Bug 514775

Summary:	Third-party EMR pen does not reflect s-pen action settings (Wacom One pen on Galaxy Tab)
Product:	[Applications] krita	Reporter:	eiedail
Component:	Shortcuts and Canvas Input Settings	Assignee:	Krita Bugs <krita-bugs-null>
Status:	REPORTED ---
Severity:	minor	CC:	dra.w.p.il.e+bugskde
Priority:	NOR
Version First Reported In:	5.2.14
Target Milestone:	---
Platform:	Android
OS:	Other
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description eiedail 2026-01-18 02:09:03 UTC

SUMMARY
Using a Wacom One standard pen (second generation) on a Samsung Galaxy Tab S10 Lite running Android 16.
The Wacom One pen has two side buttons, both of which are customizable in Clip Studio Paint.

The lower button functions as desired in Krita; it registers as the middle mouse button and can be remapped normally. I currently have it set to toggle the eraser preset after deleting the middle mouse pan input, and have had no issues so far.

The upper button on the pen does not register as an input at all in Krita when setting hotkeys and shortcuts, though it functions as a button. Setting S-pen action functions does nothing and it seems like it might be coded as a tail switch rather than a side button; when it is clicked, the cursor becomes a generic black pointer, and toggles the eraser on, regardless of chosen function in s-pen settings. The eraser itself can be toggled off while this mode is active to access the intended tool, but as it stands, the button is not functioning as desired and/or the button type is not supported correctly in Krita.


STEPS TO REPRODUCE
1. Krita Settings Configuration > S-Pen Actions > Set single click to desired function other than "erase"
2. Click upper button while drawing; cursor becomes a solid black pointer and the eraser is activated instead of the desired tool/function
3. Manually select desired tool while still in this black pointer mode.
3. Toggle eraser off while still holding pen close to screen; selected tool appears as expected and the toggle works thereafter (mostly)


OBSERVED RESULT
After setting the S-Pen button function to "sample screen color" or "color sampler" (I tried both) the upper button on the Wacom One pen instead activates the eraser, displaying a black pointer over the cursor. The desired tool must then be selected manually while taking care not to move the nib away from the screen. Once the tool has been selected and eraser toggled off while still in the black cursor mode, the button toggles the tool as expected until the program is closed, even when the pen is moved away and back.

(Note that it also did this when MMB was set to pan)

When the program is restarted, the shortcut activated by the upper button reverts completely to eraser by default, and will require the user to manually choose the correct tool again for the button to function as desired.

The S-pen action settings do not seem to have any effect on button functionality at all.


EXPECTED RESULT
Clicking the side button should activate whatever function has been assigned in the S-Pen Action settings and/or the button should be recognized as an input for shortcuts so that custom functions can be assigned.

Alternately, some kind of tail switch customization/input option may alleviate this problem, if it is in fact an issue with the button being read as a tail switch rather than a side button. Clip Studio Paint has functional tail switch customization, so I have to imagine it's possible to implement somehow.

- - -
SOFTWARE/HARDWARE:
Android 16, One UI 8.0 (Samsung Galaxy Tab S10 Lite)
Krita 5.2.14
Wacom One Standard Pen (CP92303B2Z) with two side buttons
- - -

ADDITIONAL INFORMATION
In Krita's Tablet Settings tablet tester interface, clicking this upper button and touching the nib to the test screen activates the "eraser brought near" text. (If it is merely clicked without touching the screen, no text is displayed, unlike the primary button which displays "stylus release" coordinates when clicked near the screen.) 

I have to assume the top button on the Wacom One pen (and on single-button styluses with the same problem) is coded as an eraser button rather than a side button, and in fact in Clip Studio Paint its functionality is mapped to "tail switch," so this might be why it forces the eraser and may also be why it doesn't register as an input for shortcuts, but unfortunately I don't see any tail switch options in Krita.

Comment 1 dra.w.p.il.e+bugskde 2026-01-18 03:33:51 UTC

It's a hard for me to comprehend the behavior you're observing.

1. I don't understand at all what you're describing with regards to erase mode and tool switching. What do these have to do with each other? Switching tools and toggling a brush mode should be unrelated functions.

2. When does the upper button react, when you press it while the pen is in the air or when you hold it and press the pen down? You say that it switches to the eraser when pressed, but then later that the tablet tester only reacts when you press the button and put then pen down.

