Merge branch 'aui_splitter_overlay'

Use wxOverlay to show sash feedback in wxAUI and in wxSplitterWindow to
implement non-live resizing in ports where it didn't work before (wxGTK3
with Wayland, wxOSX).

See #24193.

interface/wx/aui/framemanager.h

@@ -228,6 +228,8 @@ public:
         @param window The associated window, may be null (this parameter was
             added in wxWidgets 3.3.0)
 
+        @note As of wxWidgets 3.3.0 this function always returns false.
+
         @since 3.1.4
      */
     static bool AlwaysUsesLiveResize(const wxWindow* window);

interface/wx/overlay.h

@@ -27,6 +27,25 @@ public:
        example, when the window content has been changed and repainted.
     */
     void Reset();
+
+    /**
+        Sets or unsets constant opacity of the overlay window.
+
+        If @a alpha is `-1`, use per-pixel alpha blending, otherwise use the
+        given alpha value for all pixels.
+
+        @note Drawing on the overlay window is opaque by default under wxMSW.
+        You have to call SetOpacity(-1) before initializing the overlay and use
+        a graphics context to do the actual drawing if you want per-pixel alpha
+        blending. Or, assuming that SetOpacity(-1) wasn't called, explicitly set
+        the alpha value (at any time) to change the overlay window's opacity.
+
+        @note This is currently only implemented for wxMSW and does nothing in
+        the other ports.
+
+        @since 3.3.0
+    */
+    void SetOpacity(int alpha);
 };
 
 

interface/wx/splitter.h

@@ -142,20 +142,6 @@ public:
     */
     virtual ~wxSplitterWindow();
 
-    /**
-        Returns true if splitter always behaves as if wxSP_LIVE_UPDATE were
-        specified.
-
-        This function returns true if non-live update mode is not supported and
-        live update is always used, even if wxSP_LIVE_UPDATE was not explicitly
-        specified.
-
-        @see wxClientDC::CanBeUsedForDrawing()
-
-        @since 3.3.0
-    */
-    bool AlwaysUsesLiveUpdate() const;
-
     /**
         Creation function, for two-step construction.
         See wxSplitterWindow() for details.