The abstract base class for all items in a plot. More...

#include <plot2d.h>

Inheritance diagram for QCPAbstractItem:

Signals
void	selectionChanged (bool selected)

Public Member Functions
	QCPAbstractItem (QCustomPlot *parentPlot)

virtual	~QCPAbstractItem ()

bool	clipToAxisRect () const

QCPAxis *	clipKeyAxis () const

QCPAxis *	clipValueAxis () const

bool	selectable () const

bool	selected () const

void	setClipToAxisRect (bool clip)

void	setClipAxes (QCPAxis keyAxis, QCPAxis valueAxis)

void	setClipKeyAxis (QCPAxis *axis)

void	setClipValueAxis (QCPAxis *axis)

void	setSelectable (bool selectable)

void	setSelected (bool selected)

virtual double	selectTest (const QPointF &pos) const =0

QList< QCPItemPosition * >	positions () const

QList< QCPItemAnchor * >	anchors () const

QCPItemPosition *	position (const QString &name) const

QCPItemAnchor *	anchor (const QString &name) const

bool	hasAnchor (const QString &name) const

Public Member Functions inherited from QCPLayerable
	QCPLayerable (QCustomPlot *parentPlot)

	~QCPLayerable ()

bool	visible () const

QCustomPlot *	parentPlot () const

QCPLayer *	layer () const

bool	antialiased () const

void	setVisible (bool on)

bool	setLayer (QCPLayer *layer)

bool	setLayer (const QString &layerName)

void	setAntialiased (bool enabled)

Protected Member Functions
virtual QRect	clipRect () const

virtual void	applyDefaultAntialiasingHint (QCPPainter *painter) const

virtual void	draw (QCPPainter *painter)=0

double	distSqrToLine (const QPointF &start, const QPointF &end, const QPointF &point) const

double	rectSelectTest (const QRectF &rect, const QPointF &pos, bool filledRect) const

virtual QPointF	anchorPixelPoint (int anchorId) const

QCPItemPosition *	createPosition (const QString &name)

QCPItemAnchor *	createAnchor (const QString &name, int anchorId)

Protected Member Functions inherited from QCPLayerable
bool	moveToLayer (QCPLayer *layer, bool prepend)

void	applyAntialiasingHint (QCPPainter *painter, bool localAntialiased, QCP::AntialiasedElement overrideElement) const

Protected Attributes
bool	mClipToAxisRect

QCPAxis *	mClipKeyAxis

QCPAxis *	mClipValueAxis

bool	mSelectable

bool	mSelected

QList< QCPItemPosition * >	mPositions

QList< QCPItemAnchor * >	mAnchors

Protected Attributes inherited from QCPLayerable
bool	mVisible

QCustomPlot *	mParentPlot

QCPLayer *	mLayer

bool	mAntialiased

Friends
class	QCustomPlot

class	QCPItemAnchor

Detailed Description

The abstract base class for all items in a plot.

In QCustomPlot, items are supplemental graphical elements that are neither plottables (QCPAbstractPlottable) nor axes (QCPAxis). While plottables are always tied to two axes and thus plot coordinates, items can also be placed in absolute coordinates independent of any axes. Each specific item has at least one QCPItemPosition member which controls the positioning. Some items are defined by more than one coordinate and thus have two or more QCPItemPosition members (For example, QCPItemRect has topLeft and bottomRight).

This abstract base class defines a very basic interface like visibility and clipping. Since this class is abstract, it can't be instantiated. Use one of the subclasses or create a subclass yourself to create new items.

The built-in items are:

QCPItemLine	A line defined by a start and an end point. May have different ending styles on each side (e.g. arrows).
QCPItemStraightLine	A straight line defined by a start and a direction point. Unlike QCPItemLine, the straight line is infinitely long and has no endings.
QCPItemCurve	A curve defined by start, end and two intermediate control points. May have different ending styles on each side (e.g. arrows).
QCPItemRect	A rectangle
QCPItemEllipse	An ellipse
QCPItemPixmap	An arbitrary pixmap
QCPItemText	A text label
QCPItemBracket	A bracket which may be used to reference/highlight certain parts in the plot.
QCPItemTracer	An item that can be attached to a QCPGraph and sticks to its data points, given a key coordinate.

Using items

First you instantiate the item you want to use and add it to the plot:

QCPItemLine *line = new QCPItemLine(customPlot);

customPlot->addItem(line);

by default, the positions of the item are bound to the x- and y-Axis of the plot. So we can just set the plot coordinates where the line should start/end:

line->start->setCoords(-0.1, 0.8);

line->end->setCoords(1.1, 0.2);

If we wanted the line to be positioned not in plot coordinates but a different coordinate system, e.g. absolute pixel positions on the QCustomPlot surface, we would have changed the position type like this:

line->start->setType(QCPItemPosition::ptAbsolute);

line->end->setType(QCPItemPosition::ptAbsolute);

Then we can set the coordinates, this time in pixels:

line->start->setCoords(100, 200);

line->end->setCoords(450, 320);

Creating own items

To create an own item, you implement a subclass of QCPAbstractItem. These are the pure virtual functions, you must implement:

See the documentation of those functions for what they need to do.

