Additional Behavior

The actions determine the orientation of characters by using the Layout Services transformation OutToInp and Property buffers (for the nesting level). The widget's behavior is therefore dependent on the locale-specific transformation. If the information in the OutToInp or, especially, Property buffers is inaccurate, the widget may behave unexpectedly. Moreover, as the locale-specific modules fall outside of the scope of this specification, bi-directional editing behavior may differ from platform to platform for the same text, application, resource values, and LayoutObject configuration.

The visual mode actions result in display cell-based behavior. The logical mode actions result in logical character-based behavior. For example, the delete-right-character() operation deletes the input buffer characters that correspond to the display cell (that is, one input buffer character whole LayoutObject transformation "property" byte "new cell indicator" is 1, and all of the succeeding characters whose "new cell indicator" [For more information on the Property buffer, see the specification for m_transform_layout() in CAE Specification.] is 0).

Similarly, for backward-character(), the insertion point is moved backward one character in the input buffer, and the cursor is redrawn at the visual location corresponding to the associated output buffer character. This means that several keystrokes are required to move across a composite display cell; the cursor does not actually change display location as the insertion point moves across input buffer characters whose "new cell indicator" is 0 (that is, diacritics or ligature fragments).

This means deletion operates either from the logical/input buffer side, or from the display cell level of the physical/output side. There is no mode for a strict, physical character-by-character deletion, since there is no one-to-one correspondence between the input and output buffers. A given physical character may represent only a fragment of a logical character, for example.