Esme Povirk (@madewokherd) commented about dlls/gdiplus/graphics.c:
for (x = dst_area.left, src_pointf = src_pointf_row; x < dst_area.right; x++, src_pointf.X += x_dx, src_pointf.Y += x_dy) {
if (src_pointf.X >= srcx && src_pointf.X < srcx + srcwidth &&
src_pointf.Y >= srcy && src_pointf.Y < srcy + srcheight)
We still need this check for non-aligned destination rectangles.