Coordinate averaging is useful for producing smooth strokes, but this averaging can cause button events to be sent at the wrong location. In particular, when making a series of quick strokes with an AES pen, the actual location the pen contacts the display can be some distance away from the first (low-quality) position report. This can result in "hook" artifacts if it is still influencing the averaged pointer position when the pen goes down.
To prevent these artifacts from appearing, we reset the averaging filter whenever a button is pressed. This ensures that button events are sent at the pen's actual location, plus or minus some (much smaller) noise. Resetting the filter should not significantly impact stroke quality since buttons are rarely pressed mid-stroke. https://sourceforge.net/p/linuxwacom/bugs/338/ Signed-off-by: Jason Gerecke <jason.gere...@wacom.com> --- src/wcmCommon.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/wcmCommon.c b/src/wcmCommon.c index 900544b..e515078 100644 --- a/src/wcmCommon.c +++ b/src/wcmCommon.c @@ -1241,6 +1241,15 @@ static void commonDispatchDevice(InputInfoPtr pInfo, if (!priv->oldState.proximity) wcmResetSampleCounter(pChannel); + /* Reset filter whenever a button is pressed to + * ensure the clicks are sent at the pen's actual + * position. This prevents "hooks" from appearing + * at the beginning of series of rapidly-drawn or + * highly-averaged strokes. + */ + if ((priv->oldState.buttons ^ filtered.buttons) & filtered.buttons) + wcmResetSampleCounter(pChannel); + wcmFilterCoord(common,pChannel,&filtered); } -- 2.15.1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linuxwacom-devel mailing list Linuxwacom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxwacom-devel
