Prefer use of gtk_snapshot_set_snap()

meson.build

@@ -34,17 +34,20 @@ add_project_arguments('-DHAVE_CONFIG_H', language: 'c')
 # so it can find config.h
 add_project_arguments('-I.', language: 'c')
 
+gtk_dep = dependency('gtk4', version: '>=4.14')
+# use this to fix tile alignment, not yet merged
+config_h.set('HAVE_GTK_SNAPSHOT_SET_SNAP', cc.has_header_symbol('gtk.h', 'gtk_snapshot_set_snap', dependencies: gtk_dep))
+
 configure_file(
   output: 'config.h',
   configuration: config_h,
 )
 
 # need vips_thread_execute()
 vips_dep = dependency('vips', version: '>=8.17')
-glib_dep = dependency('glib-2.0')
-gtk_dep = dependency('gtk4')
 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 HAVE_GTK_SNAPSHOT_SET_SNAP
+	/* Round tile bounds to the closest pixel edge on all sides to prevent
+	 * seams.
+	 */
+	gtk_snapshot_set_snap(snapshot, GSK_RECT_SNAP_ROUND);
+#endif /*HAVE_GTK_SNAPSHOT_SET_SNAP*/
+
 	/* 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

@@ -1023,11 +1023,18 @@ 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;
-			bounds.size.width = tile->bounds.width * scale + 1;
-			bounds.size.height = tile->bounds.height * scale + 1;
+			bounds.size.width = tile->bounds.width * scale;
+			bounds.size.height = tile->bounds.height * scale;
+
+#ifndef HAVE_GTK_SNAPSHOT_SET_SNAP
+			/* Without set snap, we have to hide tile edges by expanding the
+			 * tile.
+			 */
+			bounds.size.width += 1;
+			bounds.size.height += 1;
+#endif /*!HAVE_GTK_SNAPSHOT_SET_SNAP*/
 
 			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 \
 	{ \