Hands-on Projects for the Linux Graphics Subsystem
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We continue with other initialization in InitOutput().
/*
* Collect all pixmap formats and check for conflicts at the display
* level. Should we die here? Or just delete the offending screens?
* Also, should this be done for -probeonly?
*/
screenpix24 = Pix24DontCare;
for (i = 0; i < xf86NumScreens; i++) {
if (xf86Screens[i]->imageByteOrder !=
xf86Screens[0]->imageByteOrder)
FatalError("Inconsistent display bitmapBitOrder. Exiting\n");
if (xf86Screens[i]->bitmapScanlinePad !=
xf86Screens[0]->bitmapScanlinePad)
FatalError("Inconsistent display bitmapScanlinePad. Exiting\n");
if (xf86Screens[i]->bitmapScanlineUnit !=
xf86Screens[0]->bitmapScanlineUnit)
FatalError("Inconsistent display bitmapScanlineUnit. Exiting\n");
if (xf86Screens[i]->bitmapBitOrder !=
xf86Screens[0]->bitmapBitOrder)
FatalError("Inconsistent display bitmapBitOrder. Exiting\n");
/* Determine the depth 24 pixmap format the screens would like */
if (xf86Screens[i]->pixmap24 != Pix24DontCare) {
if (screenpix24 == Pix24DontCare)
screenpix24 = xf86Screens[i]->pixmap24;
else if (screenpix24 != xf86Screens[i]->pixmap24)
FatalError("Inconsistent depth 24 pixmap format. Exiting\n");
}
}
/* check if screenpix24 is consistent with the config/cmdline */
if (xf86Info.pixmap24 != Pix24DontCare) {
pix24 = xf86Info.pixmap24;
pix24From = xf86Info.pix24From;
if (screenpix24 != Pix24DontCare && screenpix24 != xf86Info.pixmap24)
pix24Fail = TRUE;
} else if (screenpix24 != Pix24DontCare) {
pix24 = screenpix24;
pix24From = X_PROBED;
} else
pix24 = Pix24Use32;
if (pix24Fail)
FatalError("Screen(s) can't use the required depth 24 pixmap format"
" (%d). Exiting\n", PIX24TOBPP(pix24));
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The previous code checks first id the pixmap value, pix24, is obtained from xorg.conf. In that case xf86Info.pixmap24 is set to a non 'Pix24DontCare' value. For an exlpanation on xf86Info see section 3.2.2.
Then it checks for a xf86Screens[i]->pixmap24 value other than 'Pix24DontCare'. This value was set by xf86SetDepthBpp(), which was called by MGAPreInit(), as seen in section 3.2.2.8.
If this check also fails it assigns the pixmap value Pix24Use32.
/* Initialise the depth 24 format */
for (j = 0; j < numFormats && formats[j].depth != 24; j++)
;
formats[j].bitsPerPixel = PIX24TOBPP(pix24);
/* Collect additional formats */
for (i = 0; i < xf86NumScreens; i++) {
for (j = 0; j < xf86Screens[i]->numFormats; j++) {
for (k = 0; ; k++) {
if (k >= numFormats) {
if (k >= MAXFORMATS)
FatalError("Too many pixmap formats! Exiting\n");
formats[k] = xf86Screens[i]->formats[j];
numFormats++;
break;
}
if (formats[k].depth == xf86Screens[i]->formats[j].depth) {
if ((formats[k].bitsPerPixel ==
xf86Screens[i]->formats[j].bitsPerPixel) &&
(formats[k].scanlinePad ==
xf86Screens[i]->formats[j].scanlinePad))
break;
FatalError("Inconsistent pixmap format for depth %d."
" Exiting\n", formats[k].depth);
}
}
}
}
formatsDone = TRUE;
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Array formats[] is defined in xf86Init.c as:
/* Common pixmap formats */
static PixmapFormatRec formats[MAXFORMATS] = {
{ 1, 1, BITMAP_SCANLINE_PAD },
{ 4, 8, BITMAP_SCANLINE_PAD },
{ 8, 8, BITMAP_SCANLINE_PAD },
{ 15, 16, BITMAP_SCANLINE_PAD },
{ 16, 16, BITMAP_SCANLINE_PAD },
{ 24, 32, BITMAP_SCANLINE_PAD },
#ifdef RENDER
{ 32, 32, BITMAP_SCANLINE_PAD },
#endif
};
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numFormats is defined in the same file as:
#ifdef RENDER static int numFormats = 7; #else static int numFormats = 6; #endif |
Struct PixmapFormatRec is defined in scrnintstr.h as:
typedef struct _PixmapFormat {
unsigned char depth;
unsigned char bitsPerPixel;
unsigned char scanlinePad;
} PixmapFormatRec;
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Macro PIX24TOBPP converts pixmap value to bits per pixel. It is defined in xf86.h as:
#define PIX24TOBPP(p) (((p) == Pix24Use24) ? 24 : \ (((p) == Pix24Use32) ? 32 : 0)) |
With the help of the previous definitions we see that the instruction:
for (j = 0; j < numFormats && formats[j].depth != 24; j++)
;
finds the format element with depth 24 and then the instruction that follows it:
formats[j].bitsPerPixel = PIX24TOBPP(pix24);
assigns to this record (with depth 24) the right number to the 'bitsPerPixel' field.
/*
* Use the previously collected parts to setup pScreenInfo
*/
pScreenInfo->imageByteOrder = xf86Screens[0]->imageByteOrder;
pScreenInfo->bitmapScanlinePad = xf86Screens[0]->bitmapScanlinePad;
pScreenInfo->bitmapScanlineUnit = xf86Screens[0]->bitmapScanlineUnit;
pScreenInfo->bitmapBitOrder = xf86Screens[0]->bitmapBitOrder;
pScreenInfo->numPixmapFormats = numFormats;
for (i = 0; i < numFormats; i++)
pScreenInfo->formats[i] = formats[i];
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For the first time the some of the screenInfo fields are filled. Struct screenInfo is the main struct that InitOutput() fills. For an overview in this struct see section 3.2.2. As we see the first element of xf86Screens[] determines the values of the first five pScreenInfo fields.
NOTES:
Green code text indicate that values are assigned to screenInfo fields.