Otherwise, there have been some recent fixes with how stylus buttons on external Wacom tablets behave. I don't think it should have an effect on how this stylus is behaving, but can you check if that makes a difference? You can do so by installing Krita Next, which is available on the downloads page on krita.org when you scroll down: https://krita.org/en/download/. It should be a separate application to the regular Krita, so you shouldn't need to uninstall the one you already have.

With regards to your expectations, "S-Pen Actions" are something that interacts with the setting under the same unfortunate name in the Samsung Android system. That setting only show up with the S-Pen Pro I think, so anything you're doing here is unrelated, since you're not performing "S-Pen Actions", it's just normal stylus inputs.

Comment 2 eiedail 2026-01-18 04:19:26 UTC

(In reply to dra.w.p.il.e+bugskde from comment #1)
> It's a hard for me to comprehend the behavior you're observing.
> 
> 1. I don't understand at all what you're describing with regards to erase
> mode and tool switching. What do these have to do with each other? Switching
> tools and toggling a brush mode should be unrelated functions.
> 
> 2. When does the upper button react, when you press it while the pen is in
> the air or when you hold it and press the pen down? You say that it switches
> to the eraser when pressed, but then later that the tablet tester only
> reacts when you press the button and put then pen down.
> 
> Otherwise, there have been some recent fixes with how stylus buttons on
> external Wacom tablets behave. I don't think it should have an effect on how
> this stylus is behaving, but can you check if that makes a difference? You
> can do so by installing Krita Next, which is available on the downloads page
> on krita.org when you scroll down: https://krita.org/en/download/. It should
> be a separate application to the regular Krita, so you shouldn't need to
> uninstall the one you already have.
> 
> With regards to your expectations, "S-Pen Actions" are something that
> interacts with the setting under the same unfortunate name in the Samsung
> Android system. That setting only show up with the S-Pen Pro I think, so
> anything you're doing here is unrelated, since you're not performing "S-Pen
> Actions", it's just normal stylus inputs.


Sorry, tried to be as clear as possible but hopefully I can clarify.

1. What I meant was just that I'm trying to set the button to toggle to a specific function, whether that is the eraser, or some other brush or tool. One of the buttons is easily set to a custom function, while the other seems to not work the same, since I can't actually use it as an input when adding shortcuts. But if the s-pen actions are only for pro pens as you mention, I guess that means I just can't change that particular button's function.

2. While drawing, the button can be clicked to activate its function by simply hovering over the screen with the cursor visible, as expected. I don't need to touch the screen to do this. The only place it needs to have the nib touch the screen is in the testing window, nowhere else. I didn't know if this was useful information but I wanted to be thorough. It might have just been an irrelevant quirk in how the program tests pen function. Apologies for the confusion.

I didn't know that about s-pen actions, so I appreciate the heads-up! It would certainly explain why nothing seems to change when I adjust those settings. So I guess that means the button just isn't really remappable as-is, which is unfortunate, but not a huge problem, at least.

I'll try installing Krita Next and see if that helps, thanks for the tip!

Comment 3 dra.w.p.il.e+bugskde 2026-01-18 13:08:06 UTC

Alright, thanks! So, then my understanding is: the lower button is always middle-click and the upper button always acts as if you switched the stylus to an eraser tip? Like, basically emulating a stylus where you have a pen tip on one side and an eraser tip on the other, but with a button instead.

In which case I guess there wouldn't be a bug, but a feature request to let you assign some other action to switching between pen tips. Which does make sense as a feature in general.

And I guess maybe we should rename those "S-Pen Actions" or add some kind of note that it's only for the S-Pen Pro, I can see how it's confusing in the current state.

Comment 4 eiedail 2026-01-18 23:14:17 UTC

Yes that seems to be what's happening.
so you're right, it is more of a feature request now that I better understand what it's actually trying to do. Not sure how to change that myself.

And yeah, a little note about the s-pen actions being specific to the pro stylus would definitely help clarify what that does.

Comment 5 Bug Janitor Service 2026-01-19 03:47:35 UTC

🐛🧹 Thanks for your comment!

Automatically switching the status to REPORTED so the team can perform further triage.

In the future you may also do this yourself when providing needed information.