Client: Refactor cursors and fix various bugs

This patch is mostly a cleanup to prepare for implementations of
xcursor-configuration, but also fixes a couple of issues.

Most of the logic has now been moved out of QWaylandDisplay and QWaylandCursor
and into QWaylandInputDevice and QWaylandInputDevice::Pointer. QWaylandDisplay
now only contains mechanisms for avoiding loading the same theme multiple
times.

There is now only one setCursor method on QWaylandInputDevice, accepting a
QCursor and storing its values so changing scale factor doesn't require calling
setCursor again. QWaylandInputDevice::Pointer::updateCursor() is called
instead.

Cursor buffer scale is now set according to enter/leave events of the cursor
surface itself instead of the current window, this fixes incorrect buffer
scales for cursors on windows that span multiple outputs. The window buffer
scale can still be passed into the seat as a fallback until the first enter
event is received.

This also fixes a bug where the QWaylandBuffer of a bitmap cursor could be
deleted while it was being used as a cursor.

[ChangeLog][QPA plugin] Fixed a bug where the DPI of bitmap cursors were not
sent to the compositor, leading to the compositor incorrectly scaling the
cursor up or down.

[ChangeLog][QPA plugin] Fixed a bug where bitmap cursor hotspots were off when
the screen scale factor was different from the bitmap cursor device pixel
ratio.

Task-number: QTBUG-68571
Change-Id: I747a47ffff01b7b5f6a0ede3552ab37884c4fa60
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 171 insertions, 78 deletions

diff --git a/src/client/qwaylandinputdevice.cpp b/src/client/qwaylandinputdevice.cpp
index 31495a453..cb26def68 100644
--- a/src/client/qwaylandinputdevice.cpp
+++ b/src/client/qwaylandinputdevice.cpp
@@ -173,8 +173,8 @@ void QWaylandInputDevice::Keyboard::stopRepeat()
     mRepeatTimer.stop();
 }
 
-QWaylandInputDevice::Pointer::Pointer(QWaylandInputDevice *p)
-    : mParent(p)
+QWaylandInputDevice::Pointer::Pointer(QWaylandInputDevice *seat)
+    : mParent(seat)
 {
 }
 
@@ -186,6 +186,153 @@ QWaylandInputDevice::Pointer::~Pointer()
         wl_pointer_destroy(object());
 }
 
+#if QT_CONFIG(cursor)
+
+class CursorSurface : public QtWayland::wl_surface {
+public:
+    explicit CursorSurface(QWaylandInputDevice::Pointer *pointer, QWaylandDisplay *display)
+        : m_pointer(pointer)
+    {
+        init(display->createSurface(this));
+        //TODO: When we upgrade to libwayland 1.10, use wl_surface_get_version instead.
+        m_version = display->compositorVersion();
+    }
+
+    void hide()
+    {
+        m_pointer->set_cursor(m_pointer->mEnterSerial, nullptr, 0, 0);
+        m_setSerial = 0;
+    }
+
+    // Size and hotspot are in surface coordinates
+    void update(wl_buffer *buffer, const QPoint &hotspot, const QSize &size, int bufferScale)
+    {
+        // Calling code needs to ensure buffer scale is supported if != 1
+        Q_ASSERT(bufferScale == 1 || m_version >= 3);
+
+        auto enterSerial = m_pointer->mEnterSerial;
+        if (m_setSerial < enterSerial || m_hotspot != hotspot) {
+            m_pointer->set_cursor(m_pointer->mEnterSerial, object(), hotspot.x(), hotspot.y());
+            m_setSerial = enterSerial;
+            m_hotspot = hotspot;
+        }
+
+        if (m_version >= 3)
+            set_buffer_scale(bufferScale);
+
+        attach(buffer, 0, 0);
+        damage(0, 0, size.width(), size.height());
+        commit();
+    }
+
+    int outputScale() const { return m_outputScale; }
+
+protected:
+    void surface_enter(struct ::wl_output *output) override
+    {
+        //TODO: Can be improved to keep track of all entered screens
+        int scale = QWaylandScreen::fromWlOutput(output)->scale();
+        if (scale == m_outputScale)
+            return;
+
+        m_outputScale = scale;
+        m_pointer->updateCursor();
+    }
+
+private:
+    QWaylandInputDevice::Pointer *m_pointer = nullptr;
+    uint m_version = 0;
+    uint m_setSerial = 0;
+    QPoint m_hotspot;
+    int m_outputScale = 0;
+};
+
+QString QWaylandInputDevice::Pointer::cursorThemeName() const
+{
+    static QString themeName = qEnvironmentVariable("XCURSOR_THEME", QStringLiteral("default"));
+    return themeName;
+}
+
+int QWaylandInputDevice::Pointer::cursorSize() const
+{
+    constexpr int defaultCursorSize = 32;
+    static const int xCursorSize = qEnvironmentVariableIntValue("XCURSOR_SIZE");
+    return xCursorSize > 0 ? xCursorSize : defaultCursorSize;
+}
+
+int QWaylandInputDevice::Pointer::idealCursorScale() const
+{
+    // set_buffer_scale is not supported on earlier versions
+    if (seat()->mQDisplay->compositorVersion() < 3)
+        return 1;
+
+    if (auto *s = mCursor.surface.data()) {
+        if (s->outputScale() > 0)
+            return s->outputScale();
+    }
+
+    return seat()->mCursor.fallbackOutputScale;
+}
+
+void QWaylandInputDevice::Pointer::updateCursorTheme()
+{
+    int scale = idealCursorScale();
+    int pixelSize = cursorSize() * scale;
+    auto *display = seat()->mQDisplay;
+    mCursor.theme = display->loadCursorTheme(cursorThemeName(), pixelSize);
+    mCursor.themeBufferScale = scale;
+}
+
+void QWaylandInputDevice::Pointer::updateCursor()
+{
+    if (mEnterSerial == 0)
+        return;
+
+    auto shape = seat()->mCursor.shape;
+
+    if (shape == Qt::BlankCursor) {
+        if (mCursor.surface)
+            mCursor.surface->hide();
+        return;
+    }
+
+    if (shape == Qt::BitmapCursor) {
+        auto buffer = seat()->mCursor.bitmapBuffer;
+        if (!buffer) {
+            qCWarning(lcQpaWayland) << "No buffer for bitmap cursor, can't set cursor";
+            return;
+        }
+        auto hotspot = seat()->mCursor.hotspot;
+        int bufferScale = seat()->mCursor.bitmapScale;
+        getOrCreateCursorSurface()->update(buffer->buffer(), hotspot, buffer->size(), bufferScale);
+        return;
+    }
+
+    if (!mCursor.theme || idealCursorScale() != mCursor.themeBufferScale)
+        updateCursorTheme();
+
+    // Set from shape using theme
+    if (struct ::wl_cursor_image *image = mCursor.theme->cursorImage(shape)) {
+        struct wl_buffer *buffer = wl_cursor_image_get_buffer(image);
+        int bufferScale = mCursor.themeBufferScale;
+        QPoint hotspot = QPoint(image->hotspot_x, image->hotspot_y) / bufferScale;
+        QSize size = QSize(image->width, image->height) / bufferScale;
+        getOrCreateCursorSurface()->update(buffer, hotspot, size, bufferScale);
+        return;
+    }
+
+    qCWarning(lcQpaWayland) << "Unable to change to cursor" << shape;
+}
+
+CursorSurface *QWaylandInputDevice::Pointer::getOrCreateCursorSurface()
+{
+    if (!mCursor.surface)
+        mCursor.surface.reset(new CursorSurface(this, seat()->mQDisplay));
+    return mCursor.surface.get();
+}
+
+#endif // QT_CONFIG(cursor)
+
 QWaylandInputDevice::Touch::Touch(QWaylandInputDevice *p)
     : mParent(p)
 {
@@ -359,87 +506,33 @@ Qt::KeyboardModifiers QWaylandInputDevice::Keyboard::modifiers() const
 }
 
 #if QT_CONFIG(cursor)
-uint32_t QWaylandInputDevice::cursorSerial() const
-{
-    if (mPointer)
-        return mPointer->mCursorSerial;
-    return 0;
-}
-
-void QWaylandInputDevice::setCursor(Qt::CursorShape newShape, QWaylandScreen *screen)
+void QWaylandInputDevice::setCursor(const QCursor *cursor, const QSharedPointer<QWaylandBuffer> &cachedBuffer, int fallbackOutputScale)
 {
-    struct wl_cursor_image *image = screen->waylandCursor()->cursorImage(newShape);
-    if (!image) {
-        return;
+    CursorState oldCursor = mCursor;
+    mCursor = CursorState(); // Clear any previous state
+    mCursor.shape = cursor ? cursor->shape() : Qt::ArrowCursor;
+    mCursor.hotspot = cursor ? cursor->hotSpot() : QPoint();
+    mCursor.fallbackOutputScale = fallbackOutputScale;
+
+    if (mCursor.shape == Qt::BitmapCursor) {
+        mCursor.bitmapBuffer = cachedBuffer ? cachedBuffer : QWaylandCursor::cursorBitmapBuffer(mQDisplay, cursor);
+        qreal dpr = cursor->pixmap().devicePixelRatio();
+        mCursor.bitmapScale = int(dpr); // Wayland doesn't support fractional buffer scale
+        // If there was a fractional part of the dpr, we need to scale the hotspot accordingly
+        if (mCursor.bitmapScale < dpr)
+            mCursor.hotspot *= dpr / mCursor.bitmapScale;
     }
 
