No stroke break when changing pen tools

[kelvinwop]

I use a surface pro 3 and a two button pen. I have it set so that when I press down the 'eraser' button on the pen (lower button), it automatically switches to the tool in hotkey 1 (eraser) and erases. The problem comes when I let go of the eraser button. It creates a large mess of lines right under my pen.

[edit: rotated the images so they're right side up]

Basic system details

MyPaint version: [1.3.0-alpha+git.aefccd44]
Operating system: [windows 10, default os on surface 3 pro]
Desktop environment: [windows I guess?]

Steps to reproduce

1. Start MyPaint
2. Use surface pro with pen
3. When pressing down on the pen eraser tool (doesn't erase by default), also select the hotkey with your eraser, thus binding that key to the eraser.
4. Using your pen normally (not with eraser button pressed down), draw some lines.
5. Erase some stuff (or none at all) by using the press the bound button method.
6. Let go of the eraser button
7. See lines where you erased and cry.

Backtraces or error messages

[n/a]

[achadwick]

I'm still surprised you've got so far with a surface 3, and that it's pressure-sensitive at all (still remembering the bad days of #484).

Can you expand on the detail a bit please? I'm having difficulty understanding what you've configured MyPaint or your drivers to do (hotkey means what?), and which order you do the (pen nib touches screen) (additional button pressed) (pen nib moved way from screen) (additional button released) events when it happens.

(Is there any order where it does not happen?)

(I don't have a Surface 3 myself. It might be hard to reproduce this. I can have a go with a pile of Linux, Win7, and random tablets though.)

[briend]

I have a feeling these weird lines that appear are actually delayed dabs that are catching up. So when you release the button and eraser goes back to normal, the delayed marks are getting the new setting (non-eraser) and thus... it draws lines?

You could confirm this by repeating your test... do your erasing but then stop moving the stylus for a few seconds, THEN release the button to go back to normal mode. I bet you won't have lines.

[kelvinwop]

For the erasing, when I hold down the additional button and press '1' (my eraser pen), then whenever I press that additional button, it uses the eraser pen.
But the problem comes when I'm done erasing. When I move the nib away from the screen, the stroke isn't broken or something and it creates an extra mark on the screen.

[kelvinwop]

Video.zip

[briend]

Oh I thought the "circle" you drew was part of the problem. You're just talking about that tiny dot, or very short stroke. Hmmm..

[kelvinwop]

Yeah, the strokes get really crazy when it's lagging or something. Sometimes the strokes cover like half the screen too, but I'm not really sure how that happens.

[briend]

Ok wait a second. Do you have the eraser button configured somehow to send the "1" key when you press it? If you open a notepad and press and hold the eraser button, does it send a stream of "1"s to the window? like "11111111111111111"?

[kelvinwop]

No, I configured it that way by pressing 1 when toggling the erase button. I guess mypaint recognizes the pen as a different pen when the erase button is held down which is why whenever I use the erase pen, I never have to switch to the erase tool using my keyboard.