Add element to text layer even if width === 0

[nschloe]

Some browsers render certain special characters with width 0, others with strictly positive width. (For example, the Greek Delta, Δ, has width 0 in Google Chrome, and a positive width in Firefox.) The if clause in operation so far results in different text layer DOM trees for different browsers.

This commit fixes that by adding the elements independently of their width.

For the background:
This bug was discovered when using https://github.com/timdown/rangy, a tool to create and find text ranges in a DOM tree, used primarily for adding annotations.

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This change is

[yurydelendik]

Can you provide test PDF? (For verification) It will be nice to include that as text layer test.

[nschloe]

Thanks for the swift reply! I suppose any paper with math with do, but the bug was dicovered with http://arxiv.org/pdf/1603.04246v1.pdf.

[timvandermeij]

I'm a bit confused about this PR. First of all, I wonder why the width > 0 check was added in the first place. Aren't we regressing something with this patch? Second of all, I cannot spot a difference in text selection before and after this patch with the provided document. Opening it using https://mozilla.github.io/pdf.js/web/viewer.html (latest master) and http://107.21.233.14:8877/f8c440b8fb693e9/web/viewer.html (this patch) makes it impossible to select the delta sign in both versions for me using Firefox 45.0.1 on Arch Linux. In comparison, Okular allows me to select all special characters in the PDF. Am I missing something here?

The provided file seems to have been made with LaTeX, so I'm attaching a reduced test case that I made myself that can be included in this patch if you can reproduce the issue with this file too:
delta.pdf

The LaTeX source, for those interested, is:

\documentclass{article}
\usepackage[a4paper,margin=2.5cm]{geometry}
\begin{document}
    \huge{$\Delta$}
\end{document}

[yurydelendik]

I wonder why the width > 0 check was added in the first place

It was introduced by
e086cf3#diff-dd42e9b2d2a652b8e312efa567698aa6L1850 in-place of textLength > 1 check (and also to better protect from div by 0).

[nschloe]

Thanks @timvandermeij for the comments.

(this patch) makes it impossible to select the delta sign in both versions for me using Firefox 45.0.1 on Arch Linux. In comparison, Okular allows me to select all special characters in the PDF. Am I missing something here?

The \Delta can indeed still not be selected. The purpose of this PR is to get equal text layers in both Chrome and Firefox. So far, Chrome:

<div style="left: 491.912px; top: 1323.33px; font-size: 16.6043px; font-family: monospace;">1</div>
<div class="endOfContent"></div>

Firefox:

<div style="left: 143.017px; top: 117.739px; font-size: 34.4375px; font-family: monospace;">�</div>
<div style="left: 491.912px; top: 1323.33px; font-size: 16.6043px; font-family: monospace;">1</div>
<div class="endOfContent"></div>

(The � symbol has width 0 in Chrome and is thus stripped on master.)

[timvandermeij]

/botio-linux preview

[pdfjsbot]

From: Bot.io (Linux)

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Received

Command cmd_preview from @timvandermeij received. Current queue size: 0

Live output at: http://107.21.233.14:8877/04f19be6c3ac3a2/output.txt

[pdfjsbot]

From: Bot.io (Linux)

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Success

Full output at http://107.21.233.14:8877/04f19be6c3ac3a2/output.txt

Total script time: 1.00 mins

Published

• Viewer: http://107.21.233.14:8877/04f19be6c3ac3a2/web/viewer.html
• B2G Viewer: http://107.21.233.14:8877/04f19be6c3ac3a2/extensions/b2g/content/web/viewer.html
• Extension: http://107.21.233.14:8877/04f19be6c3ac3a2/extensions/firefox/pdf.js.xpi

[timvandermeij]

/botio test

[pdfjsbot]

From: Bot.io (Windows)

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Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://107.22.172.223:8877/d08f109d8de2ff5/output.txt

[pdfjsbot]

From: Bot.io (Linux)

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Received

Command cmd_test from @timvandermeij received. Current queue size: 0

Live output at: http://107.21.233.14:8877/a5c104438626c30/output.txt

[pdfjsbot]

From: Bot.io (Windows)

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Success

Full output at http://107.22.172.223:8877/d08f109d8de2ff5/output.txt

Total script time: 20.49 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed

[pdfjsbot]

From: Bot.io (Linux)

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Success

Full output at http://107.21.233.14:8877/a5c104438626c30/output.txt

Total script time: 22.77 mins

• Font tests: Passed
• Unit tests: Passed
• Regression tests: Passed

[timvandermeij]

@yurydelendik Could you review this PR?

[yurydelendik]

I agree with the change, but it's too fragile. I see whitespace check above, so we somewhat safe from regressions in most of the cases. It might be hard to add a test case since it's different across browsers/platforms. Thank you for the patch.