Do NOT save the temporary <canvas> element as `this.canvas`.
`PDFViewer.pages[i].canvas` appears to be used to generate the thumbnail
icons. Well, that's no justification for preventing GC of those
temporary <canvas> elements used during mozPrintCallback.
With a document consisting of 79 pages, this resulted in a 600-700MB
leaked memory.
This shim does the following:
1. Intercept window.print()
2. For a window.print() call (if allowed, ie. no previous print job):
1. Dispatch the beforeprint event.
2. Render a printg progress dialog.
3. For each canvas, call mozPrintCallback if existent (one at a time, async).
4. During each mozPrintCallback callback, update the progress dialog.
5. When all <canvas>es have been rendered, invoke the real window.print().
6. Dispatch the afterprint event.
The shim is not included in Firefox through the preprocessor.
Keyboard shortcuts (Ctrl/Cmd + P) are intercepted and default behavior
(i.e. printing) is prevented, and the steps for window.print() are run.
window.attachEvent is used, in order to cancel printing in IE10 and
earlier (courtesy of Stack Overflow - http://stackoverflow.com/a/15302847).
Unfortunately, this doesn't work in IE11 - if Ctrl + P is used, the
print dialog will be shown twice: Once because of Ctrl + P, and again
when all pages have finished rendering.
This logic of this polyfill is not specific to PDF.js, so it can also
be used in other projects.
There's one additional modification in PDF.js's viewer.js: The printed
<canvas> element is wrapped in a <div>. This is needed, because Chrome
would otherwise print one canvas on two pages.
[PDFHistory] Prevent the history from skipping entries in certain edge cases, when specifying an initialBookmark in the hash parameters on document load
Before this commit there were two main issues:
- In small windows, the zoom controls visually floated above the page number
(e.g. 733px).
- In small windows, the (transparent) zoom container covered the go-to-page
input box, which prevented one from using the input field to quickly navigate
to a different page.
If focused element is a textarea, viewer should not process keyboard shortcuts (as it does with input and select elements) because while writing on a textarea, if you press k,p,l, or n, the viewer scrolls next/prev page and the letter is not added to the textarea (eg. in my case I had a viewer displaying a product specs in PDF and a "request a quote" form at it's right, the form had a textarea field and users complains that they couldn't write in it, after checking it, I've realized it was this particular issue and fixd it with the change I'm commiting.
