Simplify interval logic with min/max/clamp fns

handlers.c

@@ -318,13 +318,22 @@ void request_wl_surface_commit(
 		struct damage_record *rec = surface->damage_stack;
 		while (rec) {
 			// TODO: take into account transformations
-			int low = buf->shm_offset + buf->shm_stride * rec->y +
-				  rec->x;
-			int high = buf->shm_offset +
-				   buf->shm_stride * (rec->y + rec->height) +
-				   (rec->x + rec->width);
-			intv_max = intv_max > high ? intv_max : high;
-			intv_min = intv_min < low ? intv_min : low;
+
+			/* Clip the damage rectangle to the containing buffer.
+			 */
+			int xlow = clamp(rec->x, 0, buf->shm_width);
+			int xhigh = clamp(
+					rec->x + rec->width, 0, buf->shm_width);
+			int ylow = clamp(rec->y, 0, buf->shm_height);
+			int yhigh = clamp(rec->y + rec->height, 0,
+					buf->shm_height);
+
+			int low = buf->shm_offset + buf->shm_stride * ylow +
+				  xlow;
+			int high = buf->shm_offset + buf->shm_stride * yhigh +
+				   xhigh;
+			intv_max = max(intv_max, high);
+			intv_min = min(intv_min, low);
 
 			struct damage_record *nxt = rec->next;
 			free(rec);
@@ -333,13 +342,9 @@ void request_wl_surface_commit(
 		surface->damage_stack = NULL;
 
 		sfd->dirty_interval_max =
-				intv_max > sfd->dirty_interval_max
-						? intv_max
-						: sfd->dirty_interval_max;
+				max(sfd->dirty_interval_max, intv_max);
 		sfd->dirty_interval_min =
-				intv_min < sfd->dirty_interval_min
-						? intv_min
-						: sfd->dirty_interval_min;
+				min(sfd->dirty_interval_min, intv_min);
 	}
 }
 static void request_wl_surface_destroy(

util.c

@@ -1041,12 +1041,10 @@ void collect_updates(struct fd_translation_map *map, int *ntransfers,
 			}
 			// Clear dirty state
 			cur->is_dirty = false;
-			int intv_min = cur->dirty_interval_min > 0
-						       ? cur->dirty_interval_min
-						       : 0;
-			int intv_max = cur->dirty_interval_max < (int)cur->file_size
-						       ? cur->dirty_interval_max
-						       : (int)cur->file_size;
+			int intv_min = clamp(cur->dirty_interval_min, 0,
+					(int)cur->file_size);
+			int intv_max = clamp(cur->dirty_interval_max, 0,
+					(int)cur->file_size);
 			cur->dirty_interval_min = INT32_MAX;
 			cur->dirty_interval_max = INT32_MIN;
 
@@ -1067,7 +1065,7 @@ void collect_updates(struct fd_translation_map *map, int *ntransfers,
 				transfers[nt].obj_id = cur->remote_id;
 				transfers[nt].special = 0;
 			}
-			if (intv_min == intv_max) {
+			if (intv_min >= intv_max) {
 				continue;
 			}
 			bool delta = memcmp(cur->file_mem_local + intv_min,

util.h

@@ -36,6 +36,14 @@ extern bool shutdown_flag;
 
 void handle_sigint(int sig);
 
+/** Basic mathematical operations */
+static inline int max(int a, int b) { return a > b ? a : b; }
+static inline int min(int a, int b) { return a < b ? a : b; }
+static inline int clamp(int v, int lower, int upper)
+{
+	return max(min(v, upper), lower);
+}
+
 /** Set the given flag with fcntl. Silently return -1 on failure. */
 int set_fnctl_flag(int fd, int the_flag);
 /** Create a nonblocking AF_UNIX/SOCK_STREAM socket, and listen with