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commit 61a99aff9d
dix: pre-scale relative events from abs devices to desktop ratio (#31636)
added pre-scaling of relative coordinates coming from absolute devices to
undo uneven scaling based on the screen dimensions.
Devices have their own device width/height ratio as well (in a specific
resolution) and this must be applied for relative devices as well to avoid
scaling of the relative events into the device's ratio.
e.g. a Wacom Intuos4 6x9 is in 16:10 format with equal horiz/vert
resolution (dpi). A movement by 1000/1000 coordinates is a perfect diagonal
on the tablet and must be reflected as such on the screen.
However, we map the relative device-coordinate events to absolute screen
coordinates based on the axis ranges. This results in an effective scaling
of 1000/(1000 * 1.6) and thus an uneven x/y axis movement - the y
axis is always faster.
So we need to pre-scale not only by the desktop dimenstions but also by the
device width/height ratio _and_ the resolution ratio.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>