PlaceableTwopass

Description

A model of the PlaceableTwopass concept is an item that can be measured and placed within a visual space.

Refinement Of

Associated Type(s)

Extents Type	typename placeable_extents_type<PlaceableTwopass>::type	Models adobe::extents_t. Used by the PlaceableTwopass to relate the minimum visual extents it requires in order to be placed correctly.
Placement Data Type	typename placement_data_type<PlaceableTwopass>::type	Models adobe::place_data_t. Contains the derived information necessary for the PlaceableTwopass to position itself within the visual space

Todo

Need concepts for extents and placement data

Notation

T	A type that is a model of PlaceableTwopass
t	Object of type T
e	Object of type typename placeable_extents_type<PlaceableTwopass>::type
p	Object of type typename placement_data_type<PlaceableTwopass>::type

Definitions

Valid Expressions

Name	Expression	Type requirements	Return type
Measure Horizontal	measure_horizontal(t, e);	e is a reference parameter that on return must contain the calculated horizontal extents of t within the visual space	void
Measure Vertical	measure_vertical(t, e, p);	p contains the calculated place_data_t of t within the visual space. e is a ouput only reference parameter that on return must contain the minimum visual vertical properties required by this visual element	void
Place	place(t, p);	p contains the calculated horizontal and vertical extents of t within the visual space	void

Expression Semantics

Name	Expression	Precondition	Semantics	Postcondition
Place	place(t, p);	p must not be less than the minimum extents specified by measure_horizontal and measure_vertical	Places t within the visual space according to p	t is properly placed within the visual space

Complexity Guarantee(s)

Invariants

Type(s) Modeling this Concept

• Most text-based user interface elements are PlaceableTwopass, in that they need to be measured before they can be placed appropriately within the dialog to which they belong.

Notes

See Also

concept_placeable_twopass, measure_horizontal, measure_vertical, place

Example

PlaceableTwopass_t             p;
 
using adobe::measure_horizontal;
using adobe::measure_vertical;
using adobe::place;
 
adobe::extents_t h;
measure_horizontal(p, h);
 
adobe::extents_t v;
adobe::place_data_t(/*initialized with h and actual placement location*/);
 
measure_vertical(p, v, d);
 
/* update place data, d, with vertical info returned in v, then call: */
place(p, d);