fix: support any contet editable element

Author: caisui

common/content/buffer.js

@@ -1501,8 +1501,10 @@ const Buffer = Module("buffer", {
                         modes.set(modes.INSERT);
                     else if (Buffer.focusedWindow.getSelection().toString() != "")
                         modes.set(modes.VISUAL, modes.TEXTAREA);
-                    else
+                    else {
+                        options.setPref("accessibility.browsewithcaret", true);
                         modes.main = modes.TEXTAREA;
+                    }
                 } else {
                     // setting this option notifies an observer which takes care of the
                     // mode setting

common/content/editor.js

@@ -478,7 +478,7 @@ const Editor = Module("editor", {
 }, {
     getEditor: function () {
         let e = liberator.focus;
-        if (!e) {
+        if (!e || e.isContentEditable) {
             e = document.commandDispatcher.focusedWindow;
             if (!Editor.windowIsEditable(e))
                 return null;
@@ -509,8 +509,8 @@ const Editor = Module("editor", {
             .QueryInterface(Ci.nsIInterfaceRequestor)
             .getInterface(Ci.nsIEditingSession);
         return editingSession.windowIsEditable(win) &&
-               win.document.body &&
-               util.computedStyle(win.document.body).getPropertyValue("-moz-user-modify") == "read-write";
+               (win.document.designMode === "on" ||
+                    (services.get("focus").getFocusedElementForWindow(win, true, {})||{}).isContentEditable);
     }
 }, {
     mappings: function () {