From 4f22d5daca7d570dbd3caf3da18448350bf5f148 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 14 Dec 2021 02:11:02 +0000
Subject: Single glContext shared between windows

Created by the first window, includes simplified refresh/render for single control point
---
 application/main.cpp  |  4 +---
 ui/gameMainWindow.cpp |  3 +--
 ui/gameMainWindow.h   |  2 +-
 ui/window.cpp         | 42 +++++++++++++++++++++++++++++++++++-------
 ui/window.h           | 13 +++++++------
 5 files changed, 45 insertions(+), 19 deletions(-)

diff --git a/application/main.cpp b/application/main.cpp
index 9992ec0..68bc191 100644
--- a/application/main.cpp
+++ b/application/main.cpp
@@ -101,9 +101,7 @@ public:
 
 			world.apply(&WorldObject::tick, t_passed);
 			windows.apply(&Window::tick, t_passed);
-			windows.apply(&Window::Clear, 0.0F, 0.0F, 0.0F, 1.0F);
-			windows.apply(&Window::Refresh, this);
-			windows.apply(&Window::SwapBuffers);
+			windows.apply(&Window::refresh, this);
 
 			t_start = t_end;
 		}
diff --git a/ui/gameMainWindow.cpp b/ui/gameMainWindow.cpp
index 4421098..7d5e19b 100644
--- a/ui/gameMainWindow.cpp
+++ b/ui/gameMainWindow.cpp
@@ -33,9 +33,8 @@ GameMainWindow::tick(TickDuration)
 }
 
 void
-GameMainWindow::Refresh(const GameState * gameState) const
+GameMainWindow::render(const GameState * gameState) const
 {
-	SDL_GL_MakeCurrent(m_window, m_glContext);
 	glEnable(GL_DEPTH_TEST);
 	gameState->world.apply<Renderable>(&Renderable::render, shader);
 	glDisable(GL_DEPTH_TEST);
diff --git a/ui/gameMainWindow.h b/ui/gameMainWindow.h
index affb389..124d776 100644
--- a/ui/gameMainWindow.h
+++ b/ui/gameMainWindow.h
@@ -16,7 +16,7 @@ public:
 
 	void tick(TickDuration) override;
 
-	void Refresh(const GameState * gameState) const override;
+	void render(const GameState * gameState) const override;
 
 private:
 	UIShader uiShader;
diff --git a/ui/window.cpp b/ui/window.cpp
index c451367..2dc0c2a 100644
--- a/ui/window.cpp
+++ b/ui/window.cpp
@@ -1,32 +1,42 @@
 #include "window.h"
 #include "ui/inputHandler.h"
 #include <GL/glew.h>
+#include <optional>
 #include <stdexcept>
 
-Window::Window(int width, int height, const std::string & title) :
-	m_window {title.c_str(), static_cast<int>(SDL_WINDOWPOS_CENTERED), static_cast<int>(SDL_WINDOWPOS_CENTERED), width,
-			height, static_cast<Uint32>(SDL_WINDOW_OPENGL)},
-	m_glContext {m_window}
+static SDL_GLContext
+SDL_GL_CreateContextAndGlewInit(SDL_Window * w)
 {
+	auto ctx = SDL_GL_CreateContext(w);
 	if (glewInit() != GLEW_OK) {
 		throw std::runtime_error {"Glew failed to initialize!"};
 	}
-
 	glEnable(GL_CULL_FACE);
 	glCullFace(GL_BACK);
 	glEnable(GL_BLEND);
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	return ctx;
+}
+
+using GL_Context = std::remove_pointer_t<SDL_GLContext>;
+using SDL_GLContextPtr = wrapped_ptrt<GL_Context, SDL_GL_CreateContextAndGlewInit, SDL_GL_DeleteContext>;
+
+Window::Window(int width, int height, const std::string & title) :
+	m_window {title.c_str(), static_cast<int>(SDL_WINDOWPOS_CENTERED), static_cast<int>(SDL_WINDOWPOS_CENTERED), width,
+			height, static_cast<Uint32>(SDL_WINDOW_OPENGL)}
+{
+	glContext();
 }
 
 void
-Window::Clear(float r, float g, float b, float a) const
+Window::clear(float r, float g, float b, float a) const
 {
 	glClearColor(r, g, b, a);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 }
 
 void
-Window::SwapBuffers() const
+Window::swapBuffers() const
 {
 	SDL_GL_SwapWindow(m_window);
 }
@@ -40,3 +50,21 @@ Window::handleInput(const SDL_Event & e)
 	}
 	return false;
 }
+
+SDL_GLContext
+Window::glContext() const
+{
+	static SDL_GLContextPtr m_glContext {m_window};
+	return m_glContext;
+}
+
+void
+Window::refresh(const GameState * gameState) const
+{
+	SDL_GL_MakeCurrent(m_window, glContext());
+	clear(0.0F, 0.0F, 0.0F, 1.0F);
+
+	render(gameState);
+
+	swapBuffers();
+}
diff --git a/ui/window.h b/ui/window.h
index f6279e2..8bfc9c3 100644
--- a/ui/window.h
+++ b/ui/window.h
@@ -20,18 +20,19 @@ public:
 	NO_COPY(Window);
 	NO_MOVE(Window);
 
-	void Clear(float r, float g, float b, float a) const;
-	void SwapBuffers() const;
 	virtual void tick(TickDuration elapsed) = 0;
-	virtual void Refresh(const GameState *) const = 0;
+	void refresh(const GameState *) const;
 	bool handleInput(const SDL_Event & e);
 
+	void clear(float r, float g, float b, float a) const;
+	void swapBuffers() const;
+
 protected:
-	using GL_Context = std::remove_pointer_t<SDL_GLContext>;
+	SDL_GLContext glContext() const;
+	virtual void render(const GameState *) const = 0;
+
 	using SDL_WindowPtr = wrapped_ptrt<SDL_Window, SDL_CreateWindow, SDL_DestroyWindow>;
-	using SDL_GLContextPtr = wrapped_ptrt<GL_Context, SDL_GL_CreateContext, SDL_GL_DeleteContext>;
 	SDL_WindowPtr m_window;
-	SDL_GLContextPtr m_glContext;
 	Collection<InputHandler> inputStack;
 };
 
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