From: Chris Bagwell <ch...@cnpbagwell.com>
There is an implied agreement between kernel drivers and
user land to work around event filtering issues. Document
our current approach.
Also add some notes on issues/bugs that need to be addressed
in future patches.
Signed-off-by: Chris Bagwell <ch...@cnpbagwell.com>
---
src/wcmUSB.c | 35 +++++++++++++++++++++++++++++++++++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/src/wcmUSB.c b/src/wcmUSB.c
index 131627c..b489be0 100644
--- a/src/wcmUSB.c
+++ b/src/wcmUSB.c
@@ -1224,11 +1224,46 @@ static void usbParseEvents(InputInfoPtr pInfo)
pChannel = common->wcmChannel + channel;
dslast = pChannel->valid.state;
+ /* Because of input filtering, the kernel driver can not
+ * always force total set of data when new tool comes into
+ * proximity. Therefore, when new tool events are sent
+ * we must initialize all event values to same as previous
+ * tool to account for filtered events; for case when
+ * tools share events.
+ *
+ * To simplify things, we take advantage of fact kernel drivers
+ * force all values to zero when going out of proximity so we
+ * take a short cut and memset to align while going in-prox
+ * instead of tracking values of last tool that shares same
+ * events.
+ *
+ * TODO: The following discards data from drivers that send
+ * important non-zero data for current channel while out-of-prox.
+ * Adding "&& dslast.proximimty" to check would probably help
+ * this case.
+ * This also discards data for tablets that do not follow
+ * zero-on-out-prox rule. Adding a !WCM_PROTOCOL_GENERIC
+ * check ould probably help this case.
+ */
if (!common->wcmChannel[channel].work.proximity)
{
memset(&common->wcmChannel[channel],0,sizeof(WacomChannel));
/* in case the in-prox event was missing */
+ /* FIXME: Forcing in-prox will cause cursor
+ * jumps for drivers that send useful data
+ * while out-of-prox (WCM_PROTOCOL_GENERIC devices).
+ * This includes button presses on tablet for
+ * Bamboo touchpads.
+ *
+ * Probably, this logic was added to handle case of
+ * pen on tablet when x server first starts or before
+ * time we would process BTN_TOUCH event as replacement
+ * for missing BTN_TOOL_* event. The prior case
+ * is better handled elsewhere then each sync window
+ * and the later case needs to be imporved
+ * to know treat as BTN_TOOL_PEN instead of BTN_TOOL_DOUBLETAP.
+ */
common->wcmChannel[channel].work.proximity = 1;
}
--
1.7.3.1
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