add basic support for hooking into DocListener events

src/clj/clj_pdf/core.clj

@@ -961,6 +961,70 @@
                                      (int 0)
                                      (int 0))))))))))
 
+(defn- has-event? [k events]
+  (if-let [fns (get events k)]
+    (if (sequential? fns)
+      (not (empty? fns)))))
+
+(defn- raise-event [k events & args]
+  (if-let [fns (get events k)]
+    (if (sequential? fns)
+      (doseq [f fns]
+        (if (fn? f)
+          (apply f args)
+          (throw (Exception. (str "non-function value found in doc events list for event: " k)))))
+      (throw (Exception. (str "doc event " k " not a sequence of functions"))))))
+
+(defn- set-doc-listener [doc events]
+  (.addDocListener
+    doc
+    (reify cljpdf.text.DocListener
+      ; DocListener methods
+      (open [_]
+        (raise-event :open events doc))
+      (close [_]
+        (raise-event :close events doc))
+      (newPage [_]
+        (raise-event :new-page events doc)
+        true)
+      (setPageSize [_ pageSize]
+        (raise-event :set-page-size events doc pageSize)
+        ; return value doesn't appear to be used in itext anywhere
+        true)
+      (setMargins [_ marginLeft marginRight marginTop marginBottom]
+        (raise-event :set-margins events doc marginLeft marginRight marginTop marginBottom)
+        ; return value doesn't appear to be used in itext anywhere
+        true)
+      (setMarginMirroring [_ marginMirroring]
+        (raise-event :set-margin-mirroring events doc marginMirroring)
+        ; return value doesn't appear to be used in itext anywhere
+        true)
+      (setMarginMirroringTopBottom [_ marginMirroringTopBottom]
+        (raise-event :set-margin-mirroring-top-bottom events doc marginMirroringTopBottom)
+        ; return value doesn't appear to be used in itext anywhere
+        true)
+      (setPageCount [_ pageN]
+        (raise-event :set-page-count events doc pageN))
+      (resetPageCount [_]
+        (raise-event :reset-page-count events doc))
+      (setHeader [_ header]
+        (raise-event :set-header events doc header))
+      (resetHeader [_]
+        (raise-event :reset-header events doc))
+      (setFooter [_ footer]
+        (raise-event :set-footer events doc footer))
+      (resetFooter [_]
+        (raise-event :reset-footer events doc))
+
+      ; ElementListener methods
+      (add [_ element]
+        (if (has-event? :add events)
+          (raise-event :add events doc element)
+          ; return value IS used in Document.add()
+          ; default return of false is safe to ensure no unwanted behaviour
+          false))
+      )))
+
 (defn- setup-doc [{:keys [left-margin
                           right-margin
                           top-margin
@@ -978,6 +1042,7 @@
                           font-style
                           orientation
                           page-events
+                          doc-events
                           watermark] :as meta}
                   out]
 
@@ -999,6 +1064,8 @@
                                (merge {:align :right :start-page 1} footer)))
         header-first-page? (if letterhead false true)]
 
+    (set-doc-listener doc doc-events)
+
     ;;header and footer must be set before the doc is opened, or itext will not put them on the first page!
     ;;if we have to print total pages or add a watermark, then the document has to be post processed
     (let [output-stream-to-use (if (page-events? meta) temp-stream output-stream)