# QwtPlotZoomer Class Reference

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

`#include <qwt_plot_zoomer.h>`

Inheritance diagram for QwtPlotZoomer:

[legend]

List of all members.

## Public Slots

void | moveBy (double x, double y)
virtual void | move (double x, double y)
virtual void | zoom (const QwtDoubleRect &)
virtual void | zoom (int up)

## Signals

void | zoomed (const QwtDoubleRect &rect)

## Public Member Functions

| QwtPlotZoomer (QwtPlotCanvas *, bool doReplot=true)
| QwtPlotZoomer (int xAxis, int yAxis, QwtPlotCanvas *, bool doReplot=true)
| QwtPlotZoomer (int xAxis, int yAxis, int selectionFlags, DisplayMode trackerMode, QwtPlotCanvas *, bool doReplot=true)
virtual void | setZoomBase (bool doReplot=true)
virtual void | setZoomBase (const QwtDoubleRect &)
QwtDoubleRect | zoomBase () const
QwtDoubleRect | zoomRect () const
virtual void | setAxis (int xAxis, int yAxis)
void | setMaxStackDepth (int)
int | maxStackDepth () const
const QStack< QwtDoubleRect > & | zoomStack () const
void | setZoomStack (const QStack< QwtDoubleRect > &, int zoomRectIndex=-1)
uint | zoomRectIndex () const
virtual void | setSelectionFlags (int)

## Protected Member Functions

virtual void | rescale ()
virtual QwtDoubleSize | minZoomSize () const
virtual void | widgetMouseReleaseEvent (QMouseEvent *)
virtual void | widgetKeyPressEvent (QKeyEvent *)
virtual void | begin ()
virtual bool | end (bool ok=true)
virtual bool | accept (QwtPolygon &) const

## Detailed Description

QwtPlotZoomer provides stacked zooming for a plot widget.

QwtPlotZoomer offers rubberband selections on the plot canvas, translating the selected rectangles into plot coordinates and adjusting the axes to them. Zooming can repeated as often as possible, limited only by maxStackDepth() or minZoomSize(). Each rectangle is pushed on a stack.

Zoom rectangles can be selected depending on selectionFlags() using the mouse or keyboard (QwtEventPattern, QwtPickerMachine). QwtEventPattern::MouseSelect3/QwtEventPatternKeyUndo, or QwtEventPattern::MouseSelect6/QwtEventPatternKeyRedo walk up and down the zoom stack. QwtEventPattern::MouseSelect2 or QwtEventPattern::KeyHome unzoom to the initial size.

QwtPlotZoomer is tailored for plots with one x and y axis, but it is allowed to attach a second QwtPlotZoomer for the other axes.

Note:
  The realtime example includes an derived zoomer class that adds scrollbars to the plot canvas.

## Constructor & Destructor Documentation

QwtPlotZoomer::QwtPlotZoomer | ( | QwtPlotCanvas * | 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 selectionFlags() are set to QwtPicker::RectSelection & QwtPicker::ClickSelection, the tracker mode to QwtPicker::ActiveOnly.

Parameters:

  | canvas | Plot canvas to observe, also the parent object
  | doReplot | Call 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,
|  | QwtPlotCanvas * | canvas,
|  | bool | doReplot = `true` |
| ) |  |  | `[explicit]`

Create a zoomer for a plot canvas.

The selectionFlags() are set to QwtPicker::RectSelection & QwtPicker::ClickSelection, the tracker mode to QwtPicker::ActiveOnly.

Parameters:

  | xAxis | X axis of the zoomer
  | yAxis | Y axis of the zoomer
  | canvas | Plot canvas to observe, also the parent object
  | doReplot | Call 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,
|  | int | selectionFlags,
|  | DisplayMode | trackerMode,
|  | QwtPlotCanvas * | canvas,
|  | bool | doReplot = `true` |
| ) |  |  | `[explicit]`

Create a zoomer for a plot canvas.

