Fix wxSpinButton redrawing when using WS_EX_COMPOSITED

Explicitly redraw it ourselves instead of relying on DefWndProc() to do
it, as with 15e4f5b (Work around wxListCtrl repainting problems with
WS_EX_COMPOSITED, 2023-06-05) which did the same thing for wxListCtrl,
doing it seems to be enough to make the control draw correctly.

Closes #23656.

include/wx/msw/spinbutt.h

@@ -69,6 +69,8 @@ protected:
    virtual void NormalizeValue();
 
 private:
+    void OnPaint(wxPaintEvent& event);
+
     wxDECLARE_DYNAMIC_CLASS_NO_COPY(wxSpinButton);
 };
 

src/msw/spinbutt.cpp

@@ -23,6 +23,7 @@
 #ifndef WX_PRECOMP
     #include "wx/msw/wrapcctl.h" // include <commctrl.h> "properly"
     #include "wx/app.h"
+    #include "wx/dcclient.h"
 #endif
 
 #if wxUSE_SPINBTN
@@ -130,6 +131,8 @@ bool wxSpinButton::Create(wxWindow *parent,
 
     SubclassWin(m_hWnd);
 
+    Bind(wxEVT_PAINT, &wxSpinButton::OnPaint, this);
+
     SetInitialSize(size);
 
     return true;
@@ -165,6 +168,21 @@ wxSize wxSpinButton::DoGetBestSize() const
     return bestSize;
 }
 
+// ----------------------------------------------------------------------------
+// painting
+// ----------------------------------------------------------------------------
+
+void wxSpinButton::OnPaint(wxPaintEvent& event)
+{
+    // We need to always paint this control explicitly instead of letting
+    // DefWndProc() do it, as this avoids whichever optimization the latter
+    // function does when WS_EX_COMPOSITED is on that result in not drawing
+    // parts of the control at all (see #23656).
+    wxPaintDC dc(this);
+
+    wxSpinButtonBase::OnPaint(event);
+}
+
 // ----------------------------------------------------------------------------
 // value and range
 // ----------------------------------------------------------------------------