discarded after a call to set_current_breakpoints, since that Line_division
refers to a subset of chunks which might be different from the current
subset of chunks under consideration.
+
+ HOW TO WRITE A PAGE BREAKING ALGORITHM
+ All page breakers supported by this class work more-or-less in the same way.
+ First, they request a particular number of systems by saying
+ set_current_breakpoints (0, last_break_position (), system_count)
+ (never mind what the first two arguments do, I'll get to them later).
+ Alternatively, you can do
+ set_to_ideal_line_configuration (0, last_break_position ()),
+ and the number of systems will be automatically chosen according to what
+ the line breaker wants.
+
+ If there are multiple scores, there will be many different ways to achieve
+ a certain number of lines. You can see how many alternatives are available
+ with current_configuration_count (). For every i from 0 to
+ current_configuration_count ()-1, you can see the line division of the
+ corresponding configuration with current_configuration (i), or you can try
+ out various page configurations with one of the space_systems_xxx or
+ pack_systems_xxx functions. The first argument to each of these functions
+ is the configuration index.
+
+ When you're done trying out configurations and you've picked the one
+ you want, do
+ break_into_pieces (0, last_break_position (), line_division_that_you_want);
+ return make_pages (systems_per_page, systems ());
+ where systems_per_page is a vector of numbers telling how many systems are
+ on each page. You can get your systems_per_page vector by looking inside
+ the Page_spacing_results that are returned by space_systems_xxx or
+ pack_systems_xxx.
+
+ A note on performance: set_current_breakpoints is EXPONENTIALLY SLOW unless
+ you constrain it by giving it a lower or an upper bound on the configurations
+ it looks for. Optimal_page_breaking, for example, works by trying
+ out a bunch of configurations, increasing the system count by one, trying
+ again and so on. Each time we increase the system count, we assume that the
+ best new configurations are going to be elementwise larger than the
+ best configuration for the previous system count (in other words, we're going
+ to get a new configuration just by adding an extra line to sone score
+ and leaving the rest the same). Therefore, we pass the best previous line
+ division as an lower bound to set_current_breakpoints.
+
+ Now you should be in a position to understand Optimal_page_breaking::solve.
+ Go ahead and read that before finding out, in the next paragraph,
+ what the first two arguments to set_current_breakpoints do.
+
+ "BREAKS"
+ Sometimes, it's useful to run this whole page-breaking machinery on a subset
+ of the book. To do this, you can mark certain "breaks" in the book (a poor
+ choice of name, perhaps, since a "break" here is different from a page break)
+ and you can run page breaking between any two breaks. You mark your breaks
+ by providing a Break_predicate (and, if you want, a Prob_break_predicate)
+ to Page_breaking's constructor. You then choose a subset of your book
+ by passing the starting and ending breaks to set_current_breakpoints. You
+ can see an example of this in Page_turn_page_breaking, where there is a break
+ everywhere that a page turn is allowed.
*/
#include "page-breaking.hh"