From dd9cfd3e2f38c8f67694961acdc6b68222d067ea Mon Sep 17 00:00:00 2001 From: Alexander Orzechowski Date: Tue, 27 Sep 2022 20:07:08 -0400 Subject: [PATCH] wlr_scene: Be resilient against overflow conditions If the area calculations for output overlap overflow a signed int, we may not consider it to be a primary output. Turn this into an unsigned type so this happens less frequently. Additionally, it is possible the overflow would produce 0, we can handle this by simply changing the comparison to more than or equal. While we're here, let's assert that we always assign a primary output if there are any intersecting outputs. --- types/scene/wlr_scene.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/types/scene/wlr_scene.c b/types/scene/wlr_scene.c index dff664d2..89aae843 100644 --- a/types/scene/wlr_scene.c +++ b/types/scene/wlr_scene.c @@ -296,7 +296,7 @@ static void update_node_update_outputs(struct wlr_scene_node *node, struct wlr_scene_buffer *scene_buffer = wlr_scene_buffer_from_node(node); - int largest_overlap = 0; + uint32_t largest_overlap = 0; scene_buffer->primary_output = NULL; uint64_t active_outputs = 0; @@ -326,8 +326,8 @@ static void update_node_update_outputs(struct wlr_scene_node *node, output_box.x, output_box.y, output_box.width, output_box.height); if (pixman_region32_not_empty(&intersection)) { - int overlap = region_area(&intersection); - if (overlap > largest_overlap) { + uint32_t overlap = region_area(&intersection); + if (overlap >= largest_overlap) { largest_overlap = overlap; scene_buffer->primary_output = scene_output; } @@ -352,6 +352,10 @@ static void update_node_update_outputs(struct wlr_scene_node *node, wl_signal_emit_mutable(&scene_buffer->events.output_leave, scene_output); } } + + // if there are active outputs on this node, we should always have a primary + // output + assert(!scene_buffer->active_outputs || scene_buffer->primary_output); } static bool scene_node_update_iterator(struct wlr_scene_node *node,