/*! \page api_break Backwards Incompatible Changes

\tableofcontents

The API of QGIS libraries is allowed to be changed just between major versions of QGIS. For example, there
are various planned backwards incompatible changes between QGIS 1.8 and 2.0 because the version 2.0 is a new
major version. After a release of a major version of QGIS (e.g. 2.0) the developer team is committed to maintain
stable API for all subsequent minor releases (2.2, 2.4, ...). That roughly means we do not rename classes and methods,
remove them nor change their semantics. Existing code should keep working when the user updates QGIS
to another minor version (e.g. from 2.0 to 2.2), so all extensions of existing classes should be done in a manner that
third party developers do not need to adjust their code to work properly with newer QGIS releases.

Sometimes, however, we may need to break the API as a result of some code changes. These cases should be only exceptions
and they should happen only after consideration and agreement of the development team. Backwards incompatible changes
with too big impact should be deferred to a major version release.

This page tries to maintain a list with incompatible changes that happened in previous releases.

\section qgis_api_break_3_0 QGIS 3.0

\subsection qgis_api_break_3_0_removed_classes Removed Classes

<ul>
<li>QgsLabel and QgsLabelAttributes. Replaced by labeling based on PAL library, see QgsLabelingEngineV2.</li>
<li>QgsMapCanvasMap. It is an internal class used by map canvas.</li>
<li>QgsMapRenderer. It has been replaced by QgsMapRendererJob with subclasses and QgsMapSettings.</li>
<li>QgsCRSCache was removed. QgsCoordinateReferenceSystem now internally uses a cache for CRS creation,
so there is no longer a need for the separate cache class. Code which previously called QgsCRSCache::updateCRSCache()
should now call QgsCoordinateReferenceSystem::invalidateCache() and QgsCoordinateTransformCache::instance()->invalidateCrs( authid ).</li>
<li>QgsPseudoColorShader. This shader has been broken for some time and was replaced by QgsSingleBandPseudoColorRenderer.</li>
</ul>

\subsection qgis_api_break_3_0_global General changes

<ul>
<li>All setDestinationCRS() methods have been renamed to setDestinationCrs()</li>
<li>All destinationCRS() methods have been renamed to destinationCrs()</li>
<li>All readXML() and _readXML() methods have been renamed to readXml() and _readXml()</li>
<li>All writeXML() and _writeXML() methods have been renamed to writeXml() and _writeXml()</li>
<li>All setLayerID() methods have been renamed to setLayerId()</li>
<li>All layerID() methods have been renamed to layerId()</li>
<li>All setCRS() methods have been renamed to setCrs()</li>
<li>All srcCrs() methods have been renamed to sourceCrs()</li>
<li>All destCrs() methods have been renamed to destinationCrs()</li>
<li>All exportXML() methods have been renamed to exportXml()</li>
<li>All importXML() methods have been renamed to importXml()</li>

</ul>

\subsection qgis_api_break_3_0_Qgis Qgis

<ul>
<li>The QGis class was renamed to Qgis for capitalisation consistency with other class names</li>
<li>permissiveToDouble() and permissiveToInt() where moved out of the QGis class and renamed to qgsPermissiveToDouble() and
qgsPermissiveToInt()</li>
<li>The constants DEFAULT_IDENTIFY_RADIUS and MINIMUM_POINT_SIZE were removed</li>
<li>QGis::DecimalDegrees, DegreesMinutesSeconds and DegreesDecimalMinutes have been removed, and have all been replaced
with the general Degrees unit</li>
<li>The distance unit types QGis::UnitType (including QGis::Meters, QGis::Feet, QGis::Degrees, QGis::NauticalMiles,
QGis::Kilometers, QGis::Yards, QGis::Miles and QGis::UnknownUnit have been moved to QgsUnitTypes::DistanceUnit.
Some of these unit types have also been renamed - see the notes on QgsUnitTypes below. All methods which accepted
QGis::UnitType parameters have been updated to take QgsUnitTypes::DistanceUnit instead.</li>
<li>The unit handling methods toLiteral, fromLiteral, tr, fromTr, fromUnitToUnitFactor have been removed. Their
corresponding counterparts in QgsUnitTypes should be used instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsProject QgsProject

