Wayland backend abstraction: WMBackend vtable (Phases 0–30)
Introduce a display-system-agnostic WMBackend vtable that routes all
display operations through function pointers, making the WM policy
layer independent of X11. The X11 implementation is preserved in
src/backend/x11/ and behaviour is unchanged.
Key structural changes
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• src/backend/backend_types.h — backend-neutral type definitions:
WNativeWindow, WKeyCode, WContextKey, WBackendScreen,
WBackendEvent (+typed fields), WNormalHints, WWMHints,
WNETWindowType, WHeadGeometry, WClientAttributes, WClientVisual,
WSegment, WPoint, WM_KEY_* keysym constants, WA_* atom IDs,
WKB_GROUP*_INDEX, WCUR_NONE
• src/backend/backend.h — WMBackend vtable (~100 function-pointer
slots) covering: frame/context lifecycle, stacking, focus, grabs,
pointer, keyboard, overlays, properties, ICCCM, EWMH/NETWM,
monitors, screen setup, cursors, extensions, error handlers.
No <X11/> headers remain in this file after Phase 30.
• src/backend/x11/ — X11 backend implementation:
x11_backend.c full vtable; all display calls confined here
x11_props.c WM_NORMAL_HINTS / WM_HINTS translation
x11_event.c XEvent → WBackendEvent translation
x11_monitor.c Xinerama / RandR monitor query
Policy files cleaned
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All 47 files in WM_POLICY_CLEAN_FILES pass check-no-x11-policy
(no direct #include <X11/> anywhere). X11 types that still appear
in policy structs (Visual*, Colormap, Window, Atom …) arrive only
transitively via WINGs.h; the vtable boundary itself is X11-free.
Tests
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• tests/smoke-test.sh — full Xvfb lifecycle test (PASS)
• tests/test_geom.c — geometry / constraint unit tests
• tests/test_x11_event.c — WBackendEvent field extraction tests
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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