wlr_scene: Parse out WLR_SCENE_DEBUG_DAMAGE

docs/env_vars.md

@@ -45,6 +45,12 @@ wlroots reads these environment variables
 * *WLR_RENDERER_ALLOW_SOFTWARE*: allows the gles2 renderer to use software
   rendering
 
+## scenes
+
+* *WLR_SCENE_DEBUG_DAMAGE*: specifies debug options for screen damage related
+tasks for compositors that use scenes. (available options: NONE, RERENDER,
+HIGHLIGHT)
+
 # Generic
 
 * *DISPLAY*: if set probe X11 backend in `wlr_backend_autocreate`

include/wlr/types/wlr_scene.h

@@ -71,6 +71,12 @@ struct wlr_scene_node {
 	struct wlr_addon_set addons;
 };
 
+enum wlr_scene_debug_damage_option {
+	WLR_SCENE_DEBUG_DAMAGE_NONE,
+	WLR_SCENE_DEBUG_DAMAGE_RERENDER,
+	WLR_SCENE_DEBUG_DAMAGE_HIGHLIGHT
+};
+
 /** The root scene-graph node. */
 struct wlr_scene {
 	struct wlr_scene_node node;
@@ -83,6 +89,8 @@ struct wlr_scene {
 	// private state
 
 	struct wl_listener presentation_destroy;
+
+	enum wlr_scene_debug_damage_option debug_damage_option;
 };
 
 /** A sub-tree in the scene-graph. */

types/scene/wlr_scene.c

@@ -130,6 +130,23 @@ struct wlr_scene *wlr_scene_create(void) {
 	scene_node_init(&scene->node, WLR_SCENE_NODE_ROOT, NULL);
 	wl_list_init(&scene->outputs);
 	wl_list_init(&scene->presentation_destroy.link);
+
+	char *debug_damage = getenv("WLR_SCENE_DEBUG_DAMAGE");
+	if (debug_damage) {
+		wlr_log(WLR_INFO, "Loading WLR_SCENE_DEBUG_DAMAGE option: %s", debug_damage);
+	}
+
+	if (!debug_damage || strcmp(debug_damage, "none") == 0) {
+		scene->debug_damage_option = WLR_SCENE_DEBUG_DAMAGE_NONE;
+	} else if (strcmp(debug_damage, "rerender") == 0) {
+		scene->debug_damage_option = WLR_SCENE_DEBUG_DAMAGE_RERENDER;
+	} else if (strcmp(debug_damage, "highlight") == 0) {
+		scene->debug_damage_option = WLR_SCENE_DEBUG_DAMAGE_HIGHLIGHT;
+	} else {
+		wlr_log(WLR_ERROR, "Unknown WLR_SCENE_DEBUG_DAMAGE option: %s", debug_damage);
+		scene->debug_damage_option = WLR_SCENE_DEBUG_DAMAGE_NONE;
+	}
+
 	return scene;
 }