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SCUMM: more cleanup in ScummEngine::drawStripToScreen, added a big TODO comment explaining how to potentially speed up this code a lot

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svn-id: r27997
This commit is contained in:
Max Horn 2007-07-09 21:56:35 +00:00
parent 945be6e5f2
commit aaa987201e
1 changed files with 32 additions and 15 deletions
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47
engines/scumm/gfx.cpp
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@ -561,12 +561,10 @@ void ScummEngine::drawStripToScreen(VirtScreen *vs, int x, int width, int top, i
return;
const byte *src = vs->getPixels(x, top);
int pitch = vs->pitch;
if (_game.version >= 7) {
if (_game.version < 7) {
// For The Dig, FT and COMI, we just blit everything to the screen at once.
_system->copyRectToScreen(src, vs->pitch, x, y, width, height);
} else {
// For older games, things are more complicated. First off, we need to
// deal with the _textSurface, which needs to be composited over the
// screen contents. Secondly, a rendering mode might be active, which
@ -576,25 +574,44 @@ void ScummEngine::drawStripToScreen(VirtScreen *vs, int x, int width, int top, i
assert(_compositeBuf);
const byte *text = (byte *)_textSurface.getBasePtr(x, y);
// The values x, width, etc. are all multiples of 8 at this point,
// so loop unrolloing might be a good idea...
assert(0 == ((int)text & 3));
assert(0 == (width & 3));
// Compose the text over the game graphics
// TODO: Optimize this code. There are several things that come immediately to mind:
// (1) Loop unrolling: We could read 4 or even 8 pixels at once, since everything is
// a multiple of 8 here.
// (2) More ASM versions (in particular, the ARM code for the NDS could be used on
// all ARM systems, couldn't it?)
// (3) Better encoding of the text surface data. This is the one with the biggest
// potential.
// (a) Keep an "isEmpty" marker for each pixel row in the _textSurface. The idea
// is that most rows won't contain any text data, so we can just use memcpy.
// (b) RLE encode the _textSurface row-wise. This is an improved variant of (a),
// but also more complicated to implement, and incurs a bigger overhead when
// writing to the text surface.
#ifdef __DS__
DS::asmDrawStripToScreen(height, width, text, src, _compositeBuf, vs->pitch, width, _textSurface.pitch);
#else
// Compose the text over the game graphics
byte *dst = _compositeBuf;
for (int h = 0; h < height; ++h) {
for (int w = 0; w < width; ++w) {
if (text[w] == CHARSET_MASK_TRANSPARENCY)
*dst++ = src[w];
else
*dst++ = text[w];
byte tmp = *text++;
if (tmp == CHARSET_MASK_TRANSPARENCY)
tmp = *src;
*dst++ = tmp;
src++;
}
src += vs->pitch;
text += _textSurface.pitch;
src += vs->pitch - width;
text += _textSurface.pitch - width;
}
#endif
src = _compositeBuf;
int pitch = width;
pitch = width;
if (_renderMode == Common::kRenderHercA || _renderMode == Common::kRenderHercG) {
ditherHerc(_compositeBuf, _herculesBuf, width, &x, &y, &width, &height);
@ -621,10 +638,10 @@ void ScummEngine::drawStripToScreen(VirtScreen *vs, int x, int width, int top, i
}
}
// Finally blit the whole thing to the screen
_system->copyRectToScreen(src, pitch, x, y, width, height);
}
// Finally blit the whole thing to the screen
_system->copyRectToScreen(src, pitch, x, y, width, height);
}
// CGA