diff options
Diffstat (limited to 'src/guile/skribilo/engine.scm')
| -rw-r--r-- | src/guile/skribilo/engine.scm | 48 |
1 files changed, 44 insertions, 4 deletions
diff --git a/src/guile/skribilo/engine.scm b/src/guile/skribilo/engine.scm index 5800486..fbaf4d2 100644 --- a/src/guile/skribilo/engine.scm +++ b/src/guile/skribilo/engine.scm @@ -53,14 +53,43 @@ ;;; Class definition. ;;; +;; Note on writers +;; --------------- +;; +;; `writers' here is an `eq?' hash table where keys are markup names +;; (symbols) and values are lists of markup writers (most of the time, the +;; list will only contain one writer). Each of these writer may define a +;; predicate or class that may further restrict its applicability. +;; +;; `free-writers' is a list of writers that may apply to *any* kind of +;; markup. These are typically define by passing `#t' to `markup-writer' +;; instead of a symbol: +;; +;; (markup-writer #f (find-engine 'xml) +;; :before ... +;; ...) +;; +;; The XML engine contains an example of such free writers. Again, these +;; writers may define a predicate or a class restricting their applicability. +;; +;; The distinction between these two kinds of writers is mostly performance: +;; "free writers" are rarely used and markup-specific are the most common +;; case which we want to be fast. Therefore, for the latter case, we can't +;; afford traversing a list of markups, evaluating each and every markup +;; predicate. +;; +;; For more details, see `markup-writer-get' and `lookup-markup-writer' in +;; `(skribilo writer)'. + (define-class <engine> () (ident :init-keyword :ident :init-value '???) (format :init-keyword :format :init-value "raw") - (info :init-keyword :info :init-value '()) + (info :init-keyword :info :init-value '()) (version :init-keyword :version :init-value 'unspecified) (delegate :init-keyword :delegate :init-value #f) - (writers :init-keyword :writers :init-value '()) + (writers :init-thunk make-hash-table) + (free-writers :init-value '()) (filter :init-keyword :filter :init-value #f) (customs :init-keyword :custom :init-value '()) (symbol-table :init-keyword :symbol-table :init-value '())) @@ -268,7 +297,13 @@ otherwise the requested engine is returned." (slot-set! e 'customs (cons (list id val) customs))))) -(define (engine-add-writer! e ident pred upred opt before action after class valid) +(define (engine-add-writer! e ident pred upred opt before action + after class valid) + ;; Add a writer to engine E. If IDENT is a symbol, then it should denote + ;; a markup name and the writer being added is specific to that markup. If + ;; IDENT is `#t' (for instance), then it is assumed to be a ``free writer'' + ;; that may apply to any kind of markup for which PRED returns true. + (define (check-procedure name proc arity) (cond ((not (procedure? proc)) @@ -309,7 +344,12 @@ otherwise the requested engine is returned." :class class :pred pred :upred upred :options opt :before before :action action :after after :validate valid))) - (slot-set! e 'writers (cons n (slot-ref e 'writers))) + (if (symbol? ident) + (let ((writers (slot-ref e 'writers))) + (hashq-set! writers ident + (cons n (hashq-ref writers ident '())))) + (slot-set! e 'free-writers + (cons n (slot-ref e 'free-writers)))) n)) |