Disregard appearance state when irrelevant (fixes #949)

If /AP is a dictionary of streams rather than a dictionary of
dictionaries, disregard /AS, which is supposed to point to a subkey of
one of the dictionaries. This fix prevents qpdf's annotation
flattening from discarding some annotations when /AS is erroneously
set.

ChangeLog

@@ -5,6 +5,15 @@
         reserved object fits better in the QPDF API. The old call just
         delegates to the new one.
 
+2023-05-13  Jay Berkenbilt  <ejb@ql.org>
+
+        * When an annotation dictionary's appearance dictionary (`/AP`)
+        has a key that is a stream, disregard `/AS` (which is supposed to
+        point to a subkey). This enables qpdf to not ignore annotations
+        that have incorrect values for `/AS` when the appearance stream is
+        directly in the `/AP` dictionary instead of in a subkey. Fixes
+        #949.
+
 2023-04-02  Jay Berkenbilt  <ejb@ql.org>
         * Allow QPDFJob's workflow to be split into a reading phase and a
         writing phase to allow the caller to operate on the QPDF object

libqpdf/QPDFAnnotationObjectHelper.cc

@@ -54,7 +54,14 @@ QPDFAnnotationObjectHelper::getAppearanceStream(
     std::string desired_state = state.empty() ? getAppearanceState() : state;
     if (ap.isDictionary()) {
         QPDFObjectHandle ap_sub = ap.getKey(which);
-        if (ap_sub.isStream() && desired_state.empty()) {
+        if (ap_sub.isStream()) {
+            // According to the spec, Appearance State is supposed to
+            // refer to a subkey of the appearance stream when /AP is
+            // a dictionary, but files have been seen in the wild
+            // where Appearance State is `/N` and `/AP` is a stream.
+            // Therefore, if `which` points to a stream, disregard
+            // state and just use the stream. See qpdf issue #949 for
+            // details.
             QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP stream");
             return ap_sub;
         }

manual/release-notes.rst

@@ -26,6 +26,14 @@ For a detailed list of changes, please see the file
     - Add ``QPDF::newReserved`` as a better alternative to
       ``QPDFObjectHandle::newReserved``.
 
+  - Bug fixes
+
+    - Ignore an annotation's appearance state when the annotation only
+      has one appearance. This prevents qpdf's annotation flattening
+      logic from throwing away appearances of annotations whose
+      annotation state is set incorrectly, as has been seen in some
+      PDF files.
+
 11.3.0: February 25, 2023
   - CLI Enhancements
 

qpdf/qtest/qpdf/form-form-bad-fields-array.out

@@ -178,7 +178,7 @@ Page: 11 0 R
     Subtype: /Widget
     Rect: [123.4, 692.1, 260.9, 706.7]
     Appearance stream (/N): 14 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 14 0 R
   Annotation: 16 0 R
     Field: 16 0 R
     Subtype: /Widget
@@ -249,5 +249,5 @@ Page: 35 0 R
     Subtype: /Widget
     Rect: [113.6, 378.5, 351.3, 396.3]
     Appearance stream (/N): 36 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 36 0 R
 test 43 done

qpdf/qtest/qpdf/form-form-document-defaults.out

@@ -166,7 +166,7 @@ Page: 11 0 R
     Subtype: /Widget
     Rect: [123.4, 692.1, 260.9, 706.7]
     Appearance stream (/N): 14 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 14 0 R
   Annotation: 16 0 R
     Field: 16 0 R
     Subtype: /Widget
@@ -237,5 +237,5 @@ Page: 35 0 R
     Subtype: /Widget
     Rect: [113.6, 378.5, 351.3, 396.3]
     Appearance stream (/N): 36 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 36 0 R
 test 43 done

qpdf/qtest/qpdf/form-form-empty-from-odt.out

@@ -166,7 +166,7 @@ Page: 11 0 R
     Subtype: /Widget
     Rect: [123.4, 692.1, 260.9, 706.7]
     Appearance stream (/N): 14 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 14 0 R
   Annotation: 16 0 R
     Field: 16 0 R
     Subtype: /Widget
@@ -237,5 +237,5 @@ Page: 35 0 R
     Subtype: /Widget
     Rect: [113.6, 378.5, 351.3, 396.3]
     Appearance stream (/N): 36 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 36 0 R
 test 43 done

qpdf/qtest/qpdf/form-form-errors.out

@@ -171,7 +171,7 @@ Page: 11 0 R
     Subtype: /Widget
     Rect: [123.4, 692.1, 260.9, 706.7]
     Appearance stream (/N): 14 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 14 0 R
   Annotation: 16 0 R
     Field: 16 0 R
     Subtype: /Widget
@@ -242,5 +242,5 @@ Page: 35 0 R
     Subtype: /Widget
     Rect: [113.6, 378.5, 351.3, 396.3]
     Appearance stream (/N): 36 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 36 0 R
 test 43 done

qpdf/qtest/qpdf/form-form-mod1.out

@@ -166,7 +166,7 @@ Page: 11 0 R
     Subtype: /Widget
     Rect: [123.4, 692.1, 260.9, 706.7]
     Appearance stream (/N): 14 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 14 0 R
   Annotation: 16 0 R
     Field: 16 0 R
     Subtype: /Widget
@@ -237,5 +237,5 @@ Page: 35 0 R
     Subtype: /Widget
     Rect: [113.6, 378.5, 351.3, 396.3]
     Appearance stream (/N): 36 0 R
-    Appearance stream (/N, /3): null
+    Appearance stream (/N, /3): 36 0 R
 test 43 done