[FL-3847, FL-3513] Thread Signals (#3730)

* Add signal API
* Add signal support to loader
* Add signal support to ViewDispatcher
* Remove extra signal definitions
* Fix typos
  Co-authored-by: Silent <CookiePLMonster@users.noreply.github.com>
* scripts: runfap: close current app pre-launch
* loader: enable backlight when starting an app
* scripts: removed distfap.py
* Do not expose signal API via ViewDispatcher
* scripts: runfap: iterative retry to launch
* Add a loader signal subcommand
* Furi, Gui: move signal handling from View Dispatcher to Event Loop

Co-authored-by: Silent <CookiePLMonster@users.noreply.github.com>
Co-authored-by: hedger <hedger@nanode.su>
Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

furi/core/base.h

@@ -40,6 +40,12 @@ typedef enum {
     FuriStatusReserved = 0x7FFFFFFF ///< Prevents enum down-size compiler optimization.
 } FuriStatus;
 
+typedef enum {
+    FuriSignalExit, /**< Request (graceful) exit. */
+    // Other standard signals may be added in the future
+    FuriSignalCustom = 100, /**< Custom signal values start from here. */
+} FuriSignal;
+
 #ifdef __cplusplus
 }
 #endif

furi/core/event_loop.c

@@ -149,6 +149,9 @@ void furi_event_loop_run(FuriEventLoop* instance) {
     furi_check(instance);
     furi_check(instance->thread_id == furi_thread_get_current_id());
 
+    furi_thread_set_signal_callback(
+        instance->thread_id, furi_event_loop_signal_callback, instance);
+
     uint32_t timeout = instance->tick_callback ? instance->tick_interval : FuriWaitForever;
 
     while(true) {
@@ -194,11 +197,12 @@ void furi_event_loop_run(FuriEventLoop* instance) {
         }
         instance->state = FuriEventLoopStateIdle;
     }
+
+    furi_thread_set_signal_callback(instance->thread_id, NULL, NULL);
 }
 
 void furi_event_loop_stop(FuriEventLoop* instance) {
     furi_check(instance);
-    furi_check(instance->thread_id == furi_thread_get_current_id());
 
     xTaskNotifyIndexed(
         instance->thread_id, FURI_EVENT_LOOP_FLAG_NOTIFY_INDEX, FuriEventLoopFlagStop, eSetBits);
@@ -366,4 +370,19 @@ void furi_event_loop_link_notify(FuriEventLoopLink* instance, FuriEventLoopEvent
     }
 
     FURI_CRITICAL_EXIT();
-}
+}
+
+bool furi_event_loop_signal_callback(uint32_t signal, void* arg, void* context) {
+    furi_assert(context);
+    FuriEventLoop* instance = context;
+    UNUSED(arg);
+
+    switch(signal) {
+    case FuriSignalExit:
+        furi_event_loop_stop(instance);
+        return true;
+    // Room for possible other standard signal handlers
+    default:
+        return false;
+    }
+}

furi/core/event_loop_i.h

@@ -28,6 +28,8 @@ typedef struct {
     const FuriEventLoopContractGetLevel get_level;
 } FuriEventLoopContract;
 
+bool furi_event_loop_signal_callback(uint32_t signal, void* arg, void* context);
+
 #ifdef __cplusplus
 }
 #endif

furi/core/thread.c

@@ -42,6 +42,9 @@ struct FuriThread {
     FuriThreadStateCallback state_callback;
     void* state_context;
 
+    FuriThreadSignalCallback signal_callback;
+    void* signal_context;
+
     char* name;
     char* appid;
 
@@ -304,6 +307,29 @@ FuriThreadState furi_thread_get_state(FuriThread* thread) {
     return thread->state;
 }
 
+void furi_thread_set_signal_callback(
+    FuriThread* thread,
+    FuriThreadSignalCallback callback,
+    void* context) {
+    furi_check(thread);
+    furi_check(thread->state == FuriThreadStateStopped || thread == furi_thread_get_current());
+
+    thread->signal_callback = callback;
+    thread->signal_context = context;
+}
+
+bool furi_thread_signal(const FuriThread* thread, uint32_t signal, void* arg) {
+    furi_check(thread);
+
+    bool is_consumed = false;
+
+    if(thread->signal_callback) {
+        is_consumed = thread->signal_callback(signal, arg, thread->signal_context);
+    }
+
+    return is_consumed;
+}
+
 void furi_thread_start(FuriThread* thread) {
     furi_check(thread);
     furi_check(thread->callback);

furi/core/thread.h

@@ -86,6 +86,18 @@ typedef void (*FuriThreadStdoutWriteCallback)(const char* data, size_t size);
  */
 typedef void (*FuriThreadStateCallback)(FuriThreadState state, void* context);
 
+/**
+ * @brief Signal handler callback function pointer type.
+ *
+ * The function to be used as a signal handler callback MUS follow this signature.
+ *
+ * @param[in] signal value of the signal to be handled by the recipient
+ * @param[in,out] arg optional argument (can be of any value, including NULL)
+ * @param[in,out] context pointer to a user-specified object
+ * @returns true if the signal was handled, false otherwise
+ */
+typedef bool (*FuriThreadSignalCallback)(uint32_t signal, void* arg, void* context);
+
 /**
  * @brief Create a FuriThread instance.
  *
@@ -255,6 +267,29 @@ void furi_thread_set_state_context(FuriThread* thread, void* context);
  */
 FuriThreadState furi_thread_get_state(FuriThread* thread);
 
+/**
+ * @brief Set a signal handler callback for a FuriThread instance.
+ *
+ * The thread MUST be stopped when calling this function.
+ *
+ * @param[in,out] thread pointer to the FuriThread instance to be modified
+ * @param[in] callback pointer to a user-specified callback function
+ * @param[in] context pointer to a user-specified object (will be passed to the callback, can be NULL)
+ */
+void furi_thread_set_signal_callback(
+    FuriThread* thread,
+    FuriThreadSignalCallback callback,
+    void* context);
+
+/**
+ * @brief Send a signal to a FuriThread instance.
+ *
+ * @param[in] thread pointer to the FuriThread instance to be signaled
+ * @param[in] signal signal value to be sent
+ * @param[in,out] arg optional argument (can be of any value, including NULL)
+ */
+bool furi_thread_signal(const FuriThread* thread, uint32_t signal, void* arg);
+
 /**
  * @brief Start a FuriThread instance.
  *