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QwtWidgetOverlay Class Referenceabstract

An overlay for a widget. More...

#include <qwt_widget_overlay.h>

Inheritance diagram for QwtWidgetOverlay:
Inheritance graph
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Classes

class  PrivateData
 

Public Types

enum  MaskMode { NoMask, MaskHint, AlphaMask }
 Mask mode. More...
 
enum  RenderMode { AutoRenderMode, CopyAlphaMask, DrawOverlay }
 Render mode. More...
 

Public Slots

void updateOverlay ()
 

Public Member Functions

virtual bool eventFilter (QObject *, QEvent *)
 Event filter. More...
 
MaskMode maskMode () const
 
 QwtWidgetOverlay (QWidget *)
 Constructor. More...
 
RenderMode renderMode () const
 
void setMaskMode (MaskMode)
 Specify how to find the mask for the overlay. More...
 
void setRenderMode (RenderMode)
 
virtual ~QwtWidgetOverlay ()
 Destructor. More...
 

Protected Member Functions

virtual void drawOverlay (QPainter *painter) const =0
 
virtual QRegion maskHint () const
 Calculate an approximation for the mask. More...
 
virtual void paintEvent (QPaintEvent *event)
 
virtual void resizeEvent (QResizeEvent *event)
 

Private Member Functions

void draw (QPainter *) const
 
void updateMask ()
 

Private Attributes

PrivateDatad_data
 

Detailed Description

An overlay for a widget.

The main use case of an widget overlay is to avoid heavy repaint operation of the widget below.

F.e. in combination with the plot canvas an overlay avoid replots as the content of the canvas can be restored from its backing store.

QwtWidgetOverlay is an abstract base class. Deriving classes are supposed to reimplement the following methods:

Internally QwtPlotPicker uses overlays for displaying the rubber band and the tracker text.

See also
QwtPlotCanvas::BackingStore

Definition at line 40 of file qwt_widget_overlay.h.

Member Enumeration Documentation

Mask mode.

When using masks the widget below gets paint events for the masked regions of the overlay only. Otherwise Qt triggers full repaints. On less powerful hardware ( f.e embedded systems ) - or when using the raster paint engine on a remote desktop - bit blitting is a noticeable operation, that needs to be avoided.

If and how to mask depends on how expensive the calculation of the mask is and how many pixels can be excluded by the mask.

The default setting is MaskHint.

See also
setMaskMode(), maskMode()
Enumerator
NoMask 

Don't use a mask.

MaskHint 

Use maskHint() as mask.

For many situations a fast approximation is good enough and it is not necessary to build a more detailed mask ( f.e the bounding rectangle of a text ).

AlphaMask 

Calculate a mask by checking the alpha values.

Sometimes it is not possible to give a fast approximation and the mask needs to be calculated by drawing the overlay and testing the result.

When a valid maskHint() is available only pixels inside this approximation are checked.

Definition at line 60 of file qwt_widget_overlay.h.

Render mode.

For calculating the alpha mask the overlay has already been painted to a temporary QImage. Instead of rendering the overlay twice this buffer can be copied for drawing the overlay.

On graphic systems using the raster paint engine ( QWS, Windows ) it means usually copying some memory only. On X11 it results in an expensive operation building a pixmap and for simple overlays it might not be recommended.

Note
The render mode has no effect, when maskMode() != AlphaMask.
Enumerator
AutoRenderMode 

Copy the buffer, when using the raster paint engine.

CopyAlphaMask 

Always copy the buffer.

DrawOverlay 

Never copy the buffer.

Definition at line 102 of file qwt_widget_overlay.h.

Constructor & Destructor Documentation

QwtWidgetOverlay::QwtWidgetOverlay ( QWidget *  widget)
explicit

Constructor.

Parameters
widgetParent widget, where the overlay is aligned to

Definition at line 114 of file qwt_widget_overlay.cpp.

QwtWidgetOverlay::~QwtWidgetOverlay ( )
virtual

Destructor.

Definition at line 131 of file qwt_widget_overlay.cpp.

Member Function Documentation

void QwtWidgetOverlay::draw ( QPainter *  painter) const
private

Definition at line 307 of file qwt_widget_overlay.cpp.

virtual void QwtWidgetOverlay::drawOverlay ( QPainter *  painter) const
protectedpure virtual

Draw the widget overlay

Parameters
painterPainter

Implemented in QwtPickerTracker, and QwtPickerRubberband.

bool QwtWidgetOverlay::eventFilter ( QObject *  object,
QEvent *  event 
)
virtual

Event filter.

Resize the overlay according to the size of the parent widget.

Parameters
objectObject to be filtered
eventEvent
Returns
See QObject::eventFilter()

Definition at line 367 of file qwt_widget_overlay.cpp.

QRegion QwtWidgetOverlay::maskHint ( ) const
protectedvirtual

Calculate an approximation for the mask.

  • MaskHint The hint is used as mask.
  • AlphaMask The hint is used to speed up the algorithm for calculating a mask from non transparent pixels
  • NoMask The hint is unused.

The default implementation returns an invalid region indicating no hint.

Returns
Hint for the mask

Reimplemented in QwtPickerTracker, and QwtPickerRubberband.

Definition at line 351 of file qwt_widget_overlay.cpp.

QwtWidgetOverlay::MaskMode QwtWidgetOverlay::maskMode ( ) const
Returns
Mode how to find the mask for the overlay
See also
setMaskMode()

Definition at line 155 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::paintEvent ( QPaintEvent *  event)
protectedvirtual

Paint event

Parameters
eventPaint event
See also
drawOverlay()

Definition at line 249 of file qwt_widget_overlay.cpp.

QwtWidgetOverlay::RenderMode QwtWidgetOverlay::renderMode ( ) const
Returns
Render mode
See also
RenderMode, setRenderMode()

Definition at line 175 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::resizeEvent ( QResizeEvent *  event)
protectedvirtual

Resize event

Parameters
eventResize event

Definition at line 300 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::setMaskMode ( MaskMode  mode)

Specify how to find the mask for the overlay.

Parameters
modeNew mode
See also
maskMode()

Definition at line 142 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::setRenderMode ( RenderMode  mode)

Set the render mode

Parameters
modeRender mode
See also
RenderMode, renderMode()

Definition at line 166 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::updateMask ( )
private

Definition at line 189 of file qwt_widget_overlay.cpp.

void QwtWidgetOverlay::updateOverlay ( )
slot

Recalculate the mask and repaint the overlay

Definition at line 183 of file qwt_widget_overlay.cpp.

Member Data Documentation

PrivateData* QwtWidgetOverlay::d_data
private

Definition at line 146 of file qwt_widget_overlay.h.


The documentation for this class was generated from the following files:


plotjuggler
Author(s): Davide Faconti
autogenerated on Sat Jul 6 2019 03:44:19