diff --git a/examples/debug-ui/app.asd b/examples/debug-ui/app.asd
new file mode 100644
index 0000000..332f8f2
--- /dev/null
+++ b/examples/debug-ui/app.asd
@@ -0,0 +1,10 @@
+(defsystem :app
+  :serial t
+  :depends-on ()
+  :components ((:file "lisp/package")
+               (:file "lisp/ui-vars")
+               (:file "lisp/d-dialogs")    ; for debug-ui
+               (:file "lisp/d-input-hook") ; for debug-ui
+               (:file "lisp/d-debug-ui")   ; for debug-ui
+               (:file "lisp/main")))
+
diff --git a/examples/debug-ui/lisp/d-debug-ui.lisp b/examples/debug-ui/lisp/d-debug-ui.lisp
new file mode 100644
index 0000000..84791b2
--- /dev/null
+++ b/examples/debug-ui/lisp/d-debug-ui.lisp
@@ -0,0 +1,59 @@
+(defpackage :debug-ui
+  (:use :cl :qml)
+  (:export
+   #:*debug-dialog*))
+
+(in-package :debug-ui)
+
+(defvar *error-output-buffer* (make-string-output-stream))
+(defvar *terminal-out-buffer* (make-string-output-stream))
+(defvar *gui-debug-io*        nil)
+(defvar *gui-debug-dialog*    nil)
+
+(defun ini ()
+  (setf *gui-debug-dialog* 'dialogs:debug-dialog)
+  (ini-streams)
+  (setf *debug-io* *gui-debug-io*))
+
+(defun ini-streams ()
+  (setf *error-output* (make-broadcast-stream *error-output*
+                                              *error-output-buffer*))
+  (setf *terminal-io*  (make-two-way-stream (two-way-stream-input-stream *terminal-io*)
+                                            (make-broadcast-stream (two-way-stream-output-stream *terminal-io*)
+                                                                   *terminal-out-buffer*))
+        *gui-debug-io* (make-two-way-stream (input-hook:add 'handle-debug-io)
+                                            (two-way-stream-output-stream *terminal-io*))))
+
+(defun clear-buffers ()
+  (dolist (s (list *error-output-buffer*
+                   *terminal-out-buffer*))
+    (get-output-stream-string s)))
+
+(defun find-quit-restart ()
+  ;; find best restart for ':q' (default) to exit the debugger
+  (let ((restarts (compute-restarts)))
+    (if (= 1 (length restarts))
+        ":r1"
+        (let ((restart-names (mapcar (lambda (r)
+                                       (symbol-name (restart-name r)))
+                                     restarts)))
+          ;; precedence role
+          (dolist (name '("RESTART-TOPLEVEL"
+                          "ABORT"
+                          "RESTART-QT-EVENTS"))
+            (x:when-it (position name restart-names :test 'string=)
+              (return-from find-quit-restart (format nil ":r~D" x:it)))))))
+  ":q")
+
+(defun handle-debug-io ()
+  (let ((cmd (funcall *gui-debug-dialog*
+                      (list (cons (get-output-stream-string *error-output-buffer*)
+                                  "#d00000")
+                            (cons (get-output-stream-string *terminal-out-buffer*)
+                                  "black")))))
+    (when (string-equal ":q" cmd)
+      (setf cmd (find-quit-restart)))
+    (format nil "~A~%" (if (x:empty-string cmd) ":q" cmd))))
+
+(ini)
+
diff --git a/examples/debug-ui/lisp/d-dialogs.lisp b/examples/debug-ui/lisp/d-dialogs.lisp
new file mode 100644
index 0000000..e87708f
--- /dev/null
+++ b/examples/debug-ui/lisp/d-dialogs.lisp
@@ -0,0 +1,61 @@
+(defpackage :dialogs
+  (:use :cl :qml)
+  (:export
+   #:debug-dialog
+   #:exited
+   #:push-dialog
+   #:pop-dialog))
+
+(in-package :dialogs)
+
+(defvar *callback* nil)
+
+(defun push-dialog (name)
+  "Pushes dialog NAME onto the StackView."
+  (qjs |pushDialog| ui:*main* (string-downcase name)))
+
+(defun pop-dialog ()
+  "Pops the currently shown dialog, returning T if there was a dialog to pop."
