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, 10 insertions, 6 deletions

diff --git a/lib/wx/examples/demo/ex_canvas_paint.erl b/lib/wx/examples/demo/ex_canvas_paint.erl
index aa510f5342..75eb840b04 100644
--- a/lib/wx/examples/demo/ex_canvas_paint.erl
+++ b/lib/wx/examples/demo/ex_canvas_paint.erl
@@ -157,10 +157,15 @@ handle_event(#wx{event = #wxMouse{type = motion, x = X, y = Y}},
     {noreply, State#state{old_pos = {X,Y}}};
 %% Resize event
 handle_event(#wx{event = #wxSize{size = {W,H}}}, State = #state{bitmap=Prev}) ->
-    wxBitmap:destroy(Prev),
-    Bitmap = wxBitmap:new(W,H),
-    draw(State#state.canvas, Bitmap, fun(DC) -> wxDC:clear(DC) end),
-    {noreply, State#state{bitmap=Bitmap}};
+    case W > 0 andalso H > 0 of
+	true ->
+	    wxBitmap:destroy(Prev),
+	    Bitmap = wxBitmap:new(W,H),
+	    draw(State#state.canvas, Bitmap, fun(DC) -> wxDC:clear(DC) end),
+	    {noreply, State#state{bitmap=Bitmap}};
+	false ->
+	    {noreply, State}
+    end;
 handle_event(#wx{event = #wxMouse{type = left_dclick,x = X,y = Y}}, State = #state{}) ->
     wxPanel:connect(State#state.canvas, motion),
     {noreply, State#state{old_pos = {X,Y}}};
@@ -235,11 +240,10 @@ draw(Canvas, Bitmap, Fun) ->
     CDC = wxClientDC:new(Canvas),
 
     Fun(MemoryDC),
-    
     wxDC:blit(CDC, {0,0},
 	      {wxBitmap:getWidth(Bitmap), wxBitmap:getHeight(Bitmap)},
 	      MemoryDC, {0,0}),
-    
+
     wxClientDC:destroy(CDC),
     wxMemoryDC:destroy(MemoryDC).