From 82bfbf1f459d540b0e204bb873ca5786997b24da Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 12 Nov 2022 11:38:34 +0000
Subject: Refactor for per window context and more setup to the right places

---
 gfx/models/texture.cpp |  1 +
 ui/sceneRenderer.cpp   |  3 +++
 ui/window.cpp          | 40 +++++++++++-----------------------------
 ui/window.h            |  8 +++++++-
 4 files changed, 22 insertions(+), 30 deletions(-)

diff --git a/gfx/models/texture.cpp b/gfx/models/texture.cpp
index ff38d0f..ab1a5fe 100644
--- a/gfx/models/texture.cpp
+++ b/gfx/models/texture.cpp
@@ -23,6 +23,7 @@ Texture::Texture(const Image & tex) :
 Texture::Texture(GLsizei width, GLsizei height, const void * data)
 {
 	glBindTexture(GL_TEXTURE_2D, m_texture);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
diff --git a/ui/sceneRenderer.cpp b/ui/sceneRenderer.cpp
index 6e75dec..5ef0379 100644
--- a/ui/sceneRenderer.cpp
+++ b/ui/sceneRenderer.cpp
@@ -51,6 +51,9 @@ SceneRenderer::render(std::function<void()> content) const
 {
 	// Geometry pass
 	glEnable(GL_BLEND);
+	glEnable(GL_CULL_FACE);
+	glCullFace(GL_BACK);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	glEnable(GL_DEPTH_TEST);
 	glBindFramebuffer(GL_FRAMEBUFFER, gBuffer);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
diff --git a/ui/window.cpp b/ui/window.cpp
index 82f4d40..0d4c401 100644
--- a/ui/window.cpp
+++ b/ui/window.cpp
@@ -7,35 +7,24 @@
 #include <tuple>
 #include <type_traits>
 
-static SDL_GLContext
-SDL_GL_CreateContextAndGlewInit(SDL_Window * w)
+Window::GlewInitHelper::GlewInitHelper()
 {
-	auto ctx = SDL_GL_CreateContext(w);
-	if (glewInit() != GLEW_OK) {
-		throw std::runtime_error {"Glew failed to initialize!"};
-	}
-	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
-	glEnable(GL_CULL_FACE);
-	glCullFace(GL_BACK);
-	glEnable(GL_BLEND);
-	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	return ctx;
+	[[maybe_unused]] static auto init = []() {
+		if (const auto r = glewInit(); r != GLEW_OK) {
+			throw std::runtime_error {reinterpret_cast<const char *>(glewGetErrorString(r))};
+		}
+		else {
+			return r;
+		}
+	}();
 }
 
-using GL_Context = std::remove_pointer_t<SDL_GLContext>;
-using SDL_GLContextPtr = wrapped_ptrt<GL_Context, SDL_GL_CreateContextAndGlewInit, SDL_GL_DeleteContext>;
-
 Window::Window(size_t width, size_t height, const std::string & title) :
 	size {static_cast<int>(width), static_cast<int>(height)}, m_window {title.c_str(),
 																	  static_cast<int>(SDL_WINDOWPOS_CENTERED),
 																	  static_cast<int>(SDL_WINDOWPOS_CENTERED), size.x,
 																	  size.y, static_cast<Uint32>(SDL_WINDOW_OPENGL)},
-	uiShader {[this](auto w) {
-				  // must call glContent before creating the shader
-				  std::ignore = glContext();
-				  return w;
-			  }(width),
-			height}
+	glContext {m_window}, uiShader {width, height}
 {
 }
 
@@ -73,17 +62,10 @@ 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
 {
-	SDL_GL_MakeCurrent(m_window, glContext());
+	SDL_GL_MakeCurrent(m_window, glContext);
 	clear(0.0F, 0.0F, 0.0F, 1.0F);
 
 	render();
diff --git a/ui/window.h b/ui/window.h
index 0661915..d618976 100644
--- a/ui/window.h
+++ b/ui/window.h
@@ -26,12 +26,18 @@ public:
 	void swapBuffers() const;
 
 protected:
-	[[nodiscard]] SDL_GLContext glContext() const;
 	virtual void render() const;
+	struct GlewInitHelper {
+		GlewInitHelper();
+	};
 
 	using SDL_WindowPtr = wrapped_ptrt<SDL_Window, SDL_CreateWindow, SDL_DestroyWindow>;
+	using GL_Context = std::remove_pointer_t<SDL_GLContext>;
+	using SDL_GLContextPtr = wrapped_ptrt<GL_Context, SDL_GL_CreateContext, SDL_GL_DeleteContext>;
 	const glm::ivec2 size;
 	SDL_WindowPtr m_window;
+	SDL_GLContextPtr glContext;
+	GlewInitHelper glewinithelper;
 	Collection<UIComponent> uiComponents;
 	UIShader uiShader;
 };
-- 
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