Development/Debugging Tablet Issues
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.
 Workaround: Disable tablet support
 Workaround: Ignore low tablet pressure
 Test Input Devices in MyPaint
 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.
Note: You get the output below only for MyPaint <= 1.1.0 (GTK2), newer versions (GTK3) don't print it.
If everything is fine, MyPaint should print 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).
 Check X11/xorg pressure support (Linux)
 Testing GTK3 tablet support
The GTK+ source tree has a program called testinput.c for testing pressure sensitivity. The easiest way to compile this program is to compile the whole GTK+. (Use --enable-debug=yes while you're at it.) Then run tests/testinput.
You may also want to enable some debug prints by setting the environment variable GDK_DEBUG=input,events described in the gtk-running GTK+ documentation page. This should print all input devices to stdout when a GTK+ application starts.
GTK+ tablet bugs should be reported at gnome bugzilla.