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print: Make the firefox printing code able to fail and be re-invoked.

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This fixes a set of issues described in Mozilla bug 1662426[1].

In particular, once the print callback fails once (because the printing
operation has been canceled in Gecko / replaced by a newer one, for example) it
can't be re-invoked.

This patch fixes it by properly cancelling the render task if it throws, or if
the print callback is called again while ongoing.

[1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1662426
This commit is contained in:
Emilio Cobos Álvarez 2020-09-02 11:38:10 +02:00
parent ed9ea8f9b2
commit f4f4ec30f4
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1 changed files with 24 additions and 1 deletions
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25
web/firefox_print_service.js
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@ -41,6 +41,14 @@ function composePage(
canvasWrapper.appendChild(canvas); canvasWrapper.appendChild(canvas);
printContainer.appendChild(canvasWrapper); printContainer.appendChild(canvasWrapper);
// A callback for a given page may be executed multiple times for different
// print operations (think of changing the print settings in the browser).
//
// Since we don't support queueing multiple render tasks for the same page
// (and it'd be racy anyways if painting the page is not done in one go) we
// keep track of the last scheduled task in order to properly cancel it before
// starting the next one.
let currentRenderTask = null;
canvas.mozPrintCallback = function (obj) { canvas.mozPrintCallback = function (obj) {
// Printing/rendering the page. // Printing/rendering the page.
const ctx = obj.context; const ctx = obj.context;
@ -50,9 +58,14 @@ function composePage(
ctx.fillRect(0, 0, canvas.width, canvas.height); ctx.fillRect(0, 0, canvas.width, canvas.height);
ctx.restore(); ctx.restore();
let thisRenderTask = null;
pdfDocument pdfDocument
.getPage(pageNumber) .getPage(pageNumber)
.then(function (pdfPage) { .then(function (pdfPage) {
if (currentRenderTask) {
currentRenderTask.cancel();
currentRenderTask = null;
}
const renderContext = { const renderContext = {
canvasContext: ctx, canvasContext: ctx,
transform: [PRINT_UNITS, 0, 0, PRINT_UNITS, 0, 0], transform: [PRINT_UNITS, 0, 0, PRINT_UNITS, 0, 0],
@ -61,15 +74,25 @@ function composePage(
annotationStorage: pdfDocument.annotationStorage, annotationStorage: pdfDocument.annotationStorage,
optionalContentConfigPromise, optionalContentConfigPromise,
}; };
return pdfPage.render(renderContext).promise; currentRenderTask = thisRenderTask = pdfPage.render(renderContext);
return thisRenderTask.promise;
}) })
.then( .then(
function () { function () {
// Tell the printEngine that rendering this canvas/page has finished. // Tell the printEngine that rendering this canvas/page has finished.
if (currentRenderTask === thisRenderTask) {
currentRenderTask = null;
}
obj.done(); obj.done();
}, },
function (error) { function (error) {
console.error(error); console.error(error);
if (currentRenderTask === thisRenderTask) {
currentRenderTask.cancel();
currentRenderTask = null;
}
// Tell the printEngine that rendering this canvas/page has failed. // Tell the printEngine that rendering this canvas/page has failed.
// This will make the print process stop. // This will make the print process stop.
if ("abort" in obj) { if ("abort" in obj) {