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.

Tactility/Source/app/App.h

@@ -0,0 +1,78 @@
+#pragma once
+
+#include "AppContext.h"
+#include "Bundle.h"
+#include <Mutex.h>
+
+// Forward declarations
+typedef struct _lv_obj_t lv_obj_t;
+
+namespace tt::app {
+
+// Forward declarations
+class AppContext;
+enum class Result;
+
+class App {
+
+private:
+
+    Mutex mutex;
+
+    struct ResultHolder {
+        Result result;
+        std::unique_ptr<Bundle> resultData;
+
+        explicit ResultHolder(Result result) : result(result), resultData(nullptr) {}
+
+        ResultHolder(Result result, std::unique_ptr<Bundle> resultData) :
+            result(result),
+            resultData(std::move(resultData)) {}
+    };
+
+    std::unique_ptr<ResultHolder> resultHolder;
+
+public:
+
+    App() = default;
+    virtual ~App() = default;
+
+    virtual void onStart(AppContext& appContext) {}
+    virtual void onStop(AppContext& appContext) {}
+    virtual void onShow(AppContext& appContext, lv_obj_t* parent) {}
+    virtual void onHide(AppContext& appContext) {}
+    virtual void onResult(AppContext& appContext, Result result, std::unique_ptr<Bundle> _Nullable resultData) {}
+
+    Mutex& getMutex() { return mutex; }
+
+    bool hasResult() const { return resultHolder != nullptr; }
+
+    void setResult(Result result, std::unique_ptr<Bundle> resultData = nullptr) {
+        auto lockable = getMutex().scoped();
+        lockable->lock(portMAX_DELAY);
+        resultHolder = std::make_unique<ResultHolder>(result, std::move(resultData));
+    }
+
+    /**
+     * Used by system to extract the result data when this application is finished.
+     * Note that this removes the data from the class!
+     */
+    bool moveResult(Result& outResult, std::unique_ptr<Bundle>& outBundle) {
+        auto lockable = getMutex().scoped();
+        lockable->lock(portMAX_DELAY);
+
+        if (resultHolder != nullptr) {
+            outResult = resultHolder->result;
+            outBundle = std::move(resultHolder->resultData);
+            resultHolder = nullptr;
+            return true;
+        } else {
+            return false;
+        }
+    }
+};
+
+template<typename T>
+std::shared_ptr<App> create() { return std::shared_ptr<T>(new T); }
+
+}