DynamicSlice.py File Reference

Detailed Description

Example of function called when a mouse event occurs in a pad.

When moving the mouse in the canvas, a second canvas shows the projection along X of the bin corresponding to the Y position of the mouse. The resulting histogram is fitted with a gaussian. A "dynamic" line shows the current bin position in Y. This more elaborated example can be used as a starting point to develop more powerful interactive applications exploiting CINT as a development engine.

Note that a class is used to hold on to the canvas that display the selected slice.

 
import sys
import ctypes
 
from ROOT import gRandom, gPad, gROOT, gVirtualX
from ROOT import kTRUE, kRed
from ROOT import TCanvas, TH2, TH2F
 
 
class DynamicExec:
 
   def __init__( self ):
      self._cX   = None
      self._cY   = None
      self._old  = None
 
   def __call__( self ):
 
      h = gPad.GetSelected();
      if not h:
         return
 
      if not isinstance( h, TH2 ):
         return
 
      gPad.GetCanvas().FeedbackMode( kTRUE )
 
    # erase old position and draw a line at current position
      px = gPad.GetEventX()
      py = gPad.GetEventY()
 
      uxmin, uxmax = gPad.GetUxmin(), gPad.GetUxmax()
      uymin, uymax = gPad.GetUymin(), gPad.GetUymax()
      pxmin, pxmax = gPad.XtoAbsPixel( uxmin ), gPad.XtoAbsPixel( uxmax )
      pymin, pymax = gPad.YtoAbsPixel( uymin ), gPad.YtoAbsPixel( uymax )
 
      if self._old != None:
         gVirtualX.DrawLine( pxmin, self._old[1], pxmax, self._old[1] )
         gVirtualX.DrawLine( self._old[0], pymin, self._old[0], pymax )
      gVirtualX.DrawLine( pxmin, py, pxmax, py )
      gVirtualX.DrawLine( px, pymin, px, pymax )
 
      self._old = px, py
 
      upx = gPad.AbsPixeltoX( px )
      x = gPad.PadtoX( upx )
      upy = gPad.AbsPixeltoY( py )
      y = gPad.PadtoY( upy )
 
      padsav = gPad
 
    # create or set the display canvases
      if not self._cX:
         self._cX = TCanvas( 'c2', 'Projection Canvas in X', 730, 10, 700, 500 )
      else:
         self._DestroyPrimitive( 'X' )
 
      if not self._cY:
         self._cY = TCanvas( 'c3', 'Projection Canvas in Y', 10, 550, 700, 500 )
      else:
         self._DestroyPrimitive( 'Y' )
 
      self.DrawSlice( h, y, 'Y' )
      self.DrawSlice( h, x, 'X' )
 
      padsav.cd()
 
   def _DestroyPrimitive( self, xy ):
      proj = getattr( self, '_c'+xy ).GetPrimitive( 'Projection '+xy )
      if proj:
         proj.IsA().Destructor( proj )
 
   def DrawSlice( self, histo, value, xy ):
      yx = xy == 'X' and 'Y' or 'X'
 
    # draw slice corresponding to mouse position
      canvas = getattr( self, '_c'+xy )
      canvas.SetGrid()
      canvas.cd()
 
      bin = getattr( histo, 'Get%saxis' % xy )().FindBin( value )
      hp = getattr( histo, 'Projection' + yx )( '', bin, bin )
      hp.SetFillColor( 38 )
      hp.SetName( 'Projection ' + xy )
      hp.SetTitle( xy + 'Projection of bin=%d' % bin )
      hp.Fit( 'gaus', 'ql' )
      hp.GetFunction( 'gaus' ).SetLineColor( kRed )
      hp.GetFunction( 'gaus' ).SetLineWidth( 6 )
      canvas.Update()
 
 
if __name__ == '__main__':
 # create a new canvas.
   c1 = TCanvas('c1', 'Dynamic Slice Example', 10, 10, 700, 500 )
   c1.SetFillColor( 42 )
   c1.SetFrameFillColor( 33 )
 
 # create a 2-d histogram, fill and draw it
   hpxpy  = TH2F( 'hpxpy', 'py vs px', 40, -4, 4, 40, -4, 4 )
   hpxpy.SetStats( 0 )
   x, y = ctypes.c_double( 0.1 ), ctypes.c_double( 0.101 )
   for i in range( 50000 ):
   # pass ctypes doubles by reference, then retrieve their modified values with .value
     gRandom.Rannor( x, y )
     hpxpy.Fill( x.value, y.value )
   hpxpy.Draw( 'COL' )
 
 # Add a TExec object to the canvas (explicit use of __main__ is for IPython)
   import __main__
   __main__.slicer = DynamicExec()
   c1.AddExec( 'dynamic', 'TPython::Exec( "slicer()" );' )
   c1.Update()

Author

Rene Brun, Johann Cohen-Tanugi, Wim Lavrijsen, Enric Tejedor

Definition in file DynamicSlice.py.