<ul>
<li>visibilityPresetCollection() has been renamed to mapThemeCollection()</li>
</ul>

\subsection qgis_api_break_3_0_QgsVisibilityPresetCollection QgsVisibilityPresetCollection

<ul>
<li>Has been renamed to QgsMapThemeCollection</li>
</ul>

\subsection qgis_api_break_3_0_QgsAuthConfigUriEdit QgsAuthConfigUriEdit

<ul>
<li>hasConfigID() has been renamed to hasConfigId()</li>
</ul>

\subsection qgis_api_break_3_0_QgsAtlasComposition QgsAtlasComposition

<ul>
<li>readXMLMapSettings() has been renamed to readXmlMapSettings()</li>
</ul>

\subsection qgis_api_break_3_0_QgsComposerLegendItem QgsComposerLegendItem

<ul>
<li>writeXMLChildren() has been renamed to writeXmlChildren()</li>
</ul>

\subsection qgis_api_break_3_0_QgsComposerMap QgsComposerMap

<ul>
<li>containsWMSLayer() has been renamed to containsWmsLayer()</li>
<li>mapRenderer() has been removed. Use mapSettings() instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsComposerNodesItem QgsComposerNodesItem

<ul>
<li>_readXMLStyle() has been renamed to _readXmlStyle()</li>
<li>_writeXMLStyle() has been renamed to _writeXMLStyle()</li>
</ul>

\subsection qgis_api_break_3_0_QgsComposerTable QgsComposerTable

<ul>
<li>tableWriteXML() has been renamed to tableWriteXml()</li>
<li>tableReadXML() has been renamed to tableReadXml()</li>
</ul>


\subsection qgis_api_break_3_0_QgsComposition QgsComposition

<ul>
<li>addItemsFromXML() has been renamed to addItemsFromXml()</li>
<li>Constructor with QgsMapRenderer parameter has been removed. Use the variant with QgsMapSettings parameter.</li>
<li>mapRenderer() has been removed. Use mapSettings() instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsCoordinateReferenceSystem QgsCoordinateReferenceSystem

<ul>
<li>QgsCoordinateReferenceSystem now uses internal caches to avoid expensive database lookups
when CRS objects are initialized. This is handled internally, but invalidateCache() must be
called if changes are made to the CRS database.</li>
<li>setCustomSrsValidation() has been renamed to setCustomCrsValidation()</li>
<li>saveAsUserCRS() has been renamed to saveAsUserCrs()</li>
<li>geographicCRSAuthId() has been renamed to geographicCrsAuthId()</li>
<li>geographicFlag() was renamed to isGeographic()</li>
<li>axisInverted() was renamed to hasAxisInverted()</li>
</ul>

\subsection qgis_api_break_3_0_QgsCoordinateTransform QgsCoordinateTransform

<ul>
<li>QgsCoordinateTransform is no longer a QObject. readXml, writeXml and initialise are all normal public members now,
not slots. The invalidTransformInput() signal has been removed.</li>
<li>The extra QgsCoordinateTransform constructors (those not taking QgsCoordinateReferenceSystem arguments) have been
removed. Now, QgsCoordinateTransform must be created using an already existing source and destination
QgsCoordinateReferenceSystem object.</li>
<li>QgsCoordinateTransform::clone() has been removed. Just use direct copies instead.</li>
<li>sourceCrs() and destCrs() now return a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++
plugins calling these methods will need to be updated.</li>
<li>isInitialised() has been renamed to isValid()</li>
<li>theCRS parameter in setSourceCrs has been renamed to 'crs'</li>
<li>setDestCRS() has been renamed to setDestinationCrs() for consistency</li>
<li>destCRS() has been renamed to destinationCrs() for consistency</li>
<li>theSource, theDest, theSourceSrsId, theDestSrsId, theSourceWkt, theDestWkt, theSourceCRSType parameters in the QgsCoordinateTransform constructors have been renamed to source, destination, sourceSrsId, destinationSrsId, sourceWkt, destinationWkt, sourceCrsType respectively</li>
<li>'p' argument in transform() has been renamed to 'point', 'theRect' to 'rectangle', 'poly' to 'polygon'</li>
<li>setDestCRSID has been removed, use setDestinationCrs() instead</li>
<li>'theNode', 'theDoc' parameters in readXML and writeXML have been renamed to 'node' and 'document' respectively</li>
<li>readXML() and writeXML() have been renamed to readXml() and writeXml() for consistency</li>
</ul>

