QCPLayer Class Reference

A layer that may contain objects, to control the rendering order. More...

#include <qcustomplot.h>

Inheritance diagram for QCPLayer:

Public Types
enum	LayerMode { lmLogical, lmBuffered }

Public Member Functions
QList< QCPLayerable * >	children () const
int	index () const
LayerMode	mode () const
QString	name () const
QCustomPlot *	parentPlot () const
	QCPLayer (QCustomPlot *parentPlot, const QString &layerName)
void	replot ()
void	setMode (LayerMode mode)
void	setVisible (bool visible)
bool	visible () const
virtual	~QCPLayer ()

Protected Member Functions
void	addChild (QCPLayerable *layerable, bool prepend)
void	draw (QCPPainter *painter)
void	drawToPaintBuffer ()
void	removeChild (QCPLayerable *layerable)

Protected Attributes
QList< QCPLayerable * >	mChildren
int	mIndex
LayerMode	mMode
QString	mName
QWeakPointer< QCPAbstractPaintBuffer >	mPaintBuffer
QCustomPlot *	mParentPlot
bool	mVisible

Friends
class	QCPLayerable
class	QCustomPlot

Detailed Description

A layer that may contain objects, to control the rendering order.

The Layering system of QCustomPlot is the mechanism to control the rendering order of the elements inside the plot.

It is based on the two classes QCPLayer and QCPLayerable. QCustomPlot holds an ordered list of one or more instances of QCPLayer (see QCustomPlot::addLayer, QCustomPlot::layer, QCustomPlot::moveLayer, etc.). When replotting, QCustomPlot goes through the list of layers bottom to top and successively draws the layerables of the layers into the paint buffer(s).

A QCPLayer contains an ordered list of QCPLayerable instances. QCPLayerable is an abstract base class from which almost all visible objects derive, like axes, grids, graphs, items, etc.

Default layers

Initially, QCustomPlot has six layers: "background", "grid", "main", "axes", "legend" and "overlay" (in that order). On top is the "overlay" layer, which only contains the QCustomPlot's selection rect (QCustomPlot::selectionRect). The next two layers "axes" and "legend" contain the default axes and legend, so they will be drawn above plottables. In the middle, there is the "main" layer. It is initially empty and set as the current layer (see QCustomPlot::setCurrentLayer). This means, all new plottables, items etc. are created on this layer by default. Then comes the "grid" layer which contains the QCPGrid instances (which belong tightly to QCPAxis, see QCPAxis::grid). The Axis rect background shall be drawn behind everything else, thus the default QCPAxisRect instance is placed on the "background" layer. Of course, the layer affiliation of the individual objects can be changed as required (QCPLayerable::setLayer).

Controlling the rendering order via layers

Controlling the ordering of layerables in the plot is easy: Create a new layer in the position you want the layerable to be in, e.g. above "main", with QCustomPlot::addLayer. Then set the current layer with QCustomPlot::setCurrentLayer to that new layer and finally create the objects normally. They will be placed on the new layer automatically, due to the current layer setting. Alternatively you could have also ignored the current layer setting and just moved the objects with QCPLayerable::setLayer to the desired layer after creating them.

It is also possible to move whole layers. For example, If you want the grid to be shown in front of all plottables/items on the "main" layer, just move it above "main" with QCustomPlot::moveLayer.

The rendering order within one layer is simply by order of creation or insertion. The item created last (or added last to the layer), is drawn on top of all other objects on that layer.

When a layer is deleted, the objects on it are not deleted with it, but fall on the layer below the deleted layer, see QCustomPlot::removeLayer.

Replotting only a specific layer

If the layer mode (setMode) is set to lmBuffered, you can replot only this specific layer by calling replot. In certain situations this can provide better replot performance, compared with a full replot of all layers. Upon creation of a new layer, the layer mode is initialized to lmLogical. The only layer that is set to lmBuffered in a new QCustomPlot instance is the "overlay" layer, containing the selection rect.

Definition at line 628 of file qcustomplot.h.

Member Enumeration Documentation

LayerMode

enum QCPLayer::LayerMode

Defines the different rendering modes of a layer. Depending on the mode, certain layers can be replotted individually, without the need to replot (possibly complex) layerables on other layers.

See also

setMode

Enumerator
lmLogical	Layer is used only for rendering order, and shares paint buffer with all other adjacent logical layers.
lmBuffered	Layer has its own paint buffer and may be replotted individually (see replot).

Definition at line 648 of file qcustomplot.h.

Constructor & Destructor Documentation

QCPLayer()

QCPLayer::QCPLayer	(	QCustomPlot *	parentPlot,
		const QString &	layerName
	)

Creates a new QCPLayer instance.

Normally you shouldn't directly instantiate layers, use QCustomPlot::addLayer instead.

Warning

It is not checked that layerName is actually a unique layer name in parentPlot. This check is only performed by QCustomPlot::addLayer.

