fix(scenefx): union cursor history into damage instead of punching blur padding

Software cursors are baked into the reused offscreen buffer, so stale
cursor footprints showed artifacts under blur. Previously the cursor
history rects were subtracted from the blur padding region, which left
holes where stale content could survive. Now the recent cursor
footprints are unioned into the damage region (render + output state)
before blur compensation geometry is computed: inside damage they get
re-blurred with full sampling context, and the padding restore (which
excludes damage) can never paste a stale cursor back.

Co-Authored-By: Claude Fable 5 <[email protected]>

 scenefx/types/scene/wlr_scene.c | 82 +++++++++++++++++++++++------------------
 1 file changed, 46 insertions(+), 36 deletions(-)

diff --git a/scenefx/types/scene/wlr_scene.c b/scenefx/types/scene/wlr_scene.c
index 9c9b3b3..69a7e59 100644
--- a/scenefx/types/scene/wlr_scene.c
+++ b/scenefx/types/scene/wlr_scene.c
@@ -3378,6 +3378,52 @@ bool wlr_scene_output_build_state(struct wlr_scene_output *scene_output,
 	bool should_compensate_blur = false;
 	if (fx_render_pass_init_offscreen_buffers(render_pass, output)
 			&& pixman_region32_not_empty(&render_data.damage)) {
+		// Software cursors are baked into the reused buffer, so their recent
+		// footprints must be treated as damage before the blur compensation
+		// geometry is computed: inside the damage they get re-blurred with
+		// full sampling context, and the padding restore (which excludes
+		// damage) can never paste a stale cursor back. The live cursor is
+		// redrawn on top afterwards since
+		// wlr_output_add_software_cursors_to_render_pass() clips to this
+		// damage.
+		if (is_scene_blur_enabled(&scene_output->scene->blur_data)) {
+			struct wlr_output_cursor *cursor;
+			wl_list_for_each(cursor, &output->cursors, link) {
+				if (!cursor->enabled || !cursor->visible) {
+					continue;
+				}
+				double scale = output->scale;
+				g_cursor_history[g_cursor_history_index].x =
+					(cursor->x - cursor->hotspot_x) * scale;
+				g_cursor_history[g_cursor_history_index].y =
+					(cursor->y - cursor->hotspot_y) * scale;
+				g_cursor_history[g_cursor_history_index].w = cursor->width;
+				g_cursor_history[g_cursor_history_index].h = cursor->height;
+				g_cursor_history[g_cursor_history_index].valid = true;
+				g_cursor_history_index =
+					(g_cursor_history_index + 1) % CURSOR_HISTORY_SIZE;
+			}
+
+			for (int i = 0; i < CURSOR_HISTORY_SIZE; i++) {
+				if (!g_cursor_history[i].valid) {
+					continue;
+				}
+				pixman_region32_union_rect(&render_data.damage, &render_data.damage,
+						g_cursor_history[i].x - 16,
+						g_cursor_history[i].y - 16,
+						g_cursor_history[i].w + 32,
+						g_cursor_history[i].h + 32);
+				pixman_region32_union_rect(&state->damage, &state->damage,
+						g_cursor_history[i].x - 16,
+						g_cursor_history[i].y - 16,
+						g_cursor_history[i].w + 32,
+						g_cursor_history[i].h + 32);
+				state->committed |= WLR_OUTPUT_STATE_DAMAGE;
+			}
+			pixman_region32_intersect_rect(&render_data.damage, &render_data.damage,
+					0, 0, output->width, output->height);
+		}
+
 		// Blur artifact prevention
 		// Note: Supports individual blur node blur_data
 		pixman_region32_t original_damage;
@@ -3442,42 +3488,6 @@ bool wlr_scene_output_build_state(struct wlr_scene_output *scene_output,
 			pixman_region32_intersect_rect(&render_data.damage, &render_data.damage,
 					0, 0, output->width, output->height);
 
-			// Add current software cursors to the history
-			struct wlr_output_cursor *cursor;
-			wl_list_for_each(cursor, &output->cursors, link) {
-				if (!cursor->enabled || !cursor->visible) {
-					continue;
-				}
-				double scale = output->scale;
-				int cx = (cursor->x - cursor->hotspot_x) * scale;
-				int cy = (cursor->y - cursor->hotspot_y) * scale;
-				int cw = cursor->width;
-				int ch = cursor->height;
-
-				g_cursor_history[g_cursor_history_index].x = cx;
-				g_cursor_history[g_cursor_history_index].y = cy;
-				g_cursor_history[g_cursor_history_index].w = cw;
-				g_cursor_history[g_cursor_history_index].h = ch;
-				g_cursor_history[g_cursor_history_index].valid = true;
-				g_cursor_history_index = (g_cursor_history_index + 1) % CURSOR_HISTORY_SIZE;
-			}
-
-			// Subtract all historical cursor regions from the blur padding region
-			for (int i = 0; i < CURSOR_HISTORY_SIZE; i++) {
-				if (!g_cursor_history[i].valid) {
-					continue;
-				}
-				pixman_region32_t cursor_reg;
-				pixman_region32_init_rect(&cursor_reg,
-						g_cursor_history[i].x - 16,
-						g_cursor_history[i].y - 16,
-						g_cursor_history[i].w + 32,
-						g_cursor_history[i].h + 32);
-				pixman_region32_subtract(&fx_pass->blur_padding_region,
-						&fx_pass->blur_padding_region, &cursor_reg);
-				pixman_region32_fini(&cursor_reg);
-			}
-
 			// Copy the surrounding content where the blur would display artifacts
 			// and draw it above the artifacts. Otherwise The old rendered
 			// content would be included into the new blur. This means that