Posted by Sven Gothel on Mar 04, 2023; 3:33pm
URL: https://forum.jogamp.org/DPI-scaling-not-working-tp4042206p4042280.html

Great, but warning .. this may become a deep dive :)

The last related git commits include NEWT Soft-PixelScale in the subject.
Bugs related and new commented are in Bug 1374.

In NEWT, we have different means to pull the pixel-scale from the system
- Windows: GDI, see GDIUtil.GetMonitorPixelScale()
- OSX: OSXUtil.getScreenPixelScaleByDisplayID()
  - Note: NEWT also considers the specific native view/window configuration.
- Linux: Environment variable, see SurfaceScaleUtil.getPixelScaleEnv()

Currently, in our AWT GLCanvas, we use:
- JAWTUtil.getPixelScale()
and this might be an issue or something, despite the fact that we use floats.
This method sort of does the very same path as all other are using for a workaround.

However, it uses one method for Java < 9
and one method for Java >= 9.
The latter (Java >= 9) simply uses the generic GraphicsConfiguration's AffineTransform's x/y scale factor
which is a double, so float compatible if you want.

This JAWTUtil method is currently used in
- GLJPanel
- JAWTWindow
  - used in GLCanvas

When I would start this journey, I would first hack-in code to show me
the actual pixel-scale (using the mentioned NEWT methods)
and the JAWTUtil scales used.

Assuming full integer scales work, but we got a 'float bug',
probably AWT using just integer.
In the latter case, we would need to use the ceiling of rounded float, done :)

Hope it helps a little.