Bug 651307 Don't commit composition string on plugins at changing input source r=smichaud

modules/libpref/src/init/all.js

@@ -2288,6 +2288,8 @@ pref("print.print_extra_margin", 90); // twips (90 twips is an eigth of an inch)
 // See bug 404131, topmost <panel> element wins to Dashboard on MacOSX.
 pref("ui.panel.default_level_parent", false);
 
+pref("ui.plugin.cancel_composition_at_input_source_changed", false);
+
 pref("mousewheel.system_scroll_override_on_root_content.enabled", false);
 
 # XP_MACOSX

widget/src/cocoa/ComplexTextInputPanel.mm

@@ -26,6 +26,9 @@
  */
 
 #import "ComplexTextInputPanel.h"
+#include "nsIPrefService.h"
+#include "nsIPrefBranch.h"
+#include "nsServiceManagerUtils.h"
 
 #define kInputWindowHeight 20
 
@@ -83,7 +86,23 @@
 
 - (void)keyboardInputSourceChanged:(NSNotification *)notification
 {
-  [self cancelComposition];
+  static PRInt8 sDoCancel = -1;
+  if (!sDoCancel || ![self inComposition]) {
+    return;
+  }
+  if (sDoCancel < 0) {
+    nsCOMPtr<nsIPrefBranch> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID);
+    NS_ENSURE_TRUE(prefs, );
+    PRBool cancelComposition = PR_FALSE;
+    nsresult rv =
+      prefs->GetBoolPref("ui.plugin.cancel_composition_at_input_source_changed",
+                         &cancelComposition);
+    NS_ENSURE_SUCCESS(rv, );
+    sDoCancel = cancelComposition ? 1 : 0;
+  }
+  if (sDoCancel) {
+    [self cancelComposition];
+  }
 }
 
 - (BOOL)interpretKeyEvent:(NSEvent*)event string:(NSString**)string