+  (prog1
+      (> (q< |depth| ui:*main*) 1)
+    (qjs |popDialog| ui:*main*)))
+
+(defun wait-while-transition ()
+  ;; needed for evtl. recursive calls
+  (x:while (q< |busy| ui:*main*)
+    (qsleep 0.1)))
+
+(defun append-debug-output (text color bold)
+  (qjs |appendOutput| ui:*d-debug-model*
+       (list :text  text
+             :color color
+             :bold  bold)))
+
+(defun debug-dialog (messages)
+  (qrun*
+   (q! |clear| ui:*d-debug-model*)
+   (q> |text| ui:*d-debug-input* ":q")
+   (dolist (text/color messages)
+     (let* ((text (string-trim '(#\Newline) (car text/color)))
+            (color (cdr text/color))
+            (bold (not (string= "black" color)))) ; boolean
+       (append-debug-output text color bold)))
+   (wait-while-transition)
+   (push-dialog :debug)
+   (q! |forceActiveFocus| ui:*d-debug-input*)
+   (qsingle-shot 500 (lambda () (q! |positionViewAtEnd| ui:*d-debug-text*)))
+   (wait-for-closed)
+   (q< |text| ui:*d-debug-input*)))
+
+(let (waiting)
+  (defun wait-for-closed ()
+    (setf waiting t)
+    ;; busy waiting is safer than suspending a thread, especially on mobile
+    (x:while waiting
+      (qsleep 0.1))
+    (pop-dialog))
+  (defun exited () ; called from QML
+    (unless waiting
+      (pop-dialog))
+    (setf waiting nil)))
+
diff --git a/examples/debug-ui/lisp/d-input-hook.lisp b/examples/debug-ui/lisp/d-input-hook.lisp
new file mode 100644
index 0000000..040317e
--- /dev/null
+++ b/examples/debug-ui/lisp/d-input-hook.lisp
@@ -0,0 +1,53 @@
+;;; idea & most code from "ecl-readline.lisp"
+
+(defpackage input-hook
+  (:use :cl)
+  (:export
+   #:add))
+
+(provide :input-hook)
+
+(in-package :input-hook)
+
+(defvar *functions* nil)
+
+(defun add (function)
+  (let ((stream (make-instance 'input-hook-stream)))
+    (push (cons stream function) *functions*)
+    stream))
+
+(defclass input-hook-stream (gray:fundamental-character-input-stream)
+  ((buffer :initform (make-string 0))
+   (index  :initform 0)))
+
+(defmethod gray:stream-read-char ((stream input-hook-stream))
+  (if (ensure-stream-data stream)
+      (with-slots (buffer index) stream
+        (let ((ch (char buffer index)))
+          (incf index)
+          ch))
+      :eof))
+
+(defmethod gray:stream-unread-char ((stream input-hook-stream) character)
+  (with-slots (index) stream
+    (when (> index 0)
+      (decf index))))
+
+(defmethod gray:stream-listen ((stream input-hook-stream))
+  nil)
+
+(defmethod gray:stream-clear-input ((stream input-hook-stream))
+  nil)
+
+(defmethod gray:stream-peek-char ((stream input-hook-stream))
+  (if (ensure-stream-data stream)
+      (with-slots (buffer index) stream
+        (char buffer index))
+      :eof))
+
+(defun ensure-stream-data (stream)
+  (with-slots (buffer index) stream
+    (when (= index (length buffer))
+      (setf buffer (funcall (cdr (assoc stream *functions*)))
+            index 0))
+    buffer))
diff --git a/examples/debug-ui/lisp/main.lisp b/examples/debug-ui/lisp/main.lisp
new file mode 100644
index 0000000..d37504c
--- /dev/null
+++ b/examples/debug-ui/lisp/main.lisp
@@ -0,0 +1,4 @@
+(in-package :app)
+
+;; intentional division by zero after 5 seconds
+(qsingle-shot 5000 (lambda () (dotimes (i 1) (/ 1 i))))
diff --git a/examples/debug-ui/lisp/package.lisp b/examples/debug-ui/lisp/package.lisp
new file mode 100644
index 0000000..6689a82
--- /dev/null
+++ b/examples/debug-ui/lisp/package.lisp
@@ -0,0 +1,4 @@
+(defpackage :app
+  (:use :cl :qml)
+  (:export))
+
diff --git a/examples/debug-ui/lisp/ui-vars.lisp b/examples/debug-ui/lisp/ui-vars.lisp
new file mode 100644
index 0000000..dbcd0c4
--- /dev/null
+++ b/examples/debug-ui/lisp/ui-vars.lisp
@@ -0,0 +1,17 @@
+;;; keep sorted to recognize eventual name clashes
+
+(defpackage ui
+  (:use :cl)
+  (:export
+   #:*d-debug-input*
+   #:*d-debug-model*
+   #:*d-debug-text*
+   #:*main*))
+
+(in-package :ui)
+
+(defparameter *d-debug-input*  "debug_input")
