Re: Large files.

[Peter B. West]

Finn Bock wrote:
...
The problem with Keirons layout code (with respect to large input files) 
is that it works top-down on the LM tree and thus require the creating 
of the complete LM tree for the page sequence. To better fit within SAX 
event model the layout process should also be event driven, triggered 
f.ex by the endBlock() and character() events. That means that the 
traversing of the FOTree cannot be easily done using recursive decend. 
Instead the main loop over the FO tree could use a non-recusive tree 
treverse like this:

        public Element traverse(Node q, Node end, int mode) {
            while (q != end) {
                switch (mode) {
                case FIRST:
                    // First time in the node.
                    preorder(q);
                    if (q.hasChildNodes()) {
                        q = q.getFirstChild();
                        break;
                    }
                    mode = NEXT;
                    // fallthrough
                case NEXT:
                    // All children are handled.
                    postorder(q);
                    // Add the node to its parent.
                    if (q.getParentNode() != null) {
                        child(q.getParentNode(), q);
                    }
                    // fallthrough
                case RESTART:
                    // Attempt to move vertically to next sibling.
                                         horizontally?
                    if (q.getNextSibling() != null) {
                        q = q.getNextSibling();
                        mode = FIRST;
                        break;
                    }
                    // No sibling found, move to the parent to
                    // do postorder.
                    q = q.getParentNode();
                    mode = NEXT;
                }
            }
            return null;
        }
...
The loop can be stopped when we temporary run out of FO tree nodes and 
restarted again when new nodes has been added. I suppose that the FO 
tree can then be viewed as a stream of FO nodes.
I suppose so.  And I suppose that making layout event-driven would 
better fit in with the SAX event model.  It just doesn't make sense from 
the point of view of layout which is basically a top-down process.

BTW, datatypes.Node has getPrecedingSibling(), getFollowingSibling() and 
many other doodads.  First code I ever wrote for FOP.

Peter