Scroll to navigation

Tray(3I) InterViews Reference Manual Tray(3I)


Tray - compose interactors into arbitrary or constrained layouts


#include <InterViews/tray.h>


A tray is a scene of interactors that overlap, tile, or have other constraints on their alignment relative to each other. One of the interactors in a tray can serve as a background for the other interactors.

Constraints on the layout of interactors are made by aligning interactors to each other. Two interactors are aligned by specifying which edges coincide. For example, the lower left corner of one interactor may be aligned to the upper right of another. TGlue objects can be used to introduce transparent space between aligned interactors. TGlue has a natural size, shrinkability, and stretchability (though TGlue objects are not interactors). Trays stretch or shrink the TGlue along with the aligned interactors to satisfy the alignment constraints.

The tray adopts the shape of the background interactor if there is one; otherwise, the tray's shape depends on the shapes of its components and potentially on their alignments. By default, a tray without a background takes on a width and height equal to the largest of the widths and heights of its components. However, alignments involving the tray can in effect override this default.

For example, if the left and right sides of a particular component are aligned to the tray's left and right sides, respectively, then the tray's sides are constrained to coincide with the component's sides. Thus the tray will adopt the width, horizontal shrinkability, and horizontal stretchability of that component. Another example: To ensure that a tray circumscribes a collection of (mutually aligned) components, align the outer edges of the components on the periphery of the collection to the outer edges of the tray, thereby constraining the tray to assume the shape of the collection.


Define TGlue of a minimum size. The TGlue can stretch from the given size but cannot shrink.
Define general TGlue with a given natural size (width and height), shrinkability, and stretchability.


Create a new tray, optionally having an interactor as a background.
Align an interactor to another interactor (the tray itself by default), optionally with TGlue between them. Align operations insert interactors into the tray if they have not been inserted already.
Apply an alignment to a set of interactors. This operation is shorthand for aligning the interactors to each other explicitly. For example, Align(Left, i1, i2, i3, i4) aligns the left sides of interactors i1 through i4. Two to seven interactors can be aligned at once.
The HBox and VBox operations align the specified interactors such that they tile left-to-right and top-to-bottom, respectively. These operations align in one dimension only. Two to seven interactors can be aligned at once. If the first (last) component is the tray or the background interactor, then the leftmost (rightmost) component will be aligned with the left (right) side of the tray.
Insert an interactor into the tray without an alignment. The interactor will appear in the lower left corner of the tray.
Notify the tray that the given interactor's shape has changed. The tray will recompute the layout of its component interactors to satisfy any alignments. If the tray does not contain a background, then a change in the shape of one of its components may in turn change the tray's shape. If the tray has a background, then the tray's shape will change only if the shape of the background changes.
Take an interactor out of a tray and eliminate any alignments that have been made to it.


Interactor(3I), Scene(3I), Shape(3I)

8 September 1988 InterViews