Add a container for Signature with their own canvas

src/display/annotation_layer.js

@@ -100,6 +100,8 @@ class AnnotationElementFactory {
             return new PushButtonWidgetAnnotationElement(parameters);
           case "Ch":
             return new ChoiceWidgetAnnotationElement(parameters);
+          case "Sig":
+            return new SignatureWidgetAnnotationElement(parameters);
         }
         return new WidgetAnnotationElement(parameters);
 
@@ -1373,6 +1375,12 @@ class TextWidgetAnnotationElement extends WidgetAnnotationElement {
   }
 }
 
+class SignatureWidgetAnnotationElement extends WidgetAnnotationElement {
+  constructor(parameters) {
+    super(parameters, { isRenderable: !!parameters.data.hasOwnCanvas });
+  }
+}
+
 class CheckboxWidgetAnnotationElement extends WidgetAnnotationElement {
   constructor(parameters) {
     super(parameters, { isRenderable: parameters.renderForms });

test/pdfs/.gitignore

@@ -600,3 +600,4 @@
 !issue16500.pdf
 !issue16538.pdf
 !freetexts.pdf
+!issue16553.pdf

test/test_manifest.json

@@ -7806,5 +7806,13 @@
             "id": "53R"
          }
       }
+   },
+   {
+      "id": "issue16553",
+      "file": "pdfs/issue16553.pdf",
+      "md5": "9b67d31ccfd21572b10f77c5449ce97d",
+      "rounds": 1,
+      "type": "eq",
+      "annotations": true
    }
 ]