Added an "InteractiveAnnotation" class to homogenize the annotations' structure (highlighting) and user interactions (for now, used for text and link annotations).
Text annotations:
The appearance (AP) has priority over the icon (Name).
The popup extends horizontally (up to a limit) as well as vertically.
Reduced the title's font size.
The annotation's color (C) is used to color the popup's background.
On top of the mouseover show/hide behavior, a click on the icon will lock the annotation open (for mobile purposes). It can be closed with another click on either the icon or the popup.
An annotation printing is conditioned by its "print" bit
Unsupported annotations are not displayed at all.
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.
