From bf0aca86d72d2b7a6b8d24333a11fdaf187b7ac8 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Thu, 28 Jun 2018 22:38:09 +0200
Subject: [PATCH] Fix re-rendering, using the same canvas, when rendering was
 previously cancelled (PR 8519 follow-up)

Currently if `RenderTask.cancel` is called *immediately* after rendering was started, then by the time that `InternalRenderTask.initializeGraphics` is called rendering will already have been cancelled.
However, we're still inserting the canvas into the `canvasInRendering` map, thus breaking any future attempts at re-rendering using the same canvas. Considering that `InternalRenderTask.cancel` always removes the canvas from the map, I cannot imagine that we'd ever want to re-add it *after* rendering was cancelled (it was likely just a simple oversight in PR 8519).

Fixes 9456.
---
 src/display/api.js    | 10 ++++------
 test/unit/api_spec.js | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/display/api.js b/src/display/api.js
index ede847f9e..92b418b10 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -2380,9 +2380,10 @@ var InternalRenderTask = (function InternalRenderTaskClosure() {
 
   InternalRenderTask.prototype = {
 
-    initializeGraphics:
-        function InternalRenderTask_initializeGraphics(transparency) {
-
+    initializeGraphics(transparency) {
+      if (this.cancelled) {
+        return;
+      }
       if (this._canvas) {
         if (canvasInRendering.has(this._canvas)) {
           throw new Error(
@@ -2393,9 +2394,6 @@ var InternalRenderTask = (function InternalRenderTaskClosure() {
         canvasInRendering.set(this._canvas, this);
       }
 
-      if (this.cancelled) {
-        return;
-      }
       if (this._pdfBug && globalScope.StepperManager &&
           globalScope.StepperManager.enabled) {
         this.stepper = globalScope.StepperManager.create(this.pageNumber - 1);
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index fcb1558be..ec23a6fae 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -1253,6 +1253,37 @@ describe('api', function() {
         done();
       });
     });
+
+    it('re-render page, using the same canvas, after cancelling rendering',
+        function(done) {
+      if (isNodeJS()) {
+        pending('TODO: Support Canvas testing in Node.js.');
+      }
+      let viewport = page.getViewport(1);
+      let canvasAndCtx = CanvasFactory.create(viewport.width, viewport.height);
+
+      let renderTask = page.render({
+        canvasContext: canvasAndCtx.context,
+        viewport,
+      });
+      renderTask.cancel();
+
+      renderTask.promise.then(() => {
+        throw new Error('shall cancel rendering');
+      }, (reason) => {
+        expect(reason instanceof RenderingCancelledException).toEqual(true);
+      }).then(() => {
+        let reRenderTask = page.render({
+          canvasContext: canvasAndCtx.context,
+          viewport,
+        });
+        return reRenderTask.promise;
+      }).then(() => {
+        CanvasFactory.destroy(canvasAndCtx);
+        done();
+      }, done.fail);
+    });
+
     it('multiple render() on the same canvas', function(done) {
       if (isNodeJS()) {
         pending('TODO: Support Canvas testing in Node.js.');