Allowing the item to be positioned

As mentioned, item positions are represented by QCPItemPosition members. Let's assume the new item shall have only one coordinate as its position (as opposed to two like a rect or multiple like a polygon). You then add a public member of type QCPItemPosition like so:

QCPItemPosition * const myPosition;

the const makes sure the pointer itself can't be modified from the user of your new item (the QCPItemPosition instance it points to, can be modified, of course). The initialization of this pointer is made easy with the createPosition function. Just assign the return value of this function to each QCPItemPosition in the constructor of your item. createPosition takes a string which is the name of the position, typically this is identical to the variable name. For example, the constructor of QCPItemExample could look like this:

QCPItemExample::QCPItemExample(QCustomPlot *parentPlot) :
  QCPAbstractItem(parentPlot),
  myPosition(createPosition("myPosition"))
{
  //other constructor code
}

The draw function

Your implementation of the draw function should check whether the item is visible (mVisible) and then draw the item. You can retrieve its position in pixel coordinates from the position member(s) via QCPItemPosition::pixelPoint.

To optimize performance you should calculate a bounding rect first (don't forget to take the pen width into account), check whether it intersects the clipRect, and only draw the item at all if this is the case.

The selectTest function

Your implementation of the selectTest function may use the helpers distSqrToLine and rectSelectTest. With these, the implementation of the selection test becomes significantly simpler for most items.

Providing anchors

Providing anchors (QCPItemAnchor) starts off like adding a position. First you create a public member, e.g.

QCPItemAnchor * const bottom;

and create it in the constructor with the createAnchor function, assigning it a name and an anchor id (an integer enumerating all anchors on the item, you may create an own enum for this). Since anchors can be placed anywhere, relative to the item's position(s), your item needs to provide the position of every anchor with the reimplementation of the anchorPixelPoint(int anchorId) function.

In essence the QCPItemAnchor is merely an intermediary that itself asks your item for the pixel position when anything attached to the anchor needs to know the coordinates.

Constructor & Destructor Documentation

QCPAbstractItem::QCPAbstractItem ( QCustomPlot * parentPlot )

Base class constructor which initializes base class members.

QCPAbstractItem::~QCPAbstractItem ( )

virtual

Member Function Documentation

QCPItemAnchor * QCPAbstractItem::anchor ( const QString & name ) const

Returns the QCPItemAnchor with the specified name. If this item doesn't have an anchor by that name, returns 0.

This function provides an alternative way to access item anchors. Normally, you access anchors direcly by their member pointers (which typically have the same variable name as name).

See Also: anchors, position

QPointF QCPAbstractItem::anchorPixelPoint ( int anchorId ) const

protectedvirtual

Reimplemented in QCPItemBracket, QCPItemText, QCPItemPixmap, QCPItemRect, and QCPItemEllipse.

QList< QCPItemAnchor * > QCPAbstractItem::anchors ( ) const

inline

Returns all anchors of the item in a list. Note that since a position (QCPItemPosition) is always also an anchor, the list will also contain the positions of this item.

See Also: positions, anchor

void QCPAbstractItem::applyDefaultAntialiasingHint ( QCPPainter * painter ) const

protectedvirtual

Implements QCPLayerable.

QCPAxis* QCPAbstractItem::clipKeyAxis ( ) const

inline

QRect QCPAbstractItem::clipRect ( ) const

protectedvirtual

Reimplemented from QCPLayerable.

bool QCPAbstractItem::clipToAxisRect ( ) const

inline

QCPAxis* QCPAbstractItem::clipValueAxis ( ) const

inline

QCPItemAnchor * QCPAbstractItem::createAnchor	(	const QString &	name,
		int	anchorId
	)

protected

QCPItemPosition * QCPAbstractItem::createPosition ( const QString & name )

protected

double QCPAbstractItem::distSqrToLine	(	const QPointF &	start,
		const QPointF &	end,
		const QPointF &	point
	)		const

protected

void QCPAbstractItem::draw ( QCPPainter * painter )

protectedpure virtual

Implements QCPLayerable.

Implemented in QCPItemTracer, QCPItemBracket, QCPItemCurve, QCPItemText, QCPItemPixmap, QCPItemRect, QCPItemEllipse, QCPItemLine, and QCPItemStraightLine.

bool QCPAbstractItem::hasAnchor ( const QString & name ) const

Returns whether this item has an anchor with the specified name.

Note that you can check for positions with this function, too, because every position is also an anchor (QCPItemPosition inherits from QCPItemAnchor).

See Also: anchor, position

QCPItemPosition * QCPAbstractItem::position ( const QString & name ) const

Returns the QCPItemPosition with the specified name. If this item doesn't have a position by that name, returns 0.

