Layout managers

+ Layout managers in FOP +

+ What do the layout managers do? Most layout is is "automatic" + in the sense of being a straightforward stacking operation. + Sibling inline-areas, including fo:character areas, are + stacked in line-areas in the inline-progression-direction. + Sibling block-areas, including line-areas, are stacked in the + block-progression-direction. +

+ In the simple cases in which both the available + block-progression-dimension and the available + inline-progression-dimension are known, this process can be + driven bottom-up. Available dimensions trickle down from the + top, and the bottom level galleys can determine when their + available areas are full and suspend pending the arrival of + more areas. Such full notifications bubble back up the tree + of active galleys. E.g., if an inline galley fills a + line-area of a given inline-p-d and suspends while still + within the available block-p-d, the parent block-area galley + will simply stack the inline-area and notify the inline galley + to continue. If the inline-galley discovers that the next + line-area that it would generate will not fit in the the + block-p-d, it suspends with a notification to that effect to + its parent. +

+ In more complex cases the dimensions may not be fully + specified, or decisions about layout may depend on later + layout. In all such cases some layout look-ahead is required + which can report results back to higher layout levels. The + job for a layout manager in these cirucmstances is to evaluate + the information flowing back and set parameters for the best + fit layout. +