Re: [PATCH v4 0/5] MR8969: opengl32, win32u: Fix 16-bit PFD_DRAW_TO_BITMAP rendering.

[Rémi Bernon (＠rbernon)]

Rémi Bernon (@rbernon) commented about dlls/win32u/opengl.c:
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>                float clear_color[4];
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>                /* Note: Despite asking for BGRA we actually get ABGR, with
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>                 *       the alpha bits being the eight highest bits. */
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>                funcs->p_glReadPixels( 0, 0, width, height, GL_BGRA, GL_UNSIGNED_BYTE, temp_image );
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>                for (int i = 0; i < pixel_count; i++)
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>                    bitmap_pixels[i] = blend_8888_pixel_onto_555( temp_image[i], bitmap_pixels[i] );
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>                /* Something difficult to fake about bitmap rendering is that a program can use
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>                 * a mix of blitting and OpenGL operations. Civilization 3 and SimGolf depend on
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>                 * this. There's no easy way to replicate the direct memory edits on the
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>                 * GPU-based pbuffer (since there's no API call), so instead I'm using a
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>                 * workaround: Each time after we draw the pbuffer onto the bitmap, we clear the
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>                 * pbuffer with transparent. In the end, this gives you the same bitmap as a
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>                 * result (unless you call glReadPixels, which will give you pixels from the
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>                 * transparent-background pbuffer). */

Hmm, so maybe RGB565 would make the trick with alpha bit more difficult. Another option I was thinking about would be to use the FBO-based surface instead of a pbuffer, now that we have it, with a GL_RGB5_A1 renderbuffer.