map_view: Fix zoom calculation for pixel snapping

src/map_view.rs

         let tile_screen_size = f64::powf(2.0, self.zoom - f64::from(uzoom)) * f64::from(self.tile_size);
 
         if snap_to_pixel {
-            // only snap to pixel if apparent zoom is integer
-            let apparent_zoom = self.zoom + self.tile_zoom_offset;
-            let apparent_zoom_int = (apparent_zoom + 0.5).floor();
-            if (apparent_zoom - apparent_zoom_int).abs() < 1e-10 {
+            // only snap to pixel if zoom has integral value
+            if (self.zoom - (self.zoom + 0.5).floor()).abs() < 1e-10 {
                 top_left_tile_screen_coord.snap_to_pixel();
             }
         }