[orca] Fall back on described-by relation to get description

[Joanmarie Diggs <joanied src gnome org>]

commit 29cf83f731e73fa3a31710c47361f0f604ded4a7
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Sat Apr 28 10:42:19 2018 -0400

    Fall back on described-by relation to get description

 src/orca/generator.py        |    6 ++++++
 src/orca/script_utilities.py |   28 ++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 0 deletions(-)
---
diff --git a/src/orca/generator.py b/src/orca/generator.py
index 2d38f97..bcc565b 100644
--- a/src/orca/generator.py
+++ b/src/orca/generator.py
@@ -414,6 +414,12 @@ class Generator:
             desc = obj.description.lower()
             if not (desc in name.lower() or desc in label.lower()):
                 result.append(obj.description)
+
+        if not result:
+            desc = self._script.utilities.displayedDescription(obj)
+            if desc:
+                result.append(desc)
+
         return result
 
     def _generateLabel(self, obj, **args):
diff --git a/src/orca/script_utilities.py b/src/orca/script_utilities.py
index b930e88..12c124a 100644
--- a/src/orca/script_utilities.py
+++ b/src/orca/script_utilities.py
@@ -82,6 +82,7 @@ class Utilities:
 
     # generatorCache
     #
+    DISPLAYED_DESCRIPTION = 'displayedDescription'
     DISPLAYED_LABEL = 'displayedLabel'
     DISPLAYED_TEXT = 'displayedText'
     KEY_BINDING = 'keyBinding'
@@ -436,6 +437,33 @@ class Utilities:
         self._script.generatorCache[self.DISPLAYED_LABEL][obj] = labelString
         return self._script.generatorCache[self.DISPLAYED_LABEL][obj]
 
+    def descriptionsForObject(self, obj):
+        """Return a list of objects describing obj."""
+
+        try:
+            relations = obj.getRelationSet()
+        except (LookupError, RuntimeError):
+            msg = 'ERROR: Exception getting relationset for %s' % obj
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return []
+
+        describedBy = lambda x: x.getRelationType() == pyatspi.RELATION_DESCRIBED_BY
+        relation = filter(describedBy, relations)
+        return [r.getTarget(i) for r in relation for i in range(r.getNTargets())]
+
+    def displayedDescription(self, obj):
+        """Returns the text being displayed for the object describing obj."""
+
+        try:
+            return self._script.generatorCache[self.DISPLAYED_DESCRIPTION][obj]
+        except:
+            if self.DISPLAYED_DESCRIPTION not in self._script.generatorCache:
+                self._script.generatorCache[self.DISPLAYED_DESCRIPTION] = {}
+
+        string = " ".join(map(self.displayedText, self.descriptionsForObject(obj)))
+        self._script.generatorCache[self.DISPLAYED_DESCRIPTION][obj] = string
+        return self._script.generatorCache[self.DISPLAYED_DESCRIPTION][obj]
+
     def displayedText(self, obj):
         """Returns the text being displayed for an object.