Text selection classes

Text selections

An editable text component always has a current text selection, defined by one of the following:

• An insertion offset (an insertion point created by clicking the mouse)
• A single text range (a selected sequence of characters created by clicking and dragging the mouse)
• A text region (discontiguous sequences of characters created by clicking and dragging the mouse, and then holding down a modifier key and clicking and dragging the mouse to create other discontiguous selected ranges)

A text selection object stores one each of these elements, regardless of the current value of the selection. For example, if the selection is a nonzero-length text range, the GetInsertionOffset function returns the last offset in the range. If the selection is an insertion offset, the GetRegion function returns a zero-length range.

MTextSelection defines the abstract protocol for text selections, including access functions for the value of the selection and access to the data represented by the selection. Each text selection object is bound to a specific text representation object. A text selection uses a primitive class, TTextArea, to encapsulate the value of the selection--the insertion offset, text range, and text region. MTextSelection delegates the selection data access functions to TTextArea. See "Representing a text selection" on page 39 for more information on TTextArea.

TDocumentTextSelection is a concrete text selection class used for selections on editable text document components. TDocumentTextSelection derives from TModelSelection, MToolTarget, and MDataExchanger, and implements the protocol for data exchange operations (cut, copy, and paste). A TDocumentTextSelection object is bound to a TTextModel object.

TEmbedderTextSelection adds the protocol for selecting text ranges that contain embedded components.

TSimpleTextSelection is a concrete text selection class used for selections on lightweight text components. A TSimpleTextSelection object is bound to a TSimpleTextStore object.

Presenter state selections

TTextPresenterStateSelection, derived from the Compound Document framework class TPresenterStateSelection, identifies a selected document presentation. The selection is represented by the presenter state for the document. To create a TTextPresenterStateSelection, you pass a reference to the presenter state to select. TTextPresenterStateSelection also mixes in MToolTarget.