bugGNUstep - Bugs: bug #47109, Cairo/Windows: Unexpected DPI may...

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bug #47109: Cairo/Windows: Unexpected DPI may cause font rendering issues

Submitter:  Ivan Vučica <ivucica>
Submitted:  Wed 10 Feb 2016 03:49:39 PM UTC
   
 
Category:  Backend Severity:  2 - Minor
Item Group:  Bug Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open
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Wed 10 Feb 2016 04:40:43 PM UTC, comment #1: 

If someone wants to continue looking into fixing this, I've spent a few minutes trying to track this down completely blindly (i.e. I didn't actually run any code).

The number 16 in '16 characters until whitespace appears' seems to come from:
  http://svn.gna.org/svn/gnustep/libs/gui/trunk/Source/NSLayoutManager.m
method -drawGlyphsForGlyphRange:atPoint: line "#define GBUF_SIZE 16 /* TODO: tweak */".

Combined with Riccardo's mention that this may be related to DPI, and following the call to C function GSShowGlyphsWithAdvances() from
  http://svn.gna.org/svn/gnustep/libs/gui/trunk/Source/NSGraphicsContext.m
I'd say the fixer will want to look at
  http://svn.gna.org/svn/gnustep/libs/back/trunk/Source/cairo/CairoGState.m
method -GSShowGlyphsWithAdvances:::, and
  http://svn.gna.org/svn/gnustep/libs/back/trunk/Source/cairo/CairoFontInfo.m
method -drawGlyphs:length:on:.

 Ivan Vučica <ivucica>
Group Member
Wed 10 Feb 2016 03:49:39 PM UTC, original submission:  

From James Carthew:
"Attached is a picture showing the rendering error. This was generated using the pre-built windows files from the GNUstep website. "

Commentary from Riccardo:
"Hi,

I am pretty sure you have a resolution problem, I have seen this several times on windows (and also on X11 on one FreeBSD workstation).

Please set your Windows to "100%" and do not enlarge text and icons.

For some reason, we enlarge the controls, but then use a small font to draw the text. It would be best of course to "scale" up also the the font, or, at least to ignore the resize and keep everything pixels-sized to GNUstep, but currently it is hybrid.


Riccardo"

Commentary from me:
"Odd whitespace in the middle of a word is also a bug. It seems to happen after exactly 16 glyphs."


Ivan Vučica <ivucica>
Group Member

 

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file #36298:  47c19cd2-0e50-400c-982f-a8a52df8c17b.png added by ivucica (30KiB - image/png)

 

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    Date Changed by Updated Field Previous Value => Replaced by
    2016-02-10 ivucica Attached File- Added 47c19cd2-0e50-400c-982f-a8a52df8c17b.png, #36298

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