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dix: if the scroll valuator reaches INT_MAX, reset to 0 

Too much scrolling down may eventually trigger an overflow of the valuator.
If this happens, reset the valuator to 0 and skip this event for button
emulation. Clients will have to figure out a way to deal with this, but a
scroll event from (close to) INT_MAX to 0 is a hint of that it needs to be
ignored.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
This commit is contained in:
Peter Hutterer 2012-06-07 16:52:20 +10:00
parent 8dc70acbf3
commit 54476b5e44
1 changed files with 34 additions and 6 deletions
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38
dix/getevents.c
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@ -35,6 +35,7 @@
#include <X11/keysym.h>
#include <X11/Xproto.h>
#include <math.h>
#include <limits.h>
#include "misc.h"
#include "resource.h"
@ -756,6 +757,29 @@ clipAbsolute(DeviceIntPtr dev, ValuatorMask *mask)
}
}
static void
add_to_scroll_valuator(DeviceIntPtr dev, ValuatorMask *mask, int valuator, double value)
{
double v;
if (!valuator_mask_fetch_double(mask, valuator, &v))
return;
/* protect against scrolling overflow. INT_MAX for double, because
* we'll eventually write this as 32.32 fixed point */
if ((value > 0 && v > INT_MAX - value) || (value < 0 && v < INT_MIN - value)) {
v = 0;
/* reset last.scroll to avoid a button storm */
valuator_mask_set_double(dev->last.scroll, valuator, 0);
}
else
v += value;
valuator_mask_set_double(mask, valuator, v);
}
/**
* Move the device's pointer by the values given in @valuators.
*
@ -774,15 +798,19 @@ moveRelative(DeviceIntPtr dev, ValuatorMask *mask)
if (!valuator_mask_isset(mask, i))
continue;
val += valuator_mask_get_double(mask, i);
add_to_scroll_valuator(dev, mask, i, val);
/* x & y need to go over the limits to cross screens if the SD
* isn't currently attached; otherwise, clip to screen bounds. */
if (valuator_get_mode(dev, i) == Absolute &&
((i != 0 && i != 1) || clip_xy))
((i != 0 && i != 1) || clip_xy)) {
val = valuator_mask_get_double(mask, i);
clipAxis(dev, i, &val);
valuator_mask_set_double(mask, i, val);
}
}
}
/**
* Accelerate the data in valuators based on the device's acceleration scheme.
@ -1506,6 +1534,7 @@ emulate_scroll_button_events(InternalEvent *events,
return num_events;
}
/**
* Generate a complete series of InternalEvents (filled into the EventList)
* representing pointer motion, or button presses. If the device is a slave
@ -1560,7 +1589,7 @@ GetPointerEvents(InternalEvent *events, DeviceIntPtr pDev, int type,
* necessary. This only needs to cater for the XIScrollFlagPreferred
* axis (if more than one scrolling axis is present) */
if (type == ButtonPress) {
double val, adj;
double adj;
int axis;
int h_scroll_axis = -1;
int v_scroll_axis = -1;
@ -1596,8 +1625,7 @@ GetPointerEvents(InternalEvent *events, DeviceIntPtr pDev, int type,
if (adj != 0.0 && axis != -1) {
adj *= pDev->valuator->axes[axis].scroll.increment;
val = valuator_mask_get_double(&mask, axis) + adj;
valuator_mask_set_double(&mask, axis, val);
add_to_scroll_valuator(pDev, &mask, axis, adj);
type = MotionNotify;
buttons = 0;
flags |= POINTER_EMULATED;