HighDPI: Assert messagebox is not readable

[SDLBugzilla]

This bug report was migrated from our old Bugzilla tracker.

Reported in version: HG 2.0
Reported for operating system, platform: Linux, All

Comments on the original bug report:

On 2020-07-02 14:31:32 +0000, Martin Gerhardy wrote:

Looks like on high-dpi screens the x11 messagebox with the assert buttons the dpi settings are not taken into account.

[icculus]

Pretty sure this means SDL message boxes are broken, more generally. Have to look into the rules of X11 highdpi support.

[slouken]

We now have the information to fix this properly. :)