[Backport release-3_40] qgsvectorlayer: Properly invalidate extent cache on feature addition or deletion #60504
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When a new feature is added to a `QgsVectorLayer` `QgsVectorLayer::addFeature` is called. This function makes mostly 2 things in case of a successful operation: 1. it calls `QgsVectorLayerEditBuffer::addFeature` which itself will emit the `QgsVectorLayerEditBuffer::featureAdded` signal. Finally, `QgsVectorLayer` listend to this signal to directly emit the `QgsVectorLayer::featureAdded` signal 2. Call `QgsVectorLayer::updateExtents()` to invalidate the cache of the extent In practice, this means that the `QgsVectorLayer::featureAdded` signal may be emitted before the cache of the extent is invalidated. This can cause some issues. For example, in the elevation profile tool, `QgsElevationProfileCanvas` listens to the `QgsVectorLayer::featureAdded` signal in order to regenerate the profile of a vector layer when a feature is added. This causes the creation of a new `QgsVectorLayerProfileGenerator` which needs to copy the extent of the vector layer. However, `QgsVectorLayer::updateExtents()` has not been called yet. Thus, it will use an outdated version of the extent. This issue is solved by calling `updateExtents()` before emitting the `featureAdded` signal.
This change is similar to the previous commit on feature addition. When a feature is removed from a `QgsVectorLayer` `QgsVectorLayer::deleteFeature` is called. This function makes mostly 2 things in case of a successful operation: 1. it calls `QgsVectorLayerEditBuffer::deleteFeature` which itself will emit the `QgsVectorLayerEditBuffer::featureDeleted` signal. Finally, `QgsVectorLayer` listend to this signal to directly emit the `QgsVectorLayer::featureDeleted` signal 2. Call `QgsVectorLayer::updateExtents()` to invalidate the cache of the extent In practice, this means that the `QgsVectorLayer::featureDeleted` signal may be emitted before the cache of the extent is invalidated. This can cause some issues. This issue is solved by calling `updateExtents()` before emitting the `featureDeleted` signal.
nyalldawson
approved these changes
Feb 7, 2025
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Backport #60431
Authored by: @ptitjano