[vtkusers] Using fontconfig with vtkTextMapper/vtkTextProperty?

[David Lonie]

On Thu, Oct 20, 2016 at 12:29 PM, David Lonie <david.lonie at kitware.com>
wrote:

> On Thu, Oct 20, 2016 at 12:25 PM, Elvis Stansvik <
> elvis.stansvik at orexplore.com> wrote:
>
>> Den 20 okt. 2016 5:30 em skrev "David Lonie" <david.lonie at kitware.com>:
>> >
>> > On Thu, Oct 20, 2016 at 11:27 AM, Elvis Stansvik <
>> elvis.stansvik at orexplore.com> wrote:
>> >>
>> >> Using built-in fonts I also get text rendered smaller than expected.
>> >>
>> >> However, I think it's a matter of DPI. I guess VTK assumes a DPI of 72
>> >> somewhere?
>> >>
>> >> With the following, the text is rendered in the expected size:
>> >>
>> >>     auto logicalDpiY = QApplication::screens().at(0)-
>> >logicalDotsPerInchY();
>> >>     ...
>> >>     textProperty->SetFontSize(qRound(10 * (logicalDpiY / 72.0)));
>> >>     textProperty->SetFontFamilyAsString("Noto Sans");
>> >>
>> >> So I'm compensating for VTK's assumption about 72 DPI by increasing
>> >> the font size (on my system Qt's logicalDotsPerInchY() reports
>> >> 96.2526).
>> >>
>> >> I guess I should also figure out how to be notified when the widget is
>> >> moved to another screen and update the size, since the DPI of the
>> >> other screen might be different.
>> >
>> >
>> > Aha, yes, VTK does assume 72 DPI by default. We very recently added the
>> ability to change that for text rendering purposes. Call
>> vtkRenderWindow::SetDPI to update it to what Qt is using, and the text
>> rendering should adjust accordingly. Let me know if that fixes it.
>>
>> Aha, thanks for the tip. On my way home now but will test tomorrow. Do
>> you know if it's in 7.1rc1? I'm building my Debian package from that tag
>>
>
> It is. We added this about a year ago, but like the fontconfig stuff, it
> hasn't seen widespread use yet so any feedback would be great :)
>

Also I should point out the vtkWindow::DetectDPI() method, which detects
and sets the DPI automatically. It's only available on Windows atm (IIRC),
but the return boolean will indicate if it worked or not.

Dave
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