[Gdal-dev] GDALScaledProgress confusion

[Frank Warmerdam]

Stefan Klug wrote:
> Hi,
> 
> I'm trying to use GDALScaledProgress and GDALCreateScaledProgress and 
> I'm a bit confused by its correct usage.
> 
> The docs say at http://www.gdal.org/gdal_8h.html
> 
> pScaledProgress = GDALCreateScaledProgress 
> <http://www.gdal.org/gdal_8h.html#462c1d7aa414cdacd608d62e1830ef43>( 
> 0.0, 0.5, pfnProgress, pProgressData );
> GDALDoLongSlowOperation( ..., GDALScaledProgressFunc, pProgressData );
> GDALDestroyScaledProgress 
> <http://www.gdal.org/gdal_8h.html#f1ac4100ae77f94983d45a33fc1b6fcd>( 
> pScaledProgress );
> 
> shouldn't pScaledProgress be passed to GDALDoLongSlowOperation() instead 
> of pProgressData?
> This is the way it is used in /frmts/gtiff/geotiff.cpp.
> 
> I even got more confused when I read /frmts/gtiff/gt_overview.cpp where 
> in line 330... it is used like this:
> pScaledProgressData =  GDALCreateScaledProgress( ...,pfnProgress, 
> pProgressData );
> GDALRegenerateOverviews( ...,pfnProgress,pProgressData);
> GDALDestroyScaledProgress( pScaledProgressData );
> 
> Here the scaled progress seems to be completely left out.
> To me it looks like a small bug...
> 
> Would be nice if someone could shed some light on this.

Stefan,

You are completely correct.  I have corrected the documentation and it
should be reflected on the website in the upcoming hours.  It should be:

  *   int MyOperation( ..., GDALProgressFunc pfnProgress, void *pProgressData );
  *
  *   {
  *       void *pScaledProgress;
  *
  *       pScaledProgress = GDALCreateScaledProgress( 0.0, 0.5, pfnProgress,
  *                                                   pProgressData );
  *       GDALDoLongSlowOperation(...,GDALScaledProgressFunc, pScaledProgress );
  *       GDALDestroyScaledProgress( pScaledProgress );
  *
  *       pScaledProgress = GDALCreateScaledProgress( 0.5, 1.0, pfnProgress,
  *                                                   pProgressData );
  *       GDALDoAnotherOperation(..., GDALScaledProgressFunc, pScaledProgress );
  *       GDALDestroyScaledProgress( pScaledProgress );
  *
  *       return ...;
  *   }

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org