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+# How 5-tapping power launches Emergency Sos
+
+_as of Jan 2021_
+
+Note that the flow is a simplified version of the camera launch flow.
+
+
+### Sequence of events
+
+
+1. [PhoneWindowManager.java](/services/core/java/com/android/server/policy/PhoneWindowManager.java) is responsible for all power button presses (see `interceptPowerKeyDown`).
+2. Even though PWMgr has a lot of logic to detect all manner of power button multipresses and gestures, it also checks with GestureLauncherService, which is also [offered the chance](/services/core/java/com/android/server/policy/PhoneWindowManager.java#943) to [intercept](/services/core/java/com/android/server/GestureLauncherService.java#358) the power key.
+3. GLS is responsible for the emergoncy sos timeout, and if it detects one, it [forwards it to the StatusBarManagerService](/services/core/java/com/android/server/GestureLauncherService.java#475) (which hands it off to SystemUI).
+4. Inside SystemUI, [onEmergencyActionLaunchGestureDetected](/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java#4039) and determines
+    1. If the gesture is enabled (else do nothing)
+    2. If there is an app to handle the gesture (else do nothing)
+    2. whether the screen is on; if not, we need to delay until that happens
+5. Assuming there is an app, and the setting is one launch Emergengy Flow immediately. [Callsite](/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java#4077)
+    1. Note that we cannot have an intent resolver, so we launch the default.
+
+**Which intent launches?**
+
+Due to the nature of the gesture, we need the flow to work behind the lockscreen, and without disambiguation.
+Thus, we always launch the same intent, and verify that there is only one matching intent-filter in the system image.
+
+[The emergengy sos intent action](packages/SystemUI/src/com/android/systemui/emergency/EmergencyGesture.java#36).