From 0ae4eb4d26e4fe857ace987bee310334859689e9 Mon Sep 17 00:00:00 2001
From: Doug Binks <doug@enkisoftware.com>
Date: Sun, 12 Jul 2020 12:21:18 +0100
Subject: [PATCH] Improved User Context Win32 implementation

_glfwCreateContextWGL and _glfwPlatformCreateUserContext now use  new function _glfwCreateContextForDCWGL.
---
 src/wgl_context.c | 112 +++++++++++++++++++++++++---------------------
 src/wgl_context.h |   2 +
 2 files changed, 64 insertions(+), 50 deletions(-)

diff --git a/src/wgl_context.c b/src/wgl_context.c
index 16bd167c..5a57aed7 100644
--- a/src/wgl_context.c
+++ b/src/wgl_context.c
@@ -538,46 +538,17 @@ void _glfwTerminateWGL(void)
     attribs[index++] = v; \
 }
 
-// Create the OpenGL or OpenGL ES context
+// Create the OpenGL or OpenGL ES context for the given HDC
 //
-GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
-                               const _GLFWctxconfig* ctxconfig,
-                               const _GLFWfbconfig* fbconfig)
+GLFWbool _glfwCreateContextForDCWGL(HDC dc, const _GLFWctxconfig* ctxconfig, HGLRC* context)
 {
     int attribs[40];
-    int pixelFormat;
-    PIXELFORMATDESCRIPTOR pfd;
     HGLRC share = NULL;
 
+    *context = NULL;
     if (ctxconfig->share)
         share = ctxconfig->share->context.wgl.handle;
 
-    window->context.wgl.dc = GetDC(window->win32.handle);
-    if (!window->context.wgl.dc)
-    {
-        _glfwInputError(GLFW_PLATFORM_ERROR,
-                        "WGL: Failed to retrieve DC for window");
-        return GLFW_FALSE;
-    }
-
-    pixelFormat = choosePixelFormat(window, ctxconfig, fbconfig);
-    if (!pixelFormat)
-        return GLFW_FALSE;
-
-    if (!DescribePixelFormat(window->context.wgl.dc,
-                             pixelFormat, sizeof(pfd), &pfd))
-    {
-        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
-                             "WGL: Failed to retrieve PFD for selected pixel format");
-        return GLFW_FALSE;
-    }
-
-    if (!SetPixelFormat(window->context.wgl.dc, pixelFormat, &pfd))
-    {
-        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
-                             "WGL: Failed to set selected pixel format");
-        return GLFW_FALSE;
-    }
 
     if (ctxconfig->client == GLFW_OPENGL_API)
     {
@@ -692,9 +663,9 @@ GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
 
         setAttrib(0, 0);
 
-        window->context.wgl.handle =
-            wglCreateContextAttribsARB(window->context.wgl.dc, share, attribs);
-        if (!window->context.wgl.handle)
+        *context =
+            wglCreateContextAttribsARB(dc, share, attribs);
+        if (!(*context))
         {
             const DWORD error = GetLastError();
 
@@ -744,8 +715,8 @@ GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
     }
     else
     {
-        window->context.wgl.handle = wglCreateContext(window->context.wgl.dc);
-        if (!window->context.wgl.handle)
+        *context = wglCreateContext(dc);
+        if (!(*context) )
         {
             _glfwInputErrorWin32(GLFW_VERSION_UNAVAILABLE,
                                  "WGL: Failed to create OpenGL context");
@@ -754,7 +725,7 @@ GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
 
         if (share)
         {
-            if (!wglShareLists(share, window->context.wgl.handle))
+            if (!wglShareLists(share, *context))
             {
                 _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
                                      "WGL: Failed to enable sharing with specified OpenGL context");
@@ -763,6 +734,50 @@ GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
         }
     }
 
+    return GLFW_TRUE;
+}
+
+// Create the OpenGL or OpenGL ES context
+//
+GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
+                               const _GLFWctxconfig* ctxconfig,
+                               const _GLFWfbconfig* fbconfig)
+{
+    int pixelFormat;
+    PIXELFORMATDESCRIPTOR pfd;
+
+    window->context.wgl.dc = GetDC(window->win32.handle);
+    if (!window->context.wgl.dc)
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "WGL: Failed to retrieve DC for window");
+        return GLFW_FALSE;
+    }
+
+    pixelFormat = choosePixelFormat(window, ctxconfig, fbconfig);
+    if (!pixelFormat)
+        return GLFW_FALSE;
+
+    if (!DescribePixelFormat(window->context.wgl.dc,
+                             pixelFormat, sizeof(pfd), &pfd))
+    {
+        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
+                             "WGL: Failed to retrieve PFD for selected pixel format");
+        return GLFW_FALSE;
+    }
+
+    if (!SetPixelFormat(window->context.wgl.dc, pixelFormat, &pfd))
+    {
+        _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
+                             "WGL: Failed to set selected pixel format");
+        return GLFW_FALSE;
+    }
+
+    if(!_glfwCreateContextForDCWGL( window->context.wgl.dc, ctxconfig, &window->context.wgl.handle ))
+    {
+        return GLFW_FALSE;
+    }
+
     window->context.makeCurrent = makeContextCurrentWGL;
     window->context.swapBuffers = swapBuffersWGL;
     window->context.swapInterval = swapIntervalWGL;
@@ -783,25 +798,22 @@ GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
 _GLFWusercontext* _glfwPlatformCreateUserContext(_GLFWwindow* window)
 {
     _GLFWusercontext* context;
+    _GLFWctxconfig ctxconfig;
+
     context = calloc(1, sizeof(_GLFWusercontext));
-
-    context->handle = wglCreateContext(window->context.wgl.dc);
     context->window = window;
-    if (!context->handle)
-    {
-        _glfwInputErrorWin32(GLFW_VERSION_UNAVAILABLE,
-                                "WGL: Failed to create user OpenGL context");
-        free(context);
-        return GLFW_FALSE;
-    }
 
-    if (!wglShareLists(window->context.wgl.handle,context->handle))
+    ctxconfig = _glfw.hints.context;
+    ctxconfig.share = window;
+
+    if (!_glfwCreateContextForDCWGL(window->context.wgl.dc, &ctxconfig, &context->handle))
     {
         _glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
-                                "WGL: Failed to enable sharing with window OpenGL context and user context");
+                                "WGL: Failed to create user OpenGL context");
         free(context);
-        return GLFW_FALSE;
+        return NULL;
     }
+
     return context;
 }
 
diff --git a/src/wgl_context.h b/src/wgl_context.h
index 6cb6d050..abf97559 100644
--- a/src/wgl_context.h
+++ b/src/wgl_context.h
@@ -151,6 +151,8 @@ typedef struct _GLFWlibraryWGL
 
 } _GLFWlibraryWGL;
 
+// WGL-specific user context data
+//
 typedef struct _GLFWusercontext
 {
     _GLFWwindow* window;