skins2(win): fix mouse wheel ineffective on Windows

This patch adds isScrollable() to a control, so that we can distinguish
controls that require mouse wheel (playtree, slider) from those that don't.
In the latter case, we can then forward events to vlc core.

this fixes #6457.

modules/gui/skins2/controls/ctrl_generic.hpp

@@ -81,6 +81,9 @@ public:
     /// Return true if the control can gain the focus
     virtual bool isFocusable() const { return false; }
 
+    /// Return true if the control can be scrollable
+    virtual bool isScrollable() const { return false; }
+
     /// Return true if the control is visible
     virtual bool isVisible() const;
 

modules/gui/skins2/controls/ctrl_list.hpp

@@ -61,6 +61,9 @@ public:
     /// Return true if the control can gain the focus
     virtual bool isFocusable() const { return true; }
 
+    /// Return true if the control can be scrollable
+    virtual bool isScrollable() const { return true; }
+
     /// Get the type of control (custom RTTI)
     virtual string getType() const { return "list"; }
 

modules/gui/skins2/controls/ctrl_slider.hpp

@@ -55,6 +55,9 @@ public:
     /// Handle an event
     virtual void handleEvent( EvtGeneric &rEvent );
 
+    /// Return true if the control can be scrollable
+    virtual bool isScrollable() const { return true; }
+
     /// Check whether coordinates are inside the control
     virtual bool mouseOver( int x, int y ) const;
 
@@ -132,6 +135,9 @@ public:
                   const UString &rHelp );
     virtual ~CtrlSliderBg();
 
+    /// Return true if the control can be scrollable
+    virtual bool isScrollable() const { return true; }
+
     /// Tell whether the mouse is over the control
     virtual bool mouseOver( int x, int y ) const;
 

modules/gui/skins2/controls/ctrl_tree.hpp

@@ -71,6 +71,9 @@ public:
     /// Return true if the control can gain the focus
     virtual bool isFocusable() const { return true; }
 
+    /// Return true if the control can be scrollable
+    virtual bool isScrollable() const { return true; }
+
     /// Get the type of control (custom RTTI)
     virtual string getType() const { return "tree"; }
 

modules/gui/skins2/src/top_window.cpp

@@ -247,17 +247,14 @@ void TopWindow::processEvent( EvtScroll &rEvtScroll )
                                                   rEvtScroll.getYPos());
     setLastHit( pNewHitControl );
 
-    // Send a mouse event to the hit control, or to the control
-    // that captured the mouse, if any
-    CtrlGeneric *pActiveControl = pNewHitControl;
+    // send a mouse event to the right control when scrollable
+    // if none, send it directly to the vlc core
+    CtrlGeneric *pHitControl = m_pCapturingControl ?
+                               m_pCapturingControl : pNewHitControl;
 
-    if( m_pCapturingControl )
-    {
-        pActiveControl = m_pCapturingControl;
-    }
-    if( pActiveControl )
+    if( pHitControl && pHitControl->isScrollable() )
     {
-        pActiveControl->handleEvent( rEvtScroll );
+        pHitControl->handleEvent( rEvtScroll );
     }
     else
     {