-    struct wl_buffer *buffer = wl_cursor_image_get_buffer(image);
-    setCursor(buffer, image, screen->devicePixelRatio());
-}
-
-void QWaylandInputDevice::setCursor(const QCursor &cursor, QWaylandScreen *screen)
-{
-    if (mPointer->mCursorSerial >= mPointer->mEnterSerial && (cursor.shape() != Qt::BitmapCursor && cursor.shape() == mPointer->mCursorShape))
-        return;
-
-    mPointer->mCursorShape = cursor.shape();
-    if (cursor.shape() == Qt::BitmapCursor) {
-        setCursor(screen->waylandCursor()->cursorBitmapImage(&cursor), cursor.hotSpot(), screen->devicePixelRatio());
+    // Return early if setCursor was called redundantly (mostly happens from decorations)
+    if (mCursor.shape != Qt::BitmapCursor
+            && mCursor.shape == oldCursor.shape
+            && mCursor.hotspot == oldCursor.hotspot
+            && mCursor.fallbackOutputScale == oldCursor.fallbackOutputScale) {
         return;
     }
-    setCursor(cursor.shape(), screen);
-}
-
-void QWaylandInputDevice::setCursor(struct wl_buffer *buffer, struct wl_cursor_image *image, int bufferScale)
-{
-    if (image) {
-        // Convert from pixel coordinates to surface coordinates
-        QPoint hotspot = QPoint(image->hotspot_x, image->hotspot_y) / bufferScale;
-        QSize size = QSize(image->width, image->height) / bufferScale;
-        setCursor(buffer, hotspot, size, bufferScale);
-    } else {
-        setCursor(buffer, QPoint(), QSize(), bufferScale);
-    }
-}
-
-// size and hotspot are in surface coordinates
-void QWaylandInputDevice::setCursor(struct wl_buffer *buffer, const QPoint &hotSpot, const QSize &size, int bufferScale)
-{
-    if (mCaps & WL_SEAT_CAPABILITY_POINTER) {
-        bool force = mPointer->mEnterSerial > mPointer->mCursorSerial;
-
-        if (!force && mPointer->mCursorBuffer == buffer)
-            return;
-
-        mPixmapCursor.clear();
-        mPointer->mCursorSerial = mPointer->mEnterSerial;
-
-        mPointer->mCursorBuffer = buffer;
-
-        /* Hide cursor */
-        if (!buffer)
-        {
-            mPointer->set_cursor(mPointer->mEnterSerial, nullptr, 0, 0);
-            return;
-        }
-
-        if (!pointerSurface)
-            pointerSurface = mQDisplay->createSurface(this);
-
-        mPointer->set_cursor(mPointer->mEnterSerial, pointerSurface,
-                             hotSpot.x(), hotSpot.y());
-        wl_surface_attach(pointerSurface, buffer, 0, 0);
-        if (mQDisplay->compositorVersion() >= 3)
-            wl_surface_set_buffer_scale(pointerSurface, bufferScale);
-        wl_surface_damage(pointerSurface, 0, 0, size.width(), size.height());
-        wl_surface_commit(pointerSurface);
-    }
-}
 
-void QWaylandInputDevice::setCursor(const QSharedPointer<QWaylandBuffer> &buffer, const QPoint &hotSpot, int bufferScale)
-{
-    setCursor(buffer->buffer(), hotSpot, buffer->size(), bufferScale);
-    mPixmapCursor = buffer;
+    if (mPointer)
+        mPointer->updateCursor();
 }
 #endif
 
@@ -467,7 +560,7 @@ void QWaylandInputDevice::Pointer::pointer_enter(uint32_t serial, struct wl_surf
 
 #if QT_CONFIG(cursor)
     // Depends on mEnterSerial being updated
-    window->window()->setCursor(window->window()->cursor());
+    updateCursor();
 #endif
 
     QWaylandWindow *grab = QWaylandWindow::mouseGrab();