HiDPI support in GTK+

[Andoni Morales <ylatuya gmail com>]

Hi everyone!

We have a cross platform application named LongoMatch running in several platforms in which we use GTK+, Linux, Windows and OS X. For historical reasons and being a Mono C# app we are still using GTK+ 2, the latest release in the 2.24 series and Cairo 1.14.
We are having some troubles rendering correctly images and themes in HiDPI displays. Fonts and our custom widgets using Cairo are rendered correctly so GDK and Cairo seems to be doing their job correctly with respect to device scales. But Gtk.Images, like the ones in buttons, and icons/resources from the theme are being upscaled. All our image resources are SVG, so they can scale correctly. For example, in a retina display with x2, a GTK image of 22x22 dp is being drawn in 22x22px and than upscaled to 44X44px. If I have a button of 22dp I would like to pass it an Image of 22px x Scale = 44px so that the image is rendered correctly without being upscaled.

Is this possible with the current release of Gtk+2 or should I backport something from Gtk+3 to make it happen?

Cheers,

Andoni