\subsection qgis_api_break_3_0_QgsCoordinateTransformCache QgsCoordinateTransformCache

<ul>
<li>transform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned in place of a null pointer.</li>
</ul>

\subsection qgis_api_break_3_0_QgsCptCitySelectionItem QgsCptCitySelectionItem

<ul>
<li>parseXML() has been renamed to parseXml()</li>
</ul>

\subsection qgis_api_break_3_0_QgsCRSCache QgsCRSCache

<ul>
<li>QgsCRSCache has been renamed to QgsCrsCache</li>
<li>updateCRSCache() has been renamed to updateCrsCache</li>
</ul>

\subsection qgis_api_break_3_0_QgsDataDefinedSymbolDialog QgsDataDefinedSymbolDialog

<ul>
<li>QgsDataDefinedSymbolDialog was removed. Code using this dialog should be reworked to use QgsDataDefinedButton
instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsDataItem QgsDataItem

<ul>
<li>supportedCRS() has been renamed to supportedCrs()</li>
</ul>

\subsection qgis_api_break_3_0_QgsDiagramLayerSettings QgsDiagramLayerSettings

<ul>
<li>coordinateTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned in place of a null pointer.</li>
<li>setCoordinateTransform() now takes a QgsCoordinateTransform object, not a pointer. Use an invalid QgsCoordinateTransform in
place of a null pointer.</li>
<li>The ct member has been removed. Use coordinateTransform() and setCoordinateTransform() instead.
</ul>

\subsection qgis_api_break_3_0_QgsDatumTransformStore QgsDatumTransformStore

<ul>
<li>transformation() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned in place of a null pointer.</li>
</ul>

\subsection qgis_api_break_3_0_DataProviders Data Providers

<ul>
<li>Many methods in QgsDataProvider, QgsVectorDataProvider and QgsRasterDataProvider have been made const-correct.
This has no effect on PyQGIS code, but c++ code implementing third-party providers will need to update the
signatures of these methods to match. Affected methods are:
<ul>
<li>QgsDataProvider: crs(), extent(), isValid(), supportsSubsetString(), subsetString()</li>
<li>QgsVectorDataProvider: getFeatures(), minimumValue(), maximumValue(), uniqueValues(), enumValues(), defaultValue(),
attributeIndexes(), pkAttributeIndexes(), isSaveAndLoadStyleToDBSupported()</li>
<li>QgsRasterInterface: extent()</li>
</ul
</li>
</ul>

\subsection qgis_api_break_3_0_QgsFeature QgsFeature

<ul>
<li>geometryAndOwnership() has been removed. Use geometry() instead.</li>
<li>setGeometryAndOwnership() has been removed. Use setGeometry() instead.</li>
<li>The setGeometry( QgsGeometry* ) method has been removed, use setGeometry( const QgsGeometry& ) instead.</li>
<li>The geometry() method now returns a copy of the geometry, not a pointer. Since QgsGeometry objects are
implicitly shared this is a low-cost copy, and avoids ownership and dangling pointer issues. <b>Very important: Testing that
a feature has a geometry is now done using the new hasGeometry() method. Any code which compares QgsFeature::geometry() to 
None will need to be modified, as the method will return an empty geometry if the feature has no geometry.</b></li>
<li>The temporary constGeometry() method has been removed. Use geometry() instead.</li>
<li>setFields( const QgsFields*, bool ) has been removed, use setFields( const QgsFields&, bool ) instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsGeometry QgsGeometry

