[wayland] Provide correct input geometry for client-side decorated clients

Summary:
Currently, the input geometry for client-side decorated clients matches
the frame geometry, which makes it impossible for a user to resize such
clients by just dragging invisible area near window borders.

BUG: 416346

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: cblack, ngraham, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D26716

input.cpp

@@ -2207,7 +2207,9 @@ static bool acceptsInput(Toplevel *t, const QPoint &pos)
     if (input.isEmpty()) {
         return true;
     }
-    return input.translated(t->pos()).contains(pos);
+    // TODO: What about sub-surfaces sticking outside the main surface?
+    const QPoint localPoint = pos - t->bufferGeometry().topLeft();
+    return input.contains(localPoint);
 }
 
 Toplevel *InputRedirection::findToplevel(const QPoint &pos)

xdgshellclient.cpp

@@ -295,6 +295,15 @@ void XdgShellClient::deleteClient(XdgShellClient *c)
     delete c;
 }
 
+QRect XdgShellClient::inputGeometry() const
+{
+    if (isDecorated()) {
+        return AbstractClient::inputGeometry();
+    }
+    // TODO: What about sub-surfaces sticking outside the main surface?
+    return m_bufferGeometry;
+}
+
 QRect XdgShellClient::bufferGeometry() const
 {
     return m_bufferGeometry;

xdgshellclient.h

@@ -58,6 +58,7 @@ public:
     XdgShellClient(KWayland::Server::XdgShellPopupInterface *surface);
     ~XdgShellClient() override;
 
+    QRect inputGeometry() const override;
     QRect bufferGeometry() const override;
     QStringList activities() const override;
     QPoint clientContentPos() const override;