[tor-bugs] #12684 [Firefox Patch Issues]: Make "Not Now" the default button for TorBrowser's canvas permission dialogue

[Tor Bug Tracker & Wiki]

#12684: Make "Not Now" the default button for TorBrowser's canvas permission
dialogue
-------------------------------------+-------------------------------------
     Reporter:  isis                 |      Owner:  isis
         Type:  defect               |     Status:  needs_information
     Priority:  critical             |  Milestone:
    Component:  Firefox Patch        |    Version:
  Issues                             |   Keywords:  tbb-usability, tbb-
   Resolution:                       |  linkability, MikePerry201408R,
Actual Points:                       |  TorBrowserTeam201408
       Points:                       |  Parent ID:
-------------------------------------+-------------------------------------
Changes (by isis):

 * status:  needs_review => needs_information


Comment:

 Replying to [comment:21 mcs]:
 > Replying to [comment:18 isis]:
 > > Problem !#1: That `<separator class="groove">` part between the
 sentences. For the life of me, I can't get this thing to insert a newline.
 I've tried `\n\n`, a [https://developer.mozilla.org/en-
 US/docs/Mozilla/Tech/XUL/separator XUL separator] and a
 [https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/spacer XUL
 spacer]. All of them actually show up in the text.
 >
 > The text ends up in a XUL <description> element.  If we can apply a CSS
 rule like white-space: pre-wrap, then newlines (\n) will not be ignored.
 There might be a better way, but here is something that seems to work:
 add the following code to the CanvasPermissionPromptHelper_init()
 function:
 > {{{
 > if (document.styleSheets && (document.styleSheets.length > 0)) try {
 >   let ruleText = "panel[popupid=canvas-permissions-prompt] description {
 white-space: pre-wrap";
 >   let sheet = document.styleSheets[0];
 >   sheet.insertRule(ruleText, sheet.cssRules.length);
 > } catch (e) {}
 >
 > }}}

 Okay, I added that stanza after the

     {{{Services.obs.addObserver(this, this._permissionsPrompt, false);}}}

 line, and rebuilt Firefox. However, the resulting build was all kinds of
 broken, and running the `firefox` binary with `-jsconsole` had some errors
 about unterminated string literals in `browser/content/browser.js`.

 I thought it was due to the missing CSS `}` at the end of the `ruleText`
 variable above, but after adding the `}` and rebuilding a second time it
 still came out janky and broken.

 Was I supposed to add the CSS hack before the ServiceObserver gets added?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12684#comment:25>
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