Class: QgsMapRendererJob

class qgis.core.QgsMapRendererJob

Bases: PyQt5.QtCore.QObject

Abstract base class for map rendering implementations.

The API is designed in a way that rendering is done asynchronously, therefore the caller is not blocked while the rendering is in progress. Non-blocking operation is quite important because the rendering can take considerable amount of time.

Common use case: 0. prepare QgsMapSettings with rendering configuration (extent, layer, map size, …) 1. create QgsMapRendererJob subclass with QgsMapSettings instance 2. connect to job’s finished() signal 3. call start(). Map rendering will start in background, the function immediately returns 4. at some point, slot connected to finished() signal is called, map rendering is done

It is possible to cancel the rendering job while it is active by calling cancel() function.

The following subclasses are available: - QgsMapRendererSequentialJob - renders map in one background thread to an image - QgsMapRendererParallelJob - renders map in multiple background threads to an image - QgsMapRendererCustomPainterJob - renders map with given QPainter in one background thread

New in version 2.4: Enums

Methods

cancel Stop the rendering job - does not return until the job has terminated.
cancelWithoutBlocking Triggers cancellation of the rendering job without blocking.
childEvent
connectNotify
customEvent
disconnectNotify
errors List of errors that happened during the rendering job - available when the rendering has been finished
featureFilterProvider Returns the feature filter provider used by the QgsRenderContext of each LayerRenderJob.
isActive Tell whether the rendering job is currently running in background.
isSignalConnected
mapSettings Returns map settings with which this job was started.
receivers
renderingTime Returns the total time it took to finish the job (in milliseconds).
sender
senderSignalIndex
setCache Assign a cache to be used for reading and storing rendered images of individual layers.
setFeatureFilterProvider Set the feature filter provider used by the QgsRenderContext of each LayerRenderJob.
start Start the rendering job and immediately return.
takeLabelingResults Gets pointer to internal labeling engine (in order to get access to the results).
timerEvent
usedCachedLabels Returns True if the render job was able to use a cached labeling solution.
waitForFinished Block until the job has finished.

Signals

finished emitted when asynchronous rendering is finished (or canceled).
renderingLayersFinished Emitted when the layers are rendered.

Attributes

class Error(lid: str, msg: str)

Bases: sip.wrapper

QgsMapRendererJob.Error(QgsMapRendererJob.Error)

layerID
message
cancel(self)

Stop the rendering job - does not return until the job has terminated. Does nothing if the rendering is not active.

cancelWithoutBlocking(self)

Triggers cancellation of the rendering job without blocking. The render job will continue to operate until it is able to cancel, at which stage the finished() signal will be emitted. Does nothing if the rendering is not active.

childEvent()
connectNotify()
customEvent()
disconnectNotify()
errors(self) → object

List of errors that happened during the rendering job - available when the rendering has been finished

featureFilterProvider(self) → QgsFeatureFilterProvider

Returns the feature filter provider used by the QgsRenderContext of each LayerRenderJob.

New in version 3.0.

finished

emitted when asynchronous rendering is finished (or canceled). [signal]

isActive(self) → bool

Tell whether the rendering job is currently running in background.

isSignalConnected()
mapSettings(self) → QgsMapSettings

Returns map settings with which this job was started.

Returns:A QgsMapSettings instance with render settings

New in version 2.8.

receivers()
renderingLayersFinished

Emitted when the layers are rendered. Rendering labels is not yet done. If the fully rendered layer including labels is required use finished() instead.

New in version 3.0: [signal]

renderingTime(self) → int

Returns the total time it took to finish the job (in milliseconds).

See also

perLayerRenderingTime()

sender()
senderSignalIndex()
setCache(self, cache: QgsMapRendererCache)

Assign a cache to be used for reading and storing rendered images of individual layers. Does not take ownership of the object.

setFeatureFilterProvider(self, f: QgsFeatureFilterProvider)

Set the feature filter provider used by the QgsRenderContext of each LayerRenderJob. Ownership is not transferred and the provider must not be deleted before the render job.

New in version 3.0.

start(self)

Start the rendering job and immediately return. Does nothing if the rendering is already in progress.

takeLabelingResults(self) → QgsLabelingResults

Gets pointer to internal labeling engine (in order to get access to the results). This should not be used if cached labeling was redrawn - see usedCachedLabels().

timerEvent()
usedCachedLabels(self) → bool

Returns True if the render job was able to use a cached labeling solution. If so, any previously stored labeling results (see takeLabelingResults()) should be retained.

New in version 3.0.

waitForFinished(self)

Block until the job has finished.