general_frontend: Add frontend scaffold for PhotoViewer applet

src/core/frontend/applets/general_frontend.h

@@ -0,0 +1,28 @@
+// Copyright 2019 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <functional>
+#include "common/common_types.h"
+
+namespace Core::Frontend {
+
+class PhotoViewerApplet {
+public:
+    virtual ~PhotoViewerApplet();
+
+    virtual void ShowPhotosForApplication(u64 title_id, std::function<void()> finished) const = 0;
+    virtual void ShowAllPhotos(std::function<void()> finished) const = 0;
+};
+
+class DefaultPhotoViewerApplet final : public PhotoViewerApplet {
+public:
+    ~DefaultPhotoViewerApplet() override;
+
+    void ShowPhotosForApplication(u64 title_id, std::function<void()> finished) const override;
+    void ShowAllPhotos(std::function<void()> finished) const override;
+};
+
+} // namespace Core::Frontend