🚀 go-pugleaf

Helen Chang asks about updating Compositions and offers some sample
code.

Compositions take a list of glyphs and break it into smaller pieces.
Then they build composite glyphs for each of the pieces.  This
functionality is usually associated with formatting text; breaking
paragraphs into lines and lines into columns are classic applications
of Compositions.

Helen, I can't see why your example needs a Composition at all.  If
you just want to display a column of Labels (and have the display
update when you add new items) then a simpler arrangement will
suffice.  Something like this, perhaps...

========
class TestViewer : public MonoGlyph, public Handler {
public:
	TestViewer(Font*, Color*);
	virtual void event() {}
	void item_append(Glyph* );
	void update();

private:
	Listener*	_listener;
        TBBox*          _lines;
	Patch*		_textPatch;
};

TestViewer::TestViewer(Font* f, Color* fg)
	: MonoGlyph(nil), Handler()
{
	_lines = new TBBox();
	_textPatch = new Patch(_lines);

	_listener = new Listener(_textPatch, this);
	_listener->sensor()->button(true, Event::any);
	_listener->sensor()->key(true);

	body(_listener);
}

void TestViewer::item_append(Glyph* g)
{	_lines->append(g);
}

void TestViewer::update()
{	_textPatch->reallocate();

}
--
Paul Calder
Computer Systems Lab
Stanford University
calder@lurch.stanford.edu