[vtkusers] Using fontconfig with vtkTextMapper/vtkTextProperty?

[Elvis Stansvik]

2016-10-20 18:31 GMT+02:00 David Lonie <david.lonie at kitware.com>:
> 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.

Alright, no problem. We're on Linux only so far, but I can rely on Qt
for cross-platform detection for now.

Elvis

>
> Dave