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Abstract

An object-oriented text layout engine that implements an efficient two-pass text placement procedure. The interface allows the text layout engine to receive parameters that define the document space into which text is to be placed. The interface also allows the text layout engine to receive parameters that define one or more constraints around which the text is to be placed. The text layout engine then places the around the constraint within the document space and returns the text layout to the client program. The text layout engine may be configured in three components, a Fill Constrained Display Rectangle (FCDR) module, a Format Line module, and a Compute Unobstructed Spans (CUS) module. The FCDR module controls the operation of the text layout engine, interacts with the client program, and calls the Format Line and CUS modules as necessary. The CUS module receives a set of parameters that define a candidate rectangle and a constraint that may intersect the candidate rectangle. The CUS module breaks the candidate rectangle to avoid the constraint and returns zero or more unobstructed spans that do not intersect the constraint. The Format Line module receives text characters and a span definition and assigns the text characters to the span.

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