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# QwtPlotZoomer Class Reference

Inheritance diagram for QwtPlotZoomer:

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Collaboration diagram for QwtPlotZoomer:

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List of all members.

## 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/QwtEventPattern::KeyUndo, or QwtEventPattern::MouseSelect6/QwtEventPattern::KeyRedo 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, even when one or both of them are disabled. In most situations it is recommended to disable rubber band and cursor label for one of the zoomers.

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

Warning:
  Calling QwtPlot::setAxisScale() while QwtPlot::autoReplot() is FALSE leaves the axis in an 'intermediate' state. In this case, to prevent buggy behaviour, your must call QwtPlot::replot() before calling QwtPlotPicker::scaleRect(), QwtPlotZoomer::scaleRect(), QwtPlotPicker::QwtPlotPicker() or QwtPlotZoomer::QwtPlotZoomer(). This quirk will be removed in a future release.

Definition at line 59 of file qwt_plot_zoomer.h.

## 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 *, const char *name=0)
| QwtPlotZoomer (int xAxis, int yAxis, QwtPlotCanvas *, const char *name=0)
| QwtPlotZoomer (int xAxis, int yAxis, int selectionFlags, DisplayMode cursorLabelMode, QwtPlotCanvas *, const char *name=0)
virtual void | setZoomBase ()
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 QValueStack< QwtDoubleRect > & | zoomStack () const
uint | zoomRectIndex () const
virtual void | setSelectionFlags (int)
## Protected Member Functions
QValueStack< QwtDoubleRect > & | zoomStack ()
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 (QPointArray &) const

## Constructor & Destructor Documentation

QwtPlotZoomer::QwtPlotZoomer | ( | QwtPlotCanvas * | canvas,
|  | const char * | name = `0`
| ) |

  | 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 cursor label mode to QwtPicker::ActiveOnly. Parameters:
  | canvas | Plot canvas to observe, also the parent object
  | name | Object name
Warning: Calling QwtPlot::setAxisScale() while QwtPlot::autoReplot() is FALSE leaves the axis in an 'intermediate' state. In this case, to prevent buggy behaviour, you must call QwtPlot::replot() before calling QwtPlotZoomer(). This quirk will be removed in a future release. See also: QwtPlot::autoReplot(), QwtPlot::replot(), QwtPlotPicker::setZoomBase() Definition at line 40 of file qwt_plot_zoomer.cpp.

QwtPlotZoomer::QwtPlotZoomer | ( | int | xAxis,
|  | int | yAxis,
|  | QwtPlotCanvas * | canvas,
|  | const char * | name = `0`
| ) |

  | Create a zoomer for a plot canvas. The selectionFlags() are set to QwtPicker::RectSelection & QwtPicker::ClickSelection, the cursor label 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
  | name | Object name
Warning: Calling QwtPlot::setAxisScale() while QwtPlot::autoReplot() is FALSE leaves the axis in an 'intermediate' state. In this case, to prevent buggy behaviour, you must call QwtPlot::replot() before calling QwtPlotZoomer(). This quirk will be removed in a future release. See also: QwtPlot::autoReplot(), QwtPlot::replot(), QwtPlotPicker::setZoomBase() Definition at line 68 of file qwt_plot_zoomer.cpp.

QwtPlotZoomer::QwtPlotZoomer | ( | int | xAxis,
|  | int | yAxis,
|  | int | selectionFlags,
|  | DisplayMode | cursorLabelMode,
|  | QwtPlotCanvas * | canvas,
|  | const char * | name = `0`
| ) |

  | Create a zoomer for a plot canvas. Parameters:
  | xAxis | X axis of the zoomer
  | yAxis | Y axis of the zoomer
  | selectionFlags | Orīd value of QwtPicker::RectSelectionType and QwtPicker::SelectionMode. QwtPicker::RectSelection will be auto added.
  | cursorLabelMode | Cursor label mode
  | canvas | Plot canvas to observe, also the parent object
  | name | Object name
See also: QwtPicker, QwtPicker::setSelectionFlags(), QwtPicker::setRubberBand(), QwtPicker::setCursorLabelMode Warning: Calling QwtPlot::setAxisScale() while QwtPlot::autoReplot() is FALSE leaves the axis in an 'intermediate' state. In this case, to prevent buggy behaviour, you must call QwtPlot::replot() before calling QwtPlotZoomer(). This quirk will be removed in a future release. See also: QwtPlot::autoReplot(), QwtPlot::replot(), QwtPlotPicker::setZoomBase() Definition at line 102 of file qwt_plot_zoomer.cpp.

## Member Function Documentation

bool QwtPlotZoomer::accept | ( | QPointArray & | 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. Definition at line 456 of file qwt_plot_zoomer.cpp. References minZoomSize().

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. Definition at line 508 of file qwt_plot_zoomer.cpp. References QwtPicker::begin(), QwtDoubleSize::height(), QwtDoubleSize::isValid(), minZoomSize(), and QwtDoubleSize::width().

bool QwtPlotZoomer::end | ( | bool | ok = `TRUE` | ) | `[protected, virtual]`

| Expand the selected rectangle to minZoomSize() and zoom in if accepted. Note: The zoomed signal is emitted. See also: QwtPlotZoomer::accept()a, QwtPlotZoomer::minZoomSize() Reimplemented from QwtPlotPicker. Definition at line 539 of file qwt_plot_zoomer.cpp. References QwtDoubleRect::center(), QwtPlotPicker::end(), QwtDoubleSize::expandedTo(), QwtPlotPicker::invTransform(), minZoomSize(), QwtDoubleRect::moveCenter(), QwtDoubleRect::normalize(), QwtPlotPicker::plot(), QwtPicker::selection(), QwtDoubleRect::setSize(), QwtDoubleRect::size(), zoom(), zoomed(), and zoomRect().

