Public Types¶

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

Public Member Functions¶

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

Protected Member Functions¶

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

enum QwtWidgetOverlay::MaskMode¶

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:

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.

enum QwtWidgetOverlay::RenderMode¶

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:

Enumerator

AutoRenderMode

Copy the buffer, when using the raster paint engine.

CopyAlphaMask

Always copy the buffer.

DrawOverlay

Never copy the buffer.

QwtWidgetOverlay::QwtWidgetOverlay (QWidget * widget)¶

Constructor.

Parameters:

virtual void QwtWidgetOverlay::drawOverlay (QPainter * painter) const [protected], [pure virtual]¶

Draw the widget overlay

Parameters:

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

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

Parameters:

Returns:

QRegion QwtWidgetOverlay::maskHint () const [protected], [virtual]¶

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:

QwtWidgetOverlay::MaskMode QwtWidgetOverlay::maskMode () const¶

Returns:

See also:

void QwtWidgetOverlay::paintEvent (QPaintEvent * event) [protected], [virtual]¶

Paint event

Parameters:

See also:

QwtWidgetOverlay::RenderMode QwtWidgetOverlay::renderMode () const¶

Returns:

See also:

void QwtWidgetOverlay::resizeEvent (QResizeEvent * event) [protected], [virtual]¶

Resize event

Parameters:

void QwtWidgetOverlay::setMaskMode (MaskMode mode)¶

Specify how to find the mask for the overlay.

Parameters:

See also:

void QwtWidgetOverlay::setRenderMode (RenderMode mode)¶

Set the render mode

Parameters:

See also:

void QwtWidgetOverlay::updateOverlay ()¶

Recalculate the mask and repaint the overlay