Qwt User's Guide
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#include <qwt_plot_canvas.h>
Public Types | |
enum | PaintAttribute { BackingStore = 1, Opaque = 2, HackStyledBackground = 4, ImmediatePaint = 8 } |
Paint attributes. More... | |
enum | FocusIndicator { NoFocusIndicator, CanvasFocusIndicator, ItemFocusIndicator } |
Focus indicator The default setting is NoFocusIndicator. More... | |
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. |
Canvas of a QwtPlot.
Canvas is the widget where all plot items are displayed
Focus indicator The default setting is NoFocusIndicator.
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. |
Paint attributes.
The default setting enables BackingStore and Opaque.
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 ).
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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.
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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().
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QwtPlotCanvas::QwtPlotCanvas | ( | QwtPlot * | plot = NULL | ) | [explicit] |
const QPixmap * QwtPlotCanvas::backingStore | ( | ) | const |
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.
rect | Bounding rectangle of the canvas |
double QwtPlotCanvas::borderRadius | ( | ) | const |
void QwtPlotCanvas::drawBorder | ( | QPainter * | painter | ) | [protected, virtual] |
void QwtPlotCanvas::drawFocusIndicator | ( | QPainter * | painter | ) | [protected, virtual] |
Draw the focus indication
painter | Painter |
bool QwtPlotCanvas::event | ( | QEvent * | event | ) | [virtual] |
Qt event handler for QEvent::PolishRequest and QEvent::StyleChange
event | Qt Event |
void QwtPlotCanvas::paintEvent | ( | QPaintEvent * | event | ) | [protected, virtual] |
Paint event
event | Paint event |
void QwtPlotCanvas::replot | ( | ) | [slot] |
Invalidate the paint cache and repaint the canvas
void QwtPlotCanvas::resizeEvent | ( | QResizeEvent * | event | ) | [protected, virtual] |
Resize event
event | Resize event |
void QwtPlotCanvas::setBorderRadius | ( | double | radius | ) |
Set the radius for the corners of the border frame
radius | Radius of a rounded corner |
void QwtPlotCanvas::setFocusIndicator | ( | FocusIndicator | focusIndicator | ) |
Set the focus indicator
void QwtPlotCanvas::setPaintAttribute | ( | PaintAttribute | attribute, |
bool | on = true |
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Changing the paint attributes.
attribute | Paint attribute |
on | On/Off |
bool QwtPlotCanvas::testPaintAttribute | ( | PaintAttribute | attribute | ) | const |
Test whether a paint attribute is enabled
attribute | Paint attribute |