Use Explorer style for wxTreeCtrl with wxTR_TWIST_BUTTONS in wxMSW.

The tree control style used by Explorer uses rotating triangles instead of the
standard "+/-" buttons and so seems to correspond relatively well to this
style. And this provides a possibility to have a more standard-looking tree
controls in wxWidgets programs.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66850 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -42,6 +42,7 @@
 
 #include "wx/imaglist.h"
 #include "wx/msw/dragimag.h"
+#include "wx/msw/uxtheme.h"
 
 // macros to hide the cast ugliness
 // --------------------------------
@@ -741,6 +742,20 @@ bool wxTreeCtrl::Create(wxWindow *parent,
 
     wxSetCCUnicodeFormat(GetHwnd());
 
+    if ( m_windowStyle & wxTR_TWIST_BUTTONS )
+    {
+        // Under Vista and later Explorer uses rotating ("twist") buttons
+        // instead of the default "+/-" ones so apply its theme to the tree
+        // control to implement this style.
+        if ( wxGetWinVersion() >= wxWinVersion_Vista )
+        {
+            if ( wxUxThemeEngine *theme = wxUxThemeEngine::GetIfActive() )
+            {
+                theme->SetWindowTheme(GetHwnd(), L"EXPLORER", NULL);
+            }
+        }
+    }
+
     return true;
 }