From 434178ef49ddd34e27788c30e7b8eb146289b269 Mon Sep 17 00:00:00 2001
From: ahocevar <andreas.hocevar@gmail.com>
Date: Wed, 27 Mar 2013 17:46:36 +0100
Subject: [PATCH] Making backbuffer order configurable

In OpenLayers 2.12, the backbuffer for each layer was placed right below
the layer itself. With animated zooming, that was changed so backbuffers
are all placed below the base layer. As it turned out, this is only good
for certain kinds of layers (e.g. street labels), so the default now is
to place the backbuffer right below its layer again. But the
transitionEffect option can now have a new value, 'map-resize', which will
cause the backbuffer to be placed below the base layer.
---
 lib/OpenLayers/Layer/Grid.js | 19 ++++++++++++++-----
 tests/Layer/Grid.html        | 12 ++++++++++--
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/lib/OpenLayers/Layer/Grid.js b/lib/OpenLayers/Layer/Grid.js
index 6e69c35f6b..034c72c3f8 100644
--- a/lib/OpenLayers/Layer/Grid.js
+++ b/lib/OpenLayers/Layer/Grid.js
@@ -98,9 +98,14 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
      * Two posible values:
      *
      * "resize" - Existing tiles are resized on zoom to provide a visual
-     * effect of the zoom having taken place immediately.  As the
-     * new tiles become available, they are drawn over top of the
-     * resized tiles (this is the default setting).
+     *     effect of the zoom having taken place immediately.  As the
+     *     new tiles become available, they are drawn over top of the
+     *     resized tiles (this is the default setting).
+     * "map-resize" - Existing tiles are resized on zoom and placed below the
+     *     base layer.  New tiles for the base layer will cover existing tiles.
+     *     This setting is recommended when having an overlay duplicated during
+     *     the transition is undesirable (e.g. street labels or big transparent
+     *     fills). 
      * null - No transition effect.
      *
      * Using "resize" on non-opaque layers can cause undesired visual
@@ -705,8 +710,12 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
             backBuffer.id = this.div.id + '_bb';
             backBuffer.className = 'olBackBuffer';
             backBuffer.style.position = 'absolute';
-            backBuffer.style.zIndex = this.map.Z_INDEX_BASE.BaseLayer -
-                    (this.map.getNumLayers() - this.map.getLayerIndex(this));
+            var map = this.map;
+            backBuffer.style.zIndex = this.transitionEffect === 'resize' ?
+                    this.getZIndex() - 1 :
+                    // 'map-resize':
+                    map.Z_INDEX_BASE.BaseLayer -
+                            (map.getNumLayers() - map.getLayerIndex(this));
             for(var i=0, lenI=this.grid.length; i<lenI; i++) {
                 for(var j=0, lenJ=this.grid[i].length; j<lenJ; j++) {
                     var tile = this.grid[i][j],
diff --git a/tests/Layer/Grid.html b/tests/Layer/Grid.html
index 3ec61818f9..439310d419 100644
--- a/tests/Layer/Grid.html
+++ b/tests/Layer/Grid.html
@@ -1049,7 +1049,7 @@
     }
 
     function test_createBackBuffer(t) {
-        t.plan(8);
+        t.plan(9);
 
         var map = new OpenLayers.Map('map');
         var layer = new OpenLayers.Layer.WMS('', '', {}, {
@@ -1074,7 +1074,16 @@
         OpenLayers.Tile.Image.prototype.createBackBuffer = function() {
             return document.createElement('div');
         };
+        
+        layer.transitionEffect = 'map-resize';
         backBuffer = layer.createBackBuffer();
+        t.ok(backBuffer.style.zIndex == 99, 'z-index of backbuffer correct for "map-resize".');
+        layer.removeBackBuffer();
+        
+        layer.transitionEffect = 'resize';
+        backBuffer = layer.createBackBuffer();
+        t.ok(backBuffer.style.zIndex == layer.getZIndex() - 1, 'z-index of backbuffer correct for "resize",');
+
         layer.backBufferResolution = 1;
         layer.gridResolution = 1;
         layer.backBuffer = backBuffer;
@@ -1083,7 +1092,6 @@
         layer.applyBackBuffer(1);
         t.ok(backBuffer != undefined,
              'createBackBuffer returns a back buffer');
-        t.eq(layer.backBuffer.style.zIndex, '99', 'z-index of backbuffer correct.');
         t.eq(backBuffer.childNodes[0].style.left, '0px',
              'first tile has correct left');
         t.eq(backBuffer.childNodes[0].style.top, '0px',