<ul>
<li>All QgsGeometry methods now accept geometry references instead of pointers, and return a QgsGeometry
value instead of a pointer. The biggest impact with this change is that PyQGIS code should not compare a geometry
result to None, but instead either use a boolean test (`if g.buffer(10):`) or explicitly use the isEmpty()
method to determine if a geometry is valid.</li>
</ul>

\subsection qgis_api_break_3_0_QgsGeometryAnalyzer QgsGeometryAnalyzer

<ul>
<li>locateBetweenMeasures() and locateAlongMeasure() now take geometry references, not pointers, and return 
a QgsGeometry value rather than a pointer.</li>
</ul>

\subsection qgis_api_break_3_0_QgsGroupWMSDataDialog QgsGroupWMSDataDialog

<ul>
<li>QgsGroupWMSDataDialo has been renamed to QgsGroupWmsDataDialog</li>
</ul>

\subsection qgis_api_break_3_0_QgsHighlight QgsHighlight

<ul>
<li>The QgsHighlight constructor now takes a geometry reference, not a pointer.</li>
</ul>



\subsection qgis_api_break_3_0_QgsVectorDataProvider QgsVectorDataProvider

<ul>
<li>QgsVectorDataProvider::fields() now returns a copy, rather than a const reference. Since QgsFields
objects are implicitly shared, returning a copy helps simplify and make code more robust. This change
only affects third party c++ providers, and does not affect PyQGIS scripts.</li>
<li>The SaveAsShapefile, SelectGeometryAtId, RandomSelectGeometryAtId and SequentialSelectGeometryAtId
capabilities have been removed, as they were unused and had no effect.</li>
<li>capabilities() now returns a typesafe QgsVectorDataProvider::Capabilities object, not an integer.</li>
<li>convertToProviderType() now takes a geometry reference, not a pointer.</li>
</ul>

\subsection qgis_api_break_3_0_QgsLabelingEngineInterface QgsLabelingEngineInterface

<ul>
<li>init(QgsMapRenderer*) has been removed. Use init(const QgsMapSettings&) instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsLayerTreeGroup QgsLayerTreeGroup

<ul>
<li>readChildrenFromXML() has been renamed to readChildrenFromXml()</li>
</ul>

\subsection qgis_api_break_3_0_QgsLayerTreeNode QgsLayerTreeNode

<ul>
<li>readCommonXML() has been renamed to readCommonXml()</li>
<li>writeCommonXML() has been renamed to writeCommonXml()</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapCanvas QgsMapCanvas

<ul>
<li>rotationEnabled() and enableRotation() have been removed, since map rotation is now always supported</li>
<li>The "name" parameter has been removed from constructor. Use QObject::setObjectName() to set canvas name if necessary.</li>
<li>map() has been removed because QgsMapCanvasMap is not available in API anymore.</li>
<li>mapRenderer() has been removed. Use directly map canvas methods to get/set configuration or mapSettings() (for reading only).</li>
<li>canvasPaintDevice() has been removed. Use map canvas items to draw anything on top of canvas.</li>
<li>clear() has been removed. Use refresh() instead.</li>
<li>setCanvasColor() and canvasColor() are not virtual methods anymore.</li>
<li>updateFullExtent() has been removed. No need to call it explicitly. Full extent calculation is done in QgsMapSettings.</li>
<li>setDirty() and isDirty() have been removed. Use refresh() to refresh canvas content.</li>
<li>setWheelAction() and WheelAction enum have been removed. Custom wheel actions are not supported anymore.</li>
<li>updateMap(), showError(), useImageToRender() have been removed. They did nothing since 2.4.</li>
<li>setProgress() signal has been removed. It was not emitted since 2.0.</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapLayer QgsMapLayer

