Implement wxWindow::DoGetBorderSize() in wxUniv.

As some wxUniv classes implement DoGetBestClientSize(), the new code in
wxWindow::DoGetBestSize() implementation calls DoGetBorderSize() which asserts
because it's not implemented, making it impossible to even start the minimal
sample -- fix this.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62002 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/window.h

@@ -243,6 +243,9 @@ protected:
     virtual wxSize DoGetBestClientSize() const;
     virtual wxSize DoGetBestSize() const;
 
+    // override the base class method to return the size of the window borders
+    virtual wxSize DoGetBorderSize() const;
+
     // adjust the size of the window to take into account its borders
     wxSize AdjustSize(const wxSize& size) const;
 

include/wx/window.h

@@ -1661,8 +1661,8 @@ protected:
     // of the left and the right border in the x component of the returned size
     // and the sum of the heights of the top and bottom borders in the y one
     //
-    // NB: this is new/temporary API only implemented by wxMSW so far and
-    //     subject to change, don't use
+    // NB: this is new/temporary API only implemented by wxMSW and wxUniv so
+    //     far and subject to change, don't use
     virtual wxSize DoGetBorderSize() const
     {
         wxFAIL_MSG( "must be overridden if called" );

src/univ/winuniv.cpp

@@ -728,6 +728,11 @@ wxSize wxWindow::DoGetBestClientSize() const
     return wxWindowNative::DoGetBestSize();
 }
 
+wxSize wxWindow::DoGetBorderSize() const
+{
+    return AdjustSize(wxSize(0, 0));
+}
+
 wxSize wxWindow::AdjustSize(const wxSize& size) const
 {
     wxSize sz = size;