Fix DTK titlebar minimize/close buttons disabled on Wayland (winId truncation)

[svan71]

Problem

On Wayland, DTK client-side titlebars (e.g. dde-control-center) render their minimize and close buttons permanently disabled — grayed out, no hover, no action. Only the menu/hamburger button works. The same binaries work correctly on X11 and worked on older Qt.

WindowButtonGroup.qml enables minimize/maximize/close only when D.DWindow.motifFunctions includes the corresponding FUNC_* bit. A runtime probe (a minimal DTK ApplicationWindow) shows motifFunctions stuck at 0x0 for the window's entire lifetime under a Wayland session.

Root cause

DQuickWindowAttachedPrivate::_q_onWindowMotifHintsChanged(quint32 winId) guards on window identity:

if (q->window()->winId() != winId)
    return;

The winId argument is a quint32 — both callers deliver it truncated to 32 bits: the SurfaceCreated path in eventFilter casts static_cast<quint32>(window->winId()), and the DWindowManagerHelper::windowMotifWMHintsChanged(quint32) signal is 32-bit by definition. But the guard compares it against QWindow::winId(), which returns the full-width WId (quintptr).

• On X11, WId is a 32-bit XID, so the comparison holds.
• On Wayland with Qt 6.11, WId is a pointer-derived value greater than 32 bits, so full64 != truncated32 is always true. The slot returns early, DWindowManagerHelper::getMotifFunctions() is never called, and motifFunctions is never updated from its 0 default — leaving all window buttons disabled.

This is why the regression appears "version-less": the DTK sources are unchanged; it is the Qt QtWayland winId assignment that shifted, exposing the latent width mismatch.

Fix

Compare the low 32 bits on both sides, matching the width the codebase already delivers. No public API/ABI change (windowMotifWMHintsChanged(quint32) is unchanged).

if (static_cast<quint32>(q->window()->winId()) != winId)
    return;

Verification

Minimal reproducer — a DTK ApplicationWindow that logs D.DWindow.motifFunctions on each poll, run inside a Treeland/Wayland session:

• Before: motifFunctions = 0 (0x0) for the whole run; minimize/close disabled.
• After: motifFunctions = 62 (0x3e) (FUNC_RESIZE|MOVE|MINIMIZE|MAXIMIZE|CLOSE); minimize/close enabled. dde-control-center titlebar buttons hover and work again.

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This pull-request has been approved by: svan71

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[deepin-ci-robot]

Hi @svan71. Thanks for your PR. 😃

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