function readFromClipboard() {
    var url;
    try {
        var clipboard = Components.classes['@mozilla.org/widget/clipboard;1'].getService(Components.interfaces.nsIClipboard);
        var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);
        trans.addDataFlavor("text/unicode");
        if (clipboard.supportsSelectionClipboard()) {
            clipboard.getData(trans, clipboard.kSelectionClipboard);
        } else {
            clipboard.getData(trans, clipboard.kGlobalClipboard);
        }
        var data = {};
        var dataLen = {};
        trans.getTransferData("text/unicode", data, dataLen);
        if (data) {
            data = data.value.QueryInterface(Components.interfaces.nsISupportsString);
            url = data.data.substring(0, dataLen.value / 2);
        }
    } catch (ex) {
    }
    return url;
}

var text = "...";

var cmd = "cmd_insertText";
var controller = document.commandDispatcher.getControllerForCommand(cmd);
if(controller && controller.isCommandEnabled(cmd)) {
    controller = controller.QueryInterface(Components.interfaces.nsICommandController);
    var params = Components.classes["@mozilla.org/embedcomp/command-params;1"]
        .createInstance(Components.interfaces.nsICommandParams);
    params.setStringValue("state_data", text);
    controller.doCommandWithParams(cmd, params);
}