +, the directory will open. Click «Add»: a dialogue for adding bookmarks will appear. The URL will be already filled in. Change the name if you want. Click «OK» and the bookmark will be added into the directory. You can close the bookmark manager by clicking «Close».

Running links in the X-Window system on the remote machine hammer-5.forge.cz and display 0:0

Problems and frequently asked questions

Solving problems

I wanted to run the browser in graphics mode but it’s still running in text mode.
You forget to include the -g switch in the command line. Run the browser with this option.

I am running the browser in graphics mode on a remote computer and I am getting the message «Not running in a graphics capable console, and unable to find one.»
Your environment variable DISPLAY is not set and the browser doesn’t know to which X server it should connect. Set the DISPLAY variable to match your display, or run the browser with the -mode display option, where «display» determines your display.

When I am using Links in SVGAlib, the browser (or the whole system) crashes. What should I do?
This is a bug in SVGAlib and the design of virtual consoles in the Linux kernel. Ask their authors to fix the bug.

When I run Links in SVGAlib, switch to another console and then switch back, Links stops running and a message reads «Segmentation fault». What should I do?
We know about this problem. It’s an error of SVGAlib, more precisely of its kernel part, which crashes during console switches. The only solution to the problem is that the authors of SVGAlib fix it. Therefore write an e-mail to them so that they have a motivation.

After running the browser on the X-Window system an error message «No supported color depth found» pops up and the program terminates. Can I do anything with that?
Unfortunately you have a display that is not supported by Links. It may be either a grayscale display, a display with a low number of colours (less than 16), or it is not possible to set a private colour palette. The program requires a colour display with at least 16 colours and a possibility to set a private palette. This problem occurs in some X-servers for Windows and unfortunately nothing can be done about it.

Why is the mouse cursor on the framebuffer moving in jerks and not smoothly?
Because gpm is used for reading the mouse and gpm is character-oriented. Text mode has fewer pixels than graphics mode, which could lead to the mouse pointer moving very slowly. To prevent this, the movement is multiplied by a constant and therefore forms little steps.

Can anything be done about that?
Yes, patch gpm to support graphics. Write to the gpm authors that they should build in graphics support. If you have administrator privileges, apply the enclosed patch PATCH-gpm-1.20.0-smooth-cursor on the gpm sources. The patch is for the 1.20.0 version but it will probably work with other versions too. Then recompile gpm .

Can I move the mouse more smoothly in this situation?
Yes, using the keys F5 , F6 , F7 and F8 .

And why is gpm being used then?
Because on the framebuffer there is no other way to read the mouse.

The mouse on my framebuffer doesn’t work but gpm is running and works. What can I do about that?
Try and see whether the mouse works in other applications on the console (for example Midnight Commander). If it doesn’t work, this is not a fault in Links; your gpm is installed improperly.

I am connected through an SSH connection to an X-server and Links is slow on pages with a lot of images. Why?
This is not caused by Links, but by the SSH connection, over which the megabytes of image data have to be transfered. As all the data have to be encrypted, it takes long time. Therefore do not use SSH but connect to the X-server directly.

Why does the left arrow not work for going back in history in graphics mode?
Because the arrows are used for scrolling. Use the z key. Left arrow works only in text mode for backward compatibility with older versions and Lynx.

The page looks «fallen apart». What is the cause?
You have probably changed the text font size or image zoom factor in HTML options and the page is assuming a certain text size or image size. If you want the page to be displayed correctly, set text size to 16 and image magnification to 100

Why don’t animated GIFs work?
Because Links contains an active filter which displays only the first frame of an animated GIF. Animated GIFs don’t provide any additional information and they unnecessarily load the network during remote execution. In Links the user is not pestered by constantly flashing adverts and can concentrate on reading the text. Furthermore expensive bandwidth is not wasted.

On my web page the text is blue on a dark blue background. Why does Links display yellow text on a dark blue background?
Blue text on a dark blue background is VERY hard to read. When Links evaluates text as poorly legible, it displays the text with as much color contrast as possible against the original background. Unfortunately there are authors of web pages who think that this type of colouring makes their pages look original and irresistible. With Links you will be able to read them without problems.

Frequently asked questions

How do I.

1. How do I restart a connections when it’s stuck?
   Quit the connection (with the back function or by stopping the download), click «Kill all connections» in the menu and run the connection once more.

How do I refresh a stale page or image?
With the «Reload» function, or leave the page with the «Back» function, click «Flush all caches» and load the page once more.

General questions

Does Links support JavaScript? If yes, then what version and with what limitations?
Not currently. But see Appendix 1.

I have heard that links supports gamma correction. Is that true?
Yes. But only in graphics mode.

