Luca,
Do you know of a web-accessible version of the paper, or summary of the algorithm?
Peter
Luca Furini wrote:
Hi all
I am still thinking about justification and the more general problem of line-breaking, and I have come to think that it's quite "strange" that the LineLayoutManager should make choices about breaking points using only the information provided by the TextLayoutManagers, while it should have a wider knowledge of all the text. (I see bug 28706 as an example of this strangeness: the LLM wants the TLM to say if there is other text after the returned BreakPoss, but the TLM doesn't know of the other TLMs' text)
At the moment, lines are built one at a time, and in "normal" cases only underfull lines are taken into account: as both bpDim and availIPD have .min == .opt == .max, no BreakPoss is added to vecPossEnd and the chosen one is simply the last "short" BP returned by a TLM. Even if bpDim had .min != .max, the choice would be made between a few alternatives for the current line, without considering what will happen next; this could generate an output alternating tight and loose lines, which is not very beautiful.
So, I have tried to implement Knuth's line-breaking algorithm [1], which calculates breaking points after having gathered information about a whole paragraph. Here are a few advantages of this algorithm: - first of all, the output is very beautiful; there is not a big difference in width between spaces in consecutive lines, and the max space width is smaller than before - the interaction between LLM and TLM is quite the same; the TLM returns a different kind of objects, much smaller - the TLM code is simplified a bit, as it has no more to handle leading spaces, or calculate flags (which IMO are rather line-related than text-related) - the LLM now can quite easily handle properties such as text-indent, text-align-last, word-spacing and letter-spacing
Could I open a bugzilla issue and attach a patch? It would be quite a raw patch, as I took some short cuts to make it work and there could be some useless variables, anyway it works and could be used to show the quality of the output. I have tested it with text-only blocks, so I don't know what could happen in more complex situations.
-- Peter B. West <http://www.powerup.com.au/~pbwest/resume.html>
