Fix mouse input interference when drawing with stylus (Wine/Bottles + OTD)

[jaivu]

Fix: Mouse Input Interference When Drawing with Stylus

Problem

When using Krita (and other drawing apps) under Wine/Bottles with XWinTab, the stylus produced dual input both a Wintab stroke and a mouse stroke simultaneously. This caused red (mouse) lines to appear alongside blue (stylus) lines when drawing.

The root cause: Wine's X11 driver subscribes to core X11 pointer events independently of XWinTab's XInput subscription. When the stylus moves, the X server generates two events one for XWinTab (XInput) and one for Wine (core pointer) so the app sees both pen and mouse input at the same time.

Additionally, the existing g_PenIsDown branching in on_event() had both branches doing identical work, so it wasn't actually filtering anything.

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Changes in WinTab.c

1. Per-app mouse suppression hook (WH_MOUSE)

Installed on the app's message thread via SetWindowsHookExW in WTOpenW(), removed in WTClose().

App behavior is detected at open time using GetModuleFileNameW():

• Generic apps (Krita etc.) block WM_LBUTTONDOWN/UP while pen is down. This stops the duplicate mouse stroke while still allowing WM_MOUSEMOVE so the brush cursor follows the pen.
• Simple apps (MediBang, FireAlpaca) no mouse events blocked. These apps use WM_LBUTTONDOWN to trigger drawing mode but read position/pressure from Wintab packets directly, so blocking mouse events breaks pressure sensitivity. The x=0,y=0 button packet fix below is sufficient.

2. Fix x=0,y=0 button press packets

XCB button press/release events carry no coordinates (x=0, y=0). Previously these were forwarded as-is, causing MediBang and FireAlpaca to see the cursor jump to the top-left corner on every pen touch.

Fixed by tracking the last known position (g_lastPkX, g_lastPkY) from motion events and substituting it into button event packets.

3. Mouse mode toggle via barrel button (WH_KEYBOARD_LL)

For Krita users who need to interact with the UI using the pen (clicking buttons, panning etc.), a toggle is provided via the stylus lower barrel button.

Since OTD (OpenTabletDriver) injects barrel button events on its own thread, a thread-local WH_MOUSE hook cannot catch them. Instead, a system-wide WH_KEYBOARD_LL hook detects the mapped key (PageDown by default — configurable in OTD) and toggles g_mouseModeOverride. When active, WM_LBUTTONDOWN/UP suppression is disabled so the pen behaves like a mouse.

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Tested with

• Wacom CTL-490 + OpenTabletDriver v0.6.7
• Krita (Windows) under Bottles/Wine
• MediBang Paint (Windows) under Bottles/Wine
• FireAlpaca (Windows) under Bottles/Wine

Result

• No dual strokes in Krita
• Pen pressure working in MediBang and FireAlpaca
• Brush cursor follows pen during drawing
• Barrel button toggles mouse mode in Krita