Yes, I have a quick fix on two files to solve the compile issue already. Thanks for your help!

for qwt_slider.cpp, modify line 781, 782

Qt Code:
  1. const int sdExtent = (int)ceil((double)scaleDraw()->extent( QPen(), font() ));
  2. const int sdLength = (int)ceil((double)scaleDraw()->minLength( QPen(), font() ));
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same for qwt_thermo.cpp, modify line 836, 837

Qt Code:
  1. const int sdExtent = (int) ceil((double)scaleDraw()->extent( QPen(), font() ));
  2. const int sdLength = (int) ceil((double)scaleDraw()->minLength( QPen(), font() ));
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