Fix positioning of ComboBoxEditor in wxPG (wxOSX)

Position of the combo box editor associated with properties having custom
bitmaps like e.g. ColourProperty, needs to be adjusted in order to display
edited text at the same position as the text which is displayed as
a property value prior to the editing.

src/propgrid/editors.cpp

@@ -710,7 +710,7 @@ public:
   #define wxPG_TEXTCTRLXADJUST3 0
   #endif // wxGTK3/!wxGTK3
 #elif defined(__WXOSX__)
-#define wxPG_TEXTCTRLXADJUST3 0
+#define wxPG_TEXTCTRLXADJUST3 6
 #else
 #define wxPG_TEXTCTRLXADJUST3 0
 #endif
@@ -724,8 +724,7 @@ public:
     #endif
         wxOwnerDrawnComboBox::PositionTextCtrl(
             textCtrlXAdjust + wxPG_TEXTCTRLXADJUST3,
-            0 // Under MSW, GTK vertical position is already properly adjusted.
-              // Note: This parameter is not used by other ports.
+            0
         );
     }
 
@@ -1019,8 +1018,6 @@ wxWindow* wxPGChoiceEditor::CreateControlsBase( wxPropertyGrid* propGrid,
 
     wxArrayString labels = choices.GetLabels();
 
-    wxPGComboBox* cb;
-
     wxPoint po(pos);
     wxSize si(sz);
     po.y += wxPG_CHOICEYADJUST;
@@ -1054,7 +1051,7 @@ wxWindow* wxPGChoiceEditor::CreateControlsBase( wxPropertyGrid* propGrid,
             labels.Add(propGrid->GetCommonValueLabel(i));
     }
 
-    cb = new wxPGComboBox();
+    wxPGComboBox* cb = new wxPGComboBox();
 #ifdef __WXMSW__
     cb->Hide();
 #endif
@@ -1066,7 +1063,11 @@ wxWindow* wxPGChoiceEditor::CreateControlsBase( wxPropertyGrid* propGrid,
                labels,
                odcbFlags);
 
+    // Under OSX default button seems to look fine
+    // so there is no need to change it.
+#ifndef __WXOSX__
     cb->SetButtonPosition(si.y,0,wxRIGHT);
+#endif // !__WXOSX__
     cb->SetMargins(wxPG_XBEFORETEXT-1);
 
     // Set hint text