The driver has historically normalized the pressure range of all kernel
devices to 0..2047 rather than using their native range to keep things
like the application of the pressure curve simple. Pens that report more
than 2048 pressure levels are also normalized down to this range though,
reducing their precision. In order to accomodate the new 8K pen (and any
future pens with even higher precision), this patch bumps up the full-
scale range to be 0..65535. This number was chosen both because it far
exceeds anything currently known about, and also because it matches the
normalization range used over the wire by the Wayland tablet protocol.
Note that the WACOM_PROP_PRESSURE_THRESHOLD value has been tied to the
normalized (2048-level) pressure range for some time, meaning that we
cannot simply change the range without causing a change in the perceived
threshold for users. To ensure compatibility, the value is interpreted
as a fraction of 2048 and then scaled to the actual normalization range.
Signed-off-by: Jason Gerecke <jason.gere...@wacom.com>
---
Changes from v1:
* Added helper functions to isolate the scaling to/from the 2048-level
range historically used.
src/wcmXCommand.c | 26 +++++++++++++++++++++++++-
src/xf86WacomDefs.h | 2 +-
2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/src/wcmXCommand.c b/src/wcmXCommand.c
index 02278ba..df7fcea 100644
--- a/src/wcmXCommand.c
+++ b/src/wcmXCommand.c
@@ -104,6 +104,26 @@ static Atom prop_debuglevels;
#endif
/**
+ * Calculate a user-visible pressure level from a driver-internal pressure
+ * level. Pressure settings exposed to the user assume a range of 0-2047
+ * while the driver scales everything to a range of 0-FILTER_PRESSURE_RES.
+ */
+static inline int wcmInternalToUserPressure(int pressure)
+{
+ return pressure / (FILTER_PRESSURE_RES / 2048);
+}
+
+/**
+ * Calculate a driver-internal pressure level from a user-visible pressure
+ * level. Pressure settings exposed to the user assume a range of 0-2047
+ * while the driver scales everything to a range of 0-FILTER_PRESSURE_RES.
+ */
+static inline int wcmUserToInternalPressure(int pressure)
+{
+ return pressure * (FILTER_PRESSURE_RES / 2048);
+}
+
+/**
* Resets an arbitrary Action property, given a pointer to the old
* handler and information about the new Action.
*/
@@ -256,6 +276,7 @@ void InitWcmDeviceProperties(InputInfoPtr pInfo)
}
values[0] = (!common->wcmMaxZ) ? 0 : common->wcmThreshold;
+ values[0] = wcmInternalToUserPressure(values[0]);
prop_threshold = InitWcmAtom(pInfo->dev, WACOM_PROP_PRESSURE_THRESHOLD,
XA_INTEGER, 32, 1, values);
values[0] = common->wcmSuppress;
@@ -827,6 +848,7 @@ int wcmSetProperty(DeviceIntPtr dev, Atom property,
XIPropertyValuePtr prop,
common->wcmCursorProxoutDist = value;
} else if (property == prop_threshold)
{
+ const INT32 MAXIMUM =
wcmInternalToUserPressure(FILTER_PRESSURE_RES);
INT32 value;
if (prop->size != 1 || prop->format != 32)
@@ -836,8 +858,10 @@ int wcmSetProperty(DeviceIntPtr dev, Atom property,
XIPropertyValuePtr prop,
if (value == -1)
value = DEFAULT_THRESHOLD;
- else if ((value < 1) || (value > FILTER_PRESSURE_RES))
+ else if ((value < 1) || (value > MAXIMUM))
return BadValue;
+ else
+ value = wcmUserToInternalPressure(value);
if (!checkonly)
common->wcmThreshold = value;
diff --git a/src/xf86WacomDefs.h b/src/xf86WacomDefs.h
index 31355ed..3961545 100644
--- a/src/xf86WacomDefs.h
+++ b/src/xf86WacomDefs.h
@@ -180,7 +180,7 @@ struct _WacomModel
#define IsUSBDevice(common) ((common)->wcmDevCls == &gWacomUSBDevice)
-#define FILTER_PRESSURE_RES 2048 /* maximum points in pressure curve */
+#define FILTER_PRESSURE_RES 65536 /* maximum points in pressure curve */
/* Tested result for setting the pressure threshold to a reasonable value */
#define THRESHOLD_TOLERANCE (FILTER_PRESSURE_RES / 125)
#define DEFAULT_THRESHOLD (FILTER_PRESSURE_RES / 75)
--
2.10.1
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