Add wxNativeWindow allowing to easily embed native widgets in wx.

Implement the class for wxMSW, wxGTK and wxOSX/Cocoa, show it in the widgets
sample and add documentation for it.

src/gtk/nativewin.cpp

@@ -38,6 +38,45 @@
 // implementation
 // ============================================================================
 
+// ----------------------------------------------------------------------------
+// wxNativeWindow
+// ----------------------------------------------------------------------------
+
+bool
+wxNativeWindow::Create(wxWindow* parent,
+                       wxWindowID winid,
+                       wxNativeWindowHandle widget)
+{
+    wxCHECK_MSG( widget, false, wxS("Invalid null GtkWidget") );
+
+    // Standard wxGTK controls use PreCreation() but we never have any size
+    // specified at this stage, so don't bother with it.
+    if ( !CreateBase(parent, winid) )
+        return false;
+
+    // Add a reference to the widget to match g_object_unref() in wxWindow dtor
+    // (and by using the "_sink" version we avoid memory leaks when we're
+    // passed a newly allocated widget, as is typically the case).
+    m_widget = widget;
+    g_object_ref_sink(m_widget);
+
+    parent->DoAddChild(this);
+
+    PostCreation();
+
+    // Ensure that the best (and minimal) size is set to fully display the
+    // widget.
+    GtkRequisition req;
+    gtk_widget_size_request(widget, &req);
+    SetInitialSize(wxSize(req.width, req.height));
+
+    return true;
+}
+
+// ----------------------------------------------------------------------------
+// wxNativeContainerWindow
+// ----------------------------------------------------------------------------
+
 // TODO: we probably need equivalent code for other GDK platforms
 #ifdef GDK_WINDOWING_X11
 

src/msw/nativewin.cpp

@@ -32,6 +32,57 @@
 // implementation
 // ============================================================================
 
+// ----------------------------------------------------------------------------
+// wxNativeWindow
+// ----------------------------------------------------------------------------
+
+bool
+wxNativeWindow::Create(wxWindow* parent,
+                       wxWindowID winid,
+                       wxNativeWindowHandle hwnd)
+{
+    wxCHECK_MSG( hwnd, false, wxS("Invalid null HWND") );
+    wxCHECK_MSG( parent, false, wxS("Must have a valid parent") );
+    wxASSERT_MSG( ::GetParent(hwnd) == GetHwndOf(parent),
+                  wxS("The native window has incorrect parent") );
+
+    const wxRect r = wxRectFromRECT(wxGetWindowRect(hwnd));
+
+    // Skip wxWindow::Create() which would try to create a new HWND, we don't
+    // want this as we already have one.
+    if ( !CreateBase(parent, winid,
+                     r.GetPosition(), r.GetSize(),
+                     0, wxDefaultValidator, wxS("nativewindow")) )
+        return false;
+
+    parent->AddChild(this);
+
+    SubclassWin(hwnd);
+
+    if ( winid == wxID_ANY )
+    {
+        // We allocated a new ID to the control, use it at Windows level as
+        // well because we assume that our and MSW IDs are the same in many
+        // places and it seems prudent to avoid breaking this assumption.
+        SetId(GetId());
+    }
+    else // We used a fixed ID.
+    {
+        // For the same reason as above, check that it's the same as the one
+        // used by the native HWND.
+        wxASSERT_MSG( ::GetWindowLong(hwnd, GWL_ID) == winid,
+                      wxS("Mismatch between wx and native IDs") );
+    }
+
+    InheritAttributes();
+
+    return true;
+}
+
+// ----------------------------------------------------------------------------
+// wxNativeContainerWindow
+// ----------------------------------------------------------------------------
+
 bool wxNativeContainerWindow::Create(wxNativeContainerWindowHandle hwnd)
 {
     if ( !::IsWindow(hwnd) )

src/osx/cocoa/nativewin.mm

@@ -0,0 +1,68 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        src/osx/cocoa/nativewin.mm
+// Purpose:     wxNativeWindow implementation for wxOSX/Cocoa
+// Author:      Vadim Zeitlin
+// Created:     2015-08-01
+// Copyright:   (c) 2015 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+// ============================================================================
+// declarations
+// ============================================================================
+
+// ----------------------------------------------------------------------------
+// headers
+// ----------------------------------------------------------------------------
+
+// for compilers that support precompilation, includes "wx.h".
+#include "wx/wxprec.h"
+
+#ifdef __BORLANDC__
+    #pragma hdrstop
+#endif
+
+#include "wx/nativewin.h"
+
+#include "wx/osx/private.h"
+
+// ============================================================================
+// implementation
+// ============================================================================
+
+bool
+wxNativeWindow::Create(wxWindow* parent,
+                       wxWindowID winid,
+                       wxNativeWindowHandle view)
+{
+    wxCHECK_MSG( view, false, wxS("NULL NSView pointer") );
+
+    DontCreatePeer();
+
+    if ( !wxWindow::Create(parent, winid) )
+        return false;
+
+    // We have to ensure that the internal label is synchronized with the label
+    // at the native window, otherwise calling SetLabel() later might not work
+    // and, even worse, the native label would be reset to match the (empty) wx
+    // label by SetPeer().
+    //
+    // Notice that the selectors tested here are the same ones currently used
+    // by wxWidgetCocoaImpl::SetLabel() and this code would need to be updated
+    // if that method is.
+    //
+    // Also note the casts to "id" needed to suppress the "NSView may not
+    // respond to selector" warnings: we do test that it responds to them, so
+    // these warnings are not useful here.
+    if ( [view respondsToSelector:@selector(title)] )
+        m_label = wxCFStringRef::AsString([(id)view title]);
+    else if ( [view respondsToSelector:@selector(stringValue)] )
+        m_label = wxCFStringRef::AsString([(id)view stringValue]);
+
+    SetPeer(new wxWidgetCocoaImpl(this, view));
+
+    // It doesn't seem necessary to use MacPostControlCreate() here as we never
+    // change the native control geometry here.
+
+    return true;
+}