fix typo in drawing slider ticks; added assert to check for it (slightly modified patch 646256)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18069 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/renderer.h

@@ -655,7 +655,7 @@ public:
                                  int step = 1,
                                  int flags = 0)
         { m_renderer->DrawSliderTicks(dc, rect, sizeThumb, orient,
-                                      start, end, start, flags); }
+                                      start, end, step, flags); }
 
     virtual void DrawMenuBarItem(wxDC& dc,
                                  const wxRect& rect,

src/univ/themes/win32.cpp

@@ -2771,6 +2771,9 @@ void wxWin32Renderer::DrawSliderTicks(wxDC& dc,
         return;
     }
 
+    // this would lead to an infinite loop below
+    wxCHECK_RET( step > 1, _T("invalid step in wxRenderer::DrawSliderTicks") );
+
     // the variable names correspond to horizontal case, but they can be used
     // for both orientations
     wxCoord x1, x2, y1, y2, len, widthThumb;