Fix #4967: a drawing tablet's pen draws on a Wayland session by default

On a Wayland session Linux Display Server's default, Automatic, opened
the window on native Wayland. winit 0.30 doesn't bind the Wayland tablet
protocol, and KWin (since Plasma 6.3) and Mutter turn no tablet input
into pointer input, so the pen moved only the compositor's cursor and
the app got no motion or presses. Only X11 (XWayland) When a Pen Is
Attached, which users had to find and choose, sent the window through
XWayland, where the pen works as a mouse with its pressure.

Automatic now opens the window through XWayland when a pen is attached
as the app starts, as PhotoCraft does by default.
VECTORCRAFT_NATIVE_WAYLAND=1 keeps the window on Wayland, like
PhotoCraft's PHOTOCRAFT_NATIVE_WAYLAND. The X11 choice is unchanged.

docs/hardware-parity.md

@@ -1,6 +1,6 @@
 # Hardware parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-30 · **Change:** patch (a second finger cancels the tool press the first finger began, and a finger landing while another is down presses nothing; the pinch only navigates, #4198) · **Target:** Adobe Illustrator 2026 (30.x)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-01 · **Change:** patch (Linux: on a Wayland session with a pen attached, Automatic opens the window through XWayland, where the pen draws, #4967) · **Target:** Adobe Illustrator 2026 (30.x)
 
 What hardware Illustrator uses, per platform, against VectorCraft. Illustrator's side is from its public
 documentation (GPU Performance, touch workspace, pen pressure pages); ours from the code
@@ -21,7 +21,7 @@ reads the pen's eraser end on Windows, on macOS and on Linux under X11 and XWayl
 | Multithreaded rendering off the UI thread | partial | yes | yes | yes | single-threaded | beyond Illustrator |
 | Hybrid-graphics GPU choice | automatic | power-saving GPU by default, Preferences › Graphics Processor | same; DX12 then OpenGL; no Vulkan unless asked (#545, #806) | the desktop's GPU | browser | done |
 | Restart on another GPU when the first fails to present | — | yes (#502, #964) | yes | yes | restart on lost device (#369) | done |
-| Pen pressure | yes (Wacom, Windows Ink, macOS tablet events) | yes, read from AppKit's tablet events before the window gets them (winit reports none), each move of a stroke with its own pressure, mouse event coalescing off (#852; not yet tried on a Mac) | yes (pointer force via `WM_POINTER`) | under X11 and XWayland (Preferences › Performance › Linux Display Server, #1151, #2028), read from XInput2 raw events (#764); **no** on native Wayland, where winit reports none and the pen may not reach the window (#491) | browser pointer events, with coalesced events; Apple Pencil on iPad (hover, palm rejection: fingers navigate after a pen contact until reload) | partial: 2–4 h for Wayland (winit 0.31), plus a check on a Mac |
+| Pen pressure | yes (Wacom, Windows Ink, macOS tablet events) | yes, read from AppKit's tablet events before the window gets them (winit reports none), each move of a stroke with its own pressure, mouse event coalescing off (#852; not yet tried on a Mac) | yes (pointer force via `WM_POINTER`) | under X11 and XWayland (Preferences › Performance › Linux Display Server, #1151, #2028; Automatic uses XWayland when a pen is attached on a Wayland session, #4967), read from XInput2 raw events (#764); **no** on native Wayland, where winit reports none and the pen may not reach the window (#491) | browser pointer events, with coalesced events; Apple Pencil on iPad (hover, palm rejection: fingers navigate after a pen contact until reload) | partial: 2–4 h for Wayland (winit 0.31), plus a check on a Mac |
 | Pen tilt, bearing, barrel rotation (6D Art Pen) | yes, drives brushes | no | no | no | no | missing: 4–8 h after the input layer (#372) |
 | Pen eraser end | yes | the eraser end (AppKit's tablet proximity events) selects the Eraser tool and the tip brings back the tool used before, as on Linux (#852; not yet tried on a Mac) | no | under X11 and XWayland, the eraser end selects the Eraser tool and the tip brings back the tool used before (#764); **no** on native Wayland | a press of the eraser end (Pointer Events eraser button, `button` 5) selects the Eraser tool, and that press erases; a press of the tip brings back the tool used before; Pointer Events report no end while the pen hovers | partial |
 | Pen eraser end | yes | the eraser end (AppKit's tablet proximity events) selects the Eraser tool and the tip brings back the tool used before, as on Linux (#852; not yet tried on a Mac) | with Windows Ink, an inverted pen or its eraser button (`PEN_FLAG_INVERTED`, `PEN_FLAG_ERASER` in the pen's pointer messages) selects the Eraser tool and the tip brings back the tool used before, as on Linux (not yet tried with a pen) | under X11 and XWayland, the eraser end selects the Eraser tool and the tip brings back the tool used before (#764); **no** on native Wayland | no | partial |
@@ -36,6 +36,7 @@ reads the pen's eraser end on Windows, on macOS and on Linux under X11 and XWayl
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-11-01 | patch | Linux (#4967): on a Wayland session, Linux Display Server › Automatic opens the window through XWayland when a pen is attached as the app starts, as X11 (XWayland) When a Pen Is Attached does and as PhotoCraft does; on native Wayland winit 0.30 gets no tablet input and KWin 6.3+ and Mutter emulate no pointer, so the pen moved only the compositor's cursor. `VECTORCRAFT_NATIVE_WAYLAND=1` keeps Wayland. Unit-tested (`xwayland::tests`); not tried with a tablet; score unchanged (estimated) |
 | 2026-10-30 | patch | Touch (#4198): a second finger landing cancels the tool press the first finger began, also in the same frame (the Pencil's stroke and a Selection move are rolled back, nothing enters the undo history), and a finger landing while another is down presses nothing, so a pinch or two-finger pan only navigates. Headless canvas test `a_second_finger_cancels_the_tool_gesture_the_first_began`; not tried on a touch screen; score unchanged (estimated) |
 | 2026-10-24 | minor | macOS: an AppKit local event monitor reads each mouse and tablet event's pen pressure and the pen's end before the window gets it and writes them into the canvas's pen feed (#852): each pointer move of a stroke keeps its own pressure, mouse event coalescing is off, and the eraser end selects the Eraser tool. The mapping is unit-tested on every platform and the macOS code type-checks for `aarch64-apple-darwin`; not yet tried on a Mac with a tablet, so the score is unchanged (estimated) |
 | 2026-10-15 | patch | Web review: preserve pen buttons and modifiers; leave fingers to eframe before the first pen contact; remove persistent pen policy. Canvas regression tests cover intermediate moves and long-touch cancellation on native and web input. Physical-device QA pending. |