NAME

       QwtPlotCanvas - Canvas of a QwtPlot.

SYNOPSIS

       #include <qwt_plot_canvas.h>

       Inherits QFrame.

   Public Types
       enum PaintAttribute { BackingStore = 1, Opaque = 2, HackStyledBackground = 4,
           ImmediatePaint = 8 }
           Paint attributes.
       enum FocusIndicator { NoFocusIndicator, CanvasFocusIndicator, ItemFocusIndicator }
           Focus indicator The default setting is NoFocusIndicator.
       typedef QFlags< PaintAttribute > PaintAttributes
           Paint attributes.

   Public Slots
       void replot ()

   Public Member Functions
       QwtPlotCanvas (QwtPlot *=NULL)
           Constructor.
       virtual ~QwtPlotCanvas ()
           Destructor.
       QwtPlot * plot ()
           Return parent plot widget.
       const QwtPlot * plot () const
           Return parent plot widget.
       void setFocusIndicator (FocusIndicator)
       FocusIndicator focusIndicator () const
       void setBorderRadius (double)
       double borderRadius () const
       void setPaintAttribute (PaintAttribute, bool on=true)
           Changing the paint attributes.
       bool testPaintAttribute (PaintAttribute) const
       const QPixmap * backingStore () const
       void invalidateBackingStore ()
           Invalidate the internal backing store.
       virtual bool event (QEvent *)
       Q_INVOKABLE QPainterPath borderPath (const QRect &) const

   Protected Member Functions
       virtual void paintEvent (QPaintEvent *)
       virtual void resizeEvent (QResizeEvent *)
       virtual void drawFocusIndicator (QPainter *)
       virtual void drawBorder (QPainter *)
       void updateStyleSheetInfo ()
           Update the cached information about the current style sheet.

Detailed Description

       Canvas of a QwtPlot.

       Canvas is the widget where all plot items are displayed

       See also:
           QwtPlot::setCanvas(), QwtPlotGLCanvas

Member Enumeration Documentation

   enum QwtPlotCanvas::FocusIndicator
       Focus indicator The default setting is NoFocusIndicator.

       See also:
           setFocusIndicator(), focusIndicator(), drawFocusIndicator()

       Enumerator

       NoFocusIndicator
              Don't paint a focus indicator.

       CanvasFocusIndicator
              The focus is related to the complete canvas. Paint the focus indicator using
              drawFocusIndicator()

       ItemFocusIndicator
              The focus is related to an item (curve, point, ...) on the canvas. It is up to the
              application to display a focus indication using f.e. highlighting.

   enum QwtPlotCanvas::PaintAttribute
       Paint attributes. The default setting enables BackingStore and Opaque.

       See also:
           setPaintAttribute(), testPaintAttribute()

       Enumerator

       BackingStore
              Paint double buffered reusing the content of the pixmap buffer when possible. Using
              a backing store might improve the performance significantly, when working with
              widget overlays ( like rubber bands ). Disabling the cache might improve the
              performance for incremental paints (using QwtPlotDirectPainter ).

       See also:
           backingStore(), invalidateBackingStore()

       Opaque Try to fill the complete contents rectangle of the plot canvas. When using styled
              backgrounds Qt assumes, that the canvas doesn't fill its area completely ( f.e
              because of rounded borders ) and fills the area below the canvas. When this is done
              with gradients it might result in a serious performance bottleneck - depending on
              the size.

       When the Opaque attribute is enabled the canvas tries to identify the gaps with some
       heuristics and to fill those only.

       Warning:
           Will not work for semitransparent backgrounds

       HackStyledBackground
              Try to improve painting of styled backgrounds. QwtPlotCanvas supports the box model
              attributes for customizing the layout with style sheets. Unfortunately the design
              of Qt style sheets has no concept how to handle backgrounds with rounded corners -
              beside of padding.

       When HackStyledBackground is enabled the plot canvas tries to separate the background from
       the background border by reverse engineering to paint the background before and the border
       after the plot items. In this order the border gets perfectly antialiased and you can
       avoid some pixel artifacts in the corners.

       ImmediatePaint
              When ImmediatePaint is set replot() calls repaint() instead of update().

       See also:
           replot(), QWidget::repaint(), QWidget::update()

Constructor & Destructor Documentation

   QwtPlotCanvas::QwtPlotCanvas (QwtPlot * plot = NULL) [explicit]
       Constructor.

       Parameters:
           plot Parent plot widget

       See also:
           QwtPlot::setCanvas()

Member Function Documentation

   const QPixmap * QwtPlotCanvas::backingStore () const
       Returns:
           Backing store, might be null

   QPainterPath QwtPlotCanvas::borderPath (const QRect & rect) const
       Calculate the painter path for a styled or rounded border

       When the canvas has no styled background or rounded borders the painter path is empty.

       Parameters:
           rect Bounding rectangle of the canvas

       Returns:
           Painter path, that can be used for clipping

   double QwtPlotCanvas::borderRadius () const
       Returns:
           Radius for the corners of the border frame

       See also:
           setBorderRadius()

   void QwtPlotCanvas::drawBorder (QPainter * painter) [protected],  [virtual]
       Draw the border of the plot canvas

       Parameters:
           painter Painter

       See also:
           setBorderRadius()

   void QwtPlotCanvas::drawFocusIndicator (QPainter * painter) [protected],  [virtual]
       Draw the focus indication

       Parameters:
           painter Painter

   bool QwtPlotCanvas::event (QEvent * event) [virtual]
       Qt event handler for QEvent::PolishRequest and QEvent::StyleChange

       Parameters:
           event Qt Event

       Returns:
           See QFrame::event()

   QwtPlotCanvas::FocusIndicator QwtPlotCanvas::focusIndicator () const
       Returns:
           Focus indicator

       See also:
           FocusIndicator, setFocusIndicator()

   void QwtPlotCanvas::paintEvent (QPaintEvent * event) [protected],  [virtual]
       Paint event

       Parameters:
           event Paint event

   void QwtPlotCanvas::replot () [slot]
       Invalidate the paint cache and repaint the canvas

       See also:
           invalidatePaintCache()

   void QwtPlotCanvas::resizeEvent (QResizeEvent * event) [protected],  [virtual]
       Resize event

       Parameters:
           event Resize event

   void QwtPlotCanvas::setBorderRadius (double radius)
       Set the radius for the corners of the border frame

       Parameters:
           radius Radius of a rounded corner

       See also:
           borderRadius()

   void QwtPlotCanvas::setFocusIndicator (FocusIndicator focusIndicator)
       Set the focus indicator

       See also:
           FocusIndicator, focusIndicator()

   void QwtPlotCanvas::setPaintAttribute (PaintAttribute attribute, bool on = true)
       Changing the paint attributes.

       Parameters:
           attribute Paint attribute
           on On/Off

       See also:
           testPaintAttribute(), backingStore()

   bool QwtPlotCanvas::testPaintAttribute (PaintAttribute attribute) const
       Test whether a paint attribute is enabled

       Parameters:
           attribute Paint attribute

       Returns:
           true, when attribute is enabled

       See also:
           setPaintAttribute()

Author

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