From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 25 Jan 2021 23:30:56 +0000 (+0200)
Subject: Add support for using the latest available OpenGL version
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgui.git;a=commitdiff_plain;h=be455be47a214f8fba1224ef1fb4158a073bc4e3

Add support for using the latest available OpenGL version
---

diff --git a/source/graphics/glcontext.cpp b/source/graphics/glcontext.cpp
index 0274c9e..ec073cb 100644
--- a/source/graphics/glcontext.cpp
+++ b/source/graphics/glcontext.cpp
@@ -15,16 +15,26 @@ GLOptions::GLOptions():
 	multisample(0),
 	forward_compatible(false),
 	core_profile(false),
-	gl_version_major(0),
-	gl_version_minor(0)
+	gl_version_major(DEFAULT_VERSION),
+	gl_version_minor(DEFAULT_VERSION)
 { }
 
 
 unsupported_gl_mode::unsupported_gl_mode(const GLOptions &opts):
-	runtime_error(format("{ .alpha=%s, .stencil=%s, .doublebuffer=%s, .multisample=%d, .forward_compatible=%s, .core_profile=%s, .gl_version=%d.%d }",
-		opts.alpha, opts.stencil, opts.doublebuffer, opts.multisample, opts.forward_compatible, opts.core_profile, opts.gl_version_major, opts.gl_version_minor))
+	runtime_error(format("{ .alpha=%s, .stencil=%s, .doublebuffer=%s, .multisample=%d, .forward_compatible=%s, .core_profile=%s, .gl_version=%s }",
+		opts.alpha, opts.stencil, opts.doublebuffer, opts.multisample, opts.forward_compatible, opts.core_profile, format_version(opts)))
 { }
 
+string unsupported_gl_mode::format_version(const GLOptions &opts)
+{
+	if(opts.gl_version_major==GLOptions::LATEST_VERSION)
+		return "LATEST";
+	else if(opts.gl_version_major==GLOptions::DEFAULT_VERSION)
+		return "DEFAULT";
+	else
+		return format("%d.%d", opts.gl_version_major, opts.gl_version_minor);
+}
+
 
 
 GLContext::GLContext(Window &wnd, const GLOptions &opts):
diff --git a/source/graphics/glcontext.h b/source/graphics/glcontext.h
index ef6ef1b..f6357c3 100644
--- a/source/graphics/glcontext.h
+++ b/source/graphics/glcontext.h
@@ -11,6 +11,12 @@ class Window;
 
 struct GLOptions
 {
+	enum
+	{
+		DEFAULT_VERSION = 0,
+		LATEST_VERSION = 0xFFFFFFFF
+	};
+
 	bool alpha;
 	bool stencil;
 	bool doublebuffer;
@@ -29,6 +35,9 @@ class unsupported_gl_mode: public std::runtime_error
 public:
 	unsupported_gl_mode(const GLOptions &);
 	virtual ~unsupported_gl_mode() throw () { }
+
+private:
+	static std::string format_version(const GLOptions &);
 };
 
 
@@ -43,6 +52,7 @@ private:
 
 public:
 	GLContext(Window &wnd, const GLOptions &opts = GLOptions());
+	GLContext(Window &wnd, unsigned, unsigned);
 private:
 	void platform_init(const GLOptions &);
 public:
diff --git a/source/graphics/glx/glcontext.cpp b/source/graphics/glx/glcontext.cpp
index 3ee8865..34daa08 100644
--- a/source/graphics/glx/glcontext.cpp
+++ b/source/graphics/glx/glcontext.cpp
@@ -2,6 +2,7 @@
 #include <vector>
 #include <GL/glx.h>
 #include <GL/glxext.h>
+#include <msp/strings/lexicalcast.h>
 #include <msp/strings/utils.h>
 #include "glcontext.h"
 #include "display_private.h"
@@ -98,11 +99,32 @@ void GLContext::platform_init(const GLOptions &opts)
 
 		priv->glxwnd = glXCreateWindow(dpy, fb_configs[0], priv->subwnd, 0);
 
-		if(opts.forward_compatible || opts.gl_version_major)
+		if(opts.forward_compatible || opts.gl_version_major!=GLOptions::DEFAULT_VERSION)
 		{
 			if(!extensions.count("GLX_ARB_create_context") || !extensions.count("GLX_ARB_get_proc_address"))
 				throw unsupported_gl_mode(opts);
 
