Timer Element

Closes #5724

docs/reference/src/language/builtins/elements.md

@@ -778,6 +778,57 @@ export component Example inherits Window {
 }
 ```
 
+## `Timer`
+<!-- FIXME: Timer is not really an element so it doesn't really belong in the `Builtin Elements` section. -->
+
+Timer is not an actual element visible in the tree, therefore it doesn't have the common properties such as `x`, `y`, `width`, `height`, etc.
+It doesn't take room in a layout and cannot have any children or be inherited from.
+
+The Timer pseudo-element is used to schedule a callback at a given interval.
+The timer is only running when the `running` property is set to `true`. To stop or start the timer, simply set that property to `true` or `false`.
+It can be also set to a binding.
+When already running, the timer will be restarted if the `interval` property is changed.
+
+Note that the default value for `running` is `true`, so if you don't specify it, it will be running.
+
+### Properties
+
+ -  **`interval`** (_in_ _duration_): The interval between timer ticks. (default value: `0ms`)
+ -  **`running`** (_in_ _bool_): `true` if the timer is running. (default value: `true`)
+
+### Callbacks
+
+ -  **`triggered()`**: Invoked every time the timer ticks (every `interval`)
+
+### Example
+
+This example shows a timer that counts down from 10 to 0 every second:
+
+```slint
+import { Button } from "std-widgets.slint";
+export component Example inherits Window {
+    property <int> value: 10;
+    timer := Timer {
+        interval: 1s;
+        running: true;
+        triggered() => {
+            value -= 1;
+            if (value == 0) {
+                self.running = false;
+            }
+        }
+    }
+    HorizontalLayout {
+        Text { text: value; }
+        Button {
+            text: "Reset";
+            clicked() => { value = 10; timer.running = true; }
+        }
+    }
+}
+```
+
+
 ## `TouchArea`
 
 Use `TouchArea` to control what happens when the region it covers is touched or interacted with