improve antialising

Author: jcupitt

CHANGELOG.md

@@ -2,6 +2,7 @@ master
 
 - much better performance for images which are very tall and thin or very wide 
   and narrow
+- better antialiasing [Linden6]
 
 ## 3.1.0 28/10/24
 

src/tilecache.c

@@ -887,6 +887,13 @@ tilecache_snapshot(Tilecache *tilecache, GtkSnapshot *snapshot,
 			graphene_rect_t bounds;
 
 #if GTK_CHECK_VERSION(4, 10, 0)
+			/* If we are zooming in beyond 1:1, we want nearest so we don't
+			 * blur the image. For zooming out, we want trilinear to get
+			 * mipmaps and antialiasing.
+			 */
+			GskScalingFilter filter = scale > 1.0 ?
+				GSK_SCALING_FILTER_NEAREST : GSK_SCALING_FILTER_TRILINEAR;
+
 			// add a margin along the right and bottom to prevent black seams
 			// at tile joins
 			bounds.origin.x = tile->bounds.left * scale - x + paint_rect->left;
@@ -896,7 +903,7 @@ tilecache_snapshot(Tilecache *tilecache, GtkSnapshot *snapshot,
 
 			gtk_snapshot_append_scaled_texture(snapshot,
 				tile_get_texture(tile),
-				GSK_SCALING_FILTER_NEAREST,
+				filter,
 				&bounds);
 #else
 			bounds.origin.x = tile->bounds.left * scale - x + paint_rect->left;