+(defparameter *d-debug-model*  "debug_model")
+(defparameter *d-debug-text*   "debug_text")
+
+(defparameter *main*           "main")
diff --git a/examples/debug-ui/qml/debug/DebugDialog.qml b/examples/debug-ui/qml/debug/DebugDialog.qml
new file mode 100644
index 0000000..2c579d9
--- /dev/null
+++ b/examples/debug-ui/qml/debug/DebugDialog.qml
@@ -0,0 +1,84 @@
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+import QtQuick.Layouts 1.15
+import "." as Ext
+
+Rectangle {
+  id: debugDialog
+  objectName: "debug_dialog"
+  color: "#f0f0f0"
+  visible: false
+
+  ColumnLayout {
+    anchors.fill: parent
+    spacing: 0
+
+    Ext.MenuBack {
+      id: menuBack
+      Layout.fillWidth: true
+      label: "Debug Dialog"
+    }
+
+    TextField {
+      id: debugInput
+      objectName: "debug_input"
+      Layout.fillWidth: true
+      font.family: "Hack"
+      font.pixelSize: 18
+      inputMethodHints: Qt.ImhNoAutoUppercase | Qt.ImhNoPredictiveText
+      text: ":q"
+
+      onAccepted: Lisp.call("dialogs:exited")
+    }
+
+    Text {
+      id: label
+      Layout.fillWidth: true
+      leftPadding: 8
+      rightPadding: 8
+      topPadding: 8
+      bottomPadding: 8
+      font.family: "Hack"
+      font.pixelSize: 14
+      text: ":r1 etc. restart / :h help / :q quit"
+    }
+
+    Rectangle {
+      id: line
+      Layout.fillWidth: true
+      height: 1
+      color: "#d0d0d0"
+    }
+
+    ListView {
+      id: debugText
+      objectName: "debug_text"
+      Layout.fillWidth: true
+      Layout.fillHeight: true
+      contentWidth: parent.width * 5
+      clip: true
+      model: debugModel
+      flickableDirection: Flickable.HorizontalAndVerticalFlick
+
+      delegate: Text {
+        padding: 8
+        textFormat: Text.PlainText
+        font.pixelSize: 16
+        font.family: "Hack"
+        font.bold: model.bold
+        text: model.text
+        color: model.color
+      }
+    }
+
+    ListModel {
+      id: debugModel
+      objectName: "debug_model"
+
+      function appendOutput(data) {
+        append(data)
+        debugText.positionViewAtEnd()
+      }
+    }
+  }
+}
diff --git a/examples/debug-ui/qml/debug/Flickable.qml b/examples/debug-ui/qml/debug/Flickable.qml
new file mode 100644
index 0000000..bb8f0c7
--- /dev/null
+++ b/examples/debug-ui/qml/debug/Flickable.qml
@@ -0,0 +1,22 @@
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+import "." as Ext
+
+Flickable {
+  clip: true
+
+  ScrollBar.vertical: Ext.ScrollBar {}
+
+  function ensureVisible(r) {
+    if (main.skipEnsureVisible)
+      return;
+    if (contentX >= r.x)
+      contentX = r.x;
+    else if (contentX + width <= r.x + r.width)
+      contentX = r.x + r.width - width;
+    if (contentY >= r.y)
+      contentY = r.y;
+    else if (contentY + height <= r.y + r.height)
+      contentY = r.y + r.height - height;
+  }
+}
diff --git a/examples/debug-ui/qml/debug/MenuBack.qml b/examples/debug-ui/qml/debug/MenuBack.qml
new file mode 100644
index 0000000..69dbd83
--- /dev/null
+++ b/examples/debug-ui/qml/debug/MenuBack.qml
@@ -0,0 +1,53 @@
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+
+Rectangle {
+  id: menuBack
+  width: main.width
+  height: backButton.height
+  color: "#f0f0f0"
+
+  property alias label: label.text
+
+  Button {
+    id: backButton
+    height: main.small ? 40 : 46
+    width: 80
+
+    background: Rectangle {
+      Text {
+        id: iconBack
+        x: 10
+        height: backButton.height
+        verticalAlignment: Text.AlignVCenter
+        font.family: fontAwesome.name
+        font.pixelSize: 32
+        color: "#007aff"
+        text: "\uf104"
+      }
+
+      Text {
+        x: 30
+        height: backButton.height * 1.1 // align correction (different font from above)
+        verticalAlignment: Text.AlignVCenter
+        font.pixelSize: 20
+        font.weight: Font.DemiBold
+        color: iconBack.color
