win: keep track of per-window damage

This is not used anywhere yet, but is intended for damage calculation
refactor.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/event.c

@@ -704,11 +704,17 @@ static inline void repair_win(session_t *ps, struct managed_win *w) {
 	}
 
 	// Remove the part in the damage area that could be ignored
+	region_t without_ignored;
+	pixman_region32_init(&without_ignored);
 	if (w->reg_ignore && win_is_region_ignore_valid(ps, w)) {
-		pixman_region32_subtract(&parts, &parts, w->reg_ignore);
+		pixman_region32_subtract(&without_ignored, &parts, w->reg_ignore);
 	}
 
-	add_damage(ps, &parts);
+	add_damage(ps, &without_ignored);
+	pixman_region32_fini(&without_ignored);
+
+	pixman_region32_translate(&parts, -w->g.x, -w->g.y);
+	pixman_region32_copy(&w->damaged, &parts);
 	pixman_region32_fini(&parts);
 }
 

src/win.c

@@ -1805,6 +1805,7 @@ struct win *attr_ret_nonnull maybe_allocate_managed_win(session_t *ps, struct wi
 	};
 	win_set_properties_stale(new, init_stale_props, ARR_SIZE(init_stale_props));
 	c2_window_state_init(ps->c2_state, &new->c2_state);
+	pixman_region32_init(&new->damaged);
 
 	return &new->base;
 }
@@ -2179,6 +2180,7 @@ void destroy_win_finish(session_t *ps, struct win *w) {
 				w2->prev_trans = NULL;
 			}
 		}
+		pixman_region32_fini(&mw->damaged);
 	}
 
 	free(w);

src/win.h

@@ -299,6 +299,9 @@ struct managed_win {
 	/// Background texture of the window
 	glx_texture_t *glx_texture_bg;
 #endif
+
+	/// The damaged region of the window, in window local coordinates.
+	region_t damaged;
 };
 
 /// Process pending updates/images flags on a window. Has to be called in X critical