Fix initial wxRadioBox buttons positions in wxMSW.

We only updated the button positions when the radio box was moved or resized
after being created but didn't do it initially, so a radio box created with
fixed position and size didn't lay out its buttons correctly. Do lay them out
immediately after creating the radio box to fix this.

Closes #13912.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70498 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/radiobox.h

@@ -149,6 +149,9 @@ protected:
     // get the total size occupied by the radio box buttons
     wxSize GetTotalButtonSize(const wxSize& sizeBtn) const;
 
+    // Adjust all the buttons to the new window size.
+    void PositionAllButtons(int x, int y, int width, int height);
+
     virtual void DoSetSize(int x, int y,
                            int width, int height,
                            int sizeFlags = wxSIZE_AUTO);

src/msw/radiobox.cpp

@@ -252,6 +252,10 @@ bool wxRadioBox::Create(wxWindow *parent,
     // Now that we have items determine what is the best size and set it.
     SetInitialSize(size);
 
+    // And update all the buttons positions to match it.
+    const wxSize actualSize = GetSize();
+    PositionAllButtons(pos.x, pos.y, actualSize.x, actualSize.y);
+
     return true;
 }
 
@@ -625,6 +629,12 @@ void wxRadioBox::DoMoveWindow(int x, int y, int width, int height)
 {
     wxStaticBox::DoMoveWindow(x, y, width, height);
 
+    PositionAllButtons(x, y, width, height);
+}
+
+void
+wxRadioBox::PositionAllButtons(int x, int y, int width, int WXUNUSED(height))
+{
     wxSize maxSize = GetMaxButtonSize();
     int maxWidth = maxSize.x,
         maxHeight = maxSize.y;