[This file explains how netrik handles syntax errors in HTML pages, why it does so, and what to do about that. See index.txt or index.html for an overview of available netrik documentation.]
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Well, it *is* OK... The problem is: Actually almost all sites *are* more or less broken.
Other browsers simply ignore the errors, hoping that the effect will resemble more or less what the author intended -- and nobody ever knows, but for some little blemish maybe, where no one cares about. (If Netscape wasn't so tolerant about ohave to be provided for those situations.
The handling is actually quite simple: Depending on the setting of "cfg.bright_background", either "color_map_bright" (from colors-bright.c) or "color_map_dark" (from colors-dark.c) is assigned to "color_map". This is done in load_color_map(), which is called after reading the command line/config file options in main().
Note that, unless explicitely overridden by --no-force-colors, "cfg.force_colors" is automatically set if "cfg.bright_background" is not set, so a black background will always be used with the dark color scheme, even on a terminal normally having a bright background. This isn't done with the bright color scheme; here, the terminal's default colors are kept.
Netrik now features an extremly crude monochrome mode, which is activated by passing the --bw command line option, or automatically in init_curses(), if the terminal definition lacks color switching capabilities.
The monochrome mode presently completely disables all color/attribute switching.
This is achieved by skipping all color initializations and making all color setting functions nops. Thus, it needs handling only in screen.c (s.b.), and is otherwise completely transparant.
screen.c contains a couple of helper functions for handling curses, both in raw and in full screen mode.
init_curses() is responsible for initializing curses in raw mode, and getting some control sequences for setting colors etc. If cfg.inverse_bold was not specified by the user, this is also done here: If the terminal name contains "xterm", cfg.inverse_bold is set, otherwise reset.
start_curses() initializes curses in full screen mode, and sets the foreground/background color pairs. (This is necessary to change colors using curses.) It also initializes several curses settings.
All 63 modifiable color pairs are initialized (pair 0 is hard-wired in curses), in such a manner that every combination of the eight foreground and eight background colors is covered. (Brightness is controled by extra flags, and not coded in the color pairs.) The upper three bits of the six-bit pair number specify the background, the lower 3 the foreground. While the background colors are mapped directly, some magic is necessary for the foreground, to ensure that color pair 0 (which is hard-wired to white on black) will actually correspond to the right color in the color scheme. This is achieved by rotating the foreground color space by one, so color 0 gets white, color 1 gets black etc., instead of color 0 being black and color 7 being white.
For color pairs having black background or white foreground, the respective parts aren't set; the terminal default is used instead. (Unless --force-colors is used.) This is to produce the expected results in most xterms (or other terminals with bright background and black text).
set_color() sets the text attributes in full screen mode. The foreground color is set, and the "bold" attribute if it is a light color.
If the background color is bright, the "blink" attribute is set, which works on most terminals. (Sadly not all...)
As this doesn't work in xterm, another approach has to be used for those: If cfg.inverse_bold was set (see above), the "blink" attribute is used in conjuction with reverse video instead. Of course we have to swap foreground and background colors to get the actually desired ones. (Note that this trick doesn't work on linux console, so we can use it *only* when in an xterm!)
The drawback is that the foreground is always bold but dark in this mode -- we can neiter prevent it getting bold nor get it bright to distinguish between bold and normal foreground as soon as a bright background is set...
set_color_raw() does the same in raw mode. As raw mode has no color pairs to be set during initialization, handling of default colors for white foreground/black background has to be done here. The respective parts simply aren't set at all, thus keeping the terminal default colors.
reset_colors_raw() resets all text attributes to their default values.
Handling of the "winch" singnal (which is raised by the terminal each time the text area changes, e.g. when resizing an xterm window) itself is quite simple, as we use the default handler provided by ncurses. On SIGWINCH, ncurses will adjust its own data structures, and also store the pseudo-key "KEY_RESIZE" in the input queue, so we know there was a change.
Only thing we have to care of here is ensuring that ncurses won't resize its data structures while we are making some changes to the screen contents, as this might cause failure when we are outside the screen unexpectedly. This is achieved by the two functions