Definition at line 1042 of file qcustomplot.cpp.

~QCPLayer()

QCPLayer::~QCPLayer ( )

virtual

Definition at line 1054 of file qcustomplot.cpp.

Member Function Documentation

addChild()

void QCPLayer::addChild ( QCPLayerable *  layerable, bool  prepend  )

protected

Definition at line 1198 of file qcustomplot.cpp.

children()

QList< QCPLayerable * > QCPLayer::children ( ) const

inline

Returns a list of all layerables on this layer. The order corresponds to the rendering order: layerables with higher indices are drawn above layerables with lower indices.

Definition at line 660 of file qcustomplot.h.

draw()

void QCPLayer::draw ( QCPPainter *  painter )

protected

Definition at line 1118 of file qcustomplot.cpp.

drawToPaintBuffer()

void QCPLayer::drawToPaintBuffer ( )

protected

Definition at line 1141 of file qcustomplot.cpp.

index()

int QCPLayer::index ( ) const

inline

Returns the index this layer has in the QCustomPlot. The index is the integer number by which this layer can be accessed via QCustomPlot::layer.

Layers with higher indices will be drawn above layers with lower indices.

Definition at line 659 of file qcustomplot.h.

mode()

LayerMode QCPLayer::mode ( ) const

inline

Definition at line 662 of file qcustomplot.h.

name()

QString QCPLayer::name ( ) const

inline

Definition at line 658 of file qcustomplot.h.

parentPlot()

QCustomPlot* QCPLayer::parentPlot ( ) const

inline

Definition at line 657 of file qcustomplot.h.

removeChild()

void QCPLayer::removeChild ( QCPLayerable *  layerable )

protected

Definition at line 1221 of file qcustomplot.cpp.

replot()

void QCPLayer::replot

(

)

If the layer mode (setMode) is set to lmBuffered, this method allows replotting only the layerables on this specific layer, without the need to replot all other layers (as a call to QCustomPlot::replot would do).

If the layer mode is lmLogical however, this method simply calls QCustomPlot::replot on the parent QCustomPlot instance.

QCustomPlot also makes sure to replot all layers instead of only this one, if the layer ordering has changed since the last full replot and the other paint buffers were thus invalidated.

See also

draw

Definition at line 1172 of file qcustomplot.cpp.

setMode()

void QCPLayer::setMode

(

QCPLayer::LayerMode

mode

)

Sets the rendering mode of this layer.

If mode is set to lmBuffered for a layer, it will be given a dedicated paint buffer by the parent QCustomPlot instance. This means it may be replotted individually by calling QCPLayer::replot, without needing to replot all other layers.

Layers which are set to lmLogical (the default) are used only to define the rendering order and can't be replotted individually.

Note that each layer which is set to lmBuffered requires additional paint buffers for the layers below, above and for the layer itself. This increases the memory consumption and (slightly) decreases the repainting speed because multiple paint buffers need to be joined. So you should carefully choose which layers benefit from having their own paint buffer. A typical example would be a layer which contains certain layerables (e.g. items) that need to be changed and thus replotted regularly, while all other layerables on other layers stay static. By default, only the topmost layer called "overlay" is in mode lmBuffered, and contains the selection rect.

See also

replot

Definition at line 1102 of file qcustomplot.cpp.

setVisible()

void QCPLayer::setVisible

(

bool

visible

)

Sets whether this layer is visible or not. If visible is set to false, all layerables on this layer will be invisible.

This function doesn't change the visibility property of the layerables (QCPLayerable::setVisible), but the QCPLayerable::realVisibility of each layerable takes the visibility of the parent layer into account.

Definition at line 1076 of file qcustomplot.cpp.

visible()

bool QCPLayer::visible ( ) const

inline

Definition at line 661 of file qcustomplot.h.

Friends And Related Function Documentation

QCPLayerable

friend class QCPLayerable

friend

Definition at line 693 of file qcustomplot.h.

QCustomPlot

friend class QCustomPlot

friend

Definition at line 692 of file qcustomplot.h.

Member Data Documentation

mChildren

QList<QCPLayerable*> QCPLayer::mChildren

protected

Definition at line 676 of file qcustomplot.h.

mIndex

int QCPLayer::mIndex

protected

Definition at line 675 of file qcustomplot.h.

mMode

LayerMode QCPLayer::mMode

protected

Definition at line 678 of file qcustomplot.h.

mName

QString QCPLayer::mName

protected

Definition at line 674 of file qcustomplot.h.

mPaintBuffer

QWeakPointer<QCPAbstractPaintBuffer> QCPLayer::mPaintBuffer

protected

Definition at line 681 of file qcustomplot.h.

mParentPlot

QCustomPlot* QCPLayer::mParentPlot

protected

Definition at line 673 of file qcustomplot.h.

mVisible

bool QCPLayer::mVisible

protected

Definition at line 677 of file qcustomplot.h.

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

• qcustomplot.h
• qcustomplot.cpp