Bug 5925 Fix: Charts are too large, resizing makes them disappear
Bug Number: 5925
Release notes (y/n): Yes
For Release Nums: 7.0.7

It was found that the ChartWidget::resizeEvent() method was computing 
negative widths and heights for Pie Chart circle during the first iteration 
of geometry adjustments when slice labels are being laid out.  Ensuring that 
those values have a minimum value (at least 50 pixels) seems to have fixed 
this problem.

   // Gnats 5925 (RW 7.0, 4-2017): The widget width and height we retrieved
   // above aren't always sufficiently current during certain transitions.
   // In such cases, the values assigned o the pie circle _width and _height
   // are pretty negative (e.g. -273) -- and things go downhill from there.
   // Ensuring a minimum width and height seems to address the Gnats 5925
   // problem ("Charts are too large, resizing makes them disappear").
  
   _width = std::max (50, newDim);
   _height = std::max (50, newDim);

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