Prefer use of gtk_snapshot_set_snap()

See: https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/8494

Author: kleisauke

meson.build

@@ -41,10 +41,10 @@ configure_file(
 
 # need vips_thread_execute()
 vips_dep = dependency('vips', version: '>=8.17')
-glib_dep = dependency('glib-2.0')
-gtk_dep = dependency('gtk4')
+gtk_dep = dependency('gtk4', version: '>=4.10')
 m_dep = cc.find_library('m')
 
+glib_dep = dependency('glib-2.0')
 if not cc.has_header_symbol('glib.h', 'g_autofree', dependencies : glib_dep)
   error('vipsdisp requires the GNU C "cleanup" attribute.')
 endif

src/imagedisplay.c

@@ -651,6 +651,13 @@ imagedisplay_snapshot(GtkWidget *widget, GtkSnapshot *snapshot)
 
 	GTK_WIDGET_CLASS(imagedisplay_parent_class)->snapshot(widget, snapshot);
 
+#ifdef GSK_RECT_SNAP_ROUND
+	/* Round tile bounds to the closest pixel edge on all sides to prevent
+	 * seams.
+	 */
+	gtk_snapshot_set_snap(snapshot, GSK_RECT_SNAP_ROUND);
+#endif
+
 	/* Clip to the widget area, or we may paint over the display control
 	 * bar.
 	 */

src/tile.c

@@ -87,7 +87,7 @@ tile_touch(Tile *tile)
 }
 
 /* Make a tile on an image. left/top in this image's coordinates (not level0
- * coordfinates).
+ * coordinates).
  */
 Tile *
 tile_new(VipsImage *level, int left, int top, int z)

src/tilecache.c

@@ -1023,12 +1023,17 @@ tilecache_snapshot(Tilecache *tilecache, GtkSnapshot *snapshot,
 
 			graphene_rect_t bounds;
 
-			// +1 to hide tile boundaries
 			bounds.origin.x = tile->bounds.left * scale - x + paint->origin.x;
 			bounds.origin.y = tile->bounds.top * scale - y + paint->origin.y;
+#ifdef GSK_RECT_SNAP_ROUND
+			// gtk_snapshot_set_snap() is available
+			bounds.size.width = tile->bounds.width * scale;
+			bounds.size.height = tile->bounds.height * scale;
+#else
+			// +1 to hide tile boundaries
 			bounds.size.width = tile->bounds.width * scale + 1;
 			bounds.size.height = tile->bounds.height * scale + 1;
-
+#endif
 			gtk_snapshot_append_scaled_texture(snapshot,
 				tile_get_texture(tile), filter, &bounds);
 

src/vipsdisp.h

@@ -28,10 +28,6 @@
  */
 #define MAX_TILES (2 * (4096 / TILE_SIZE) * (2048 / TILE_SIZE))
 
-/* We GtkInfoBar, which is going away in gtk5.
- */
-G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-
 #define FREESID(SID, OBJ) \
 	G_STMT_START \
 	{ \