fixup! Render high-res partial page views when falling back to CSS zo…

…om (bug 1492303)

Do not render PDFPageDetailView that have been removed from their parent
PDFPageView.

test/integration/viewer_spec.mjs

@@ -948,10 +948,85 @@ describe("PDF viewer", () => {
                   { pageNumber: 2, isDetailView: false, cssTransform: false },
                   { pageNumber: 1, isDetailView: false, cssTransform: false },
                 ]);
+
+              const canvasesPerPage = await page.evaluate(() =>
+                Array.from(
+                  document.querySelectorAll(".canvasWrapper"),
+                  wrapper => wrapper.childElementCount
+                )
+              );
+              expect(canvasesPerPage)
+                .withContext(`In ${browserName}, number of canvases`)
+                .toEqual([1, 1]);
             });
           });
         });
       });
     }
+
+    describe("when immediately cancelled and re-rendered", () => {
+      const forEachPage = setupPages("100%", 1, {
+        eventBusSetup: eventBus => {
+          globalThis.__pageRenderedEvents = [];
+          eventBus.on("pagerendered", ({ pageNumber, isDetailView }) => {
+            globalThis.__pageRenderedEvents.push({ pageNumber, isDetailView });
+          });
+        },
+      });
+
+      it("propely cleans up old canvases from the dom", async () => {
+        await forEachPage(async (browserName, page) => {
+          const waitForPageRenderedEvent = filter =>
+            page.waitForFunction(
+              filterStr => {
+                // eslint-disable-next-line no-eval
+                if (globalThis.__pageRenderedEvents.some(eval(filterStr))) {
+                  globalThis.__pageRenderedEvents = [];
+                  return true;
+                }
+                return false;
+              },
+              { polling: 50 },
+              String(filter)
+            );
+          const getCanvasCount = () =>
+            page.evaluate(
+              () =>
+                document.querySelector("[data-page-number='1'] .canvasWrapper")
+                  .childElementCount
+            );
+
+          await waitForPageRenderedEvent(e => e.pageNumber === 1);
+
+          await page.evaluate(() => {
+            window.PDFViewerApplication.pdfViewer.updateScale({
+              drawingDelay: -1,
+              scaleFactor: 4,
+            });
+          });
+          await waitForPageRenderedEvent(
+            e => e.pageNumber === 1 && e.isDetailView
+          );
+          expect(await getCanvasCount())
+            .withContext(`In ${browserName}, after the first zoom-in`)
+            .toBe(2);
+
+          await page.evaluate(() => {
+            window.PDFViewerApplication.pdfViewer.updateScale({
+              drawingDelay: -1,
+              scaleFactor: 0.75,
+            });
+            window.PDFViewerApplication.pdfViewer.updateScale({
+              drawingDelay: -1,
+              scaleFactor: 0.25,
+            });
+          });
+          await waitForPageRenderedEvent(e => e.pageNumber === 1);
+          expect(await getCanvasCount())
+            .withContext(`In ${browserName}, after the two zoom-out`)
+            .toBe(1);
+        });
+      });
+    });
   });
 });

web/pdf_page_detail_view.js

@@ -185,6 +185,12 @@ class PDFPageDetailView extends BasePDFPageView {
   }
 
   async draw() {
+    // The PDFPageView might have already dropped this PDFPageDetailView. In
+    // that case, simply do nothing.
+    if (this.pageView.detailView !== this) {
+      return;
+    }
+
     // If there is already the lower resolution canvas behind,
     // we don't show the new one until when it's fully ready.
     const hideUntilComplete =

web/pdf_viewer.js

@@ -64,6 +64,7 @@ import {
   watchScroll,
 } from "./ui_utils.js";
 import { GenericL10n } from "web-null_l10n";
+import { PDFPageDetailView } from "./pdf_page_detail_view.js";
 import { PDFPageView } from "./pdf_page_view.js";
 import { PDFRenderingQueue } from "./pdf_rendering_queue.js";
 import { SimpleLinkService } from "./pdf_link_service.js";