Qwt User's Guide: QwtPlotZoomer Class Reference

Qwt User's Guide 6.1.3

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QwtPlotZoomer Class Reference

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

`#include <qwt_plot_zoomer.h>`

Inheritance diagram for QwtPlotZoomer:
[legend]

## Public Slots
void | moveBy (double x, double y)
virtual void | moveTo (const QPointF &)
virtual void | zoom (const QRectF &)
| Zoom in. More...
virtual void | zoom (int up)
| Zoom in or out. More...
Public Slots inherited from QwtPicker
void | setEnabled (bool)
| En/disable the picker. More...

## Signals
void | zoomed (const QRectF &rect)
Signals inherited from QwtPlotPicker
void | selected (const QPointF &pos)
void | selected (const QRectF &rect)
void | selected (const QVector< QPointF > &pa)
void | appended (const QPointF &pos)
void | moved (const QPointF &pos)
Signals inherited from QwtPicker
void | activated (bool on)
void | selected (const QPolygon &polygon)
void | appended (const QPoint &pos)
void | moved (const QPoint &pos)
void | removed (const QPoint &pos)
void | changed (const QPolygon &selection)

## Public Member Functions
| QwtPlotZoomer (QWidget *, bool doReplot=true)
| Create a zoomer for a plot canvas. More...
| QwtPlotZoomer (int xAxis, int yAxis, QWidget *, bool doReplot=true)
| Create a zoomer for a plot canvas. More...
virtual void | setZoomBase (bool doReplot=true)
virtual void | setZoomBase (const QRectF &)
| Set the initial size of the zoomer. More...
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. More...
int | maxStackDepth () const
const QStack< QRectF > & | zoomStack () const
void | setZoomStack (const QStack< QRectF > &, int zoomRectIndex=-1)
| Assign a zoom stack. More...
uint | zoomRectIndex () const
Public Member Functions inherited from QwtPlotPicker
| QwtPlotPicker (QWidget *canvas)
| Create a plot picker. More...
virtual | ~QwtPlotPicker ()
| Destructor.
| QwtPlotPicker (int xAxis, int yAxis, QWidget *)
| QwtPlotPicker (int xAxis, int yAxis, RubberBand rubberBand, DisplayMode trackerMode, QWidget *)
int | xAxis () const
| Return x axis.
int | yAxis () const
| Return y axis.
QwtPlot * | plot ()
const QwtPlot * | plot () const
QWidget * | canvas ()
const QWidget * | canvas () const
Public Member Functions inherited from QwtPicker
| QwtPicker (QWidget *parent)
| QwtPicker (RubberBand rubberBand, DisplayMode trackerMode, QWidget *)
virtual | ~QwtPicker ()
| Destructor.
void | setStateMachine (QwtPickerMachine *)
const QwtPickerMachine * | stateMachine () const
QwtPickerMachine * | stateMachine ()
void | setRubberBand (RubberBand)
RubberBand | rubberBand () const
void | setTrackerMode (DisplayMode)
| Set the display mode of the tracker. More...
DisplayMode | trackerMode () const
void | setResizeMode (ResizeMode)
| Set the resize mode. More...
ResizeMode | resizeMode () const
void | setRubberBandPen (const QPen &)
QPen | rubberBandPen () const
void | setTrackerPen (const QPen &)
QPen | trackerPen () const
void | setTrackerFont (const QFont &)
QFont | trackerFont () const
bool | isEnabled () const
bool | isActive () const
virtual bool | eventFilter (QObject *, QEvent *)
| Event filter. More...
QWidget * | parentWidget ()
| Return the parent widget, where the selection happens.
const QWidget * | parentWidget () const
| Return the parent widget, where the selection happens.
virtual QPainterPath | pickArea () const
virtual void | drawRubberBand (QPainter *) const
virtual void | drawTracker (QPainter *) const
virtual QRegion | rubberBandMask () const
QPoint | trackerPosition () const
virtual QRect | trackerRect (const QFont &) const
QPolygon | selection () const
Public Member Functions inherited from QwtEventPattern
| QwtEventPattern ()
virtual | ~QwtEventPattern ()
| Destructor.
void | initMousePattern (int numButtons)
void | initKeyPattern ()
void | setMousePattern (MousePatternCode, Qt::MouseButton button, Qt::KeyboardModifiers=Qt::NoModifier)
void | setKeyPattern (KeyPatternCode, int keyCode, Qt::KeyboardModifiers modifierCodes=Qt::NoModifier)
void | setMousePattern (const QVector< MousePattern > &)
| Change the mouse event patterns.
void | setKeyPattern (const QVector< KeyPattern > &)
| Change the key event patterns.
const QVector< MousePattern > & | mousePattern () const
const QVector< KeyPattern > & | keyPattern () const
QVector< MousePattern > & | mousePattern ()
QVector< KeyPattern > & | keyPattern ()
bool | mouseMatch (MousePatternCode, const QMouseEvent *) const
| Compare a mouse event with an event pattern. More...
bool | keyMatch (KeyPatternCode, const QKeyEvent *) const
| Compare a key event with an event pattern. More...

