service/vi/vi_layer: Convert Layer struct into a class

Like the previous changes made to the Display struct, this prepares the
Layer struct for changes to its interface. Given Layer will be given
more invariants in the future, we convert it into a class to better
signify that.

src/core/hle/service/vi/layer/vi_layer.cpp

@@ -2,12 +2,16 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include "common/assert.h"
 #include "core/hle/service/vi/layer/vi_layer.h"
 
 namespace Service::VI {
 
 Layer::Layer(u64 id, std::shared_ptr<NVFlinger::BufferQueue> queue)
-    : id{id}, buffer_queue{std::move(queue)} {}
+    : id{id}, buffer_queue{std::move(queue)}
+{
+    ASSERT_MSG(buffer_queue != nullptr, "buffer_queue may not be null.");
+}
 
 Layer::~Layer() = default;
 

src/core/hle/service/vi/layer/vi_layer.h

@@ -14,10 +14,39 @@ class BufferQueue;
 
 namespace Service::VI {
 
-struct Layer {
+/// Represents a single display layer.
+class Layer {
+public:
+    /// Constructs a layer with a given ID and buffer queue.
+    ///
+    /// @param id    The ID to assign to this layer.
+    /// @param queue The buffer queue for this layer to use.
+    ///
     Layer(u64 id, std::shared_ptr<NVFlinger::BufferQueue> queue);
     ~Layer();
 
+    Layer(const Layer&) = delete;
+    Layer& operator=(const Layer&) = delete;
+
+    Layer(Layer&&) = default;
+    Layer& operator=(Layer&&) = default;
+
+    /// Gets the ID for this layer.
+    u64 GetID() const {
+        return id;
+    }
+
+    /// Gets a reference to the buffer queue this layer is using.
+    NVFlinger::BufferQueue& GetBufferQueue() {
+        return *buffer_queue;
+    }
+
+    /// Gets a const reference to the buffer queue this layer is using.
+    const NVFlinger::BufferQueue& GetBufferQueue() const {
+        return *buffer_queue;
+    }
+
+private:
     u64 id;
     std::shared_ptr<NVFlinger::BufferQueue> buffer_queue;
 };