<ul>
<li>crs() now returns a QgsCoordinateReferenceSystem object, not a reference. This change has no effect for PyQGIS code.</li>
<li>setLayerName() was removed, use setName() instead. The layerNameChanged() signal has been replaced by nameChanged().</li>
<li>toggleScaleBasedVisibility() was replaced by setScaleBasedVisibility()</li>
<li>lastErrorTitle(), lastError(), cacheImage(), onCacheImageDelete(), clearCacheImage() and the signals drawingProgress(),
screenUpdateRequested() were removed. These members have had no effect for a number of QGIS 2.x releases.</li>
<li>extent(), styleURI(), exportNamedStyle(), exportSldStyle(), writeXml(), metadata() were made const. This has no effect on PyQGIS code, but c++ code implementing derived layer classes will need to update the signatures of these methods to match.</li>
<li>The lyrname parameter in the QgsMapLayer constructor was renamed to 'name'.</li>
<li>The vis parameter in setSubLayerVisibility was renamed to 'visible'.</li>
<li>theResultFlag parameter in loadDefaultStyle and saveDefaultStyle were renamed to resultFlag.</li>
<li>theURI, theResultFlag parameters in loadNamedStyle, saveNamedStyle, saveSldStyle and loadSldStyle were renamed to uri, resultFlag.</li>
<li>theURI parameter in loadNamedStyleFromDb was renamed to uri.</li>
<li>theMinScale and theMaxScale parameters in setMinimumScale and setMaximumScale were renamed to scale</li>
<li>The layerCrsChanged() signal was renamed to crsChanged()</li>
<li>theError parameter in appendError() and setError() were renamed to 'error'.</li>
<li>drawLabels() method was removed. It used old deprecated labeling. Replaced by labeling based on PAL library, see QgsLabelingEngineV2.</li>
<li>readLayerXML() was renamed to readLayerXml()</li>
<li>writeLayerXML() was renamed to writeLayerXml()</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapOverviewCanvas QgsMapOverviewCanvas

<ul>
<li>destinationSrsChanged() was renamed to destinationCrsChanged()</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapRenderer QgsMapRenderer

<ul>
<li>transformation() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned instead of a null pointer if no transformation is required.</li>
<li>destinationSrsChanged() was renamed to destinationCrsChanged()</li>
<li>getCompositionMode(), getBlendModeEnum() and BlendMode enum have been moved to QgsPainting utility class.</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapRendererJob QgsMapRendererJob

<ul>
<li>reprojectToLayerExtent() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should
be used instead of a null pointer if no transformation is required.</li>
<li>prepareJobs() and drawLabeling() (neither available in PyQGIS) do not take QgsPalLabeling parameter anymore. All drawing of labels is done by QgsLabelingEngineV2.</li>
<li>drawOldLabeling(), drawNewLabeling() were removed. The method drawLabeling() should be used instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapSettings QgsMapSettings

<ul>
<li>layerTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned instead of a null pointer if no transformation is required.</li>
</ul>

\subsection qgis_api_break_3_0_QgsPalLabeling QgsPalLabeling

<ul>
<li>init(QgsMapRenderer*) has been removed. Use init(const QgsMapSettings&) instead.</li>
<li>prepareGeometry and geometryRequiresPreparation now take geometry references, not pointers.</li>
</ul>

\subsection qgis_api_break_3_0_QgsOSMElement QgsOSMElement

<ul>
<li>elemID() has been renamed to elemId()</li>
</ul>

\subsection qgis_api_break_3_0_QgsOWSSourceSelect QgsOWSSourceSelect

<ul>
<li>selectedLayersCRSs() has been renamed selectedLayersCrses()</li>
<li>populateCRS() has been renamed to populateCrs()</li>
<li>clearCRS() has been renamed to clearCrs()</li>
<li>addWMSListRow() has been renamed to addWmsListRow()</li>
<li>addWMSListItem() has been renamed to addWmsListItem()</li>
<li>selectedCRS() has been renamed to selectedCrs()</li>
</ul>

