1730114 - [wayland] Experimental fractional scaling support causes screen size to be reported incorrectly

Status: ASSIGNED

(Core :: Graphics, defect, P3)

Description

[Chris Morgan]

Using Sway with output scale 1.5 on a 2560×1440 monitor.

Before setting widget.wayland.fractional_buffer_scale, devicePixelRatio is 2 (bad but expected because of the use of overdraw), and [screen.width, screen.height] was [2560, 1440] (correct).

After setting widget.wayland.fractional_buffer_scale to 1.5, devicePixelRatio is 1.5 (good), but [screen.width, screen.height] is [3413, 1920], which is incorrect.

I guess you’d call this a regression in bug 1707209.

Comment 1

[Brad Werth [:bradwerth]]

Putting this on Robert's list.

Comment 2

[Chris Morgan]

This has just changed again: it’s now getting screen dimensions wrong in the other direction, reporting [screen.width, screen.height] as [1137, 640]—dividing the 2560×1440 device pixel size by 1.5 twice. My educated guess is that the bug 1730476 patch is responsible for it changing.

This will need checking in GNOME and KDE Wayland sessions too.

Comment 3

[Robert Mader [:rmader]]

Thanks, will look into it. Technically it's IMO not a regression from bug 1707209 - it's a bug in a new feature. Regressions imply that reverting the regressing patches would solve the issue. In other words, this would only become a regression if we decided to somehow enable fractional scaling by default.