Output transforms 90 and 270 are inverted

Submitted by emersion

Assigned to Wayland bug list

Link to original bug (#104389)

Description

The spec [1] says that wl_output::transform's rotation is counter-clockwise.

However, configuring an output with a 90 degree rotation results in a clockwise rotation. The output rotation reported by weston-info is 90.

90 and 270 degree rotations are swapped. Their flipped variants are swapped too.

This isn't a big issue inside weston because weston apps (like weston-terminal) will behave correctly: they'll rotate their surfaces of 90 degrees clockwise and advertize via wl_surface::set_buffer_transform a 90 degree rotation.

This is more of an issue with other compositors. If another compositor wants to follow the spec, weston apps won't work correctly in this compositor.

[1] https://wayland.freedesktop.org/docs/html/apa.html#protocol-spec-wl_output-enum-transform