Qwt User's Guide
QwtPlotZoomer Class Reference

QwtPlotZoomer provides stacked zooming for a plot widget. More...

#include <qwt_plot_zoomer.h>

Inheritance diagram for QwtPlotZoomer:

Public Slots

void moveBy (double x, double y)
virtual void moveTo (const QPointF &)
virtual void zoom (const QRectF &)
 Zoom in.
virtual void zoom (int up)
 Zoom in or out.

Signals

void zoomed (const QRectF &rect)

Public Member Functions

 QwtPlotZoomer (QWidget *, bool doReplot=true)
 Create a zoomer for a plot canvas.
 QwtPlotZoomer (int xAxis, int yAxis, QWidget *, bool doReplot=true)
 Create a zoomer for a plot canvas.
virtual void setZoomBase (bool doReplot=true)
virtual void setZoomBase (const QRectF &)
 Set the initial size of the zoomer.
QRectF zoomBase () const
QRectF zoomRect () const
virtual void setAxis (int xAxis, int yAxis)
void setMaxStackDepth (int)
 Limit the number of recursive zoom operations to depth.
int maxStackDepth () const
const QStack< QRectF > & zoomStack () const
void setZoomStack (const QStack< QRectF > &, int zoomRectIndex=-1)
 Assign a zoom stack.
uint zoomRectIndex () const

Protected Member Functions

virtual void rescale ()
virtual QSizeF minZoomSize () const
 Limit zooming by a minimum rectangle.
virtual void widgetMouseReleaseEvent (QMouseEvent *)
virtual void widgetKeyPressEvent (QKeyEvent *)
virtual void begin ()
virtual bool end (bool ok=true)
virtual bool accept (QPolygon &) const
 Check and correct a selected rectangle.

Detailed Description

QwtPlotZoomer provides stacked zooming for a plot widget.

QwtPlotZoomer selects rectangles from user inputs ( mouse or keyboard ) translates them into plot coordinates and adjusts the axes to them. The selection is supported by a rubber band and optionally by displaying the coordinates of the current mouse position.

Zooming can be repeated as often as possible, limited only by maxStackDepth() or minZoomSize(). Each rectangle is pushed on a stack.

The default setting how to select rectangles is a QwtPickerDragRectMachine with the following bindings:

  • QwtEventPattern::MouseSelect1
    The first point of the zoom rectangle is selected by a mouse press, the second point from the position, where the mouse is released.

To traverse the zoom stack the following bindings are used:

The setKeyPattern() and setMousePattern() functions can be used to configure the zoomer actions. The following example shows, how to configure the 'I' and 'O' keys for zooming in and out one position on the zoom stack. The "Home" key is used to "unzoom" the plot.

   zoomer = new QwtPlotZoomer( plot );
   zoomer->setKeyPattern( QwtEventPattern::KeyRedo, Qt::Key_I, Qt::ShiftModifier );
   zoomer->setKeyPattern( QwtEventPattern::KeyUndo, Qt::Key_O, Qt::ShiftModifier );
   zoomer->setKeyPattern( QwtEventPattern::KeyHome, Qt::Key_Home );

QwtPlotZoomer is tailored for plots with one x and y axis, but it is allowed to attach a second QwtPlotZoomer ( without rubber band and tracker ) for the other axes.

Note:
The realtime example includes an derived zoomer class that adds scrollbars to the plot canvas.
See also:
QwtPlotPanner, QwtPlotMagnifier

Constructor & Destructor Documentation

QwtPlotZoomer::QwtPlotZoomer ( QWidget *  canvas,
bool  doReplot = true 
) [explicit]

Create a zoomer for a plot canvas.

The zoomer is set to those x- and y-axis of the parent plot of the canvas that are enabled. If both or no x-axis are enabled, the picker is set to QwtPlot::xBottom. If both or no y-axis are enabled, it is set to QwtPlot::yLeft.

The zoomer is initialized with a QwtPickerDragRectMachine, the tracker mode is set to QwtPicker::ActiveOnly and the rubber band is set to QwtPicker::RectRubberBand

Parameters:
canvasPlot canvas to observe, also the parent object
doReplotCall QwtPlot::replot() for the attached plot before initializing the zoomer with its scales. This might be necessary, when the plot is in a state with pending scale changes.
See also:
QwtPlot::autoReplot(), QwtPlot::replot(), setZoomBase()
QwtPlotZoomer::QwtPlotZoomer ( int  xAxis,
int  yAxis,
QWidget *  canvas,
bool  doReplot = true 
) [explicit]

Create a zoomer for a plot canvas.

The zoomer is initialized with a QwtPickerDragRectMachine, the tracker mode is set to QwtPicker::ActiveOnly and the rubber band is set to QwtPicker;;RectRubberBand

Parameters:
xAxisX axis of the zoomer
yAxisY axis of the zoomer
canvasPlot canvas to observe, also the parent object
doReplotCall QwtPlot::replot() for the attached plot before initializing the zoomer with its scales. This might be necessary, when the plot is in a state with pending scale changes.
See also:
QwtPlot::autoReplot(), QwtPlot::replot(), setZoomBase()

Member Function Documentation

bool QwtPlotZoomer::accept ( QPolygon &  pa) const [protected, virtual]

Check and correct a selected rectangle.

Reject rectangles with a height or width < 2, otherwise expand the selected rectangle to a minimum size of 11x11 and accept it.

Returns:
true If the rectangle is accepted, or has been changed to an accepted one.

Reimplemented from QwtPicker.

void QwtPlotZoomer::begin ( ) [protected, virtual]

Rejects selections, when the stack depth is too deep, or the zoomed rectangle is minZoomSize().