## Protected Member Functions
virtual void | rescale ()
virtual QSizeF | minZoomSize () const
| Limit zooming by a minimum rectangle. More...
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. More...
Protected Member Functions inherited from QwtPlotPicker
QRectF | scaleRect () const
QRectF | invTransform (const QRect &) const
QRect | transform (const QRectF &) const
QPointF | invTransform (const QPoint &) const
QPoint | transform (const QPointF &) const
virtual QwtText | trackerText (const QPoint &) const
virtual QwtText | trackerTextF (const QPointF &) const
| Translate a position into a position string. More...
virtual void | move (const QPoint &)
virtual void | append (const QPoint &)
Protected Member Functions inherited from QwtPicker
virtual QPolygon | adjustedPoints (const QPolygon &) const
| Map the pickedPoints() into a selection() More...
virtual void | transition (const QEvent *)
virtual void | remove ()
virtual void | reset ()
virtual void | widgetMousePressEvent (QMouseEvent *)
virtual void | widgetMouseDoubleClickEvent (QMouseEvent *)
virtual void | widgetMouseMoveEvent (QMouseEvent *)
virtual void | widgetWheelEvent (QWheelEvent *)
virtual void | widgetKeyReleaseEvent (QKeyEvent *)
virtual void | widgetEnterEvent (QEvent *)
virtual void | widgetLeaveEvent (QEvent *)
virtual void | stretchSelection (const QSize &oldSize, const QSize &newSize)
virtual void | updateDisplay ()
| Update the state of rubber band and tracker label.
const QwtWidgetOverlay * | rubberBandOverlay () const
const QwtWidgetOverlay * | trackerOverlay () const
const QPolygon & | pickedPoints () const
Protected Member Functions inherited from QwtEventPattern
virtual bool | mouseMatch (const MousePattern &, const QMouseEvent *) const
| Compare a mouse event with an event pattern. More...
virtual bool | keyMatch (const KeyPattern &, const QKeyEvent *) const
| Compare a key event with an event pattern. More...

## Additional Inherited Members
Public Types inherited from QwtPicker
enum | RubberBand { NoRubberBand = 0, HLineRubberBand, VLineRubberBand, CrossRubberBand, RectRubberBand, EllipseRubberBand, PolygonRubberBand, UserRubberBand = 100 }
enum | DisplayMode { AlwaysOff, AlwaysOn, ActiveOnly }
| Display mode. More...
enum | ResizeMode { Stretch, KeepSize }
Public Types inherited from QwtEventPattern
enum | MousePatternCode { MouseSelect1, MouseSelect2, MouseSelect3, MouseSelect4, MouseSelect5, MouseSelect6, MousePatternCount }
| Symbolic mouse input codes. More...
enum | KeyPatternCode { KeySelect1, KeySelect2, KeyAbort, KeyLeft, KeyRight, KeyUp, KeyDown, KeyRedo, KeyUndo, KeyHome, KeyPatternCount }
| Symbolic keyboard input codes. More...

## 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.
- QwtEventPattern::KeySelect1
  The first key press selects the first, the second key press selects the second point.
- QwtEventPattern::KeyAbort
  Discard the selection in the state, where the first point is selected.

To traverse the zoom stack the following bindings are used:

- QwtEventPattern::MouseSelect3, QwtEventPattern::KeyUndo
  Zoom out one position on the zoom stack
- QwtEventPattern::MouseSelect6, QwtEventPattern::KeyRedo
  Zoom in one position on the zoom stack
- QwtEventPattern::MouseSelect2, QwtEventPattern::KeyHome
  Zoom to the zoom base

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

  canvas | Plot canvas to observe, also the parent object
  doReplot | Call 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

  xAxis | X axis of the zoomer
  yAxis | Y axis of the zoomer
  canvas | Plot canvas to observe, also the parent object
  doReplot | Call 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
| protectedvirtual

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 | ( |  | ) |
| protectedvirtual

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` | ) |
| protectedvirtual

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

Parameters

  ok | If 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.

int QwtPlotZoomer::maxStackDepth | ( |  | ) | const

Returns
  Maximal depth of the zoom stack.

See also
  setMaxStackDepth()

QSizeF QwtPlotZoomer::minZoomSize | ( |  | ) | const
| protectedvirtual

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

  dx | X offset
  dy | Y offset

Note
  The changed rectangle is limited by the zoom base

void QwtPlotZoomer::moveTo | ( | const QPointF & | pos | ) |
| virtualslot

Move the the current zoom rectangle.

Parameters

  pos | New position

See also
  QRectF::moveTo()

Note
  The changed rectangle is limited by the zoom base

void QwtPlotZoomer::rescale | ( |  | ) |
| protectedvirtual

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

  xAxis | X axis
  yAxis | Y 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

  depth | Maximum 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

  doReplot | Call 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

  base | Zoom 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

  zoomStack | New zoom stack
  zoomRectIndex | Index 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 | ) |
| protectedvirtual

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 | ) |
| protectedvirtual

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 | ) |
| virtualslot

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 | ) |
| virtualslot

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

  offset | Offset 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

  rect | Current zoom rectangle.

QRectF QwtPlotZoomer::zoomRect | ( |  | ) | const

Returns
  Rectangle at the current position on the zoom stack.

See also
  zoomRectIndex(), scaleRect().

uint QwtPlotZoomer::zoomRectIndex | ( |  | ) | const

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()