Add a new setExclusiveEdge call in the protocol

This can be used to disambiguate the exclusive edge when the anchors are
on a corner (so there  would be 2 candidates)

it's quite quick and dirty mostly to understand if we do want to push
for something along the lines

src/interfaces/window.cpp

@@ -28,6 +28,7 @@ public:
     QString scope = QStringLiteral("window");
     Window::Anchors anchors = {Window::AnchorTop | Window::AnchorBottom | Window::AnchorLeft | Window::AnchorRight};
     int32_t exclusionZone = 0;
+    Window::Anchor exclusiveEdge = Window::AnchorNone;
     Window::KeyboardInteractivity keyboardInteractivity = Window::KeyboardInteractivityOnDemand;
     Window::Layer layer = Window::LayerTop;
     QMargins margins;
@@ -68,6 +69,21 @@ int32_t Window::exclusionZone() const
     return d->exclusionZone;
 }
 
+void Window::setExclusiveEdge(Window::Anchor edge)
+{
+    if (d->exclusiveEdge == edge) {
+        return;
+    }
+
+    d->exclusiveEdge = edge;
+    Q_EMIT exclusiveEdgeChanged();
+}
+
+Window::Anchor Window::exclusiveEdge() const
+{
+    return d->exclusiveEdge;
+}
+
 void Window::setMargins(const QMargins &margins)
 {
     if (d->margins != margins) {

src/interfaces/window.h

@@ -33,6 +33,7 @@ public:
     ~Window() override;
 
     enum Anchor {
+        AnchorNone = 0,
         AnchorTop = 1, ///< The top edge of the anchor rectangle
         AnchorBottom = 2, ///< The bottom edge of the anchor rectangle
         AnchorLeft = 4, ///< The left edge of the anchor rectangle
@@ -79,6 +80,9 @@ public:
     void setExclusiveZone(int32_t zone);
     int32_t exclusionZone() const;
 
+    void setExclusiveEdge(Window::Anchor edge);
+    Window::Anchor exclusiveEdge() const;
+
     void setMargins(const QMargins &margins);
     QMargins margins() const;
 
@@ -121,6 +125,7 @@ public:
 Q_SIGNALS:
     void anchorsChanged();
     void exclusionZoneChanged();
+    void exclusiveEdgeChanged();
     void marginsChanged();
     void keyboardInteractivityChanged();
     void layerChanged();

src/qwaylandlayersurface.cpp

@@ -48,6 +48,10 @@ QWaylandLayerSurface::QWaylandLayerSurface(QWaylandLayerShellIntegration *shell,
     connect(m_interface, &Window::exclusionZoneChanged, this, [this]() {
         setExclusiveZone(m_interface->exclusionZone());
     });
+    setExclusiveEdge(m_interface->exclusiveEdge());
+    connect(m_interface, &Window::exclusiveEdgeChanged, this, [this]() {
+        setExclusiveEdge(m_interface->exclusiveEdge());
+    });
 
     setMargins(m_interface->margins());
     connect(m_interface, &Window::marginsChanged, this, [this]() {
@@ -127,6 +131,11 @@ void QWaylandLayerSurface::setExclusiveZone(int32_t zone)
     set_exclusive_zone(zone);
 }
 
+void QWaylandLayerSurface::setExclusiveEdge(uint32_t edge)
+{
+    set_exclusive_edge(edge);
+}
+
 void QWaylandLayerSurface::setMargins(const QMargins &margins)
 {
     set_margin(margins.top(), margins.right(), margins.bottom(), margins.left());

src/qwaylandlayersurface_p.h

@@ -36,6 +36,7 @@ public:
 
     void setAnchor(uint32_t anchor);
     void setExclusiveZone(int32_t zone);
+    void setExclusiveEdge(uint32_t edge);
     void setMargins(const QMargins &margins);
     void setKeyboardInteractivity(uint32_t interactivity);
     void setLayer(uint32_t layer);

src/wlr-layer-shell-unstable-v1.xml

@@ -187,6 +187,10 @@
       <arg name="zone" type="int"/>
     </request>
 
+    <request name="set_exclusive_edge">
+      <arg name="edge" type="uint"/>
+    </request>
+
     <request name="set_margin">
       <description summary="sets a margin from the anchor point">
         Requests that the surface be placed some distance away from the anchor