Add StateManager page

Author: m-bert

packages/docs-gesture-handler/docs/fundamentals/state-manager.md

@@ -0,0 +1,79 @@
+---
+id: state-manager
+title: State manager
+sidebar_label: State manager
+sidebar_position: 6
+---
+
+RNGH3 allows to manually control gestures lifecycle by using `GestureStateManager`.
+
+## State management
+
+Manual state management is based on `handlerTag`. There are two ways of manual state control.
+
+### Inside gesture definition
+
+If you want to manipulate gesture's state in its callbacks, you can get `handlerTag` from event parameter.
+
+```tsx {3}
+const longPress = useLongPressGesture({
+  onTouchesDown: (e) => {
+    GestureStateManager.activate(e.handlerTag);
+  },
+  onActivate: () => {
+    console.log('LongPress activated!');
+  },
+});
+```
+
+### Outside gesture definition
+
+If you want to control gesture lifecycle outside of it, you can use `tag` from created gesture object.
+
+```tsx {9}
+const longPress = useLongPressGesture({
+  onActivate: () => {
+    console.log('LongPress activated!');
+  },
+});
+
+const pan = usePanGesture({
+  onBegin: () => {
+    GestureStateManager.activate(longPress.tag);
+  },
+});
+```
+
+## Methods
+
+### begin
+
+```tsx
+begin: (handlerTag: number) => void;
+```
+
+Triggers [`onBegin`](/docs/fundamentals/callbacks-events#onbegin) callback on gesture with specified `handlerTag`.
+
+### activate
+
+```tsx
+activate: (handlerTag: number) => void;
+```
+
+Triggers [`onActivate`](/docs/fundamentals/callbacks-events#onactivate) callback on gesture with specified `handlerTag`.
+
+### deactivate
+
+```tsx
+deactivate: (handlerTag: number) => void;
+```
+
+Triggers first [`onDeactivate`](/docs/fundamentals/callbacks-events#ondeactivate), then [`onFinalize`](/docs/fundamentals/callbacks-events#onfinalize) callbacks on gesture with specified `handlerTag`.
+
+### fail
+
+```tsx
+fail: (handlerTag: number) => void;
+```
+
+Triggers [`onFinalize`](/docs/fundamentals/callbacks-events#onfinalize) callback on gesture with specified `handlerTag`. If gesture had activated, it will also trigger [`onDeactivate`](/docs/fundamentals/callbacks-events#ondeactivate) callback.