[vtkusers] Using fontconfig with vtkTextMapper/vtkTextProperty?

[David Lonie]

Excellent! Glad to hear that it worked for you :)

On Fri, Oct 21, 2016 at 4:22 AM, Elvis Stansvik <
elvis.stansvik at orexplore.com> wrote:

> 2016-10-20 18:29 GMT+02:00 David Lonie <david.lonie at kitware.com>:
> > 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
>
> SetDPI(...) worked great.
>
> So in summary, in a VTK/Qt application, you can set the DPI to the one
> Qt detects with
>
>     GetRenderWindow()->SetDPI(qRound(windowHandle()->screen(
> )->logicalDotsPerInch()));
>
> in your QVTKWidget, and then configure the vtkTextProperty to
> approximate the general system font with
>
>     auto font = QFontDatabase::systemFont(QFontDatabase::GeneralFont);
>     textProperty->SetFontSize(font.pointSize());
>     textProperty->SetFontFamilyAsString(font.
> family().toUtf8().constData());
>     textProperty->SetBold(font.bold());
>     textProperty->SetItalic(font.italic());
>
> Thanks for the pointers David!
>
> Elvis
>
> >
> >
> > 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 :)
> >
> > Dave
>
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