From 68d838e9bf69809bebe36eb3a6b4742f3b8a8769 Mon Sep 17 00:00:00 2001
From: Sebastian <sjeltsch@gmail.com>
Date: Mon, 6 Nov 2023 21:32:37 +0100
Subject: [PATCH] Review comments.

---
 lib/src/layer/tile_layer/tile_image.dart      |  4 ---
 lib/src/layer/tile_layer/tile_image_view.dart | 34 +++++++++----------
 lib/src/layer/tile_layer/tile_layer.dart      | 15 +++++---
 3 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/lib/src/layer/tile_layer/tile_image.dart b/lib/src/layer/tile_layer/tile_image.dart
index cbb414d00..cb8502001 100644
--- a/lib/src/layer/tile_layer/tile_image.dart
+++ b/lib/src/layer/tile_layer/tile_image.dart
@@ -92,10 +92,6 @@ class TileImage extends ChangeNotifier {
   /// tile display is used with a maximum opacity less than 1.
   bool get readyToDisplay => _readyToDisplay;
 
-  // Used to sort TileImages by their distance from the current zoom.
-  double zIndex(double maxZoom, int currentZoom) =>
-      maxZoom - (currentZoom - coordinates.z).abs();
-
   /// Change the tile display options.
   set tileDisplay(TileDisplay newTileDisplay) {
     final oldTileDisplay = _tileDisplay;
diff --git a/lib/src/layer/tile_layer/tile_image_view.dart b/lib/src/layer/tile_layer/tile_image_view.dart
index 2423b78ca..fd8774bde 100644
--- a/lib/src/layer/tile_layer/tile_image_view.dart
+++ b/lib/src/layer/tile_layer/tile_image_view.dart
@@ -33,16 +33,14 @@ class TileImageView {
 
     for (final tile in _tileImages.values) {
       final c = tile.coordinates;
-      if (_keepRange.contains(c)) {
-        if (!tile.readyToDisplay) {
-          final retainedAncestor =
-              _retainAncestor(retain, c.x, c.y, c.z, c.z - 5);
-          if (!retainedAncestor) {
-            _retainChildren(retain, c.x, c.y, c.z, c.z + 2);
-          }
-        }
-      } else {
+      if (!_keepRange.contains(c)) {
         stale.add(tile);
+        continue;
+      }
+
+      final retainedAncestor = _retainAncestor(retain, c.x, c.y, c.z, c.z - 5);
+      if (!retainedAncestor) {
+        _retainChildren(retain, c.x, c.y, c.z, c.z + 2);
       }
     }
 
@@ -54,15 +52,17 @@ class TileImageView {
 
     for (final tile in _tileImages.values) {
       final c = tile.coordinates;
-      if (_visibleRange.contains(c)) {
-        retain.add(tile);
+      if (!_visibleRange.contains(c)) {
+        continue;
+      }
+
+      retain.add(tile);
 
-        if (!tile.readyToDisplay) {
-          final retainedAncestor =
-              _retainAncestor(retain, c.x, c.y, c.z, c.z - 5);
-          if (!retainedAncestor) {
-            _retainChildren(retain, c.x, c.y, c.z, c.z + 2);
-          }
+      if (!tile.readyToDisplay) {
+        final retainedAncestor =
+            _retainAncestor(retain, c.x, c.y, c.z, c.z - 5);
+        if (!retainedAncestor) {
+          _retainChildren(retain, c.x, c.y, c.z, c.z + 2);
         }
       }
     }
diff --git a/lib/src/layer/tile_layer/tile_layer.dart b/lib/src/layer/tile_layer/tile_layer.dart
index 7f641d656..dcd5b741a 100644
--- a/lib/src/layer/tile_layer/tile_layer.dart
+++ b/lib/src/layer/tile_layer/tile_layer.dart
@@ -554,15 +554,20 @@ class _TileLayerState extends State<TileLayer> with TickerProviderStateMixin {
             ))
         .toList();
 
-    // Sort in render order;
+    // Sort in render order. In reverse:
     //   1. Tiles at the current zoom.
     //   2. Tiles at the current zoom +/- 1.
     //   3. Tiles at the current zoom +/- 2.
     //   4. ...etc
-    final maxZoom = widget.maxZoom;
-    int renderOrder(Tile a, Tile b) => a.tileImage
-        .zIndex(maxZoom, tileZoom)
-        .compareTo(b.tileImage.zIndex(maxZoom, tileZoom));
+    int renderOrder(Tile a, Tile b) {
+      final (za, zb) = (a.tileImage.coordinates.z, b.tileImage.coordinates.z);
+      final cmp = (zb - tileZoom).abs().compareTo((za - tileZoom).abs());
+      if (cmp == 0) {
+        // When compare parent/child tiles of equal distance, prefer higher res images.
+        return zb.compareTo(za);
+      }
+      return cmp;
+    }
 
     return MobileLayerTransformer(
       // ignore: deprecated_member_use_from_same_package