Start with the device class
Why does Xournal++ think my pen is a mouse?
Xournal++ identifies input devices and assigns each one a class. A drawing tablet stylus may be detected as a mouse, a touchscreen may be classified incorrectly, or a wireless mouse and keyboard receiver may need to be treated as a combined device. When the class is wrong, pressure sensitivity, button behavior and text input can all feel broken even though the hardware works in another application.
Open Edit → Preferences and inspect the Input System tab. Each detected device is listed with its guessed type, and the device class can be overridden. A pen tip normally needs the Pen class for pressure-sensitive drawing. An eraser end can use the Eraser class when the hardware reports it separately. A normal pointer should remain a Mouse, while a touch display belongs in the Touchscreen class when you want gestures and touch behavior.
Input system choices
Which Xournal++ device class should you use?
| Device | Class to test | Common symptom when wrong |
|---|---|---|
| Drawing stylus tip | Pen | No pressure or pointer-like strokes |
| Stylus eraser end | Eraser | Eraser button behaves like a pen |
| Ordinary mouse | Mouse | Unexpected keyboard events from a receiver |
| Wireless mouse and keyboard receiver | Mouse + Keyboard Combo | Clicks or typing are ignored or misread |
| Pen-enabled display or touch panel | Touchscreen or Pen | Gestures, taps and strokes conflict |
| Problematic device | Disabled for testing | Useful to isolate the source of an event |
Troubleshooting sequence
Fix a stylus that is not drawing correctly
Test a blank page
Open a new page and draw with the pen, mouse and eraser separately. Note which device produces the wrong result.
Inspect Input System
Open Edit → Preferences → Input System and compare the detected device name with its assigned class.
Override the class
Set the stylus to Pen, the eraser to Eraser and a wireless combo receiver to Mouse + Keyboard Combo when appropriate.
Test pressure and buttons
Draw slow and fast strokes, try the side button and check whether the result changes before editing more preferences.
Pressure and smoothing
What if pressure sensitivity is still missing?
A pressure-sensitive device normally needs to be assigned to the Pen class. Check the tablet driver, the desktop session and the selected tool after making that change. If the device has no real pressure data, Xournal++ can use Enable Pressure Inference to estimate pressure from stroke speed. This can make a non-pressure input feel less uniform, but it is an inference rather than hardware pressure.
Smoothing changes the feel of handwriting but does not repair a device that is assigned to the wrong class. Test pressure first, then adjust smoothing and tool thickness on a blank page. If the mouse draws when you want to scroll, select the hand or selection workflow and review touch-drawing preferences. If only one application has a problem, compare the device in a simple drawing program before changing system drivers.
Mouse and touch behavior
Separate pointer problems from pen problems
A mouse that draws is not always a pressure-sensitivity issue. The active tool may still be the pen, the touch-drawing preference may allow a finger to create strokes, or a device may be sending both pointer and tablet events. Test one input at a time on a blank page: draw with the stylus, click with the mouse, touch once if you use a display, then switch to the eraser end. Write down which action creates the unexpected mark.
If only the side button behaves incorrectly, check the tablet driver's button mapping before changing the Xournal++ device class. If the eraser end changes tools but does not erase, verify that it is recognized as an Eraser and that the eraser tool or mode is available. If input becomes unstable after a driver update, restart Xournal++, reconnect the tablet and repeat the test before changing several preferences at once.
Repeatable calibration
Use a short test before changing smoothing
Pressure and smoothing are easier to judge with the same test every time. Draw a slow line, a fast line, a light line and a firm line, then write a few letters at the size you normally use. If the stroke width changes in a predictable way, the device is probably sending usable pressure data. If every mark has the same width, check the device class and driver before increasing smoothing. Smoothing can soften a shaky stroke, but it cannot create missing pressure events or repair a broken button mapping.
Input troubleshooting
A practical Xournal++ stylus setup checklist
Start a Xournal++ stylus check on a blank page so the PDF background cannot hide an input problem. Confirm that the pen creates a stroke, that the eraser end behaves as expected and that pressure changes line width when the device and driver support it. If the pen is detected as a mouse, inspect the Input System and device class before changing smoothing or pressure inference. A mouse drawing problem can also come from the active tool or a touch setting, so test a physical mouse separately.
Change one Xournal++ stylus setting at a time and record the original value. Pressure, button events, eraser handling and smoothing can interact, and a large group of changes makes it difficult to know which one fixed or caused the issue. Test the same device in a small .xopp notebook, then reopen it after saving. Tilt is a separate capability that depends on the tablet, driver and input stack; a missing tilt effect does not automatically mean the notebook is damaged. This Xournal++ stylus checklist keeps hardware, operating-system and application causes separate.
For a repeatable Xournal++ stylus test, use the same pen, mouse, blank page and four sample strokes after each change. This stylus routine separates pressure, eraser, button and smoothing behavior so a driver issue is not mistaken for an application preference.
Keep the Xournal++ stylus test consistent across sessions: use one blank page, one pen tool and one short set of strokes. A written Xournal++ stylus note can record the device class, driver and pressure result. This Xournal++ stylus record makes future troubleshooting faster after an operating-system or tablet-driver update.
Use the Xournal++ stylus procedure after every major driver change, save the Xournal++ stylus result beside the notebook and review the Xournal++ stylus log when behavior changes. A short Xournal++ stylus record is more useful than changing several pressure controls at once.
Frequently asked questions
Xournal++ Frequently asked questions
How do I get a pen icon or pen input in Xournal++?
Select the Pen tool in the toolbar, then check Edit → Preferences → Input System if the stylus is not recognized or behaves like a mouse.
Why is my Xournal++ mouse drawing instead of scrolling?
The active tool, touch-drawing setting or device class may be sending drawing events. Test the mouse on a blank page and inspect the Input System and drawing-area preferences.
How do I enable pressure sensitivity?
Assign the tablet stylus to the Pen device class and verify the tablet driver. Pressure Inference can estimate pressure for a device without native pressure data.
Can Xournal++ detect pen tilt?
Tilt support depends on the device, driver and input stack. First confirm that the stylus is correctly detected as a Pen; do not assume a missing tilt effect is caused by the notebook file.