What is gamma correction?
The luminance generated by a physical device is generally not a linear function of the applied signal. A conventional CRT has a power-law response to voltage: luminance produced at the face of the display is approximately proportional to the applied voltage raised to the 2.5 power. The numerical value of the exponent of this power function is colloquially known as gamma. You can find more on
http://www.inforamp.net/

Why has Links become a graphical browser?
To make it possible to display images. It’s a bit difficult to display images in text mode.

Why did you write Links?
Because we like it and we want to view web pages with a good browser.

Why didn’t you just add image display in AAlib into the text version of Links?
Because AAlib has mediocre resolution.

Why doesn’t Links have a graphics driver for AAlib?
Because AAlib has a mediocre resolution.

Are you going to implement Java in Links?
No.

Why is Links written in C? Because C is an universal programming language characterized by efficient expressions, modern flow control and a multitude of operators. The generality of the C language makes it more suitable and efficient for much tasks than other «more powerful» languages.

Have you written Links according to some standard? If so, which one? We have written it according to ANSI C, to attain portability on as many systems as possible.

Why isn’t Links object oriented? Becuase the C language doesn’t have objects.

Why isn’t Links multiprocessor/multithreaded? Because a single processor and single threading is more efficient.

Why didn’t you use GTK or another toolkit for Links development?
Because these toolkits take up too much space, are not portable, need not necessarily be installed on every computer (why should a user install a multimegabyte toolkit together with Links?), bring unnecessary program slowdown, annoy with thousands of windows and are incompetent. For example in GTK it is impossible to dictate the gamma with which the dialogues should be displayed, and it is also impossible to scroll with the middle mouse button in the file selection dialogue.

Why doesn’t Links have a button bar and a line for entering URLs?
Because these don’t have a practical use and just take up 1/5 of the screen; effectively they make a 15-inch monitor out of a 17-inch one. This feature will be appreciated especially by users of low resolution monitors, for example 640×480.

The URL entry line is utterly impractical because the user has to try laboriously to hit it with the mouse. Pressing one key more (to invoke the URL entry dialogue) is much more practical and faster. The dialogue takes up screen space only while entering URLs.

Why can plugins from browser XXX not be plugged into links?
Because there is no standardized interface for plugins; each browser has its own. The plugins are also insecure in that a crash of the plugin often causes a crash of the whole browser (which should not happen!).

Appendix 1: Links and JavaScript

When Links was created, one of the main differences from Lynx was that Links supported JavaScript, even in text mode. It was controlled by the JavaScript 1.1 specification from Netscape Corporation.

However JavaScript support was removed in release 2.1pre29 because it was buggy. In case it is restored, this appendix contains information on how to use it. The material in this appendix is not currently valid.

To compile Links with JavaScript support, use the configure option —enable-javascript.

Javascript Options

When JavaScript is enabled, this option appears in the Setup menu.

In this dialogue you can set up various parameters of the javascript interpreter.

• Kill all scripts: If you check this field and you confirm the setting by pressing the OK button, the javascript interpretation on the page will be forcefully ended. This helps for example in cases where the script loops infinitely, or causes annoyance.
• Enable javascript: This switches javascript on and off.
• Verbose javascript errors: The purpose of this switch is to suppress or enable the display of errors in javascript.
• Verbose javascript warnings: This suppresses or enables the display of warning messages when javascript is running.
• Enable all conversions: Allows the use of undefined variables, converting a function into a number and so on. However it will not allow, for example, converting an undefined object into an object.
• Enable global name resolution: Allows resolution of names in the document in the main address space. It is meant for cases when the page authors refer to items from the document object without explicitly stating this.
• Recursion depth: With this value you can set maximum allowed depth of recursion for javascript functions. The default setting is 1000. This parameter is set for security reasons. If the recursion depth were unlimited, it could happen that the javascript function on some page will call itself infinitely, which would understandably exhaust all available memory. If the default value is not enough for you, you can increase it (up to 999999).
• Memory dedicated to javascript (kB): Maximum allowed amount of memory (in kilobytes) the javascript is allowed to ocupy. Again for security reasons to prevent javascript from taking too much memory and unnecessarily overloading your system. The minimum value is 1024 kB, maximum value is 30720 kB, default value is 5120 kB.

prev: Links and Javascript

contents

Appendix 2: GNU general public licence

GNU GENERAL PUBLIC LICENSE Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software — to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps:

1. copyright the software, and
2. offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors’ reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

GNU GENERAL PUBLIC LICENSE TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0) This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The «Program», below, refers to any such program or work, and a «work based on the Program» means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term «modification».) Each licensee is addressed as «you».

Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.
If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and «any later version», you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM «AS IS» WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the «copyright» line and a pointer to where the full notice is found.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

You should also get your employer (if you work as a programmer) or your school, if any, to sign a «copyright disclaimer» for the program, if necessary. Here is a sample; alter the names:

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.

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