Fix Viewport's never-drawn elements overriding display style's exclud…

…ed elements (backport #6988) [release/4.7.x] (#6989)

Co-authored-by: Paul Connelly <[email protected]>

common/changes/@itwin/core-frontend/pmc-never-drawn-overwrite_2024-07-18-17-56.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@itwin/core-frontend",
+      "comment": "Fix Viewport's never-drawn elements overriding the display style's excluded elements.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@itwin/core-frontend"
+}

core/frontend/src/render/FeatureSymbology.ts

@@ -100,20 +100,20 @@ export namespace FeatureSymbology {
      * @internal
      */
     public initFromViewport(viewport: Viewport): void {
-      const view = viewport.view;
-      this._initFromView(view);
-
+      // Set the initial always/never-drawn sets. Later, initFromView can add more elements to them.
       if (undefined !== viewport.neverDrawn)
         this.setNeverDrawnSet(viewport.neverDrawn);
 
       if (undefined !== viewport.alwaysDrawn)
         this.setAlwaysDrawnSet(viewport.alwaysDrawn, viewport.isAlwaysDrawnExclusive);
 
+      this._initFromView(viewport.view);
+
       viewport.addFeatureOverrides(this);
       viewport.addModelSubCategoryVisibilityOverrides(this, this._modelSubCategoryOverrides);
 
       // This will include any per-model subcategory visibility overrides added above.
-      this._initSubCategoryOverrides(view);
+      this._initSubCategoryOverrides(viewport.view);
     }
 
     private _initFromView(view: ViewState): void {

core/frontend/src/test/FeatureSymbologyOverrides.test.ts

@@ -0,0 +1,45 @@
+/*---------------------------------------------------------------------------------------------
+* Copyright (c) Bentley Systems, Incorporated. All rights reserved.
+* See LICENSE.md in the project root for license terms and full copyright notice.
+*--------------------------------------------------------------------------------------------*/
+
+import { expect } from "chai";
+import { testBlankViewport } from "./openBlankViewport";
+import { FeatureSymbology, IModelApp, Viewport, ViewState } from "../core-frontend";
+import { EmptyLocalization } from "@itwin/core-common";
+
+describe("FeatureSymbology.Overrides", () => {
+  before(async () => IModelApp.startup({ localization: new EmptyLocalization() }));
+  after(async () => IModelApp.shutdown());
+
+  it("combines viewport's never-drawn elements with display style's excluded elements", () => {
+    function expectNeverDrawn(view: Viewport | ViewState, ids: string[]): void {
+      const ovrs = new FeatureSymbology.Overrides(view);
+      expect(ovrs.neverDrawn.size).to.equal(ids.length);
+      for (const id of ids) {
+        expect(ovrs.neverDrawn.hasId(id)).to.be.true;
+      }
+    }
+
+    testBlankViewport((vp) => {
+      expectNeverDrawn(vp.view, []);
+      expectNeverDrawn(vp, []);
+
+      vp.view.displayStyle.settings.addExcludedElements("0x1");
+      expectNeverDrawn(vp.view, ["0x1"]);
+      expectNeverDrawn(vp, ["0x1"]);
+
+      vp.setNeverDrawn(new Set(["0x2"]));
+      expectNeverDrawn(vp.view, ["0x1"]);
+      expectNeverDrawn(vp, ["0x1", "0x2"]);
+
+      vp.view.displayStyle.settings.dropExcludedElement("0x1");
+      expectNeverDrawn(vp.view, []);
+      expectNeverDrawn(vp, ["0x2"]);
+
+      vp.clearNeverDrawn();
+      expectNeverDrawn(vp.view, []);
+      expectNeverDrawn(vp, []);
+    });
+  });
+});