WebGL / Use style filter when generating buffers

openlayers · Dec 8, 2023 · 3bef70a · 3bef70a
1 parent 630002d
commit 3bef70a
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Showing 3 changed files with 54 additions and 4 deletions.
diff --git a/src/ol/render/webgl/VectorStyleRenderer.js b/src/ol/render/webgl/VectorStyleRenderer.js
@@ -4,6 +4,16 @@
 import WebGLArrayBuffer from '../../webgl/Buffer.js';
 import {ARRAY_BUFFER, DYNAMIC_DRAW, ELEMENT_ARRAY_BUFFER} from '../../webgl.js';
 import {AttributeType} from '../../webgl/Helper.js';
+import {
+  BooleanType,
+  computeGeometryType,
+  newParsingContext,
+} from '../../expr/expression.js';
+import {
+  UNKNOWN_VALUE,
+  buildExpression,
+  newEvaluationContext,
+} from '../../expr/cpu.js';
 import {WebGLWorkerMessageType} from './constants.js';
 import {colorEncodeId} from './utils.js';
 import {
@@ -104,11 +114,13 @@ class VectorStyleRenderer {
    * @param {VectorStyle} styleOrShaders Literal style or custom shaders
    * @param {import('../../webgl/Helper.js').default} helper Helper
    * @param {boolean} enableHitDetection Whether to enable the hit detection (needs compatible shader)
+   * @param {import("../../expr/expression.js").ExpressionValue} [filter] Optional filter expression
    */
-  constructor(styleOrShaders, helper, enableHitDetection) {
+  constructor(styleOrShaders, helper, enableHitDetection, filter) {
     this.helper_ = helper;
 
     this.hitDetectionEnabled_ = enableHitDetection;
+
     let shaders = /** @type {StyleShaders} */ (styleOrShaders);
     const isShaders = 'builder' in styleOrShaders;
     if (!isShaders) {
@@ -166,6 +178,31 @@ class VectorStyleRenderer {
       );
     }
 
+    /**
+     * @type {function(import('../../Feature.js').FeatureLike): boolean}
+     * @private
+     */
+    this.featureFilter_ = null;
+    if (filter) {
+      const parsingContext = newParsingContext();
+      const compiled = buildExpression(filter, BooleanType, parsingContext);
+      this.featureFilter_ = (feature) => {
+        const evalContext = newEvaluationContext();
+        evalContext.properties = feature.getPropertiesInternal();
+        if (parsingContext.featureId) {
+          const id = feature.getId();
+          if (id !== undefined) {
+            evalContext.featureId = id;
+          } else {
+            evalContext.featureId = null;
+          }
+        }
+        evalContext.geometryType = computeGeometryType(feature.getGeometry());
+        const result = /** @type {boolean} */ (compiled(evalContext));
+        return result === UNKNOWN_VALUE || result;
+      };
+    }
+
     const hitDetectionAttributes = this.hitDetectionEnabled_
       ? {
           hitColor: {
@@ -261,11 +298,18 @@ class VectorStyleRenderer {
   /**
    * @param {import('./MixedGeometryBatch.js').default} geometryBatch Geometry batch
    * @param {import("../../transform.js").Transform} transform Transform to apply to coordinates
-   * @return {Promise<WebGLBuffers>} A promise resolving to WebGL buffers
+   * @return {Promise<WebGLBuffers|null>} A promise resolving to WebGL buffers; returns null if buffers are empty
    */
   async generateBuffers(geometryBatch, transform) {
+    let filteredBatch = geometryBatch;
+    if (this.featureFilter_) {
+      filteredBatch = filteredBatch.filter(this.featureFilter_);
+      if (filteredBatch.isEmpty()) {
+        return null;
+      }
+    }
     const renderInstructions = this.generateRenderInstructions_(
-      geometryBatch,
+      filteredBatch,
       transform
     );
     const [polygonBuffers, lineStringBuffers, pointBuffers] = await Promise.all(

diff --git a/src/ol/renderer/webgl/VectorTileLayer.js b/src/ol/renderer/webgl/VectorTileLayer.js
@@ -198,7 +198,8 @@ class WebGLVectorTileLayerRenderer extends WebGLBaseTileLayerRenderer {
       return new VectorStyleRenderer(
         shaders,
         this.helper,
-        this.hitDetectionEnabled_
+        this.hitDetectionEnabled_,
+        'filter' in style ? style.filter : null
       );
     });
   }
@@ -339,6 +340,9 @@ class WebGLVectorTileLayerRenderer extends WebGLBaseTileLayerRenderer {
     for (let i = 0, ii = this.styleRenderers_.length; i < ii; i++) {
       const renderer = this.styleRenderers_[i];
       const buffers = tileRepresentation.buffers[i];
+      if (!buffers) {
+        continue;
+      }
       renderer.render(buffers, frameState, () => {
         this.applyUniforms_(
           alpha,

diff --git a/src/ol/webgl/styleparser.js b/src/ol/webgl/styleparser.js
@@ -921,6 +921,8 @@ export function parseLiteralStyle(style) {
   parseStrokeProperties(style, builder, uniforms, vertContext, fragContext);
   parseFillProperties(style, builder, uniforms, vertContext, fragContext);
 
+  // note that the style filter may have already been applied earlier when building the rendering instructions
+  // this is still needed in case a filter cannot be evaluated statically beforehand (e.g. depending on time)
   if (style.filter) {
     const parsedFilter = expressionToGlsl(
       fragContext,