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NAME

       QwtPlotCanvas -

       Canvas of a QwtPlot.

SYNOPSIS

       #include <qwt_plot_canvas.h>

   Public Types
       enum PaintAttribute { BackingStore =  1, Opaque =  2, HackStyledBackground =  4,
           ImmediatePaint =  8 }
       enum FocusIndicator { NoFocusIndicator, CanvasFocusIndicator, ItemFocusIndicator }
       typedef QFlags< PaintAttribute > PaintAttributes

   Public Member Functions
       QwtPlotCanvas (QwtPlot *)
       virtual ~QwtPlotCanvas ()
       QwtPlot * plot ()
       const QwtPlot * plot () const
       void setFocusIndicator (FocusIndicator)
       FocusIndicator focusIndicator () const
       void setBorderRadius (double)
       double borderRadius () const
       QPainterPath borderPath (const QRect &rect) const
       QBitmap borderMask (const QSize &) const
       void setPaintAttribute (PaintAttribute, bool on=true)
       bool testPaintAttribute (PaintAttribute) const
       const QPixmap * backingStore () const
       void invalidateBackingStore ()
       void replot ()
       virtual bool event (QEvent *)

   Protected Member Functions
       virtual void paintEvent (QPaintEvent *)
       virtual void resizeEvent (QResizeEvent *)
       virtual void drawFocusIndicator (QPainter *)
       virtual void drawBorder (QPainter *)
       void updateStyleSheetInfo ()

Detailed Description

       Canvas of a QwtPlot.

       See also:
           QwtPlot

Member Typedef Documentation

   typedef QFlags<PaintAttribute> QwtPlotCanvas::PaintAttributes
       Paint attributes.

Member Enumeration Documentation

   enum QwtPlotCanvas::FocusIndicator
       Focus indicator. .IP "·" 2 NoFocusIndicator
        Don't paint a focus indicator

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

       · 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.

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

   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 workin with
              widget overlays ( like rubberbands ). 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 seperate the background from
       the background border by reverse engeneering to paint the background before and the border
       after the plot items. In this order the border gets prefectly 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) [explicit]
       Sets a cross cursor, enables QwtPlotCanvas::BackingStore.

   QwtPlotCanvas::~QwtPlotCanvas () [virtual]
       Destructor.

Member Function Documentation

   const QPixmap * QwtPlotCanvas::backingStore () const
       Return the backing store, might be null.

   QBitmap QwtPlotCanvas::borderMask (const QSize &size) const Calculate a mask, that can be used
       to clip away the border frame
       Parameters:
           size Size including the frame

   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(), QFrame::drawFrame()

   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

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

       See also:
           FocusIndicator, setFocusIndicator()

   void QwtPlotCanvas::invalidateBackingStore ()
       Invalidate the internal backing store.

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

   QwtPlot * QwtPlotCanvas::plot ()
       Return parent plot widget.

   const QwtPlot * QwtPlotCanvas::plot () const
       Return parent plot widget.

   void QwtPlotCanvas::replot () 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 (doubleradius) Set the radius for the corners of the
       border frame
       Parameters:
           radius Radius of a rounded corner

       See also:
           borderRadius()

   void QwtPlotCanvas::setFocusIndicator (FocusIndicatorfocusIndicator) Set the focus indicator
       See also:
           FocusIndicator, focusIndicator()

   void QwtPlotCanvas::setPaintAttribute (PaintAttributeattribute, boolon = true)
       Changing the paint attributes. Parameters:
           attribute Paint attribute
           on On/Off

       See also:
           testPaintAttribute(), backingStore()

   bool QwtPlotCanvas::testPaintAttribute (PaintAttributeattribute) const Test wether a paint
       attribute is enabled
       Parameters:
           attribute Paint attribute

       Returns:
           true if the attribute is enabled

       See also:
           setPaintAttribute()

   void QwtPlotCanvas::updateStyleSheetInfo () [protected]
       Update the cached informations about the current style sheet.

Author

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