Refactor app launching (#174)

- Refactor the way apps work: Instead of a C interface, they are now C++ classes. The main reasoning is that attaching data to an app was cumbersome. Having different implementations for different kinds of apps was cumbersome too. (3 or 4 layers of manifest nesting for the TactilityC project)
- External apps are still written in C, but they get a createData/destroyData in their manifest, so:
- External apps now have their own manifest.
- All functions in the original AppManifest are removed and replaced by a single `createApp` function
- External apps now automatically register (each app individually!) when they run the first time. As a side-effect they become visible in the `AppList` app!
- Adapted all apps for the new interface.
- Adapted all internal logic for these changes (Gui, ViewPort, Loader, AppContext, AppInstance, etc.)
- Rewrote parts of Loader to use std::shared_ptr to make the code much safer.
- Added a refcount check for the `AppInstance` and `App` at the end of their lifecycle. Show warning if refcount is too high.

TactilityC/Source/tt_app_manifest.h

@@ -7,39 +7,47 @@
 extern "C" {
 #endif
 
+/** Important: These values must map to tt::app::Result values exactly */
 typedef enum {
-    AppResultOk,
-    AppResultCancelled,
-    AppResultError
+    AppResultOk = 0,
+    AppResultCancelled = 1,
+    AppResultError = 2
 } Result;
 
 typedef void* AppContextHandle;
 
-typedef void (*AppOnStart)(AppContextHandle app);
-typedef void (*AppOnStop)(AppContextHandle app);
-typedef void (*AppOnShow)(AppContextHandle app, lv_obj_t* parent);
-typedef void (*AppOnHide)(AppContextHandle app);
-typedef void (*AppOnResult)(AppContextHandle app, Result result, BundleHandle resultData);
+/** Important: These function types must map to t::app types exactly */
+typedef void* (*AppCreateData)();
+typedef void (*AppDestroyData)(void* data);
+typedef void (*AppOnStart)(AppContextHandle app, void* _Nullable data);
+typedef void (*AppOnStop)(AppContextHandle app, void* _Nullable data);
+typedef void (*AppOnShow)(AppContextHandle app, void* _Nullable data, lv_obj_t* parent);
+typedef void (*AppOnHide)(AppContextHandle app, void* _Nullable data);
+typedef void (*AppOnResult)(AppContextHandle app, void* _Nullable data, Result result, BundleHandle resultData);
 
-/**
- * This is used to register the manifest of an external app.
- * @param[in] name the application's human-readable name
- * @param[in] icon the optional application icon (you can use LV_SYMBOL_* too)
- * @param[in] onStart called when the app is launched (started)
- * @param[in] onStop called when the app is exited (stopped)
- * @param[in] onShow called when the app is about to be shown to the user (app becomes visible)
- * @param[in] onHide called when the app is about to be invisible to the user (e.g. other app was launched by this app, and this app goes to the background)
- * @param[in] onResult called when the app receives a result after launching another app
- */
-void tt_set_app_manifest(
-    const char* name,
-    const char* _Nullable icon,
-    AppOnStart onStart,
-    AppOnStop _Nullable onStop,
-    AppOnShow _Nullable onShow,
-    AppOnHide _Nullable onHide,
-    AppOnResult _Nullable onResult
-);
+typedef struct {
+    /** The application's human-readable name */
+    const char* name;
+    /** The application icon (you can use LV_SYMBOL_* too) */
+    const char* _Nullable icon;
+    /** The application can allocate data to re-use later (e.g. struct with state) */
+    AppCreateData _Nullable createData;
+    /** If createData is specified, this one must be specified too */
+    AppDestroyData _Nullable destroyData;
+    /** Called when the app is launched (started) */
+    AppOnStart _Nullable onStart;
+    /** Called when the app is exited (stopped) */
+    AppOnStop _Nullable onStop;
+    /** Called when the app is about to be shown to the user (app becomes visible) */
+    AppOnShow _Nullable onShow;
+    /** Called when the app is about to be invisible to the user (e.g. other app was launched by this app, and this app goes to the background) */
+    AppOnHide _Nullable onHide;
+    /** Called when the app receives a result after launching another app */
+    AppOnResult _Nullable onResult;
+} ExternalAppManifest;
+
+/** This is used to register the manifest of an external app. */
+void tt_app_register(const ExternalAppManifest* manifest);
 
 #ifdef __cplusplus
 }