Add wxDataViewCtrlBase::SetAlternateRowColour()

Previously this method was only available in the generic wxDataViewCtrl,
move it to the base class to make it possible calling it in portable
code and document it.

Closes #14617.

include/wx/dataview.h

@@ -755,6 +755,12 @@ public:
     virtual bool SetHeaderAttr(const wxItemAttr& WXUNUSED(attr))
         { return false; }
 
+    // Set the colour used for the "alternate" rows when wxDV_ROW_LINES is on.
+    // Also only supported in the generic version, which returns true to
+    // indicate it.
+    virtual bool SetAlternateRowColour(const wxColour& WXUNUSED(colour))
+        { return false; }
+
     virtual wxVisualAttributes GetDefaultAttributes() const wxOVERRIDE
     {
         return GetClassDefaultAttributes(GetWindowVariant());

include/wx/generic/dataview.h

@@ -277,10 +277,11 @@ public:
 
     virtual bool SetHeaderAttr(const wxItemAttr& attr) wxOVERRIDE;
 
-    // These methods are specific to generic wxDataViewCtrl implementation and
+    virtual bool SetAlternateRowColour(const wxColour& colour) wxOVERRIDE;
+
+    // This method is specific to generic wxDataViewCtrl implementation and
     // should not be used in portable code.
     wxColour GetAlternateRowColour() const { return m_alternateRowColour; }
-    void SetAlternateRowColour(const wxColour& colour);
 
     // The returned pointer is null if the control has wxDV_NO_HEADER style.
     //

interface/wx/dataview.h

@@ -1566,6 +1566,21 @@ public:
     */
     virtual void SelectAll();
 
+    /**
+        Set custom colour for the alternate rows used with wxDV_ROW_LINES
+        style.
+
+        Note that calling this method has no effect if wxDV_ROW_LINES is off.
+
+        @param colour The colour to use for the alternate rows.
+        @return @true if customizing this colour is supported (currently only
+            in the generic version), @false if this method is not implemented
+            under this platform.
+
+        @since 3.1.1
+     */
+    bool SetAlternateRowColour(const wxColour& colour);
+
     /**
         Set which column shall contain the tree-like expanders.
     */

src/generic/datavgen.cpp

@@ -5781,9 +5781,10 @@ bool wxDataViewCtrl::SetHeaderAttr(const wxItemAttr& attr)
     return true;
 }
 
-void wxDataViewCtrl::SetAlternateRowColour(const wxColour& colour)
+bool wxDataViewCtrl::SetAlternateRowColour(const wxColour& colour)
 {
     m_alternateRowColour = colour;
+    return true;
 }
 
 void wxDataViewCtrl::SelectAll()