QgsMapRendererCache Class Reference

This class is responsible for keeping cache of rendered images resulting from a map rendering job. More...

#include <qgsmaprenderercache.h>

Inheritance diagram for QgsMapRendererCache:

Public Member Functions
	QgsMapRendererCache ()
QImage	cacheImage (const QString &cacheKey) const
	Returns the cached image for the specified cacheKey. More...
void	clear ()
	Invalidates the cache contents, clearing all cached images. More...
void	clearCacheImage (const QString &cacheKey)
	Removes an image from the cache with matching cacheKey. More...
QList< QgsMapLayer * >	dependentLayers (const QString &cacheKey) const
	Returns a list of map layers on which an image in the cache depends. More...
bool	hasCacheImage (const QString &cacheKey) const
	Returns true if the cache contains an image with the specified cacheKey. More...
bool	init (const QgsRectangle &extent, double scale)
	Initialize cache: set new parameters and clears the cache if any parameters have changed since last initialization. More...
void	setCacheImage (const QString &cacheKey, const QImage &image, const QList< QgsMapLayer * > &dependentLayers=QList< QgsMapLayer * >())
	Set the cached image for a particular cacheKey. More...

Detailed Description

This class is responsible for keeping cache of rendered images resulting from a map rendering job.

Once a job has a rendered image stored in the cache (using setCacheImage(...)), the cache listens to repaintRequested() signals from dependent layers. If triggered, the cache removes the rendered image (and disconnects from the layers).

The class is thread-safe (multiple classes can access the same instance safely).

Since

QGIS 2.4

Definition at line 42 of file qgsmaprenderercache.h.

Constructor & Destructor Documentation

QgsMapRendererCache::QgsMapRendererCache

(

)

Definition at line 21 of file qgsmaprenderercache.cpp.

Member Function Documentation

QImage QgsMapRendererCache::cacheImage

(

const QString &

cacheKey

)

const

Returns the cached image for the specified cacheKey.

The cacheKey usually matches the QgsMapLayer::id() which the image is a render of. Returns a null image if it is not cached.

See also

setCacheImage()

hasCacheImage()

Definition at line 129 of file qgsmaprenderercache.cpp.

void QgsMapRendererCache::clear

(

)

Invalidates the cache contents, clearing all cached images.

See also

clearCacheImage()

Definition at line 26 of file qgsmaprenderercache.cpp.

void QgsMapRendererCache::clearCacheImage

(

const QString &

cacheKey

)

Removes an image from the cache with matching cacheKey.

See also

clear()

Definition at line 167 of file qgsmaprenderercache.cpp.

QList< QgsMapLayer * > QgsMapRendererCache::dependentLayers

(

const QString &

cacheKey

)

const

Returns a list of map layers on which an image in the cache depends.

Since

QGIS 3.0

Definition at line 135 of file qgsmaprenderercache.cpp.

bool QgsMapRendererCache::hasCacheImage

(

const QString &

cacheKey

)

const

Returns true if the cache contains an image with the specified cacheKey.

See also

cacheImage()

Since

QGIS 3.0

Definition at line 124 of file qgsmaprenderercache.cpp.

bool QgsMapRendererCache::init	(	const QgsRectangle &	extent,
		double	scale
	)

Initialize cache: set new parameters and clears the cache if any parameters have changed since last initialization.

Returns

flag whether the parameters are the same as last time

Definition at line 81 of file qgsmaprenderercache.cpp.

void QgsMapRendererCache::setCacheImage	(	const QString &	cacheKey,
		const QImage &	image,
		const QList< QgsMapLayer * > &	dependentLayers = QList< QgsMapLayer * >()
	)

Set the cached image for a particular cacheKey.

The cacheKey usually matches the QgsMapLayer::id() which the image is a render of. A list of dependentLayers should be passed containing all layer on which this cache image is dependent. If any of these layers triggers a repaint then the cache image will be cleared.

See also

cacheImage()

Definition at line 99 of file qgsmaprenderercache.cpp.

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

• /build/qgis-3.4.15+24xenial/src/core/qgsmaprenderercache.h
• /build/qgis-3.4.15+24xenial/src/core/qgsmaprenderercache.cpp