Merge branch 'statbox-any-label'

Add support for using any wxWindow (and not just the equivalent of
wxStaticText) as wxStaticBox label.

See https://github.com/wxWidgets/wxWidgets/pull/650

interface/wx/statbox.h

@@ -71,7 +71,11 @@ public:
             Checkbox size.
             If ::wxDefaultSize is specified then a default size is chosen.
         @param style
-            Window style. See wxStaticBox.
+            Window style. There are no wxStaticBox-specific styles, but generic
+            ::wxALIGN_LEFT, ::wxALIGN_CENTRE_HORIZONTAL and ::wxALIGN_RIGHT can
+            be used here to change the position of the static box label when
+            using wxGTK (these styles are ignored under the other platforms
+            currently).
         @param name
             Window name.
 
@@ -84,6 +88,42 @@ public:
                 long style = 0,
                 const wxString& name = wxStaticBoxNameStr);
 
+    /**
+        Constructor for a static box using the given window as label.
+
+        This constructor takes a pointer to an arbitrary window (although
+        usually a wxCheckBox or a wxRadioButton) instead of just the usual text
+        label and puts this window at the top of the box at the place where the
+        label would be shown.
+
+        The @a label window must be a non-null, fully created window and will
+        become a child of this wxStaticBox, i.e. it will be owned by this
+        control and will be deleted when the wxStaticBox itself is deleted.
+
+        An example of creating a wxStaticBox with window as a label:
+        @code
+        void MyFrame::CreateControls()
+        {
+            wxPanel* panel = new wxPanel(this);
+            wxCheckBox* checkbox = new wxCheckBox(panel, wxID_ANY, "Box checkbox");
+            wxStaticBox* box = new wxStaticBox(panel, wxID_ANY, checkbox);
+            ...
+        }
+        @endcode
+
+        Currently this constructor is only available in wxGTK and wxMSW, use
+        @c wxHAS_WINDOW_LABEL_IN_STATIC_BOX to check whether it can be used at
+        compile-time.
+
+        @since 3.1.1
+     */
+    wxStaticBox(wxWindow* parent, wxWindowID id,
+                wxWindow* label,
+                const wxPoint& pos = wxDefaultPosition,
+                const wxSize& size = wxDefaultSize,
+                long style = 0,
+                const wxString& name = wxStaticBoxNameStr);
+
     /**
         Destructor, destroying the group box.
     */
@@ -97,5 +137,66 @@ public:
                 const wxPoint& pos = wxDefaultPosition,
                 const wxSize& size = wxDefaultSize, long style = 0,
                 const wxString& name = wxStaticBoxNameStr);
-};
 
+    /**
+        Creates the static box with the window as a label.
+
+        This method can only be called for an object created using its default
+        constructor.
+
+        See the constructor documentation for more details.
+
+        Currently this overload is only available in wxGTK and wxMSW, use
+        @c wxHAS_WINDOW_LABEL_IN_STATIC_BOX to check whether it can be used at
+        compile-time.
+
+        @since 3.1.1
+     */
+    bool Create(wxWindow* parent, wxWindowID id,
+                wxWindow* label,
+                const wxPoint& pos = wxDefaultPosition,
+                const wxSize& size = wxDefaultSize,
+                long style = 0,
+                const wxString& name = wxStaticBoxNameStr);
+
+    /**
+        Enables or disables the box without affecting its label window, if any.
+
+        wxStaticBox overrides wxWindow::Enable() in order to avoid disabling
+        the control used as a label, if this box is using one. This is done in
+        order to allow using a wxCheckBox, for example, label and enable or
+        disable the box according to the state of the checkbox: if disabling
+        the box also disabled the checkbox in this situation, it would make it
+        impossible for the user to re-enable the box after disabling it, so the
+        checkbox stays enabled even if @c box->Enable(false) is called.
+
+        However with the actual behaviour, implemented in this overridden
+        method, the following code (shown using C++11 only for convenience,
+        this behaviour is not C++11-specific):
+        @code
+            auto check = new wxCheckBox(parent, wxID_ANY, "Use the box");
+            auto box = new wxStaticBox(parent, wxID_ANY, check);
+            check->Bind(wxEVT_CHECKBOX,
+                        [box](wxCommandEvent& event) {
+                            box->Enable(event.IsChecked());
+                        });
+        @endcode
+        does work as expected.
+
+        Please note that overriding Enable() to not actually disable this
+        window itself has two possibly unexpected consequences:
+
+        - The box retains its enabled status, i.e. IsEnabled() still returns
+          @true, after calling @c Enable(false).
+        - The box children are enabled or disabled when the box is, which can
+          result in the loss of their original state. E.g. if a box child is
+          initially disabled, then the box itself is disabled and, finally, the
+          box is enabled again, this child will end up being enabled too (this
+          wouldn't happen with any other parent window as its children would
+          inherit the disabled state from the parent instead of being really
+          disabled themselves when it is disabled). To avoid this problem,
+          consider using ::wxEVT_UPDATE_UI to ensure that the child state is
+          always correct or restoring it manually after re-enabling the box.
+     */
+    virtual bool Enable(bool enable = true);
+};