[PATCH] dix: scale y back instead of x up when pre-scaling coordinates

[Peter Hutterer]

The peculiar way we handle coordinates results in relative coordinates on
absolute devices being added to the last value, then that value is mapped to
the screen (taking the device dimensions into account). From that mapped
value we get the final coordinates, both screen and device coordinates.

To avoid uneven scaling on relative coordinates, they are pre-scaled by
screen ratio:resolution:device ratio factor before being mapped. This
ensures that a circle drawn on the device is a circle on the screen.

Previously, we used the ratio to scale x up. Synaptics already does its own
scaling based on the resolution and that is done by scaling y down by the
ratio. So we can remove the code from the driver and get approximately the
same behaviour here.

Minor ABI bump, so we can remove this from synaptics.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
This is a follow-up to 5cc2c96f824dbb28b9f8da61efc41596f8bd0561, same commit
was c-p to the 1.14 branch as 14d89b9a46 and then reverted (7dec1d38799).

What 5cc2c added was resolution-based scaling, but because the synaptics
driver applied the resolution ratio already it ended up being double-scaled.
That's the regression Emmanuel found. With this commit (and the follow-up to
synaptics) we can avoid that and get the right behaviour.


 dix/getevents.c                | 6 +++---
 hw/xfree86/common/xf86Module.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/dix/getevents.c b/dix/getevents.c
index 51d4fd4..f5ab8c4 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -773,7 +773,7 @@ add_to_scroll_valuator(DeviceIntPtr dev, ValuatorMask *mask, int valuator, doubl
 static void
 scale_for_device_resolution(DeviceIntPtr dev, ValuatorMask *mask)
 {
-    double x;
+    double 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;
@@ -783,14 +783,14 @@ scale_for_device_resolution(DeviceIntPtr dev, ValuatorMask *mask)
     double resolution_ratio = 1.0;
     double ratio;
 
-    if (!valuator_mask_fetch_double(mask, 0, &x))
+    if (!valuator_mask_fetch_double(mask, 1, &y))
         return;
 
     if (v->axes[0].resolution != 0 && v->axes[1].resolution != 0)
         resolution_ratio = 1.0 * v->axes[0].resolution/v->axes[1].resolution;
 
     ratio = device_ratio/resolution_ratio/screen_ratio;
-    valuator_mask_set_double(mask, 0, x * ratio);
+    valuator_mask_set_double(mask, 1, y / ratio);
 }
 
 /**
diff --git a/hw/xfree86/common/xf86Module.h b/hw/xfree86/common/xf86Module.h
index 1393427..e0cec05 100644
--- a/hw/xfree86/common/xf86Module.h
+++ b/hw/xfree86/common/xf86Module.h
@@ -81,7 +81,7 @@ typedef enum {
  */
 #define ABI_ANSIC_VERSION	SET_ABI_VERSION(0, 4)
 #define ABI_VIDEODRV_VERSION	SET_ABI_VERSION(14, 1)
-#define ABI_XINPUT_VERSION	SET_ABI_VERSION(19, 1)
+#define ABI_XINPUT_VERSION	SET_ABI_VERSION(19, 2)
 #define ABI_EXTENSION_VERSION	SET_ABI_VERSION(7, 0)
 #define ABI_FONT_VERSION	SET_ABI_VERSION(0, 6)
 
-- 
1.8.2.1