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dix: fix device scaling to use a [min,max[ range.

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defmin/defmax are screen coords and thus use a min-inclusive, max-exclusive
range. device axes ranges are inclusive, so bump the max up by one to get the
scaling right.

This fixes off-by-one coordinate errors if the coordinate matrix is used to
bind the device to a fraction of the screen. It introduces an off-by-one
scaling error in the device coordinate range, but since most devices have a
higher resolution than the screen (e.g. a Wacom I4 has 5080 dpi) the effect
of this should be limited.

This error manifests when we have numScreens > 1, as the scaling from
desktop size back to screen size drops one device unit.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Peter Hutterer 2013-04-26 15:10:08 +10:00
parent 5cc2c96f82
commit 756ab88d93
2 changed files with 12 additions and 6 deletions
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4
dix/devices.c
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@ -112,8 +112,8 @@ DeviceSetTransform(DeviceIntPtr dev, float *transform_data)
* Transform is the user supplied (affine) transform
* InvScale scales coordinates back up into their native range
*/
sx = dev->valuator->axes[0].max_value - dev->valuator->axes[0].min_value;
sy = dev->valuator->axes[1].max_value - dev->valuator->axes[1].min_value;
sx = dev->valuator->axes[0].max_value - dev->valuator->axes[0].min_value + 1;
sy = dev->valuator->axes[1].max_value - dev->valuator->axes[1].min_value + 1;
/* invscale */
pixman_f_transform_init_scale(&scale, sx, sy);

14
dix/getevents.c
View File

@ -298,11 +298,11 @@ rescaleValuatorAxis(double coord, AxisInfoPtr from, AxisInfoPtr to,
if (from && from->min_value < from->max_value) {
fmin = from->min_value;
fmax = from->max_value;
fmax = from->max_value + 1;
}
if (to && to->min_value < to->max_value) {
tmin = to->min_value;
tmax = to->max_value;
tmax = to->max_value + 1;
}
if (fmin == tmin && fmax == tmax)
@ -924,9 +924,9 @@ scale_to_desktop(DeviceIntPtr dev, ValuatorMask *mask,
/* scale x&y to desktop coordinates */
*screenx = rescaleValuatorAxis(x, dev->valuator->axes + 0, NULL,
screenInfo.x, screenInfo.width - 1);
screenInfo.x, screenInfo.width);
*screeny = rescaleValuatorAxis(y, dev->valuator->axes + 1, NULL,
screenInfo.y, screenInfo.height - 1);
screenInfo.y, screenInfo.height);
*devx = x;
*devy = y;
@ -1366,6 +1366,12 @@ QueuePointerEvents(DeviceIntPtr device, int type,
* is the last coordinate on the first screen and must be rescaled for the
* event to be m. XI2 clients that do their own coordinate mapping would
* otherwise interpret the position of the device elsewere to the cursor.
* However, this scaling leads to losses:
* if we have two ScreenRecs we scale from e.g. [0..44704] (Wacom I4) to
* [0..2048[. that gives us 2047.954 as desktop coord, or the per-screen
* coordinate 1023.954. Scaling that back into the device coordinate range
* gives us 44703. So off by one device unit. It's a bug, but we'll have to
* live with it because with all this scaling, we just cannot win.
*
* @return the number of events written into events.
*/