Add Metal support to Qt frontend and clean up renderer creation code (#795)

* Qt: Initial support for Metal renderer

* Clean up graphics context code

* Nits

* More nits

* Qt: Move screen-related stuff to own folder

* Qt: Make screen widget polymorphic

* Qt: Re-add Metal

* Add factory for screen widget

* Qt: Support compilation without Metal

* Qt: Fix build without Metal

* Oops

* oops

include/panda_qt/screen/screen.hpp

@@ -0,0 +1,64 @@
+#pragma once
+#include <QWidget>
+#include <functional>
+
+#include "gl/context.h"
+#include "screen_layout.hpp"
+#include "window_info.h"
+
+// Abstract screen widget for drawing the 3DS screen. We've got a child class for each graphics API (ScreenWidgetGL, ScreenWidgetMTL, ...)
+class ScreenWidget : public QWidget {
+	Q_OBJECT
+
+  public:
+	using ResizeCallback = std::function<void(u32, u32)>;
+
+	enum class API { OpenGL, Metal, Vulkan };
+
+	ScreenWidget(API api, ResizeCallback resizeCallback, QWidget* parent = nullptr);
+	virtual ~ScreenWidget() {}
+
+	void resizeEvent(QResizeEvent* event) override;
+
+	virtual GL::Context* getGLContext() { return nullptr; }
+	virtual void* getMTKLayer() { return nullptr; }
+
+	// Dimensions of our output surface
+	u32 surfaceWidth = 0;
+	u32 surfaceHeight = 0;
+	WindowInfo windowInfo;
+
+	// Cached "previous" dimensions, used when resizing our window
+	u32 previousWidth = 0;
+	u32 previousHeight = 0;
+
+	API api = API::OpenGL;
+
+	// Coordinates (x/y/width/height) for the two screens in window space, used for properly handling touchscreen
+	ScreenLayout::WindowCoordinates screenCoordinates;
+	// Screen layouts and sizes
+	ScreenLayout::Layout screenLayout = ScreenLayout::Layout::Default;
+	float topScreenSize = 0.5f;
+
+	void reloadScreenLayout(ScreenLayout::Layout newLayout, float newTopScreenSize);
+
+	// Creates a screen widget depending on the graphics API we're using
+	static ScreenWidget* getWidget(API api, ResizeCallback resizeCallback, QWidget* parent = nullptr);
+
+	// Called by the emulator thread on OpenGL for resizing the actual GL surface, since the emulator thread owns the GL context
+	virtual void resizeSurface(u32 width, u32 height) {};
+
+  protected:
+	ResizeCallback resizeCallback;
+
+	virtual bool createContext() = 0;
+	virtual void resizeDisplay() = 0;
+	std::optional<WindowInfo> getWindowInfo();
+
+  private:
+	qreal devicePixelRatioFromScreen() const;
+	int scaledWindowWidth() const;
+	int scaledWindowHeight() const;
+
+	void reloadScreenCoordinates();
+};

include/panda_qt/screen/screen_gl.hpp

@@ -0,0 +1,18 @@
+#pragma once
+#include <memory>
+
+#include "gl/context.h"
+#include "panda_qt/screen/screen.hpp"
+
+class ScreenWidgetGL : public ScreenWidget {
+	std::unique_ptr<GL::Context> glContext = nullptr;
+
+  public:
+	ScreenWidgetGL(API api, ResizeCallback resizeCallback, QWidget* parent = nullptr);
+
+	virtual GL::Context* getGLContext() override;
+	virtual bool createContext() override;
+
+	virtual void resizeDisplay() override;
+	virtual void resizeSurface(u32 width, u32 height) override;
+};

include/panda_qt/screen/screen_mtl.hpp

@@ -0,0 +1,18 @@
+#pragma once
+#include "panda_qt/screen/screen.hpp"
+
+class ScreenWidgetMTL : public ScreenWidget {
+	void* mtkLayer = nullptr;
+
+	// Objective-C++ functions for handling the Metal context
+	bool createMetalContext();
+	void resizeMetalView();
+
+  public:
+	ScreenWidgetMTL(API api, ResizeCallback resizeCallback, QWidget* parent = nullptr);
+	~ScreenWidgetMTL() override;
+
+	virtual void* getMTKLayer() override;
+	virtual bool createContext() override;
+	virtual void resizeDisplay() override;
+};