[Qgis-developer] keeping layer settings tab between layers and qgis sessions can cause problems when histogram tab is the last viewed

[G. Allegri]

A raster provider is not said it is a GDAL provider, so such
functionalitites must not be fitted to GDAL only...

giovanni

2012/5/10 Etienne Tourigny <etourigny.dev at gmail.com>

> On Thu, May 10, 2012 at 10:03 AM, Etienne Tourigny
> <etourigny.dev at gmail.com> wrote:
> > You are right, that is the best approach.  However, it might be best
> > to auto-load when the user actually switches to the tab.
> >
> > A pain gdal does not have an API to query if the histogram is already
> > computed - this would require adding PAM-aware code to the gdal
> > provider.
> >
>
> I need to correct myself - PamFindMatchingHistogram() is available in
> gdal_pam.h and could be used to test if a cached histogram exists -
> provided the raster is a pam raster.
>
> However, it seems the raster provider uses the C GDAL API - rather
> than the C++ API , could this be changed easily?
>
> Etienne
>
> > Etienne
> >
> > On Wed, May 9, 2012 at 9:53 PM, Nathan Woodrow <madmanwoo at gmail.com>
> wrote:
> >> Generally it is good practice that the UI remembers where the user left
> it
> >> last time.  In this case this has a bad user experience because of the
> slow
> >> loading.  My suggestion would be to just add a "Load histogram" button
> in
> >> the histogram tab that loads the histogram rather then when the tab is
> >> switched to.  This way even if the histogram tab is remembered as the
> >> current tab it will load like normal and user has to click
> "Load histogram"
> >> to show it.
> >>
> >> - Nathan
> >>
> >>
> >> On Thu, May 10, 2012 at 10:49 AM, Etienne Tourigny <
> etourigny.dev at gmail.com>
> >> wrote:
> >>>
> >>> I agree that this should not happen, should the default be always open
> >>> the first tab, or only when the histogram tab was previously selected?
> >>>
> >>> Unfortunately there is no function in the provider API to know if
> >>> there is a cached histogram, so it would be better to never allow the
> >>> properties window to start on the histogram tab.
> >>>
> >>> I have implemented this in a branch of mine to improve the histogram
> >>> tab, here is a snippet:
> >>>
> >>> -  tabBar->setCurrentIndex( settings.value(
> >>> "/Windows/RasterLayerProperties/row" ).toInt() );
> >>> +  int currentTabIndex = settings.value(
> >>> "/Windows/RasterLayerProperties/row" ).toInt();
> >>> +  // if current tab is disabled, use first tab
> >>> +  if ( ! tabBar->widget( currentTabIndex )->isEnabled() )
> >>> +    currentTabIndex = 0;
> >>> +  // if current tab is histogram, use first tab (to avoid long
> >>> histogram queries)
> >>> +  // there is currently no way to know if there ia a cached histogram
> >>>   int myHistogramTab = 6;
> >>> -  if ( tabBar->currentIndex() == myHistogramTab )
> >>> -  {
> >>> -    refreshHistogram();
> >>> -  }
> >>> +  if ( currentTabIndex == myHistogramTab )
> >>> +    currentTabIndex = 0;
> >>> +  tabBar->setCurrentIndex( currentTabIndex );
> >>>
> >>>
> >>> Etienne
> >>>
> >>> On Mon, May 7, 2012 at 10:15 AM, G. Allegri <giohappy at gmail.com>
> wrote:
> >>> > A complex object to say something simple :(
> >>> > When a user opens a layer settings window and hits a tab, the same
> tab
> >>> > index
> >>> > is kept when opening another layer settings, or in a new qgis
> sessions.
> >>> > I had a small raster layer, and I opened the histogram tab.
> >>> > The today I've opened a big raster layer, and opening the layer
> settings
> >>> > caused my pc running and running, till a complete qgis crash.
> >>> > I supposed it was something with the settings, so I opened the smalle
> >>> > raster, changed the tab to Style, then I was able to open the large
> >>> > raster
> >>> > settings
> >>> > It's corner case probably, and qgis shouldn't crash with huge raster
> >>> > histograms. Anyway, opening the layer settings to the frist tab would
> >>> > avoid
> >>> > heartbreaks :)
> >>> >
> >>> > giovanni
> >>> >
> >>> > _______________________________________________
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> >>> > http://lists.osgeo.org/mailman/listinfo/qgis-developer
> >>> >
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> >>
> >>
>
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