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Re: [tor-bugs] #18144 [Tor Browser]: about:tor update arrow position is wrong (Retina and zoom)
#18144: about:tor update arrow position is wrong (Retina and zoom)
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Reporter: mcs | Owner: tbb-team
Type: defect | Status: needs_information
Priority: Medium | Milestone:
Component: Tor Browser | Version:
Severity: Normal | Resolution:
Keywords: TorBrowserTeam201602R | Actual Points:
Parent ID: | Points:
Sponsor: |
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Comment (by mcs):
Replying to [comment:8 gk]:
> Looking at the diff between the first and the second patch and at the
comment that changed I am wondering why
> {{{
> tbXpos *= window.devicePixelRatio;
> }}}
> slipped in. I mean if `window.devicePixelRatio` is alaways `1.0` for
non-Chrome windows (causing the bug we have here) why do we need to
multiply `tbXpos` with it in the first place? What am I missing?
Actually, window.devicePixelRatio will be 2.0 on a Retina display because
'window' is the chrome window that contains the Torbutton toolbar item.
And then dividing by the screenPixelsPerCSSPixel value from the content
window converts the offset into device-independent units (aka CSS pixels).
Another way to look at it: the new code is similar to the old code except
we removed the "if ("devicePixelRatio" in window)" checks (FF 18 was a
long time ago now) and instead of dividing by devicePixelRatio inside
aboutTor.xhtml (the content window) we get the screenPixelsPerCSSPixel
value inside torbutton.js and do the division there. This is necessary
because screenPixelsPerCSSPixel is only available from privileged code
(e.g., inside the Torbutton overlay).
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18144#comment:9>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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