coreboot-kgpe-d16/payloads/libpayload/curses/PDCurses/doc/sdl.txt

SDL Considerations
==================

There are no special requirements to use PDCurses for SDL -- all
PDCurses-compatible code should work fine. (In fact, you can even build
against the Win32 console pdcurses.dll, and then swap in the SDL
pdcurses.dll.) Nothing extra is needed beyond the base SDL library.
However, there are some optional special features, described here.

The principal limitation of this port is that input is currently
restricted to ASCII (i.e., 0-127), plus the special keys like KEY_LEFT.
(You could have Unicode input, but then the input wouldn't match the
output, which is in Code Page 437.) Also, see the note about the
potential for incomplete output under "PDC_update_rects()", below.


Fonts
-----

The font is a simple BMP, 32 characters wide by 8 characters tall,
preferably with a palette. (BMPs without palettes still work, but in
that case, no attributes will be available, nor will the cursor work.)
The first entry in the palette (usually black) is treated as the
background color; the last entry (usually white) is treated as the
foreground. These are changed or made transparent as appropriate; any
other colors in the palette are passed through unchanged. So -- although
a one-bit depth is sufficient for a normal font -- you could redraw some
characters as multi-colored tiles.

The font must be monospaced. The size of each character is derived by
dividing the width of the BMP by 32 and the height by 8. There is no
constraint on the dimensions.

As provided in the default font and expected by acs_map[], the font is
in Code Page 437 form. But you can of course use any layout if you're
not relying on correct values for the ACS_* macros.

The font can be set via the environment variable PDC_FONT. If it's not
set, PDCurses looks for a file named "pdcfont.bmp" in the current
directory at the time of initscr(). If neither is found, it uses the
built-in default font encoded in deffont.h.


Backgrounds
-----------

PDCurses for SDL supports an optional background image BMP. This is used
whenever start_color() has not been called (see the ptest demo for an
example), or when use_default_colors() has been called after
start_color(), and the background color of a pair has been set to -1
(see newdemo, worm, and rain for examples). The usage parallels that of
ncurses in an appropriate terminal (e.g., Gnome Terminal). The image is
tiled to cover the PDCurses window, and can be any size or depth.

As with the font, you can point to a location for the background via the
environment variable PDC_BACKGROUND; "pdcback.bmp" is the fallback.
(There is no default background.)


Icons
-----

The icon (used with SDL_WM_SetIcon() -- not used for the executable
file) can be set via the environment variable PDC_ICON, and falls back
to "pdcicon.bmp", and then to the built-in icon from deficon.h. The
built-in icon is the PDCurses logo, as seen in ../x11/little_icon.xbm.
The SDL docs say that the icon must be 32x32, at least for use with MS
Windows.

If pdc_screen is preinitialized (see below), PDCurses does not attempt
to set the icon.


Screen size
-----------

The default screen size is 80x25 characters (whatever size they may be),
but you can override this via the environment variables PDC_COLS and/or
PDC_LINES. (Some other ports use COLS and LINES; this is not done here
because those values are, or should be, those of the controlling
terminal, and PDCurses for SDL is independent of the terminal.) If
pdc_screen is preinitialized (see below), these are ignored.


Integration with SDL
--------------------

If you want to go further, you can mix PDCurses and SDL functions. (Of
course this is extremely non-portable!) To aid you, there are several
external variables and functions specific to the SDL port; you could
include pdcsdl.h, or just add the declarations you need in your code:

 PDCEX SDL_Surface *pdc_screen, *pdc_font, *pdc_icon, *pdc_back;
 PDCEX int pdc_sheight, pdc_swidth, pdc_yoffset, pdc_xoffset;

 void PDC_update_rects(void);
 void PDC_retile(void);

pdc_screen is the main surface, created by SDL_SetVideoMode(), unless
it's preset before initscr(). You can perform normal SDL operations on
this surface, but PDCurses won't respect them when it updates. (For
that, see PDC_retile().) As an alternative, you can preinitialize this
surface before calling initscr(). In that case, you can use pdc_sheight,
pdc_swidth, pdc_yoffset and/or pdc_xoffset (q.v.) to confine PDCurses to
only a specific area of the surface, reserving the rest for other SDL
operations. If you preinitialize pdc_screen, you'll have to close it
yourself; PDCurses will ignore resize events, and won't try to set the
icon. Also note that if you preinitialize pdc_screen, it need not be the
display surface.

pdc_font, pdc_icon, and pdc_back are the SDL_surfaces for the font,
icon, and background, respectively. You can set any or all of them
before initscr(), and thus override any of the other ways to set them.
But note that pdc_icon will be ignored if pdc_screen is preset.

pdc_sheight and pdc_swidth are the dimensions of the area of pdc_screen
to be used by PDCurses. You can preset them before initscr(); if either
is not set, it defaults to the full screen size minus the x or y offset,
as appropriate.

pdc_xoffset and pdc_yoffset are the x and y offset for the area of
pdc_screen to be used by PDCurses. See the sdltest demo for an example.

PDC_retile() makes a copy of pdc_screen, then tiles it with the
background image, if any. The resulting surface is used as the
background for transparent character cells. PDC_retile() is called from
initscr() and resize_term(). However, you can also use it at other
times, to take advantage of the way it copies pdc_screen: Draw some SDL
stuff; call PDC_retile(); do some curses stuff -- it will use whatever
was on pdc_screen as the background. Then you can erase the curses
screen, do some more SDL stuff, and call PDC_retile() again to make a
new background. (If you don't erase the curses screen, it will be
incorporated into the background when you call PDC_retile().) But this
only works if no background image is set.

PDC_update_rects() is how the screen actually gets updated. For
performance reasons, when drawing, PDCurses for SDL maintains a table of
rectangles that need updating, and only updates (by calling this
function) during getch(), napms(), or when the table gets full.
Normally, this is sufficient; but if you're pausing in some way other
than by using napms(), and you're not doing keyboard checks, you may get
an incomplete update. If that happens, you can call PDC_update_rects()
manually.


Interaction with stdio
----------------------

As with X11, it's a bad idea to mix curses and stdio calls. (In fact,
that's true for PDCurses on any platform; but especially these two,
which don't run under terminals.) Depending on how SDL is built, stdout
and stderr may be redirected to files.