wx: Fix warnings in example

Bitmaps of size less than 1 generates asserts,
and size 0 event is before window is realized.

1 files changed, 8 insertions, 5 deletions

diff --git a/lib/wx/examples/demo/ex_canvas.erl b/lib/wx/examples/demo/ex_canvas.erl
index 2a95ea0777..b00ce81993 100644
--- a/lib/wx/examples/demo/ex_canvas.erl
+++ b/lib/wx/examples/demo/ex_canvas.erl
@@ -136,11 +136,14 @@ handle_event(#wx{event = #wxCommand{type = command_button_clicked}},
     {noreply, State};
 handle_event(#wx{event = #wxSize{size={W,H}}},
 	     State = #state{bitmap=Prev, canvas=Canvas}) ->
-    Bitmap = wxBitmap:new(W,H),
-    draw(Canvas, Bitmap, fun(DC) -> wxDC:clear(DC) end),
-    wxBitmap:destroy(Prev),
-    {noreply, State#state{bitmap = Bitmap}};
-
+    if W > 0 andalso H > 0 ->
+	    Bitmap = wxBitmap:new(W,H),
+	    draw(Canvas, Bitmap, fun(DC) -> wxDC:clear(DC) end),
+	    wxBitmap:destroy(Prev),
+	    {noreply, State#state{bitmap = Bitmap}};
+       true ->
+	    {noreply, State}
+    end;
 handle_event(#wx{event = #wxMouse{type=left_down, x=X, y=Y}}, State) ->
     {noreply, State#state{pos={X,Y}}};
 handle_event(#wx{event = #wxMouse{type=motion, x=X1, y=Y1}},