[vtk-developers] HiDPI / Retina displays and vtkTextActors

Sean McBride sean at rogue-research.com
Mon Oct 16 10:52:31 EDT 2017

On Sat, 14 Oct 2017 11:39:29 +0200, Elvis Stansvik said:

>> Thanks for the quick reply and suggestion.  We just tried this, and
>indeed it works.  Specifically, we did SetDPI(144), we didn't actually
>try to do any introspection of the actual DPI of the actual monitor.
>I'm using GetRenderWindow()->SetDPI(q
>in our Qt/VTK app. i.e. using Qt to query for the DPI of the actual

I'm not at all convinced it's better to use the actual screen DPI to achieve this.  The API to get that info on macOS is IODisplayCreateInfoDictionary(), and has just a couple of hundred google results.  It does not seem at all typical to use DPI information.  From what I can tell, the way everyone handles Retina displays is a 2x doubling.

Consider how using the actual DPI would affect the screenshot in the start of this thread... the relative sizes of the cone & text would be different on different screens.  Seems just as undesirable as the current situation.

>Of course, this in itself doesn't take care of DPI changes, and it's
>been on my TODO to fix this (listen for screen changes).

You might also want to not hardcode 'primaryScreen' in there... :)

>It looks like your MR is making VTK do this automatically internally
>on macOS?

Yes, basically.

>That would be a welcome addition indeed, but what about
>other platforms?

Probably desirable there too, but outside my expertise...


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