+			unsigned gl_version_major = opts.gl_version_major;
+			unsigned gl_version_minor = opts.gl_version_minor;
+			if(opts.gl_version_major==GLOptions::LATEST_VERSION)
+			{
+				ContextHandle probe_context = glXCreateNewContext(dpy, fb_configs[0], GLX_RGBA_TYPE, 0, true);
+				glXMakeContextCurrent(dpy, priv->glxwnd, priv->glxwnd, probe_context);
+
+				const char *gl_ver_ptr = reinterpret_cast<const char *>(glGetString(GL_VERSION));
+				if(!gl_ver_ptr)
+					throw unsupported_gl_mode(opts);
+
+				string gl_ver = gl_ver_ptr;
+				vector<string> parts = split(gl_ver.substr(0, gl_ver.find(' ')), '.');
+
+				gl_version_major = lexical_cast<unsigned>(parts[0]);
+				gl_version_minor = lexical_cast<unsigned>(parts[1]);
+
+				glXMakeContextCurrent(dpy, 0, 0, 0);
+				glXDestroyContext(dpy, probe_context);
+			}
+
 			vector<int> ctx_attribs;
 
 			ctx_attribs.push_back(GLX_RENDER_TYPE);
@@ -123,9 +145,9 @@ void GLContext::platform_init(const GLOptions &opts)
 			if(opts.gl_version_major)
 			{
 				ctx_attribs.push_back(GLX_CONTEXT_MAJOR_VERSION_ARB);
-				ctx_attribs.push_back(opts.gl_version_major);
+				ctx_attribs.push_back(gl_version_major);
 				ctx_attribs.push_back(GLX_CONTEXT_MINOR_VERSION_ARB);
-				ctx_attribs.push_back(opts.gl_version_minor);
+				ctx_attribs.push_back(gl_version_minor);
 			}
 
 			ctx_attribs.push_back(0);
diff --git a/source/graphics/wgl/glcontext.cpp b/source/graphics/wgl/glcontext.cpp
index 6808897..b0f685b 100644
--- a/source/graphics/wgl/glcontext.cpp
+++ b/source/graphics/wgl/glcontext.cpp
@@ -2,6 +2,8 @@
 #include <windows.h>
 #include <GL/gl.h>
 #include <GL/wglext.h>
+#include <msp/strings/lexicalcast.h>
+#include <msp/strings/utils.h>
 #include "glcontext.h"
 #include "window_private.h"
 
@@ -53,7 +55,7 @@ void GLContext::platform_init(const GLOptions &opts)
 	SetPixelFormat(dc, pf_index, &pfd);
 
 	priv = new Private;
-	if(opts.forward_compatible || opts.gl_version_major)
+	if(opts.forward_compatible || opts.gl_version_major!=DEFAULT_VERSION)
 	{
 		ContextHandle fake_context = wglCreateContext(dc);
 		wglMakeCurrent(dc, fake_context);
@@ -62,6 +64,21 @@ void GLContext::platform_init(const GLOptions &opts)
 		if(!wglCreateContextAttribs)
 			throw unsupported_gl_mode(opts);
 
+		unsigned gl_version_major = opts.gl_version_major;
+		unsigned gl_version_minor = opts.gl_version_minor;
+		if(opts.gl_version_major==GLOptions::LATEST_VERSION)
+		{
+			const char *gl_ver_ptr = reinterpret_cast<const char *>(glGetString(GL_VERSION));
+			if(!gl_ver_ptr)
+				throw unsupported_gl_mode(opts);
+
+			string gl_ver = gl_ver_ptr;
+			vector<string> parts = split(gl_ver.substr(0, gl_ver.find(' ')), '.');
+
+			gl_version_major = lexical_cast<unsigned>(parts[0]);
+			gl_version_minor = lexical_cast<unsigned>(parts[1]);
+		}
+
 		vector<int> ctx_attribs;
 
 		if(opts.forward_compatible)
@@ -79,9 +96,9 @@ void GLContext::platform_init(const GLOptions &opts)
 		if(opts.gl_version_major)
 		{
 			ctx_attribs.push_back(WGL_CONTEXT_MAJOR_VERSION_ARB);
-			ctx_attribs.push_back(opts.gl_version_major);
+			ctx_attribs.push_back(gl_version_major);
 			ctx_attribs.push_back(WGL_CONTEXT_MINOR_VERSION_ARB);
-			ctx_attribs.push_back(opts.gl_version_minor);
+			ctx_attribs.push_back(gl_version_minor);
 		}
 
 		ctx_attribs.push_back(0);