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Make software renderer a bit more foolproof

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This also eliminates some comparisons with mismatching signedness
This commit is contained in:
Clownacy 2020-09-15 20:48:18 +01:00
parent 11bbad7372
commit 52c2a5ceee
1 changed files with 50 additions and 3 deletions
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53
src/Backends/Rendering/Software.cpp
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@ -283,9 +283,56 @@ void RenderBackend_PrepareToDrawGlyphs(RenderBackend_GlyphAtlas *atlas, RenderBa
void RenderBackend_DrawGlyph(long x, long y, size_t glyph_x, size_t glyph_y, size_t glyph_width, size_t glyph_height) void RenderBackend_DrawGlyph(long x, long y, size_t glyph_x, size_t glyph_y, size_t glyph_width, size_t glyph_height)
{ {
for (unsigned int iy = MAX(-y, 0); y + iy < MIN(y + glyph_height, glyph_destination_surface->height); ++iy) size_t surface_x;
size_t surface_y;
// Clamp to within the destination surface's boundaries
if (x < 0)
{ {
for (unsigned int ix = MAX(-x, 0); x + ix < MIN(x + glyph_width, glyph_destination_surface->width); ++ix) surface_x = -x;
if (surface_x >= glyph_width)
return; // Glyph is offscreen to the left
glyph_x += surface_x;
glyph_width -= surface_x;
}
else
{
surface_x = x;
}
if (surface_x >= glyph_destination_surface->width)
return; // Glyph is offscreen to the right
if (glyph_width >= glyph_destination_surface->width - surface_x)
glyph_width = glyph_destination_surface->width - surface_x;
if (y < 0)
{
surface_y = -y;
if (surface_y >= glyph_height)
return; // Glyph is offscreen to the top
glyph_y += surface_y;
glyph_height -= surface_y;
}
else
{
surface_y = y;
}
if (surface_y >= glyph_destination_surface->height)
return; // Glyph is offscreen to the bottom
if (glyph_height >= glyph_destination_surface->height - surface_y)
glyph_height = glyph_destination_surface->height - surface_y;
// Do the actual drawing
for (size_t iy = 0; iy < glyph_height; ++iy)
{
for (size_t ix = 0; ix < glyph_width; ++ix)
{ {
const unsigned char alpha_int = glyph_atlas->pixels[(glyph_y + iy) * glyph_atlas->width + (glyph_x + ix)]; const unsigned char alpha_int = glyph_atlas->pixels[(glyph_y + iy) * glyph_atlas->width + (glyph_x + ix)];
@ -293,7 +340,7 @@ void RenderBackend_DrawGlyph(long x, long y, size_t glyph_x, size_t glyph_y, siz
{ {
const float alpha = alpha_int / 255.0f; const float alpha = alpha_int / 255.0f;
unsigned char *bitmap_pixel = glyph_destination_surface->pixels + (y + iy) * glyph_destination_surface->pitch + (x + ix) * 3; unsigned char *bitmap_pixel = &glyph_destination_surface->pixels[(surface_y + iy) * glyph_destination_surface->pitch + (surface_x + ix) * 3];
for (unsigned int j = 0; j < 3; ++j) for (unsigned int j = 0; j < 3; ++j)
bitmap_pixel[j] = (unsigned char)((glyph_colour_channels[j] * alpha) + (bitmap_pixel[j] * (1.0f - alpha))); // Alpha blending bitmap_pixel[j] = (unsigned char)((glyph_colour_channels[j] * alpha) + (bitmap_pixel[j] * (1.0f - alpha))); // Alpha blending