Text layout.

CTextLayout is the lowest-level text formatting class in the Text Views API. It obtains text and formatting attributes via the MLayDoc interface class and formats the text to a certain width.

It has functions for drawing the text and performing hit-detection that is, converting x-y coordinates to document positions, and vice versa. It defines many public functions that are not generally useful, but are called by the higher-level CTextView class, or exist only for the convenience of closely associated classes like the printing and pagination systems. These are identified in the documentation by the text "not generally useful".

When using the CTextLayout class, you must be aware of what functions have previously been called. For example:

1) Formatting and scrolling functions must not be called if a CTextView object owns the CTextLayout object, because the CTextView object may be reformatting the CTextLayout object asynchronously by means of an active object, or may hold some state information about the CTextLayout object that would be invalidated by reformatting. These functions are identified in the documentation by the text "Do not use if a CTextView object owns this CTextLayout object.".

2) Functions that raise out of memory exceptions can leave the object in an inconsistent state; these functions can be identified as usual by their trailing L. When this occurs, it is necessary to discard the formatting information by calling DiscardFormat().

3) Some functions change formatting parameters like the wrap width or band height, but do not reformat to reflect the change. These functions are identified in the documentation by the text "Reformat needed".