Add "Resolution" option for mice to the evdev driver

It can be used to scale the resolution of a mouse to that of a 1000 DPI
mouse. This can be useful to make high resolution mice less sensitive
without turning off acceleration. The target of 1000 DPI is used as the
same default is used in libinput. If the option is not set no scaling
will be done.

https://bugs.freedesktop.org/show_bug.cgi?id=88134
Signed-off-by: Thomas Hindoe Paaboel Andersen <phomes@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

man/evdev.man

@@ -238,6 +238,12 @@ Default: "1".  Property: "Evdev Scrolling Distance".
 .BI "Option \*qDialDelta\*q \*q" integer \*q
 The amount of motion considered one unit of turning the dial.  Default: "1".
 Property: "Evdev Scrolling Distance".
+.TP 7
+.BI "Option \*qResolution\*q \*q" integer \*q
+Sets the resolution of the device in dots per inch. The resolution is used
+to scale relative motion events from mouse devices to 1000 DPI resolution. This
+can be used to make high resolution mice less sensitive without turning off
+acceleration. If set to 0 no scaling will be performed. Default: "0".
 
 .SH SUPPORTED PROPERTIES
 The following properties are provided by the

src/emuThird.c

@@ -229,8 +229,8 @@ Evdev3BEmuProcessAbsMotion(InputInfoPtr pInfo, ValuatorMask *vals)
     {
         if (valuator_mask_isset(vals, axis))
         {
-            int delta = valuator_mask_get(vals, axis) - emu3B->startpos[axis];
+            double delta = valuator_mask_get_double(vals, axis) - emu3B->startpos[axis];
-            if (abs(delta) > emu3B->threshold)
+            if (fabs(delta) > emu3B->threshold)
                 cancel = TRUE;
         }
         axis++;
@@ -248,7 +248,7 @@ Evdev3BEmuProcessAbsMotion(InputInfoPtr pInfo, ValuatorMask *vals)
  * emulation.
  */
 void
-Evdev3BEmuProcessRelMotion(InputInfoPtr pInfo, int dx, int dy)
+Evdev3BEmuProcessRelMotion(InputInfoPtr pInfo, double dx, double dy)
 {
     EvdevPtr          pEvdev = pInfo->private;
     struct emulate3B *emu3B  = &pEvdev->emulate3B;
@@ -260,8 +260,8 @@ Evdev3BEmuProcessRelMotion(InputInfoPtr pInfo, int dx, int dy)
     emu3B->delta[1] += dy;
     emu3B->flags |= EVDEV_RELATIVE_EVENTS;
 
-    if (abs(emu3B->delta[0]) > emu3B->threshold ||
+    if (fabs(emu3B->delta[0]) > emu3B->threshold ||
-        abs(emu3B->delta[1]) > emu3B->threshold)
+        fabs(emu3B->delta[1]) > emu3B->threshold)
     {
         Evdev3BEmuPostButtonEvent(pInfo, 1, BUTTON_PRESS);
         Evdev3BCancel(pInfo);

src/evdev.c

@@ -25,6 +25,7 @@
  *	Adam Jackson (ajax@redhat.com)
  *	Peter Hutterer (peter.hutterer@redhat.com)
  *	Oliver McFadden (oliver.mcfadden@nokia.com)
+ *	Thomas H.P. Andersen (phomes@gmail.com)
  */
 
 #ifdef HAVE_CONFIG_H
@@ -432,31 +433,36 @@ EvdevProcessValuators(InputInfoPtr pInfo)
 
     /* Apply transformations on relative coordinates */
     if (pEvdev->rel_queued) {
-        int deltaX = 0, deltaY = 0;
+        double deltaX = 0, deltaY = 0;
 
         if (valuator_mask_isset(pEvdev->rel_vals, REL_X))
-            deltaX = valuator_mask_get(pEvdev->rel_vals, REL_X);
+            deltaX = valuator_mask_get_double(pEvdev->rel_vals, REL_X);
         if (valuator_mask_isset(pEvdev->rel_vals, REL_Y))
-            deltaY = valuator_mask_get(pEvdev->rel_vals, REL_Y);
+            deltaY = valuator_mask_get_double(pEvdev->rel_vals, REL_Y);
 
         if (pEvdev->swap_axes) {
-            int tmp = deltaX;
+            double tmp = deltaX;
             deltaX = deltaY;
             deltaY = tmp;
         }
 
