Edit

ITextSelection::MoveLeft method (tom.h)

  • Article

Generalizes the functionality of the Left Arrow key.

Syntax

HRESULT MoveLeft(
  long Unit,
  long Count,
  long Extend,
  long *pDelta
);

Parameters

Unit

Type: long

Unit to use. It can be one of the following.

Value Corresponding key combination Meaning
tomCharacter Left Arrow Move one character position to the left. This is the default.
tomWord Ctrl+Left Arrow Move one word to the left.
 

Note: If Count is less than zero, movement is to the right.

Count

Type: long

Number of Units to move past. The default value is 1. If Count is less than zero, movement is to the right.

Extend

Type: long

Flag that indicates how to change the selection. If Extend is zero (or tomMove), the method collapses the selection to an insertion point at the active end and then moves it. If Extend is 1 (or tomExtend), the method moves the active end and leaves the other end alone. The default value is zero. A nonzero Extend value corresponds to the Shift key being pressed in addition to the key combination described in Unit.

pDelta

Type: long*

The actual count of units the insertion point or active end is moved left. This parameter can be null. Collapsing the selection, when Extend is 0, counts as one unit.

Return value

Type: HRESULT

The method returns an HRESULT value. If the method succeeds, it returns S_OK. If the method fails, it returns one of the following error codes. For more information about COM error codes, see Error Handling in COM.

Return code Description
E_INVALIDARG
 Unit is not valid.
S_FALSE
 Failure for some other reason.

Remarks

The WordBasic move methods like CharRight, CharLeft, WordRight, and WordLeft are hybrids that can do four things that are closely related to the standard arrow-key edit behavior:

  • Move the current insertion point if there's no selection.
  • Move the active end of the selection if there is a selection.
  • Turn an insertion point into a selection and vice versa.
  • Return a Boolean stating if movement occurred.
The Extend argument of MoveLeft and MoveRight enables you to be consistent with the first three items above, and the pDelta is a generalization of the fourth. For example, given a selection consisting of a single range, you have the following correspondences (for left-to-right characters).
ITextSelection WordBasic Function
selection.MoveRight tomWord, 1, 1 WordRight 1,1 Moves active end one word right.
selection.MoveLeft tomCharacter, 1, 1 CharLeft 1,1 Moves active end one character left.
 

As in WordBasic, if Count is less than zero, the meanings of left and right are interchanged, that is MoveLeft (Unit, Count, Extend) is equivalent to MoveRight (Unit, -Count, Extend).

Similar to WordBasic and the Left Arrow key UI behavior, calling MoveLeft ( Unit, Count) on a degenerate selection moves the insertion point the specified number of Units. On a degenerate range, calling MoveLeft( Unit, Count, 1) where Count is greater than zero causes the range to become nondegenerate with the left end being the active end.

When Extend is tomExtend (or is nonzero), MoveLeft moves only the active end of the selection, leaving the other end where it is. However, if Extend equals zero and the selection starts as a nondegenerate range, MoveLeft(Unit, Count) where Count is greater than zero moves the active end Count - 1 units left, and then moves the other end to the active end. In other words, it makes an insertion point at the active end. Collapsing the range counts as one unit. Thus, MoveLeft(tomCharacter) converts a nondegenerate selection into a degenerate one at the selection's left end. Here, Count has the default value of 1 and Extend has the default value of zero. This example corresponds to pressing the Left Arrow key. MoveLeft and MoveRight are related to the ITextRange move methods, but differ in that they explicitly use the active end (the end moved by pressing the Shift key).

Requirements

Requirement Value
Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header tom.h
DLL Msftedit.dll

See also

Conceptual

ITextRange

ITextSelection

MoveRight

Reference

Text Object Model