bugMyPaint - Bugs: bug #20424, Click and Tap mode causes...

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bug #20424: Click and Tap mode causes undesired strokes with stylus buttons

Submitted by:  Carl Olsson <surt>
Submitted on:  Sat Jan 12 09:28:57 2013  
Severity: 3 - NormalPriority: 5 - Normal
Status: Need InfoPrivacy: Public
Assigned to: NoneOpen/Closed: Open
Release: 1.1.0~rc3+git20121231.5c8d4e8-1ppa1~quanPlanned Release: None
Operating System: Kubuntu 12.10 64-bit

Sun Jan 13 07:57:39 2013, comment #2:

With "Test Input Devices":
I can't figure out how to capture the output, but a button 1 press trigger single pair of BUTTON_PRESS and BUTTON_RELEASE events for "button=1", whereas a button 2 press triggers two pairs of BUTTON_PRESS and BUTTON_RELEASE events for "button=2" and "button=2 [drawWindow]". This looks to be identical on both Click and Tap mode and Hover Click mode.

With "Print Brush Input Values to Console":
Click and Tap mode:
press= 0.095, speed1=-0.4917 speed2= 0.1620 stroke= 0.002 custom= 0.000
press= 0.105, speed1=-0.5046 speed2= 0.1570 stroke= 0.003 custom= 0.000
DEBUG: mode stack updated: <ModeStack [SwitchableFreehandMode, PanViewMode]>
DEBUG: mode stack updated: <ModeStack [SwitchableFreehandMode]>
press= 0.000, speed1=-0.5078 speed2= 0.1558 stroke= 0.004 custom= 0.000
device change: Core Pointer <enum GDK_SOURCE_MOUSE of type GdkInputSource>
device change: Wacom Serial Penabled 1FG Touchscreen stylus <enum GDK_SOURCE_PEN of type GdkInputSource>
press= 0.000, speed1=-7.4696 speed2=-0.4249 stroke= 1.000 custom= 0.000
press= 0.000, speed1=-4.0536 speed2=-0.4245 stroke= 0.000 custom= 0.000

Hover Click mode:
press= 0.000, speed1= 0.3514 speed2= 0.0302 stroke= 0.351 custom= 0.000
press= 0.000, speed1= 0.3394 speed2= 0.0291 stroke= 0.352 custom= 0.000
DEBUG: mode stack updated: <ModeStack [SwitchableFreehandMode, PanViewMode]>
DEBUG: mode stack updated: <ModeStack [SwitchableFreehandMode]>
press= 0.000, speed1= 0.3341 speed2= 0.0286 stroke= 0.352 custom= 0.000
press= 0.000, speed1= 0.3724 speed2= 0.0411 stroke= 0.363 custom= 0.000

Carl Olsson <surt>
Sun Jan 13 07:27:20 2013, comment #1:

It's probably because MyPaint uses the reported pressure to paint, even when there has been no "button down" event. That's by design, because people often have a rather high "click threshold" by default. If we did only paint after "button down" (like other applications), the low pressure range of tablets becomes unusable.

It's also possible that your problems are caused by something else, though. Try to play around a bit with help->debug->test input devices to see what events are reported.

Martin Renold <martinxyz>
Project Administrator
Sat Jan 12 09:28:57 2013, original submission:

Kubuntu 12.10 64-bit on Fujitsu T5010 tablet PC

When using "Click and Tap" mode with a tablet (hold stylus button and tap tip to trigger button press) rather than "Hover Click" mode (in Kubuntu this can be toggled with the Pen "use Hover Click" setting under Graphic Tablet settings, though the checkbox seems to function opposite to its description), button 2 and button 3 taps (holding the button and tapping) seems to also produce a button 1 tap, leaving a short undesired paint stroke on the canvas.

If the brush is pressure responsive the result can be quite subtle as it only seems to stroke with a light pressure regardless of actual stylus pressure.

The attached image shows the result of button 2 and button 3 click-and-taps with a pressure-responsive brush and a non-pressure-responsive brush.

When using button 2 for panning the view this leaves lots of undesired dots over the canvas.

I've had this problem as long as I can remember (my whole experience with MyPaint as far as I can recall) on both Linux and windows, tablet and tablet PC and just been putting up with it or using space to pan the view.

The problem does not present with Gimp, Krita or anything else that I've tried.

Carl Olsson <surt>


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  • -unavailable- added by martinxyz (Posted a comment)
  • -unavailable- added by surt (Submitted the item)

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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sun Jan 13 07:27:20 2013martinxyzStatusNone=>Need Info
    Sat Jan 12 09:30:40 2013surtCarbon-CopyRemoved surt=>-
    Sat Jan 12 09:28:57 2013surtAttached File-=>Added mypaint_click_and_tap_bug.png, #16916
      Carbon-Copy-=>Added surt
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