QgsMapToolIdentify class

Map tool for identifying features in layers.

Contents

after selecting a point, performs the identification:

  • for raster layers shows value of underlying pixel
  • for vector layers shows feature attributes within search radius (allows editing values when vector layer is in editing mode)

Base classes

class QgsMapTool
Abstract base class for all map tools.

Derived classes

class QgsMapToolIdentifyFeature
The QgsMapToolIdentifyFeature class is a map tool to identify a feature on a chosen layer.

Constructors, destructors, conversion operators

QgsMapToolIdentify(QgsMapCanvas* canvas)
constructor

Public functions

void activate() override
called when set as currently active map tool
void canvasMoveEvent(QgsMapMouseEvent* e) override
Mouse move event for overriding. Default implementation does nothing.
void canvasPressEvent(QgsMapMouseEvent* e) override
Mouse press event for overriding. Default implementation does nothing.
void canvasReleaseEvent(QgsMapMouseEvent* e) override
Mouse release event for overriding. Default implementation does nothing.
void deactivate() override
called when map tool is being deactivated
auto flags() const -> Flags override
Returns the flags for the map tool.
auto identify(int x, int y, const QList<QgsMapLayer*>& layerList = QList<QgsMapLayer*>(), IdentifyMode mode = DefaultQgsSetting) -> QList<QgsMapToolIdentify::IdentifyResult>
Performs the identification.
auto identify(int x, int y, IdentifyMode mode, LayerType layerType = AllLayers) -> QList<QgsMapToolIdentify::IdentifyResult>
Performs the identification.
auto identify(const QgsGeometry& geometry, IdentifyMode mode, LayerType layerType) -> QList<QgsMapToolIdentify::IdentifyResult>
Performs identification based on a geometry (in map coordinates)
auto identify(const QgsGeometry& geometry, IdentifyMode mode, const QList<QgsMapLayer*>& layerList, LayerType layerType) -> QList<QgsMapToolIdentify::IdentifyResult>
Performs identification based on a geometry (in map coordinates)
auto identifyMenu() -> QgsIdentifyMenu*
Returns a pointer to the identify menu which will be used in layer selection mode this menu can also be customized.

Protected functions

auto derivedAttributesForPoint(const QgsPoint& point) -> QMap<QString, QString>
Returns derived attributes map for a clicked point in map coordinates. May be 2D or 3D point.
auto identify(int x, int y, IdentifyMode mode, const QList<QgsMapLayer*>& layerList, LayerType layerType = AllLayers) -> QList<QgsMapToolIdentify::IdentifyResult>
Performs the identification.
auto identifyLayer(QList<QgsMapToolIdentify::IdentifyResult>* results, QgsMapLayer* layer, const QgsPointXY& point, const QgsRectangle& viewExtent, double mapUnitsPerPixel, QgsMapToolIdentify::LayerType layerType = AllLayers) -> bool
Call the right method depending on layer type.
void restoreCanvasPropertiesOverrides()
Clears canvas properties overrides previously set with setCanvasPropertiesOverrides()
void setCanvasPropertiesOverrides(double searchRadiusMapUnits)
Overrides some map canvas properties inside the map tool for the upcoming identify requests.

Private functions

auto displayAreaUnits() const -> QgsUnitTypes::AreaUnit virtual
Desired units for area display.
auto displayDistanceUnits() const -> QgsUnitTypes::DistanceUnit virtual
Desired units for distance display.

Function documentation

Flags QgsMapToolIdentify::flags() const override

Returns the flags for the map tool.

QList<QgsMapToolIdentify::IdentifyResult> QgsMapToolIdentify::identify(int x, int y, const QList<QgsMapLayer*>& layerList = QList<QgsMapLayer*>(), IdentifyMode mode = DefaultQgsSetting)

Performs the identification.

Parameters
x x coordinates of mouseEvent
y y coordinates of mouseEvent
layerList Performs the identification within the given list of layers. Default value is an empty list, i.e. uses all the layers.
mode Identification mode. Can use Qgis default settings or a defined mode. Default mode is DefaultQgsSetting.
Returns a list of IdentifyResult

QList<QgsMapToolIdentify::IdentifyResult> QgsMapToolIdentify::identify(int x, int y, IdentifyMode mode, LayerType layerType = AllLayers)

Performs the identification.

Parameters
x x coordinates of mouseEvent
y y coordinates of mouseEvent
mode Identification mode. Can use Qgis default settings or a defined mode.
layerType Only performs identification in a certain type of layers (raster, vector). Default value is AllLayers.
Returns a list of IdentifyResult

To avoid being forced to specify IdentifyMode with a list of layers this has been made private and two publics methods are offered

QList<QgsMapToolIdentify::IdentifyResult> QgsMapToolIdentify::identify(int x, int y, IdentifyMode mode, const QList<QgsMapLayer*>& layerList, LayerType layerType = AllLayers) protected

Performs the identification.

Parameters
x x coordinates of mouseEvent
y y coordinates of mouseEvent
mode Identification mode. Can use Qgis default settings or a defined mode.
layerList Performs the identification within the given list of layers.
layerType Only performs identification in a certain type of layers (raster, vector).
Returns a list of IdentifyResult

To avoid being forced to specify IdentifyMode with a list of layers this has been made private and two publics methods are offered

void QgsMapToolIdentify::restoreCanvasPropertiesOverrides() protected

Clears canvas properties overrides previously set with setCanvasPropertiesOverrides()

void QgsMapToolIdentify::setCanvasPropertiesOverrides(double searchRadiusMapUnits) protected

Overrides some map canvas properties inside the map tool for the upcoming identify requests.

This is useful when the identification is triggered by some other piece of GUI like a 3D map view and some properties like search radius need to be adjusted so that identification returns correct results. Currently only search radius may be overridden.

When the custom identification has finished, restoreCanvasPropertiesOverrides() should be called to erase any overrides.

QgsUnitTypes::AreaUnit QgsMapToolIdentify::displayAreaUnits() const virtual private

Desired units for area display.

QgsUnitTypes::DistanceUnit QgsMapToolIdentify::displayDistanceUnits() const virtual private

Desired units for distance display.