Stefan Monnier wrote: >>The customizable variable `font-lock-lines-before' is not honored by >>jit-lock mode. > > > I know what that means in therms of what the code does, but I'm wondering in > which circumstance it makes a visible difference to the end user. > Do you have a test case? > >
Suppose not: Wouldn't that mean `font-lock-lines-before' is useless? It's not very difficult to contrive test cases for this. By default `font-lock-multiline' is nil. `font-lock-fontify-anchored-keywords' won't alter it - the appropriate lines have been commented out. Write an arbitrary multiline pattern. Now font-lock won't give it the `font-lock-multiline' text property and jit-lock not necessarily reset its `fontified' text property after a change. `font-lock-after-change', on the other hand, may refontify it provided `font-lock-lines-before' is large enough. You might argue now that the user should customize `font-lock-multiline' appropriately and major modes set it as necessary. (By the way, is the value `undecided' useful - I don't see tests like `(eq font-lock-multiline t)' or `(eq font-lock-multiline 'undecided)' anywhere?) Let's therefore suppose `font-lock-multiline' is t in the following example: I display a buffer in a new window, and jump immediately to a line within a multiline pattern. More precisely, the first line of the pattern is before window-start and the last line of the pattern appears within the window. In this case, the pattern might not be fontified properly - fontification triggered by redisplay does not fontify text before window-start. Modifying the first line of the window will cause redisplay to consider only that line (and possibly subsequent ones). The pattern will not be fontified properly unless I scroll to its beginning. Plain font-lock, on the other hand, could handle this case when `font-lock-lines-before' is set appropriately. However, I believe that `font-lock-lines-before' is a brute force approach to handle such cases and could remarkably slow down editing if it were honored by jit-lock mode. Multiline patterns are too delicate and should be treated in a completely different way. _______________________________________________ Emacs-devel mailing list Emacs-devel@gnu.org http://lists.gnu.org/mailman/listinfo/emacs-devel
