• Antelope Release 5.9 Mac OS X 10.13.2 2019-05-01

 

NAME

BQGraphicsContext - BRTT Qt graphics extension graphics context class

SYNOPSIS


$(QTNATIVELIBS) -lbqplot_native -lbanner -lbrttutil -lbumapdata $(DBLIBS) $(TRLIBS)

#include "BQ.h"

DESCRIPTION

The BQGraphicsContext class is used by certain bqplot graphics items as a means to specify and configure lists of graphics attributes, called graphics context items, that determine the appearance of displayed graphical entities. All graphical display entities are rendered according to sets of display attributes, such as pen color and fill brush color. The BQGraphicsContext class systematizes the specification of these graphical attributes and also provides functionality for attribute "coding" - the automatic variation of attribute values as a function of some independent variable. An example of attribute coding would be earthquake symbols whose background fill color is a function of earthquake depth.

BQGraphicsContext objects contain a list of individual graphics context items, typed BqGraphicsContextItem. Each graphics context item has a unique string name within the BQGraphicsContext object. An objective of the BQGraphicsContext class is to provide context sharing, including attribute coding, across a large number of graphical entities, such as glyphs. this minimizes heap storage use and also provides a simple mechanism for rapidly changing graphical entity display attributes across a large number of entities. Each of the BqGraphicsContextItem items within a BQGraphicsContext object is meant to be shared across multiple graphics display objects. Simple lists of BqGraphicsContextItem items are returned as BqGraphicsContext lists.

Currently the BQGlyphs, BQPolyline, BQPolypoint, BQMap and BQMapevents items use BQGraphicsContext objects. Another associated (but not based from) class is BQGlyphsGraphicsContext, which is used by BQGlyphs objects.

CONSTRUCTOR

BQGraphicsContext();
BQGraphicsContext(BQGraphicsContext *source);

If a source is specified, then the returned object is a deep copy of the source object.

BQViewportItem METHODS

SEE ALSO

bqplot(3), BQGlyphGraphicsContext(3), BQGlyph(3), BQGlyphs(3), BQPolyline(3), BQPolypoint(3), BqMapevents(3), BQsubs(3)

AUTHOR

Danny Harvey, BRTT
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