[orca] Chromium: Use caret-moved event to recover from object destruction

[Joanmarie Diggs <joanied src gnome org>]

commit 6cb974736fc99d2b9fd0a9f306f9f29e35a88f63
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Fri Apr 24 17:48:11 2020 -0400

    Chromium: Use caret-moved event to recover from object destruction
    
    Sometimes when objects are destroyed as a side effect of caret navigation,
    Chromium gives us a caret-moved event for the new location. Using this
    event allows us to gracefully and efficiently recover from the destruction.
    
    Solves (at least) the problem of Orca's caret-navigation failing after
    Github's actions drop-down is accessed in Browse mode and then collapses.

 src/orca/scripts/web/script.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
---
diff --git a/src/orca/scripts/web/script.py b/src/orca/scripts/web/script.py
index 2dea942d8..5c6878b70 100644
--- a/src/orca/scripts/web/script.py
+++ b/src/orca/scripts/web/script.py
@@ -1266,6 +1266,11 @@ class Script(default.Script):
             debug.println(debug.LEVEL_INFO, msg, True)
             contents = self.utilities.getLineContentsAtOffset(newFocus, 0)
             utterances = self.speechGenerator.generateContents(contents)
+        elif self.utilities.lastInputEventWasLineNav() and self.utilities.isZombie(oldFocus):
+            msg = "WEB: Last input event was line nav; oldFocus is zombie. Generating line contents."
+            debug.println(debug.LEVEL_INFO, msg, True)
+            contents = self.utilities.getLineContentsAtOffset(newFocus, caretOffset)
+            utterances = self.speechGenerator.generateContents(contents)
         else:
             msg = "WEB: New focus %s is not a special case. Generating speech." % newFocus
             debug.println(debug.LEVEL_INFO, msg, True)
@@ -1477,6 +1482,19 @@ class Script(default.Script):
             debug.println(debug.LEVEL_INFO, msg, True)
             return False
 
+        obj, offset = self.utilities.getCaretContext(getZombieReplicant=False)
+        msg = "WEB: Context: %s, %i (focus: %s)" % (obj, offset, orca_state.locusOfFocus)
+        debug.println(debug.LEVEL_INFO, msg, True)
+
+        if not obj or self.utilities.isZombie(obj):
+            obj, offset = self.utilities.findFirstCaretContext(event.source, event.detail1)
+            if obj:
+                msg = "WEB: Event handled by updating locusOfFocus and context"
+                debug.println(debug.LEVEL_INFO, msg, True)
+                orca.setLocusOfFocus(event, obj, True)
+                self.utilities.setCaretContext(obj, offset)
+                return True
+
         if self._lastCommandWasCaretNav:
             msg = "WEB: Event ignored: Last command was caret nav"
             debug.println(debug.LEVEL_INFO, msg, True)