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Refine source clipping coordinate adjustment #142

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Merged
merged 1 commit into from
Oct 20, 2025
Merged

Refine source clipping coordinate adjustment #142

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20 changes: 15 additions & 5 deletions src/draw-builtin.c
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Original file line number Diff line number Diff line change
Expand Up @@ -557,7 +557,6 @@ static const twin_src_msk_op comp3[2][4][4][3] = {
#define operand_index(o) \
((o)->source_kind == TWIN_SOLID ? 3 : o->u.pixmap->format)

/* FIXME: source clipping is busted */
static void _twin_composite_simple(twin_pixmap_t *dst,
twin_coord_t dst_x,
twin_coord_t dst_y,
Expand Down Expand Up @@ -596,29 +595,40 @@ static void _twin_composite_simple(twin_pixmap_t *dst,
if (left >= right || top >= bottom)
return;

/* Adjust source coordinates after clipping
* When destination is clipped, source coordinates must be adjusted
* to maintain correct 1:1 mapping between dst and src pixels.
*/
src_x += (left - dst_x);
src_y += (top - dst_y);

if (src->source_kind == TWIN_PIXMAP) {
src_x += src->u.pixmap->origin_x;
src_y += src->u.pixmap->origin_y;
} else {
s.c = src->u.argb;
}

sdx = src_x - dst_x;
sdy = src_y - dst_y;
sdx = src_x - left;
sdy = src_y - top;

if (msk) {
twin_source_u m;
twin_coord_t mdx, mdy;

/* Adjust mask coordinates after clipping (same as source) */
msk_x += (left - dst_x);
msk_y += (top - dst_y);

if (msk->source_kind == TWIN_PIXMAP) {
msk_x += msk->u.pixmap->origin_x;
msk_y += msk->u.pixmap->origin_y;
} else {
m.c = msk->u.argb;
}

mdx = msk_x - dst_x;
mdy = msk_y - dst_y;
mdx = msk_x - left;
mdy = msk_y - top;

twin_src_msk_op op = comp3[operator][operand_index(src)][operand_index(msk)][dst->format];
for (iy = top; iy < bottom; iy++) {
Expand Down