Overview of the PTC ALD Formatting Process
The main steps of the PTC ALD formatting process are detailed below:
1. A frame on a page contains a reference to a particular text stream that should be placed in that frame.
2. Style tags within that text stream add the stream to the format queue.
3. The PTC ALD formatter extracts the text content from the stream word by word and places it into the frame in lines sized in accordance with the frame's specifications.
4. If the formatter encounters markup (identified by the use of < > or & characters) in the stream, it marks its current position in the stream, processes the markup and all its nested children fully, then returns to the saved position in the stream and continues its format process just after the element markup. This ensures that any contextual relationships between tags is captured.
◦ <?processing instructions> control formatting or add specific properties to text
◦ <styles> add text streams to the format queue
◦ &references; add text streams to the queue
The application of physical characteristics to the text is an ongoing process throughout the format operation, rather than an extra step carried out once the content is in place. Processing instructions are included in styles or inserted into the text stream itself to add properties to the text that follows or direct the processor to some other action or area of content. The following sections explain how this is carried out and gives an introduction to the concepts of tests, which calculate the conditions when certain styling can be applied.