[tbb-bugs] #13818 [Tor Browser]: [PATCH] Active tab looks ugly (inherits system color scheme only partially)

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#13818: [PATCH] Active tab looks ugly (inherits system color scheme only partially)
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 Reporter:  gentoo_root  |          Owner:  tbb-team
     Type:  defect       |         Status:  new
 Priority:  normal       |      Milestone:
Component:  Tor Browser  |        Version:
 Keywords:               |  Actual Points:
Parent ID:               |         Points:
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 I use Tor Browser 4.5-alpha-1 on KDE, my gtk+ theme is oxygen-gtk. As I
 found from looking into sources of Tor Browser, when it renders site
 content, it uses some stand-ins for native colors to avoid browser
 fingerprinting. And these stand-ins should not be used when rendering
 browser interface - the variable useStandinsForNativeColors in
 layout/style/nsRuleNode.cpp:890 (function SetColor):

       bool useStandinsForNativeColors = aPresContext &&
 !aPresContext->IsChrome();

 But this condition is not enough to fully distinguish browser interface
 from site content. Look at the attached screenshot to see that left and
 right corners of active tab are lighter than middle of the tab - this is
 because the middle renders with system colors, and corners render with
 stand-ins while stand-ins should be really disabled for them.

 I discovered that two files correspond for corners of the tab:
 chrome://browser/skin/tabbrowser/tab-selected-start.svg and
 chrome://browser/skin/tabbrowser/tab-selected-end.svg, and IsChrome()
 function returns false for this files, so stand-ins are used when they
 shouldn't.

 I think that the attached patch should be used in order to handle
 correctly those two svg files.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13818>
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