+        if (pEvdev->resolution > 0) {
+            deltaX *= DEFAULT_MOUSE_DPI / pEvdev->resolution;
+            deltaY *= DEFAULT_MOUSE_DPI / pEvdev->resolution;
+        }
+
         if (pEvdev->invert_x)
             deltaX *= -1;
         if (pEvdev->invert_y)
             deltaY *= -1;
 
         if (deltaX)
-            valuator_mask_set(pEvdev->rel_vals, REL_X, deltaX);
+            valuator_mask_set_double(pEvdev->rel_vals, REL_X, deltaX);
         else
             valuator_mask_unset(pEvdev->rel_vals, REL_X);
 
         if (deltaY)
-            valuator_mask_set(pEvdev->rel_vals, REL_Y, deltaY);
+            valuator_mask_set_double(pEvdev->rel_vals, REL_Y, deltaY);
         else
             valuator_mask_unset(pEvdev->rel_vals, REL_Y);
 
@@ -2293,6 +2299,12 @@ EvdevProbe(InputInfoPtr pInfo)
         pEvdev->invert_y = xf86SetBoolOption(pInfo->options, "InvertY", FALSE);
         pEvdev->swap_axes = xf86SetBoolOption(pInfo->options, "SwapAxes", FALSE);
 
+        pEvdev->resolution = xf86SetIntOption(pInfo->options, "Resolution", 0);
+        if (pEvdev->resolution < 0) {
+            xf86IDrvMsg(pInfo, X_ERROR, "Resolution must be a positive number");
+            pEvdev->resolution = 0;
+        }
+
         str = xf86CheckStrOption(pInfo->options, "Calibration", NULL);
         if (str) {
             num_calibration = sscanf(str, "%d %d %d %d",

src/evdev.h

@@ -97,6 +97,8 @@
 /* Number of longs needed to hold the given number of bits */
 #define NLONGS(x) (((x) + LONG_BITS - 1) / LONG_BITS)
 
+#define DEFAULT_MOUSE_DPI 1000.0
+
 /* Function key mode */
 enum fkeymode {
     FKEYMODE_UNKNOWN = 0,
@@ -170,6 +172,7 @@ typedef struct {
     BOOL swap_axes;
     BOOL invert_x;
     BOOL invert_y;
+    int resolution;
 
     unsigned int abs_queued, rel_queued, prox_queued;
 
@@ -191,7 +194,7 @@ typedef struct {
         int                 button;      /* phys button to emit */
         int                 threshold;   /* move threshold in dev coords */
         OsTimerPtr          timer;
-        int                 delta[2];    /* delta x/y, accumulating */
+        double              delta[2];    /* delta x/y, accumulating */
         int                 startpos[2]; /* starting pos for abs devices */
         int                 flags;       /* remember if we had rel or abs movement */
     } emulate3B;
@@ -269,7 +272,7 @@ BOOL Evdev3BEmuFilterEvent(InputInfoPtr, int, BOOL);
 void Evdev3BEmuPreInit(InputInfoPtr pInfo);
 void Evdev3BEmuOn(InputInfoPtr);
 void Evdev3BEmuFinalize(InputInfoPtr);
-void Evdev3BEmuProcessRelMotion(InputInfoPtr pInfo, int dx, int dy);
+void Evdev3BEmuProcessRelMotion(InputInfoPtr pInfo, double dx, double dy);
 void Evdev3BEmuProcessAbsMotion(InputInfoPtr pInfo, ValuatorMask *vals);
 
 /* Mouse Wheel emulation */