+        text: "Repl"
+        visible: (Qt.platform.os === "ios")
+      }
+
+      implicitWidth: 90
+      color: menuBack.color
+    }
+
+    onPressed: Lisp.call("dialogs:exited")
+  }
+
+  Text {
+    id: label
+    anchors.centerIn: parent
+    font.pixelSize: 20
+    font.weight: Font.DemiBold
+  }
+}
diff --git a/examples/debug-ui/qml/debug/ScrollBar.qml b/examples/debug-ui/qml/debug/ScrollBar.qml
new file mode 100644
index 0000000..d23cbc4
--- /dev/null
+++ b/examples/debug-ui/qml/debug/ScrollBar.qml
@@ -0,0 +1,32 @@
+// This is a modified version taken from the QML sources
+
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+
+ScrollBar {
+  id: control
+  orientation: Qt.Vertical
+
+  contentItem: Rectangle {
+    implicitWidth: 12
+    implicitHeight: 100
+    radius: width / 2
+    color: control.pressed ? "#202020" : "#909090"
+    opacity: 0.0
+
+    states: State {
+      name: "active"
+      when: (control.active && control.size < 1.0)
+      PropertyChanges { target: control.contentItem; opacity: 0.75 }
+    }
+
+    transitions: Transition {
+      from: "active"
+      SequentialAnimation {
+        PauseAnimation { duration: 450 }
+        NumberAnimation { target: control.contentItem; duration: 200; property: "opacity"; to: 0.0 }
+      }
+    }
+  }
+}
+
diff --git a/examples/debug-ui/qml/debug/TextField.qml b/examples/debug-ui/qml/debug/TextField.qml
new file mode 100644
index 0000000..45f70d5
--- /dev/null
+++ b/examples/debug-ui/qml/debug/TextField.qml
@@ -0,0 +1,10 @@
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+
+TextField {
+  font.pixelSize: 18
+  palette {
+    highlight: "#007aff"
+    highlightedText: "white"
+  }
+}
diff --git a/examples/debug-ui/qml/fonts/Hack-Bold.ttf b/examples/debug-ui/qml/fonts/Hack-Bold.ttf
new file mode 100644
index 0000000..7ff4975
Binary files /dev/null and b/examples/debug-ui/qml/fonts/Hack-Bold.ttf differ
diff --git a/examples/debug-ui/qml/fonts/Hack-Regular.ttf b/examples/debug-ui/qml/fonts/Hack-Regular.ttf
new file mode 100644
index 0000000..92a90cb
Binary files /dev/null and b/examples/debug-ui/qml/fonts/Hack-Regular.ttf differ
diff --git a/examples/debug-ui/qml/main.qml b/examples/debug-ui/qml/main.qml
new file mode 100644
index 0000000..6f3fcf7
--- /dev/null
+++ b/examples/debug-ui/qml/main.qml
@@ -0,0 +1,40 @@
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+import QtQuick.Window 2.15
+import 'debug/' as Dbg
+
+StackView {
+  id: main
+  objectName: "main"
+  width: 800  // alternatively: Screen.desktopAvailableWidth
+  height: 600 // alternatively: Screen.desktopAvailableHeight
+  initialItem: mainRect
+  Screen.orientationUpdateMask: Qt.LandscapeOrientation | Qt.PortraitOrientation | Qt.InvertedLandscapeOrientation
+
+  // show/hide dialogs
+
+  function pushDialog(name)  {
+    switch (name) {
+      case "debug": main.push(dialogDebug); break
+    }
+  }
+
+  function popDialog() { main.pop() }
+
+  // fonts (must stay here, before using them below)
+
+  FontLoader { id: fontHack;     source: "fonts/Hack-Regular.ttf" }        // code
+  FontLoader { id: fontHackBold; source: "fonts/Hack-Bold.ttf" }
+  FontLoader { id: fontAwesome;  source: "fonts/fontawesome-webfont.ttf" } // icons
+
+  // items
+
+  Rectangle {
+    id: mainRect
+    color: "lavender"
+  }
+
+  // dialogs
+
+  Dbg.DebugDialog { id: dialogDebug }
+}
diff --git a/examples/debug-ui/readme.md b/examples/debug-ui/readme.md
new file mode 100644
index 0000000..945bd04
--- /dev/null
+++ b/examples/debug-ui/readme.md
@@ -0,0 +1,12 @@
+
+Info
+----
+
+This is a debug dialog (taken from example cl-repl) to be integrated in your
+app.
+
+So, if you merge this example with your app, the mobile app will not crash on
+an eventual runtime error: an interactive debug dialog will be shown instead.
+
+This is especially helpful on android, where Lisp issues are hard to debug once
+the app is installed.