Development/Debugging Tablet Issues

From MyPaint

This page aims to tell you how to collect more information if MyPaint fails because of tablet issues. This can also happen if you don't have a tablet! The symptoms are usually one of the following:

• No stroke happens when trying to paint.
• Tablet pressure does not work.
• Clicking on GUI elements has no effects.
• There is an offset between the cursor and the actual stroke.
• MyPaint crashes immediately when trying to paint.

Contents 1 Workaround: Disable tablet support 2 Workaround: Ignore low tablet pressure 3 Check MyPaint STDOUT 4 Check X11/xorg pressure support (Linux) 5 Dialog: Test Input Devices 6 Further Reading

[edit] Workaround: Disable tablet support

From the menu, choose Edit --> Preferences. This usually fixes all problems:

[edit] Workaround: Ignore low tablet pressure

This usually helps if you are seeing "ghost lines" between strokes, or if you cannot use "redo" after "undo" because you are always painting very faint (invisible) strokes:

[edit] Check MyPaint STDOUT

On Linux: start MyPaint from the console rather than from the menu. If you didn't compile it yourself: open a terminal, type "mypaint" and press return.
On Windows: after quitting MyPaint, go into the "Local Settings" folder (or similar) where you find a folder called "mypaint". Open mypaint_error.log with a text editor. Scroll down to the end for the latest log.

If everything is fine, MyPaint should print (amog other things) something like this:

Setting screen mode for "Wacom Graphire3 eraser"
Ignoring "Wacom Graphire3 cursor" (probably wacom mouse device)
Setting screen mode for "Wacom Graphire3 stylus"

If your tablet is not set into "screen mode", it was not recognized as a tablet and pressure will not work.

If "screen mode" is set for a device that doesn't sense different levels of pressure, something is wrong.

If this is your issue, a note: GTK currently detects whether a device is a pen by checking the device name. If the lowercase name contains the substring "wacom" or "pen" (but not "cursor") then GTK will report it as GDK_SOURCE_PEN. Simplified, MyPaint will look at the number of axes of all GDK_SOURCE_PEN devices, and enable "screen" mode for all devices that have a third axis (which should be the pressure axis).

[edit] Check X11/xorg pressure support (Linux)

You should see your tablet in this list, and you should see pressure change in the hilighted column:

[edit] Dialog: Test Input Devices

The second screenshot shows how it looks if everything is working fine (click to enlarge):

[edit] Further Reading

• GIMPtalk guide about wacom tablets