Print a JavaFX Node at a Specific Size

printscaling.clj

(ns printscaling.core
  (:gen-class
   :extends javafx.application.Application)
  (:import
   [javafx.application Application]
   [javafx.beans.value ChangeListener]
   [javafx.event EventHandler]
   [javafx.geometry Insets Pos]
   [javafx.print PrinterJob]
   [javafx.scene Scene]
   [javafx.scene.canvas Canvas]
   [javafx.scene.control Button]
   [javafx.scene.layout BorderPane Pane Region VBox]
   [javafx.scene.paint Color]
   [javafx.scene.transform Scale]
   [javafx.stage Screen]))

(def points-per-inch 72.0)

(defn redraw-board
  "Draw the board on the canvas."
  [canvas]
  (let [w (.getWidth canvas)
        h (.getHeight canvas)
        gc (.getGraphicsContext2D canvas)]
    
    (doto gc
      (.clearRect 0 0 w h)
      (.setLineWidth 3)
      (.setFill (Color/BLUE))
      (.setStroke (Color/BLUE))
      (.strokeRect 0 0 w h)
      (.strokeLine 0 0 w h)
      (.strokeLine w 0 0 h))))

(defn create-print-button-handler
  "Handle a click on the 'Print' button. Print a 5 inch square version
   of the board."
  [stage]
  (reify EventHandler
    (handle [this event]
      (let [job (PrinterJob/createPrinterJob)]
        (if (.showPrintDialog job stage)
          (let [dpi (.getDpi (Screen/getPrimary))
                pixels (* dpi 5)
                canvas (Canvas. pixels pixels)
                scale (/ points-per-inch dpi)]
            (.add (.getTransforms canvas) (Scale. scale scale))
            (redraw-board canvas)
            (if (.printPage job canvas)
              (.endJob job))))))))

(defn create-print-btn [stage]
  (let [btn (Button. "Print")]
    (.setOnAction btn (create-print-button-handler stage))
    btn))

(defn -start
  "Build the application interface and start it up."
  [this stage]
  (let [root (BorderPane.)
        center (Pane.)
        spacer (Region.)
        btn-pane (VBox.)
        scene (Scene. root)
        canvas (Canvas.)
        print-btn (create-print-btn stage)]

    (doto (.widthProperty canvas)
      (.bind (.widthProperty center))
      (.addListener
       (reify ChangeListener
         (changed [_ _ _ _]
           (redraw-board canvas)))))
    (doto (.heightProperty canvas)
      (.bind (.heightProperty center))
      (.addListener
       (reify ChangeListener
         (changed [_ _ _ _]
           (redraw-board canvas)))))
    
    (doto btn-pane
      (.setId "btn-pane")
      (.setPadding (Insets. 10))
      (.setAlignment Pos/CENTER)
      (.setStyle "-fx-background-color: slategray;"))

    (.setPrefHeight spacer Integer/MAX_VALUE)
    (.addAll (.getChildren btn-pane) [print-btn spacer])

    (.add (.getChildren  center) canvas)
    (.setCenter root center)
    (.setRight root btn-pane)

    (doto stage
      (.setTitle "Print Scaling")
      (.setScene scene)
      (.setHeight 400)
      (.setWidth 600)
      (.show))))

(defn -main [& args]
  (Application/launch printscaling.core args))

project.clj

(defproject print-scaling "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.7.0"]]
  :aot :all
  :main printscaling.core
  :target-path "target/%s"
  :profiles {:uberjar {:aot :all}})