A QgsTask which retrieves sublayer details for a URI. More...

#include <qgsprovidersublayertask.h>

Inheritance diagram for QgsProviderSublayerTask:

[legend]

Public Member Functions
	QgsProviderSublayerTask (const QString &uri, bool includeSystemTables=false)
	Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri.

	QgsProviderSublayerTask (const QString &uri, const QString &providerKey, bool includeSystemTables=false)
	Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri, restricted to a particular provider.

	~QgsProviderSublayerTask () override

void	cancel () override
	Notifies the task that it should terminate.

QList< QgsProviderSublayerDetails >	results () const
	Returns the sublayer details as calculated by the task.

Public Member Functions inherited from QgsTask
	QgsTask (const QString &description=QString(), QgsTask::Flags flags=AllFlags)
	Constructor for QgsTask.

	~QgsTask () override

void	addSubTask (QgsTask *subTask, const QgsTaskList &dependencies=QgsTaskList(), SubTaskDependency subTaskDependency=SubTaskIndependent)
	Adds a subtask to this task.

bool	canCancel () const
	Returns `true` if the task can be canceled.

QList< QgsMapLayer * >	dependentLayers () const
	Returns the list of layers on which the task depends.

QString	description () const
	Returns the task's description.

qint64	elapsedTime () const
	Returns the elapsed time since the task commenced, in milliseconds.

Flags	flags () const
	Returns the flags associated with the task.

void	hold ()
	Places the task on hold.

bool	isActive () const
	Returns `true` if the task is active, ie it is not complete and has not been canceled.

double	progress () const
	Returns the task's progress (between 0.0 and 100.0)

void	setDependentLayers (const QList< QgsMapLayer * > &dependentLayers)
	Sets a list of layers on which the task depends.

void	setDescription (const QString &description)
	Sets the task's description.

TaskStatus	status () const
	Returns the current task status.

void	unhold ()
	Releases the task from being held.

bool	waitForFinished (int timeout=30000)
	Blocks the current thread until the task finishes or a maximum of timeout milliseconds.

Protected Member Functions
bool	run () override
	Performs the task's operation.

Protected Member Functions inherited from QgsTask
virtual void	finished (bool result)
	If the task is managed by a QgsTaskManager, this will be called after the task has finished (whether through successful completion or via early termination).

bool	isCanceled () const
	Will return `true` if task should terminate ASAP.

Additional Inherited Members
Public Types inherited from QgsTask
enum	Flag { CanCancel = 1 << 1 , CancelWithoutPrompt = 1 << 2 , Hidden = 1 << 3 , Silent = 1 << 4 , AllFlags = CanCancel }
	Task flags. More...

typedef QFlags< Flag >	Flags

enum	SubTaskDependency { SubTaskIndependent = 0 , ParentDependsOnSubTask }
	Controls how subtasks relate to their parent task. More...

enum	TaskStatus { Queued , OnHold , Running , Complete , Terminated }
	Status of tasks. More...

Signals inherited from QgsTask
void	begun ()
	Will be emitted by task to indicate its commencement.

void	progressChanged (double progress)
	Will be emitted by task when its progress changes.

void	statusChanged (int status)
	Will be emitted by task when its status changes.

void	taskCompleted ()
	Will be emitted by task to indicate its successful completion.

void	taskTerminated ()
	Will be emitted by task if it has terminated for any reason other then completion (e.g., when a task has been canceled or encountered an internal error).

Protected Slots inherited from QgsTask
void	setProgress (double progress)
	Sets the task's current progress.

Detailed Description

A QgsTask which retrieves sublayer details for a URI.

This task executes a call to QgsProviderRegistry::querySublayers() in a background thread. Depending on the URI queried it can be expensive to calculate the sublayers (e.g. in the case where a full table scan is required to resolve mixed geometry type layers), so it is beneficial to perform these queries in the background wherever possible.

While QgsProviderRegistry::querySublayers() offers various flags to control how in-depth the querying will be, these flags are not exposed through QgsProviderSublayerTask. Rather QgsProviderSublayerTask will always execute the most thorough query possible, regardless of how expensive this may be.

Since: QGIS 3.22

Definition at line 46 of file qgsprovidersublayertask.h.

Constructor & Destructor Documentation

◆ QgsProviderSublayerTask() [1/2]

QgsProviderSublayerTask::QgsProviderSublayerTask	(	const QString &	uri,
		bool	includeSystemTables = `false`
	)

Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri.

Definition at line 25 of file qgsprovidersublayertask.cpp.

◆ QgsProviderSublayerTask() [2/2]

QgsProviderSublayerTask::QgsProviderSublayerTask	(	const QString &	uri,
		const QString &	providerKey,
		bool	includeSystemTables = `false`
	)

Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri, restricted to a particular provider.

Since: QGIS 3.30

Definition at line 32 of file qgsprovidersublayertask.cpp.

◆ ~QgsProviderSublayerTask()

QgsProviderSublayerTask::~QgsProviderSublayerTask ( )

overridedefault

Member Function Documentation

◆ cancel()

void QgsProviderSublayerTask::cancel ( )

overridevirtual

Notifies the task that it should terminate.

Calling this is not guaranteed to immediately end the task, rather it sets the isCanceled() flag which task subclasses can check and terminate their operations at an appropriate time. Any subtasks owned by this task will also be canceled. Derived classes must ensure that the base class implementation is called from any overridden version.

See also: isCanceled()

Reimplemented from QgsTask.

Definition at line 72 of file qgsprovidersublayertask.cpp.

◆ results()

QList< QgsProviderSublayerDetails > QgsProviderSublayerTask::results ( ) const

Returns the sublayer details as calculated by the task.

Definition at line 40 of file qgsprovidersublayertask.cpp.

◆ run()

bool QgsProviderSublayerTask::run ( )

overrideprotectedvirtual

Performs the task's operation.

This method will be called when the task commences (ie via calling start() ), and subclasses should implement the operation they wish to perform in the background within this method.

A task must return a boolean value to indicate whether the task was completed successfully or terminated before completion.

Implements QgsTask.

Definition at line 48 of file qgsprovidersublayertask.cpp.

The documentation for this class was generated from the following files:

/build/qgis-3.40.0+99sid/src/core/providers/qgsprovidersublayertask.h
/build/qgis-3.40.0+99sid/src/core/providers/qgsprovidersublayertask.cpp

Public Member Functions

Protected Member Functions

Additional Inherited Members