\subsection qgis_api_break_3_0_QgsOWSConnection QgsOWSConnection

<ul>
<li>QgsOWSConnection has been renamed QgsOwsConnection</li>
</ul>

\subsection qgis_api_break_3_0_QgsRasterDataProvider QgsRasterDataProvider

<ul>
<li>srcDataType() has been renamed to sourceDataType()</li>
<li>srcHasNoDataValue() has been renamed to sourceHasNoDataValue()</li>
<li>useSrcNoDataValue() has been renamed to useSourceNoDataValue()</li>
<li>setUseSrcNoDataValue() has been renamed to setUseSourceNoDataValue()</li>
<li>srcNoDataValue() has been renamed to sourceNoDataValue()</li>
</ul>

\subsection qgis_api_break_3_0_QgsRasterInterface QgsRasterInterface

<ul>
<li>srcDataType() has been renamed to sourceDataType()</li>
<li>srcInput() has been renamed to sourceInput()</li>
<li>block() has new "feedback" argument.</li>
</ul>

\subsection qgis_api_break_3_0_QgsRelation QgsRelation

<ul>
<li>createFromXML() has been renamed to createFromXml()</li>
</ul>

\subsection qgis_api_break_3_0_QgsRenderChecker QgsRenderChecker

<ul>
<li>setMapRenderer() has been removed. Use setMapSettings() instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsRenderContext QgsRenderContext

<ul>
<li>coordinateTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be returned instead of a null pointer if no transformation is required.</li>
<li>setCoordinateTransform() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
</ul>

\subsection qgis_api_break_3_0_QgsRubberBand QgsRubberBand

<ul>
<li>setToGeometry() and addGeometry() now take geometry references, not pointers.</li>
<li>QgsRubberBand( QgsMapCanvas* mapCanvas, bool isPolygon ) constructor and reset( bool isPolygon) have been removed, use constructor and function with Qgis::GeometryType as argument instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsPalLayerSettings QgsPalLayerSettings

<ul>
<li>ct is now a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
be used instead of a null pointer if no transformation is required.</li>
<li>prepareGeometry() and geometryRequiresPreparation() now take a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
</ul>

\subsection qgis_api_break_3_0_QgsSnapper QgsSnapper

<ul>
<li>Constructor variant with QgsMapRenderer has been removed. Use the variant with QgsMapSettings.</li>
</ul>

\subsection qgis_api_break_3_0_QgsTolerance QgsTolerance

<ul>
<li>vertexSearchRadius(), defaultTolerance(), toleranceInMapUnits() do not have variant with QgsMapRenderer anymore. Use the variants with QgsMapSettings.</li>
</ul>

\subsection qgis_api_break_3_0_QgsJSONExporter QgsJSONExporter

<ul>
<li>sourceCrs() now returns a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++
plugins calling this method will need to be updated.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayer QgsVectorLayer

<ul>
<li>excludeAttributesWMS() and setExcludeAttributesWMS() have been renamed to excludeAttributesWms() and 
setExcludeAttributesWms()</li>
<li>excludeAttributesWFS() and setExcludeAttributesWFS() have been renamed to excludeAttributesWfs() and 
setExcludeAttributesWfs()</li>
<li>changeGeometry() now accepts a geometry reference, not a pointer.</li>
<li>The geometryChanged() signal now uses a const QgsGeometry reference.</li>
<li>The deprecated removePolygonIntersections has been removed.</li>
<li>addTopologicalPoints() now takes a geometry reference, not a pointer.</li> 
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayerEditBuffer QgsVectorLayerEditBuffer

