[QGIS-Developer] Empty vs. Null rectangle, bogus ?

[Sandro Santilli]

I've added - in my PR https://github.com/qgis/QGIS/pull/45384 -
a test for QgsRectangle doing this:

  QgsRectangle r1( 0, 0, 0, 0 );
  QVERIFY( ! r1.isNull() );
  QVERIFY( r1.isEmpty() );

  QgsRectangle r2( 1, 1, 1, 1 );
  QVERIFY( ! r2.isNull() );
  QVERIFY( r2.isEmpty() );

The first test fails, the second succeeds.
See
https://cdash.orfeo-toolbox.org/testDetails.php?test=32862378&build=87747

This confirms the confusion in the meaning of "null"

--strk;

On Mon, Oct 18, 2021 at 08:05:22PM +0200, Sandro Santilli wrote:
> Still chasing bug
> QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator
> I reached QgsRectangle, whose "Null" or "Empty" nature changes
> behavior of QgsFeatureVectorFeatureIterator in a way that prevents
> proper WithinDistance filter from working.
> 
> Details are written in
> https://github.com/qgis/QGIS/issues/45352
> but what I wanted to ask here is:
> 
> According to the comments Empty means that some information is still
> available (bounding box of a point) but the unit test for QgsRectangle
> (and the isEmpty method implementation) seem to check for Max < Min,
> which would NOT be the case for the bounding box of a point,
> so is puzzling.
> 
> I'm not sure how to proceed for fixing the bug I'm seeing because
> one simple fix would be avoiding to call setRectangle on a QgsRequest
> if the iterator's mFilterRect is Empty, but a more complex solution
> could be to *allow* those QgsRequests to have multiple filters, rather
> than one excluding the other.
> 
> Also I've yet to understand WHY at construction time a
> QgsAbstractFeatureIterator shoul dhave an Empty rather than Null
> rectangle, which brings back to the first question (is the distinction
> really defined?).
> 
> --strk; 
> 
>   Libre GIS consultant/developer
>   https://strk.kbt.io/services.html
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-- 

  Libre GIS consultant/developer
  https://strk.kbt.io/services.html