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Selection(3U) InterViews Reference Manual Selection(3U)


Selection - maintains a list of selected graphical component views


#include <Unidraw/selection.h>


A Selection manages a set of distinguished graphical component views, usually those in which the user has expressed interest by selecting them with a tool or command. Each selection object maintains a list of graphical component views and provides operations for iterating through and manipulating the list. Components, commands, tools, and editors often rely on one or more selection objects to supply the components on which they operate.


Create a new selection object, optionally containing references to the same views as the given selection object.
Destroy a selection instance. Deleting the selection does not in turn delete the view instances it maintains.
These operations affect how the selection is represented visually in the viewer. Show instructs the views to initialize and draw their handles to highlight themselves, thus indicating that they are selected. To do so, it calls RedrawHandles on each view. Update makes handles of newly-selected, unhighlighted views appear by calling DrawHandles on all its views. Hide unhighlights the views by calling their EraseHandles operation. Finally, Init initializes each view's handles without drawing them (in case the handles' appearance may have changed) by calling InitHandles on each.
Remove all views from the Selection object, hiding their handles in the process.
Operations for modifying the selection's list of views. Append and Prepend add a GraphicView to the end and the beginning of the list, respectively. InsertAfter and InsertBefore insert a GraphicView after and before the GraphicView pointed to by the iterator, respectively. The Remove operations remove a view from the list (without deleting it). You can remove a view instance by referring to it explicitly or by specifying an iterator. If an iterator is supplied, the Remove operation will advance it to point to the following view as a side effect.
GetView returns the view to which an iterator points. SetView initializes an iterator to point to a particular view in the list; it initializes the iterator to point to a nil instance if the given GraphicView is not in the selection list.
Operations for iterating over the selection list. First and Last initialize an iterator to point to the beginning and end of the list, respectively. Next increments the iterator to point to the following view, while Prev decrements the iterator to point to the preceding view. Done returns whether or not the iterator points beyond the first or last view in the list.
Operations that return information about the selection object's contents. IsEmpty returns whether the selection list is empty, Includes returns whether the list contains the given view, and Number returns the number of views in the list.
Sort the views in the selection list to conform to their order in the given GraphicView's list of children. The selection list's order usually reflects the order in which the user selected the objects, not their order in their parent. Sort is useful in operations that modify or depend on the parent view's structure.
Operations that change the selection object's contents based on another selection's. Merge adds the views in the given selection to those already in the selection object (the union of the two sets), while Exclusive adds those views not already in this object and removes those common to both (the union minus the intersection of the two sets). Neither of these operations change the contents of their argument.
Return the bounding box circumscribing the views in the selection list.


Selection stores its views on a UList, which is accessible via the _ulist protected member. The Selection's iteration operations store the UList containing the current view in their iterator. Elem is a convenience function for returning the UList to which an iterator points, and View extracts the GraphicView that a UList element contains.


GraphicView(3U), Iterator(3U), UList(3U), Viewer(3U)

6 August 1990 Unidraw