Add support for Wayland Cursor themes

WaylandSeat can install a cursor based on Qt::CursorShape using the
Wayland cursor theme library.

CMakeLists.txt

@@ -270,6 +270,7 @@ set(kwin_XCB_LIBS
 
 set(kwin_WAYLAND_LIBS
     Wayland::Client
+    Wayland::Cursor
     XCB::XTEST
 )
 

wayland_backend.cpp

@@ -33,6 +33,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <xcb/xfixes.h>
 // Wayland
 #include <wayland-client-protocol.h>
+#include <wayland-cursor.h>
 // system
 #include <unistd.h>
 #include <sys/mman.h>
@@ -495,10 +496,12 @@ Buffer *ShmPool::getBuffer(const QSize &size, int32_t stride)
 }
 
 WaylandSeat::WaylandSeat(wl_seat *seat, WaylandBackend *backend)
-    : m_seat(seat)
+    : QObject(NULL)
+    , m_seat(seat)
     , m_pointer(NULL)
     , m_keyboard(NULL)
     , m_cursor(NULL)
+    , m_theme(NULL)
     , m_enteredSerial(0)
     , m_cursorTracker()
     , m_backend(backend)
@@ -518,6 +521,7 @@ WaylandSeat::~WaylandSeat()
     if (m_cursor) {
         wl_surface_destroy(m_cursor);
     }
+    destroyTheme();
 }
 
 void WaylandSeat::destroyPointer()
@@ -580,6 +584,42 @@ void WaylandSeat::installCursorImage(wl_buffer *image, const QSize &size, const
     wl_surface_commit(m_cursor);
 }
 
+void WaylandSeat::installCursorImage(Qt::CursorShape shape)
+{
+    if (!m_theme) {
+        loadTheme();
+    }
+    wl_cursor *c = wl_cursor_theme_get_cursor(m_theme, Cursor::self()->cursorName(shape).constData());
+    if (c->image_count <= 0) {
+        return;
+    }
+    wl_cursor_image *image = c->images[0];
+    installCursorImage(wl_cursor_image_get_buffer(image),
+                       QSize(image->width, image->height),
+                       QPoint(image->hotspot_x, image->hotspot_y));
+}
+
+void WaylandSeat::loadTheme()
+{
+    Cursor *c = Cursor::self();
+    if (!m_theme) {
+        // so far the theme had not been created, this means we need to start tracking theme changes
+        connect(c, SIGNAL(themeChanged()), SLOT(loadTheme()));
+    } else {
+        destroyTheme();
+    }
+    m_theme = wl_cursor_theme_load(c->themeName().toUtf8().constData(),
+                                   c->themeSize(), m_backend->shmPool()->shm());
+}
+
+void WaylandSeat::destroyTheme()
+{
+    if (m_theme) {
+        wl_cursor_theme_destroy(m_theme);
+        m_theme = NULL;
+    }
+}
+
 WaylandBackend *WaylandBackend::s_self = 0;
 WaylandBackend *WaylandBackend::create(QObject *parent)
 {
@@ -652,6 +692,14 @@ void WaylandBackend::createSeat(uint32_t name)
     m_seat.reset(new WaylandSeat(seat, this));
 }
 
+void WaylandBackend::installCursorImage(Qt::CursorShape shape)
+{
+    if (m_seat.isNull()) {
+        return;
+    }
+    m_seat->installCursorImage(shape);
+}
+
 void WaylandBackend::createSurface()
 {
     m_surface = wl_compositor_create_surface(m_compositor);

wayland_backend.h

@@ -32,6 +32,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 class QTemporaryFile;
 class QImage;
+struct wl_cursor_theme;
 struct wl_buffer;
 struct wl_shm;
 
@@ -112,6 +113,7 @@ public:
     wl_buffer *createBuffer(const QSize &size, int32_t stride, const void *src);
     void *poolAddress() const;
     Buffer *getBuffer(const QSize &size, int32_t stride);
+    wl_shm *shm();
 Q_SIGNALS:
     void poolResized();
 private:
@@ -127,8 +129,9 @@ private:
     QList<Buffer*> m_buffers;
 };
 
-class WaylandSeat
+class WaylandSeat : public QObject
 {
+    Q_OBJECT
 public:
     WaylandSeat(wl_seat *seat, WaylandBackend *backend);
     virtual ~WaylandSeat();
@@ -138,13 +141,18 @@ public:
     void pointerEntered(uint32_t serial);
     void resetCursor();
     void installCursorImage(wl_buffer *image, const QSize &size, const QPoint &hotspot);
+    void installCursorImage(Qt::CursorShape shape);
+private Q_SLOTS:
+    void loadTheme();
 private:
     void destroyPointer();
     void destroyKeyboard();
+    void destroyTheme();
     wl_seat *m_seat;
     wl_pointer *m_pointer;
     wl_keyboard *m_keyboard;
     wl_surface *m_cursor;
+    wl_cursor_theme *m_theme;
     uint32_t m_enteredSerial;
     QScopedPointer<X11CursorTracker> m_cursorTracker;
     WaylandBackend *m_backend;
@@ -175,6 +183,7 @@ public:
     wl_surface *surface() const;
     const QSize &shellSurfaceSize() const;
     void setShellSurfaceSize(const QSize &size);
+    void installCursorImage(Qt::CursorShape shape);
 
     void dispatchEvents();
 Q_SIGNALS:
@@ -232,6 +241,12 @@ void* ShmPool::poolAddress() const
     return m_poolData;
 }
 
+inline
+wl_shm *ShmPool::shm()
+{
+    return m_shm;
+}
+
 inline
 wl_display *WaylandBackend::display()
 {