<ul>
<li>changeGeometry() now accepts a geometry reference, not a pointer.</li>
<li>The geometryChanged() signal now uses a const QgsGeometry reference.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayerEditUtils QgsVectorLayerEditUtils

<ul>
<li>addTopologicalPoints() now accepts a geometry reference, not a pointer.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayerImport QgsVectorLayerImport

<ul>
<li>QgsVectorLayerImport now takes references instead of pointers to QgsCoordinateReferenceSystem objects. Since
QgsCoordinateReferenceSystem is now implicitly shared, using references to QgsCoordinateReferenceSystem rather than
pointers makes for more robust, safer code. Use an invalid (default constructed) QgsCoordinateReferenceSystem
in code which previously passed a null pointer to QgsVectorLayerImport.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayerUndoCommand QgsVectorLayerUndoCommand

<ul>
<li>QgsVectorLayerUndoCommandChangeGeometry constructor now accepts a geometry reference, not a pointer.</li>
</ul>


\subsection qgis_api_break_3_0_QgsPointLocator QgsPointLocator

<ul>
<li>The constructor now takes a reference rather than a pointer to a CRS.  This has no effect on PyQGIS code, but c++
plugins calling this method will need to be updated.</li>
<li>The destCRS parameter in the constructor has been renamed to destinationCrs.</li>
<li>destCRS() has been renamed to destinationCrs()</li>
<li>destinationCrs() now returns a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++
plugins calling this method will need to be updated.</li>
</ul>

\subsection qgis_api_break_3_0_QgsMapSettings QgsMapSettings

<ul>
<li>destinationCrs() now returns a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++
plugins calling this method will need to be updated.</li>
</ul>

\subsection qgis_api_break_3_0_QgsGraphBuilderInterface QgsGraphBuilderInterface

<ul>
<li>destinationCrs() now returns a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++
plugins calling this method will need to be updated.</li>
</ul>

\subsection qgis_api_break_3_0_QgsNumericSortTreeWidgetItem QgsNumericSortTreeWidgetItem

<ul>
<li>QgsNumericSortTreeWidgetItem has been removed and replaced with QgsTreeWidgetItem, which
has improved sort capabilities including the ability to set custom sort values for items
and for forcing certain items to always sort on top.</li>
</ul>

\subsection qgis_api_break_3_0_QgsSymbolV2 QgsSymbolV2

<ul>
<li>The OutputUnit enum, including QgsSymbolV2::MM, QgsSymbolV2::MapUnit, QgsSymbolV2::Mixed, QgsSymbolV2::Pixel and QgsSymbolV2::Percentage has been moved to QgsUnitTypes
and renamed to RenderUnit. QgsSymbolV2::OutputUnitList was renamed to QgsUnitTypes::RenderUnitList. All methods which previously accepted QgsSymbolV2::OutputUnit
parameters or QgsSymbolV2::OutputUnitList parameters now take QgsUnitTypes::RenderUnit or QgsUnitTypes::RenderUnitList parameters respectively.</li>
</ul>

\subsection qgis_api_break_3_0_QgsSymbolLayerV2Utils QgsSymbolLayerV2Utils

<ul>
<li>encodeOutputUnit() and decodeOutputUnit() were removed. QgsUnitTypes::encodeUnit() and QgsUnitTypes::decodeRenderUnit() should be used instead.</li>
</ul>

\subsection qgis_api_break_3_0_QgsTreeWidgetItem QgsTreeWidgetItem

<ul>
<li>QgsTreeWidgetItem is no longer a QObject and does not emit the itemEdited signal. Instead,
use QgsTreeWidgetItemObject which is an upgraded version of the original QgsTreeWidgetItem</li>
</ul>

