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Ax OverlaySurfaceKeyed(), set proper foregroundBuffer blend mode

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So, earlier in the development of 2.0, Simon Roth (I presume)
encountered a problem: Oh no, all my backgrounds aren't appearing! And
this is because my foregroundBuffer, which contains all the drawn tiles,
is drawing complete black over it!

So he had a solution that seems ingenius, but is actually really really
hacky and super 100% NOT the proper solution. Just, take the
foregroundBuffer, iterate over each pixel, and DON'T draw any pixel
that's 0xDEADBEEF. 0xDEADBEEF is a special signal meaning "don't draw
this pixel". It is called a 'key'.

Unfortunately, this causes a bug where translucent pixels on tiles
(pixels between 0% and 100% opacity) didn't get drawn correctly. They
would be drawn against this weird blue color.

Now, in #103, I came across this weird constant and decided "hey, this
looks awfully like that weird blue color I came across, maybe if I set
it to 0x00000000, i.e. complete and transparent black, the issue will be
fixed". And it DID appear to be fixed. However, I didn't look too
closely, nor did I test it that much, and all that ended up doing was
drawing the pixels against black, which more subtly disguised the
problem with translucent pixels.

So, after some investigation, I noticed that BlitSurfaceColoured() was
drawing translucent pixels just fine. And I thought at the time that
there was something wrong with BlitSurfaceStandard(), or something.
Further along later I realized that all drawn tiles were passing through
this weird OverlaySurfaceKeyed() function. And removing it in favor of a
straight SDL_BlitSurface() produced the bug I mentioned above: Oh no,
all the backgrounds don't show up, because my foregroundBuffer is
drawing pure black over them!

Well... just... set the proper blend mode for foregroundBuffer. It
should be SDL_BLENDMODE_BLEND instead of SDL_BLENDMODE_NONE.

Then you don't have to worry about your transparency at all. If you did
it right, you won't have to resort this hacky color-keying business.

*sigh*
This commit is contained in:
Misa 2020-08-04 00:24:04 -07:00 committed by Ethan Lee
parent 1a64e9c528
commit 57dca99a4e
4 changed files with 3 additions and 23 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
desktop_version/src/Graphics.cpp
View file

@ -2406,8 +2406,7 @@ void Graphics::drawmap()
}
foregrounddrawn = true;
}
OverlaySurfaceKeyed(foregroundBuffer, backBuffer, 0x00000000);
//SDL_BlitSurface(foregroundBuffer, NULL, backBuffer, NULL);
SDL_BlitSurface(foregroundBuffer, NULL, backBuffer, NULL);
}
@ -2433,7 +2432,7 @@ void Graphics::drawfinalmap()
foregrounddrawn=true;
}
OverlaySurfaceKeyed(foregroundBuffer, backBuffer, 0x00000000);
SDL_BlitSurface(foregroundBuffer, NULL, backBuffer, NULL);
}
void Graphics::drawtowermap()

17
desktop_version/src/GraphicsUtil.cpp
View file

@ -501,23 +501,6 @@ void FillRect( SDL_Surface* _surface, SDL_Rect rect, int rgba )
SDL_FillRect(_surface, &rect, rgba);
}
void OverlaySurfaceKeyed( SDL_Surface* _src, SDL_Surface* _dest, Uint32 _key )
{
// const SDL_PixelFormat& fmt = *(_src->format);
for(int x = 0; x < _src->w; x++)
{
for(int y = 0; y < _src->h; y++)
{
Uint32 pixel = ReadPixel(_src, x,y);
//endian_swap(pixel);
if (( pixel != _key))
{
DrawPixel(_dest,x,y, pixel);
}
}
}
}
void ScrollSurface( SDL_Surface* _src, int _pX, int _pY )
{
SDL_Surface* part1 = NULL;

2
desktop_version/src/GraphicsUtil.h
View file

@ -39,8 +39,6 @@ void FillRect( SDL_Surface* surface, SDL_Rect& rect, const int r, int g, int b )
void FillRect( SDL_Surface* surface, SDL_Rect rect, int rgba );
void OverlaySurfaceKeyed(SDL_Surface* _src, SDL_Surface* _dest, Uint32 _key);
void ScrollSurface(SDL_Surface* _src, int pX, int py);
SDL_Surface * FlipSurfaceHorizontal(SDL_Surface* _src);

2
desktop_version/src/main.cpp
View file

@ -247,7 +247,7 @@ int main(int argc, char *argv[])
graphics.Makebfont();
graphics.foregroundBuffer = CREATE_SURFACE(320, 240);
SDL_SetSurfaceBlendMode(graphics.foregroundBuffer, SDL_BLENDMODE_NONE);
SDL_SetSurfaceBlendMode(graphics.foregroundBuffer, SDL_BLENDMODE_BLEND);
graphics.menubuffer = CREATE_SURFACE(320, 240);
SDL_SetSurfaceBlendMode(graphics.menubuffer, SDL_BLENDMODE_NONE);