1 files changed, 60 insertions, 20 deletions

diff --git a/xorg-server/dix/getevents.c b/xorg-server/dix/getevents.c
index 366bc9558..694a8eba3 100644
--- a/xorg-server/dix/getevents.c
+++ b/xorg-server/dix/getevents.c
@@ -781,27 +781,65 @@ add_to_scroll_valuator(DeviceIntPtr dev, ValuatorMask *mask, int valuator, doubl
 }
 
 
+/* FIXME: relative events from devices with absolute axis ranges is
+   fundamentally broken. We map the device coordinate range into the screen
+   range, but don't really account for device resolution in that.
+
+   what we do here is a hack to make touchpads usable. for a given relative
+   motion vector in device coordinates:
+   1. calculate physical movement on the device in metres
+   2. calculate pixel vector that is the same physical movement on the
+      screen (times some magic number to provide sensible base speed)
+   3. calculate what percentage this vector is of the current screen
+      width/height
+   4. calculate equivalent vector in % on the device's min/max axis range
+   5. Use that device vector as the actual motion vector
+
+   e.g. 10/50mm on the device, 10/50mm on the screen are 30/100 pixels,
+   30/100 pixels are 1/3% of the width, 1/3% of the device is a vector of
+   20/80 -> use 20/80 as dx/dy.
+
+   dx/dy is then applied to the current position in device coordinates,
+   mapped to screen coordinates and thus the movement on the screen reflects
+   the motion direction on the device.
+ */
 static void
 scale_for_device_resolution(DeviceIntPtr dev, ValuatorMask *mask)
 {
-    double y;
+    double x, y;
     ValuatorClassPtr v = dev->valuator;
     int xrange = v->axes[0].max_value - v->axes[0].min_value + 1;
     int yrange = v->axes[1].max_value - v->axes[1].min_value + 1;
 
-    double screen_ratio = 1.0 * screenInfo.width/screenInfo.height;
-    double device_ratio = 1.0 * xrange/yrange;
-    double resolution_ratio = 1.0;
-    double ratio;
+    /* Assume 100 units/m for devices without resolution */
+    int xres = 100000, yres = 100000;
 
-    if (!valuator_mask_fetch_double(mask, 1, &y))
-        return;
+    /* If we have multiple screens with different dpi, it gets complicated:
+       we have to map which screen we're on and then take the dpi of that
+       screen to be somewhat accurate.  */
+    const ScreenPtr s = screenInfo.screens[0];
+    const double screen_res = 1000.0 * s->width/s->mmWidth; /* units/m */
 
-    if (v->axes[0].resolution != 0 && v->axes[1].resolution != 0)
-        resolution_ratio = 1.0 * v->axes[0].resolution/v->axes[1].resolution;
+    /* some magic multiplier, so unaccelerated movement of x mm on the
+       device reflects x * magic mm on the screen */
+    const double magic = 4;
 
-    ratio = device_ratio/resolution_ratio/screen_ratio;
-    valuator_mask_set_double(mask, 1, y / ratio);
+    if (v->axes[0].resolution != 0 && v->axes[1].resolution != 0) {
+        xres = v->axes[0].resolution;
+        yres = v->axes[1].resolution;
+    }
+
+    if (valuator_mask_isset(mask, 0)) {
+        x = valuator_mask_get_double(mask, 0);
+        x = magic * x/xres * screen_res/screenInfo.width * xrange;
+        valuator_mask_set_double(mask, 0, x);
+    }
+
+    if (valuator_mask_isset(mask, 1)) {
+        y = valuator_mask_get_double(mask, 1);
+        y = magic * y/yres * screen_res/screenInfo.height * yrange;
+        valuator_mask_set_double(mask, 1, y);
+    }
 }
 
 /**
@@ -815,15 +853,6 @@ moveRelative(DeviceIntPtr dev, int flags, ValuatorMask *mask)
 {
     int i;
     Bool clip_xy = IsMaster(dev) || !IsFloating(dev);
-    ValuatorClassPtr v = dev->valuator;
-
-    /* for abs devices in relative mode, we've just scaled wrong, since we
-       mapped the device's shape into the screen shape. Undo this. */
-    if ((flags & POINTER_ABSOLUTE) == 0 && v && v->numAxes > 1 &&
-        v->axes[0].min_value < v->axes[0].max_value &&
-        v->axes[1].min_value < v->axes[1].max_value) {
-        scale_for_device_resolution(dev, mask);
-    }
 
     /* calc other axes, clip, drop back into valuators */
     for (i = 0; i < valuator_mask_size(mask); i++) {
@@ -1457,10 +1486,21 @@ fill_pointer_events(InternalEvent *events, DeviceIntPtr pDev, int type,
             set_raw_valuators(raw, &mask, raw->valuators.data);
     }
     else {
+        ValuatorClassPtr v = pDev->valuator;
+
         transformRelative(pDev, &mask);
 
+        /* for abs devices in relative mode, we've just scaled wrong, since we
+           mapped the device's shape into the screen shape. Undo this. */
+        if (v && v->numAxes > 1 &&
+            v->axes[0].min_value < v->axes[0].max_value &&
+            v->axes[1].min_value < v->axes[1].max_value) {
+            scale_for_device_resolution(pDev, &mask);
+        }
+
         if (flags & POINTER_ACCELERATE)
             accelPointer(pDev, &mask, ms);
+
         if ((flags & POINTER_NORAW) == 0 && raw)
             set_raw_valuators(raw, &mask, raw->valuators.data);