skins2(Win32 and Linux): Don't refresh a window forcefully

A good practice is to invalidate the window and leave it to the OS to decide if a repaint is or not needed.

As a side effect, this fixes some alternative task switchers (alt-tab) on WinNT (like TaskSwitcher or ATTv) that displayed a black rectangle instead of the preview of the skin, because the skin engine was not doing things the usual way.

modules/gui/skins2/src/generic_layout.cpp

@@ -236,7 +236,7 @@ void GenericLayout::refreshRect( int x, int y, int width, int height )
         // first apply new shape to the window
         pWindow->updateShape();
 
-        pWindow->refresh( x, y, width, height );
+        pWindow->invalidateRect( x, y, width, height );
     }
 }
 

modules/gui/skins2/src/generic_window.cpp

@@ -179,3 +179,18 @@ void GenericWindow::setParent( GenericWindow* pParent, int x, int y, int w, int
     void* handle = pParent ? pParent->getOSHandle() : NULL;
     m_pOsWindow->reparent( handle, m_left, m_top, m_width, m_height );
 }
+
+
+void GenericWindow::invalidateRect( int left, int top, int width, int height )
+{
+    if( m_pOsWindow )
+    {
+        // tell the OS we invalidate a window client area
+        bool b_supported =
+            m_pOsWindow->invalidateRect( left, top, width, height );
+
+        // if not supported, directly refresh the area
+        if( !b_supported )
+            refresh( left, top, width, height );
+    }
+}

modules/gui/skins2/src/generic_window.hpp

@@ -80,6 +80,9 @@ public:
     /// Refresh an area of the window
     virtual void refresh( int left, int top, int width, int height ) { }
 
+    /// Invalidate an area of the window
+    virtual void invalidateRect( int left, int top, int width, int height );
+
     /// Get the coordinates of the window
     int getLeft() const { return m_left; }
     int getTop() const { return m_top; }

modules/gui/skins2/src/os_window.hpp

@@ -62,6 +62,9 @@ public:
     /// reparent the window
     virtual void reparent( void* OSHandle, int x, int y, int w, int h ) = 0;
 
+    /// updateWindow (tell the OS we need to update the window)
+    virtual bool invalidateRect( int x, int y, int w, int h ) const = 0;
+
 protected:
     OSWindow( intf_thread_t *pIntf ): SkinObject( pIntf ) { }
 };

modules/gui/skins2/win32/win32_window.cpp

@@ -135,7 +135,17 @@ void Win32Window::reparent( void* OSHandle, int x, int y, int w, int h )
     }
 
     SetParent( m_hWnd, (HWND)OSHandle );
-    MoveWindow( m_hWnd, x, y, w, h, true );
+    MoveWindow( m_hWnd, x, y, w, h, TRUE );
+}
+
+
+bool Win32Window::invalidateRect( int x, int y, int w, int h) const
+{
+    RECT rect = { x, y, x + w , y + h };
+    InvalidateRect( m_hWnd, &rect, FALSE );
+    UpdateWindow( m_hWnd );
+
+    return true;
 }
 
 
@@ -165,7 +175,7 @@ void Win32Window::hide() const
 
 void Win32Window::moveResize( int left, int top, int width, int height ) const
 {
-    MoveWindow( m_hWnd, left, top, width, height, true );
+    MoveWindow( m_hWnd, left, top, width, height, TRUE );
 }
 
 

modules/gui/skins2/win32/win32_window.hpp

@@ -68,6 +68,9 @@ public:
     /// reparent the window
     void reparent( void* OSHandle, int x, int y, int w, int h );
 
+    /// invalidate a window surface
+    bool invalidateRect( int x, int y, int w, int h ) const;
+
 private:
     /// Window handle
     HWND m_hWnd;

modules/gui/skins2/x11/x11_window.cpp

@@ -349,4 +349,11 @@ void X11Window::toggleOnTop( bool onTop ) const
     }
 }
 
+
+bool X11Window::invalidateRect( int x, int y, int w, int h ) const
+{
+    XClearArea( XDISPLAY, m_wnd, x, y, w, h, True );
+    return true;
+}
+
 #endif

modules/gui/skins2/x11/x11_window.hpp

@@ -76,6 +76,9 @@ public:
     /// reparent the window
     void reparent( void* OSHandle, int x, int y, int w, int h );
 
+    /// invalidate a window surface
+    bool invalidateRect( int x, int y, int w, int h ) const;
+
     void setFullscreen() const;
 
 private: