Better screen layout support

include/screen_layout.hpp

@@ -0,0 +1,58 @@
+#pragma once
+#include <string>
+
+#include "helpers.hpp"
+
+namespace ScreenLayout {
+	static constexpr u32 TOP_SCREEN_WIDTH = 400;
+	static constexpr u32 BOTTOM_SCREEN_WIDTH = 320;
+	static constexpr u32 TOP_SCREEN_HEIGHT = 240;
+	static constexpr u32 BOTTOM_SCREEN_HEIGHT = 240;
+
+	// The bottom screen is less wide by 80 pixels, so we center it by offsetting it 40 pixels right
+	static constexpr u32 BOTTOM_SCREEN_X_OFFSET = 40;
+	static constexpr u32 CONSOLE_HEIGHT = TOP_SCREEN_HEIGHT + BOTTOM_SCREEN_HEIGHT;
+
+	enum class Layout {
+		Default = 0,        // Top screen up, bottom screen down
+		DefaultFlipped,     // Top screen down, bottom screen up
+		SideBySide,         // Top screen left, bottom screen right,
+		SideBySideFlipped,  // Top screen right, bottom screen left,
+	};
+
+	// For properly handling touchscreen, we have to remember what window coordinates our screens map to
+	// We also remember some more information that is useful to our renderers, particularly for the final screen blit.
+	struct WindowCoordinates {
+		u32 topScreenX = 0;
+		u32 topScreenY = 0;
+		u32 topScreenWidth = TOP_SCREEN_WIDTH;
+		u32 topScreenHeight = TOP_SCREEN_HEIGHT;
+
+		u32 bottomScreenX = BOTTOM_SCREEN_X_OFFSET;
+		u32 bottomScreenY = TOP_SCREEN_HEIGHT;
+		u32 bottomScreenWidth = BOTTOM_SCREEN_WIDTH;
+		u32 bottomScreenHeight = BOTTOM_SCREEN_HEIGHT;
+
+		u32 windowWidth = topScreenWidth;
+		u32 windowHeight = topScreenHeight + bottomScreenHeight;
+
+		// Information used when optimizing the final screen blit into a single blit
+		struct {
+			// Can we actually render both of the screens in a single blit?
+			bool canDoSingleBlit = false;
+			// Blit information used if we can
+			int destX = 0, destY = 0;
+			int destWidth = TOP_SCREEN_WIDTH;
+			int destHeight = CONSOLE_HEIGHT;
+		} singleBlitInfo;
+	};
+
+	// Calculate screen coordinates on the screen for a given layout & a given size for the output window
+	// Used in both the renderers and in the frontends (To eg calculate touch screen boundaries)
+	void calculateCoordinates(
+		WindowCoordinates& coordinates, u32 outputWindowWidth, u32 outputWindowHeight, float topScreenPercentage, Layout layout
+	);
+
+	Layout layoutFromString(std::string inString);
+	const char* layoutToString(Layout layout);
+}  // namespace ScreenLayout