Parameters:

  | xAxis | X axis of the zoomer
  | yAxis | Y axis of the zoomer
  | selectionFlags | Or'd value of QwtPicker::RectSelectionType and QwtPicker::SelectionMode. QwtPicker::RectSelection will be auto added.
  | trackerMode | Tracker mode
  | canvas | Plot canvas to observe, also the parent object
  | doReplot | Call 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:
  QwtPicker, QwtPicker::setSelectionFlags(), QwtPicker::setRubberBand(), QwtPicker::setTrackerMode()

  QwtPlot::autoReplot(), QwtPlot::replot(), setZoomBase()

## Member Function Documentation

bool QwtPlotZoomer::accept | ( | QwtPolygon & | pa | ) | const`[protected, virtual]`

Check and correct a selected rectangle.

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

Returns:
  true If rect is accepted, or has been changed to a accepted rectangle.

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.

See also:
  accept(), minZoomSize()

Reimplemented from QwtPlotPicker.

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

Returns:
  Maximal depth of the zoom stack.

See also:
  setMaxStackDepth()

QwtDoubleSize QwtPlotZoomer::minZoomSize | ( |  | ) | const`[protected, virtual]`

Limit zooming by a minimum rectangle.

Returns:
  zoomBase().width() / 10e4, zoomBase().height() / 10e4

void QwtPlotZoomer::move | ( | double | x,
|  | double | y |
| ) |  |  | `[virtual, slot]`

Move the the current zoom rectangle.

Parameters:

  | x | X value
  | y | Y value

See also:
  QwtDoubleRect::move()

Note:
  The changed rectangle is limited by the zoom base

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::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:

  | 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::setSelectionFlags | ( | int | flags | ) | `[virtual]`

Set the selection flags

Parameters:

  | flags | Or'd value of QwtPicker::RectSelectionType and QwtPicker::SelectionMode. The default value is QwtPicker::RectSelection & QwtPicker::ClickSelection.

See also:
  selectionFlags(), SelectionType, RectSelectionType, SelectionMode

Note:
  QwtPicker::RectSelection will be auto added.

Reimplemented from QwtPicker.

void QwtPlotZoomer::setZoomBase | ( | const QwtDoubleRect & | base | ) | `[virtual]`

Set the initial size of the zoomer.

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

Parameters:

  | base | Zoom base

See also:
  zoomBase(), scaleRect()

void QwtPlotZoomer::setZoomBase | ( | bool | doReplot = `true` | ) | `[virtual]`

Reinitialized the zoom stack with scaleRect() as base.

Parameters:

  | doReplot | Call 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::widgetKeyPressEvent | ( | QKeyEvent * | ke | ) | `[protected, virtual]`

Qt::Key_Plus zooms out, Qt::Key_Minus zooms in 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 | ( | 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 offest 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()

void QwtPlotZoomer::zoom | ( | const QwtDoubleRect & | rect | ) | `[virtual, slot]`

Zoom in.

Clears all rectangles above the current position of the zoom stack and pushs the intersection of zoomRect() and the normalized rect on it.

Note:
  If the maximal stack depth is reached, zoom is ignored.

  The zoomed signal is emitted.

QwtDoubleRect QwtPlotZoomer::zoomBase | ( |  | ) | const

Returns:
  Initial rectangle of the zoomer

See also:
  setZoomBase(), zoomRect()

void QwtPlotZoomer::zoomed | ( | const QwtDoubleRect & | rect | ) | `[signal]`

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

Parameters:

  | rect | Current zoom rectangle.

QwtDoubleRect QwtPlotZoomer::zoomRect | ( |  | ) | const

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 QwtZoomStack & QwtPlotZoomer::zoomStack | ( |  | ) | const

Return the zoom stack. zoomStack()[0] is the zoom base, zoomStack()[1] the first zoomed rectangle.

See also:
  setZoomStack(), zoomRectIndex()