Start work on GL state manager object

include/gl_state.hpp

@@ -0,0 +1,58 @@
+#pragma once
+#include <type_traits>
+
+#include "opengl.hpp"
+
+// GL state manager object for use in the OpenGL GPU renderer and potentially other things in the future (such as a potential ImGui GUI)
+// This object is meant to help us avoid duplicate OpenGL calls (such as binding the same program twice, enabling/disabling a setting twice, etc)
+// by checking if we actually *need* a state change. This is meant to avoid expensive driver calls and minimize unneeded state changes
+// A lot of code is in the header file instead of the relevant source file to make sure stuff gets inlined even without LTO, and
+// because this header should ideally not be getting included in too many places
+// Code that does not need inlining however, like the reset() function should be in gl_state.cpp
+// This state manager may not handle every aspect of OpenGL, in which case anything not handled here should just be manipulated with raw
+// OpenGL/opengl.hpp calls However, anything that can be handled through the state manager should, or at least there should be an attempt to keep it
+// consistent with the current GL state to avoid bugs/suboptimal code.
+
+// The state manager must *also* be a trivially constructible/destructible type, to ensure that no OpenGL functions get called sneakily without us
+// knowing. This is important for when we want to eg add a Vulkan or misc backend. Would definitely not want to refactor all this. So we try to be as
+// backend-agnostic as possible
+
+struct GLStateManager {
+	bool blendEnabled;
+	bool depthEnabled;
+
+	void reset();
+	void resetBlend();
+	void resetDepth();
+
+	void enableDepth() {
+		if (!depthEnabled) {
+			depthEnabled = true;
+			OpenGL::enableDepth();
+		}
+	}
+
+	void disableDepth() {
+		if (depthEnabled) {
+			depthEnabled = false;
+			OpenGL::disableDepth();
+		}
+	}
+
+	void enableBlend() {
+		if (!blendEnabled) {
+			blendEnabled = true;
+			OpenGL::enableBlend();
+		}
+	}
+
+	void disableBlend() {
+		if (blendEnabled) {
+			blendEnabled = false;
+			OpenGL::disableBlend();
+		}
+	}
+};
+
+static_assert(std::is_trivially_constructible<GLStateManager>(), "OpenGL State Manager class is not trivially constructible!");
+static_assert(std::is_trivially_destructible<GLStateManager>(), "OpenGL State Manager class is not trivially destructible!");