2 files changed, 71 insertions, 1 deletions
diff --git a/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignatureParameter.java b/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignatureParameter.java
index 4356f1e0..78dda185 100644
--- a/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignatureParameter.java
+++ b/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignatureParameter.java
@@ -83,7 +83,7 @@ public class PdfAs4SignatureParameter {
     /** The signature profile in use */
     public Profile signatureProfile = Profile.getDefaultProfile();
 
-    public Image getPlaceholder() {
+    Image getPlaceholder() {
         String sigProfile = getPdfAsSignatureProfileId();
 
         String sigEmblem = (this.emblem == null ? null : this.emblem.getCachedFileName());
diff --git a/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignaturePlaceholder.java b/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignaturePlaceholder.java
new file mode 100644
index 00000000..b944bf24
--- /dev/null
+++ b/pdf-over-signer/src/main/java/at/asit/pdfover/signer/pdfas/PdfAs4SignaturePlaceholder.java
@@ -0,0 +1,70 @@
+package at.asit.pdfover.signer.pdfas;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.TreeMap;
+import java.util.function.Consumer;
+
+import at.asit.pdfover.commons.utils.ImageUtil;
+
+/**
+ * caches placeholders for signature parameters (placeholder generation is pretty slow)
+ */
+public final class PdfAs4SignaturePlaceholder implements Runnable {
+    private static TreeMap<PdfAs4SignatureParameter, PdfAs4SignaturePlaceholder> cache = new TreeMap<>(
+        Comparator
+          .comparing(PdfAs4SignatureParameter::getPdfAsSignatureProfileId)
+          .thenComparing((p) -> { return (p.emblem != null) ? p.emblem.getOriginalFileHash() : ""; })
+          .thenComparing((p) -> { return p.signatureNote; }, Comparator.nullsFirst(String::compareTo))
+    );
+
+    /**
+     * request a placeholder for the specified parameter asynchronously
+     * @param callback the callback to be invoked on completion (may also be invoked before this function returns!)
+     */
+    public static void For(PdfAs4SignatureParameter param, Consumer<PdfAs4SignaturePlaceholder> callback) {
+        synchronized(cache) {
+            cache.computeIfAbsent(param, (p) -> new PdfAs4SignaturePlaceholder(p)).AddCallback(callback);
+        }
+    }
+
+    private final PdfAs4SignatureParameter param;
+    private PdfAs4SignaturePlaceholder(PdfAs4SignatureParameter param) {
+        this.param = param;
+        new Thread(this).start();
+    }
+
+    private java.awt.image.BufferedImage awtImageData;
+    /** AWT image data for the placeholder */
+    public java.awt.image.BufferedImage getAWTImage() { return this.awtImageData; }
+    private org.eclipse.swt.graphics.ImageData swtImageData;
+    /** SWT image data for the placeholder */
+    public org.eclipse.swt.graphics.ImageData getSWTImage() { return this.swtImageData; }
+
+    private ArrayList<Consumer<PdfAs4SignaturePlaceholder>> callbacks = new ArrayList<>();
+    private void AddCallback(Consumer<PdfAs4SignaturePlaceholder> c) {
+        synchronized (this) {
+            if (this.callbacks != null)
+            {
+                this.callbacks.add(c);
+                return;
+            } /* else... */
+        }
+        /* ... else, not synchronized */
+        c.accept(this);
+    }
+
+
+    @Override
+    public void run() {
+        this.awtImageData = (java.awt.image.BufferedImage) this.param.getPlaceholder();
+        this.swtImageData = ImageUtil.convertToSWT(this.awtImageData);
+        ArrayList<Consumer<PdfAs4SignaturePlaceholder>> _callbacks;
+        synchronized (this) {
+            _callbacks = this.callbacks;
+            this.callbacks = null;
+        }
+        _callbacks.forEach((c) -> c.accept(this));
+    }
+    
+}