See also:
minZoomSize(), maxStackDepth()

Reimplemented from QwtPicker.

bool QwtPlotZoomer::end ( bool  ok = true) [protected, virtual]

Expand the selected rectangle to minZoomSize() and zoom in if accepted.

Parameters:
okIf true, complete the selection and emit selected signals otherwise discard the selection.
See also:
accept(), minZoomSize()
Returns:
True if the selection has been accepted, false otherwise

Reimplemented from QwtPlotPicker.

Returns:
Maximal depth of the zoom stack.
See also:
setMaxStackDepth()
QSizeF QwtPlotZoomer::minZoomSize ( ) const [protected, virtual]

Limit zooming by a minimum rectangle.

Returns:
zoomBase().width() / 10e4, zoomBase().height() / 10e4
void QwtPlotZoomer::moveBy ( double  dx,
double  dy 
) [slot]

Move the current zoom rectangle.

Parameters:
dxX offset
dyY offset
Note:
The changed rectangle is limited by the zoom base
void QwtPlotZoomer::moveTo ( const QPointF &  pos) [virtual, slot]

Move the the current zoom rectangle.

Parameters:
posNew position
See also:
QRectF::moveTo()
Note:
The changed rectangle is limited by the zoom base
void QwtPlotZoomer::rescale ( ) [protected, virtual]

Adjust the observed plot to zoomRect()

Note:
Initiates QwtPlot::replot()
void QwtPlotZoomer::setAxis ( int  xAxis,
int  yAxis 
) [virtual]

Reinitialize the axes, and set the zoom base to their scales.

Parameters:
xAxisX axis
yAxisY axis

Reimplemented from QwtPlotPicker.

void QwtPlotZoomer::setMaxStackDepth ( int  depth)

Limit the number of recursive zoom operations to depth.

A value of -1 set the depth to unlimited, 0 disables zooming. If the current zoom rectangle is below depth, the plot is unzoomed.

Parameters:
depthMaximum for the stack depth
See also:
maxStackDepth()
Note:
depth doesn't include the zoom base, so zoomStack().count() might be maxStackDepth() + 1.
void QwtPlotZoomer::setZoomBase ( bool  doReplot = true) [virtual]

Reinitialized the zoom stack with scaleRect() as base.

Parameters:
doReplotCall QwtPlot::replot() for the attached plot before initializing the zoomer with its scales. This might be necessary, when the plot is in a state with pending scale changes.
See also:
zoomBase(), scaleRect() QwtPlot::autoReplot(), QwtPlot::replot().
void QwtPlotZoomer::setZoomBase ( const QRectF &  base) [virtual]

Set the initial size of the zoomer.

base is united with the current scaleRect() and the zoom stack is reinitialized with it as zoom base. plot is zoomed to scaleRect().

Parameters:
baseZoom base
See also:
zoomBase(), scaleRect()
void QwtPlotZoomer::setZoomStack ( const QStack< QRectF > &  zoomStack,
int  zoomRectIndex = -1 
)

Assign a zoom stack.

In combination with other types of navigation it might be useful to modify to manipulate the complete zoom stack.

Parameters:
zoomStackNew zoom stack
zoomRectIndexIndex of the current position of zoom stack. In case of -1 the current position is at the top of the stack.
Note:
The zoomed signal might be emitted.
See also:
zoomStack(), zoomRectIndex()
void QwtPlotZoomer::widgetKeyPressEvent ( QKeyEvent *  ke) [protected, virtual]

Qt::Key_Plus zooms in, Qt::Key_Minus zooms out one position on the zoom stack, Qt::Key_Escape zooms out to the zoom base.

Changes the current position on the stack, but doesn't pop any rectangle.

Note:
The keys codes can be changed, using QwtEventPattern::setKeyPattern: 3, 4, 5

Reimplemented from QwtPicker.

void QwtPlotZoomer::widgetMouseReleaseEvent ( QMouseEvent *  me) [protected, virtual]

Qt::MidButton zooms out one position on the zoom stack, Qt::RightButton to the zoom base.

Changes the current position on the stack, but doesn't pop any rectangle.

Note:
The mouse events can be changed, using QwtEventPattern::setMousePattern: 2, 1

Reimplemented from QwtPicker.

void QwtPlotZoomer::zoom ( const QRectF &  rect) [virtual, slot]

Zoom in.

Clears all rectangles above the current position of the zoom stack and pushes the normalized rectangle on it.

Note:
If the maximal stack depth is reached, zoom is ignored.
The zoomed signal is emitted.
void QwtPlotZoomer::zoom ( int  offset) [virtual, slot]

Zoom in or out.

Activate a rectangle on the zoom stack with an offset relative to the current position. Negative values of offset will zoom out, positive zoom in. A value of 0 zooms out to the zoom base.

Parameters:
offsetOffset relative to the current position of the zoom stack.
Note:
The zoomed signal is emitted.
See also:
zoomRectIndex()
QRectF QwtPlotZoomer::zoomBase ( ) const
Returns:
Initial rectangle of the zoomer
See also:
setZoomBase(), zoomRect()
void QwtPlotZoomer::zoomed ( const QRectF &  rect) [signal]

A signal emitting the zoomRect(), when the plot has been zoomed in or out.

Parameters:
rectCurrent zoom rectangle.
QRectF QwtPlotZoomer::zoomRect ( ) const
Returns:
Rectangle at the current position on the zoom stack.
See also:
zoomRectIndex(), scaleRect().
Returns:
Index of current position of zoom stack.
const QStack< QRectF > & QwtPlotZoomer::zoomStack ( ) const
Returns:
The zoom stack. zoomStack()[0] is the zoom base, zoomStack()[1] the first zoomed rectangle.
See also:
setZoomStack(), zoomRectIndex()

List of all members.

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