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

[Etienne Tourigny]

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.

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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