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

| Returns: Maximal depth of the zoom stack. See also: setMaxStackDepth() Definition at line 159 of file qwt_plot_zoomer.cpp.

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

| Limit zooming by a minimum rectangle. Tries to stop zooming, when the precision of the axes label string conversion leads to identical values. Returns: minimum rectangle Definition at line 488 of file qwt_plot_zoomer.cpp. References QwtPlot::axisLabelFormat(), QwtPlotPicker::plot(), QwtPlotPicker::xAxis(), and QwtPlotPicker::yAxis(). Referenced by accept(), begin(), and end().

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

  | Move the the current zoom rectangle. Parameters:
  | x | X value
  | y | value
See also: QwtDoubleRect::move Note: The changed rectangle is limited by the zoom base Definition at line 430 of file qwt_plot_zoomer.cpp. References rescale(), QwtDoubleRect::x1(), QwtDoubleRect::y1(), zoomBase(), and zoomRect(). Referenced by moveBy().

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 Definition at line 415 of file qwt_plot_zoomer.cpp. References move(), QwtDoubleRect::x1(), and QwtDoubleRect::y1().

void QwtPlotZoomer::rescale | ( |  | ) | `[protected, virtual]`

| Adjust the observed plot to zoomRect() Note: Initiates QwtPlot::replot Definition at line 327 of file qwt_plot_zoomer.cpp. References QwtPlotPicker::plot(), QwtPlot::replot(), QwtPlotPicker::scaleRect(), QwtPlot::setAxisScale(), QwtDoubleRect::x1(), QwtDoubleRect::x2(), QwtPlotPicker::xAxis(), QwtDoubleRect::y1(), QwtDoubleRect::y2(), and QwtPlotPicker::yAxis(). Referenced by move(), setZoomBase(), and zoom().

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. Definition at line 350 of file qwt_plot_zoomer.cpp. References QwtPlotPicker::scaleRect(), QwtPlotPicker::setAxis(), setZoomBase(), QwtPlotPicker::xAxis(), and QwtPlotPicker::yAxis().

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 doesnīt include the zoom base, so zoomStack().count() might be maxStackDepth() + 1. Definition at line 135 of file qwt_plot_zoomer.cpp. References zoom().

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

  | Set the selection flags Parameters:
  | flags | Orīd 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. Definition at line 578 of file qwt_plot_zoomer.cpp. References QwtPicker::setSelectionFlags().

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() Definition at line 227 of file qwt_plot_zoomer.cpp. References QwtPlotPicker::plot(), rescale(), and QwtPlotPicker::scaleRect().

void QwtPlotZoomer::setZoomBase | ( |  | ) | `[virtual]`

| Reinitialized the zoom stack with scaleRect() as base. See also: zoomBase(), scaleRect() Warning: Calling QwtPlot::setAxisScale() while QwtPlot::autoReplot() is FALSE leaves the axis in an 'intermediate' state. In this case, to prevent buggy behaviour, you must call QwtPlot::replot() before calling QwtPlotZoomer::setZoomBase(). This quirk will be removed in a future release. See also: QwtPlot::autoReplot(), QwtPlot::replot(). Definition at line 204 of file qwt_plot_zoomer.cpp. References QwtPlotPicker::plot(), rescale(), and QwtPlotPicker::scaleRect(). Referenced by setAxis().

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 doesnīt pop any rectangle. Note: The keys codes can be changed, using QwtEventPattern::setKeyPattern: 3, 4, 5 Reimplemented from QwtPicker. Definition at line 392 of file qwt_plot_zoomer.cpp. References QwtPicker::isActive(), QwtEventPattern::keyMatch(), QwtPicker::widgetKeyPressEvent(), and zoom().

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 doesnīt pop any rectangle. Note: The mouse events can be changed, using QwtEventPattern::setMousePattern: 2, 1 Reimplemented from QwtPicker. Definition at line 369 of file qwt_plot_zoomer.cpp. References QwtEventPattern::mouseMatch(), QwtPicker::widgetMouseReleaseEvent(), and zoom().

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.
See also: zoomRectIndex() Definition at line 305 of file qwt_plot_zoomer.cpp. References rescale().

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. Definition at line 277 of file qwt_plot_zoomer.cpp. References QwtDoubleRect::normalize(), rescale(), and zoomRect(). Referenced by end(), setMaxStackDepth(), widgetKeyPressEvent(), and widgetMouseReleaseEvent().

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

| Returns: Initial rectangle of the zoomer See also: setZoomBase(), zoomRect() Definition at line 186 of file qwt_plot_zoomer.cpp. Referenced by move().

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.
Warning: zoomed() is only emitted after selections in end(), but never in zoom(). Referenced by end().

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

| Rectangle at the current position on the zoom stack. See also: QwtPlotZoomer::zoomRectIndex(), QwtPlotZoomer::scaleRect(). Definition at line 254 of file qwt_plot_zoomer.cpp. Referenced by end(), move(), and zoom().

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

| Returns: Index of current position of zoom stack. Definition at line 262 of file qwt_plot_zoomer.cpp.

QValueStack< QwtDoubleRect > & QwtPlotZoomer::zoomStack | ( |  | ) | `[protected]`

| Return the zoom stack. zoomStack()[0] is the zoom base, zoomStack()[1] the first zoomed rectangle. Definition at line 177 of file qwt_plot_zoomer.cpp.

const QValueStack< QwtDoubleRect > & QwtPlotZoomer::zoomStack | ( |  | ) | const

| Return the zoom stack. zoomStack()[0] is the zoom base, zoomStack()[1] the first zoomed rectangle. Definition at line 168 of file qwt_plot_zoomer.cpp.