Fix error when disposing ol/renderer/webgl/TileLayer

- helper may not exist
- tileTextureCache not cleared when canvasCacheKey changes

src/ol/renderer/webgl/Layer.js

@@ -95,7 +95,7 @@ class WebGLLayerRenderer extends LayerRenderer {
      */
     this.helper;
 
-    layer.addChangeListener(LayerProperty.MAP, this.removeHelper_.bind(this));
+    layer.addChangeListener(LayerProperty.MAP, this.removeHelper.bind(this));
 
     this.dispatchPreComposeEvent = this.dispatchPreComposeEvent.bind(this);
     this.dispatchPostComposeEvent = this.dispatchPostComposeEvent.bind(this);
@@ -148,7 +148,10 @@ class WebGLLayerRenderer extends LayerRenderer {
     }
   }
 
-  removeHelper_() {
+  /**
+   * @protected
+   */
+  removeHelper() {
     if (this.helper) {
       this.helper.dispose();
       delete this.helper;
@@ -187,9 +190,7 @@ class WebGLLayerRenderer extends LayerRenderer {
         'map/' + frameState.mapId + '/group/' + groupNumber;
 
       if (!this.helper || !this.helper.canvasCacheKeyMatches(canvasCacheKey)) {
-        if (this.helper) {
+        this.removeHelper();
-          this.helper.dispose();
-        }
 
         this.helper = new WebGLHelper({
           postProcesses: this.postProcesses_,
@@ -227,7 +228,7 @@ class WebGLLayerRenderer extends LayerRenderer {
    * Clean up.
    */
   disposeInternal() {
-    this.removeHelper_();
+    this.removeHelper();
     super.disposeInternal();
   }
 

src/ol/renderer/webgl/TileLayer.js

@@ -683,27 +683,33 @@ class WebGLTileLayerRenderer extends WebGLLayerRenderer {
     return covered;
   }
 
+  removeHelper() {
+    if (this.helper) {
+      const tileTextureCache = this.tileTextureCache_;
+      tileTextureCache.forEach((tileTexture) => tileTexture.dispose());
+      tileTextureCache.clear();
+    }
+
+    super.removeHelper();
+  }
+
   /**
    * Clean up.
    */
   disposeInternal() {
     const helper = this.helper;
-    const gl = helper.getGL();
+    if (helper) {
+      const gl = helper.getGL();
+      gl.deleteProgram(this.program_);
+      delete this.program_;
 
-    helper.deleteBuffer(this.indices_);
+      helper.deleteBuffer(this.indices_);
-    delete this.indices_;
+    }
-
-    gl.deleteProgram(this.program_);
-    delete this.program_;
-
-    const tileTextureCache = this.tileTextureCache_;
-    tileTextureCache.forEach(function (tileTexture) {
-      tileTexture.dispose();
-    });
-    tileTextureCache.clear();
-    delete this.tileTextureCache_;
 
     super.disposeInternal();
+
+    delete this.indices_;
+    delete this.tileTextureCache_;
   }
 }