\subsection qgis_api_break_3_0_QgsUnitTypes QgsUnitTypes

<ul>
<li>All distance enumeration values were renamed to have a "Distance" prefix, including
Meters (to DistanceMeters), Kilometers (to DistanceKilometers), Feet (to DistanceFeet),
NauticalMiles (to DistanceNauticalMiles), Yards (to DistanceYards), Miles (to DistanceMiles),
Degrees (to DistanceDegrees) and UnknownDistanceUnit to DistanceUnknownUnit</li>
<li>All area enumeration values were renamed to have a "Area" prefix, including
SquareMeters (to AreaSquareMeters), SquareKilometers (to AreaSquareKilometers), SquareFeet (to AreaSquareFeet),
SquareYards (to AreaSquareYards), SquareMiles (to AreaSquareMiles), Hectares (to AreaHectares),
Acres (to AreaAcres), SquareNauticalMiles (to AreaSquareNauticalMiles), SquareDegrees (to AreaSquareDegrees)
and UnknownAreaUnit to AreaUnknownUnit</li>
<li>All angle enumeration values were renamed to have a "Angle" prefix, including
Radians (to AngleRadians), Gon (to AngleGon), MinutesOfArc (to AngleMinutesOfArc),
SecondsOfArc (to AngleSecondsOfArc), Turn (to AngleTurn) and UnknownAngleUnit to AngleUnknownUnit</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayer QgsVectorLayer

<ul>
<li>commitErrors() now returns an object, rather than a reference. This has no effect on PyQGIS code.</li>
<li>subsetString() was made const. This has no effect on PyQGIS code, but c++ code implementing derived layer classes will need to update the signature of this method to match.</li>
<li>label(), enableLabels(), hasLabelsEnabled(), drawLabels() have been removed. Replaced by labeling based on PAL library, see QgsLabelingEngineV2.</li>
</ul>

\subsection qgis_api_break_3_0_QgsRasterProjector QgsRasterProjector

<ul>
<li>extentSize() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorFileWriter QgsVectorFileWriter

<ul>
<li>QgsVectorFileWriter now takes references instead of pointers to QgsCoordinateReferenceSystem objects. Since
QgsCoordinateReferenceSystem is now implicitly shared, using references to QgsCoordinateReferenceSystem rather than
pointers makes for more robust, safer code. Use an invalid (default constructed) QgsCoordinateReferenceSystem
in code which previously passed a null pointer to QgsVectorFileWriter.</li>
<li>writeAsVectorFormat() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
</ul>

\subsection qgis_api_break_3_0_QgsVectorLayerEditBuffer QgsVectorLayerEditBuffer

<ul>
<li>The addedFeatures(), changedAttributeValues(), deletedAttributeIds(), addedAttributes(), changedGeometries()
and deletedFeatureIds() functions now return values, not references. This has no effect on PyQGIS code, but c++
plugins calling these methods will need to be updated.</li>
</ul>

\subsection qgis_api_break_3_0_QgsWMSLegendNode QgsWMSLegendNode

<ul>
<li>QgsWMSLegendNode has been renamed to QgsWmsLegendNode</li>
</ul>


\section qgis_api_break_2_4 QGIS 2.4

\subsection qgis_api_break_mtr Multi-threaded Rendering

<ul>
<li>QgsMapCanvas::refresh() only schedules a map refresh (in near feature) and returns immediately - before it would do the drawing immediately
and return when the map is redrawn. A call to refresh() will have no effect if there is already a scheduled pending refresh.
When map canvas does actual rendering, it will first emit renderStarting() signal, once done it will emit mapCanvasRefreshed().
The client code doing refresh() in order to later save map image should be updated to use new QgsMapRendererJob API which is better suited for such task.
<li>QgsPluginLayer::draw() is now run in a background thread. It is recommended to implement newly added QgsPluginLayer::createMapRenderer()
method instead of using QgsPluginLayer::draw().
</ul>

\section qgis_api_break_2_6 QGIS 2.6

\subsection qgis_api_break_legend_refactoring Legend Refactoring

<ul>
<li>QgsComposerLegend::model() - not being used anymore. The model was replaced by one based on QgsLayerTreeModel class
and is available in QgsComposerLegend::modelV2()
</ul>

*/