Drop key auto-repeat in the lock screen password field

shell/plugins/lock/LockView.qml

@@ -60,6 +60,14 @@ Item {
     passwordTextEdited("")
   }
 
+  // Waking a DPMS-blanked display can stall the compositor for seconds while
+  // the monitor modesets, so the wake key's release arrives late and client-side
+  // key repeat floods the field with that character. A held key has no business
+  // typing a password; only holding Backspace/Delete to clear stays useful.
+  function dropsAutoRepeat(key) {
+    return key !== Qt.Key_Backspace && key !== Qt.Key_Delete
+  }
+
   function syncPasswordText() {
     if (passwordInput.text === passwordText) return
     syncingPasswordText = true
@@ -176,6 +184,10 @@ Item {
 
         Keys.onPressed: function(event) {
           root.wakeRequested()
+          if (event.isAutoRepeat && root.dropsAutoRepeat(event.key)) {
+            event.accepted = true
+            return
+          }
           if (event.key === Qt.Key_Escape || (event.modifiers & Qt.ControlModifier && event.key === Qt.Key_U)) {
             root.passwordTextEdited("")
             event.accepted = true