This function provides an alternative way to access item positions. Normally, you access positions direcly by their member pointers (which typically have the same variable name as name).

See Also: positions, anchor

QList< QCPItemPosition * > QCPAbstractItem::positions ( ) const

inline

Returns all positions of the item in a list.

See Also: anchors, position

double QCPAbstractItem::rectSelectTest	(	const QRectF &	rect,
		const QPointF &	pos,
		bool	filledRect
	)		const

protected

bool QCPAbstractItem::selectable ( ) const

inline

bool QCPAbstractItem::selected ( ) const

inline

void QCPAbstractItem::selectionChanged ( bool selected )

signal

This signal is emitted when the selection state of this item has changed, either by user interaction or by a direct call to setSelected.

double QCPAbstractItem::selectTest ( const QPointF & pos ) const

pure virtual

This function is used to decide whether a click hits an item or not.

pos is a point in pixel coordinates on the QCustomPlot surface. This function returns the shortest pixel distance of this point to the item. If the item is either invisible or the distance couldn't be determined, -1.0 is returned. setSelectable has no influence on the return value of this function.

If the item is represented not by single lines but by an area like QCPItemRect or QCPItemText, a click inside the area returns a constant value greater zero (typically 99% of the selectionTolerance of the parent QCustomPlot). If the click lies outside the area, this function returns -1.0.

Providing a constant value for area objects allows selecting line objects even when they are obscured by such area objects, by clicking close to the lines (i.e. closer than 0.99*selectionTolerance).

The actual setting of the selection state is not done by this function. This is handled by the parent QCustomPlot when the mouseReleaseEvent occurs.

See Also: setSelected, QCustomPlot::setInteractions

Implemented in QCPItemTracer, QCPItemBracket, QCPItemCurve, QCPItemText, QCPItemPixmap, QCPItemRect, QCPItemEllipse, QCPItemLine, and QCPItemStraightLine.

void QCPAbstractItem::setClipAxes	(	QCPAxis *	keyAxis,
		QCPAxis *	valueAxis
	)

Sets both clip axes. Together they define the axis rect that will be used to clip the item when setClipToAxisRect is set to true.

See Also: setClipToAxisRect, setClipKeyAxis, setClipValueAxis

void QCPAbstractItem::setClipKeyAxis ( QCPAxis * axis )

Sets the clip key axis. Together with the clip value axis it defines the axis rect that will be used to clip the item when setClipToAxisRect is set to true.

See Also: setClipToAxisRect, setClipAxes, setClipValueAxis

void QCPAbstractItem::setClipToAxisRect ( bool clip )

Sets whether the item shall be clipped to the axis rect or whether it shall be visible on the entire QCustomPlot. The axis rect is defined by the clip axes which can be set via setClipAxes or individually with setClipKeyAxis and setClipValueAxis.

void QCPAbstractItem::setClipValueAxis ( QCPAxis * axis )

Sets the clip value axis. Together with the clip key axis it defines the axis rect that will be used to clip the item when setClipToAxisRect is set to true.

See Also: setClipToAxisRect, setClipAxes, setClipKeyAxis

void QCPAbstractItem::setSelectable ( bool selectable )

Sets whether the user can (de-)select this item by clicking on the QCustomPlot surface. (When QCustomPlot::setInteractions contains QCustomPlot::iSelectItems.)

However, even when selectable was set to false, it is possible to set the selection manually, by calling setSelected directly.

See Also: QCustomPlot::setInteractions, setSelected

void QCPAbstractItem::setSelected ( bool selected )

Sets whether this item is selected or not. When selected, it might use a different visual appearance (e.g. pen and brush), this depends on the specific item, though.

The entire selection mechanism for items is handled automatically when QCustomPlot::setInteractions contains QCustomPlot::iSelectItems. You only need to call this function when you wish to change the selection state manually.

This function can change the selection state even when setSelectable was set to false.

emits the selectionChanged signal when selected is different from the previous selection state.

See Also: selectTest

Friends And Related Function Documentation

friend class QCPItemAnchor

friend

friend class QCustomPlot

friend

Member Data Documentation

QList<QCPItemAnchor*> QCPAbstractItem::mAnchors

protected

QCPAxis* QCPAbstractItem::mClipKeyAxis

protected

bool QCPAbstractItem::mClipToAxisRect

protected

QCPAxis * QCPAbstractItem::mClipValueAxis

protected

QList<QCPItemPosition*> QCPAbstractItem::mPositions

protected

bool QCPAbstractItem::mSelectable

protected

bool QCPAbstractItem::mSelected

protected

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

C:/Users/mpeniak/Dropbox/Aquila/trunk/aquila/include/plot2d.h
C:/Users/mpeniak/Dropbox/Aquila/trunk/aquila/src/plot2d.cpp

Signals

Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Using items

Creating own items

Allowing the item to be positioned

The draw function

The selectTest function

Providing anchors

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation