Added support for GL_KHR_context_flush_control.

README.md

@@ -63,6 +63,9 @@ GLFW bundles a number of dependencies in the `deps/` directory.
    automatically iconify (and restore the previous video mode) on focus loss
  - Added `GLFW_DONT_CARE` for indicating that any value is acceptable
  - Added `GLFW_DOUBLEBUFFER` for controlling whether to use double buffering
+ - Added `GLFW_CONTEXT_RELEASE_BEHAVIOR` and values
+   `GLFW_ANY_RELEASE_BEHAVIOR`, `GLFW_RELEASE_BEHAVIOR_FLUSH` and
+   `GLFW_RELEASE_BEHAVIOR_NONE` for `GL_KHR_context_flush_control` support
  - Added `GLFW_INCLUDE_ES31` for including the OpenGL ES 3.1 header
  - Added `GLFW_FLOATING` for creating always-on-top windowed mode windows
  - Added *partial and experimental* support for Wayland

docs/window.dox

@@ -222,11 +222,24 @@ used by the context.  This can be one of `GLFW_NO_RESET_NOTIFICATION` or
 `GLFW_LOSE_CONTEXT_ON_RESET`, or `GLFW_NO_ROBUSTNESS` to not request
 a robustness strategy.
 
+The `GLFW_CONTEXT_RELEASE_BEHAVIOR` hint specifies the release behavior to be
+used by the context.  Possible values are one of `GLFW_ANY_RELEASE_BEHAVIOR`,
+`GLFW_RELEASE_BEHAVIOR_FLUSH` or `GLFW_RELEASE_BEHAVIOR_NONE`.  If the
+behavior is `GLFW_ANY_RELEASE_BEHAVIOR`, the default behavior of the context
+creation API will be used.  If the behavior is `GLFW_RELEASE_BEHAVIOR_FLUSH`,
+the pipeline will be flushed whenever the context is released from being the
+current one.  If the behavior is `GLFW_RELEASE_BEHAVIOR_NONE`, the pipeline will
+not be flushed on release.
+
+@note Context release behaviors are described in detail by the
+[GL_KHR_context_flush_control](https://www.opengl.org/registry/specs/KHR/context_flush_control.txt)
+extension.
+
 
 @subsection window_hints_values Supported and default values
 
 | Name                            | Default value               | Supported values        |
-| ---------------------------- | ------------------------- | ----------------------- |
+| ------------------------------- | --------------------------- | ----------------------- |
 | `GLFW_RESIZABLE`                | `GL_TRUE`                   | `GL_TRUE` or `GL_FALSE` |
 | `GLFW_VISIBLE`                  | `GL_TRUE`                   | `GL_TRUE` or `GL_FALSE` |
 | `GLFW_DECORATED`                | `GL_TRUE`                   | `GL_TRUE` or `GL_FALSE` |
@@ -252,6 +265,7 @@ a robustness strategy.
 | `GLFW_CONTEXT_VERSION_MAJOR`    | 1                           | Any valid major version number of the chosen client API |
 | `GLFW_CONTEXT_VERSION_MINOR`    | 0                           | Any valid minor version number of the chosen client API |
 | `GLFW_CONTEXT_ROBUSTNESS`       | `GLFW_NO_ROBUSTNESS`        | `GLFW_NO_ROBUSTNESS`, `GLFW_NO_RESET_NOTIFICATION` or `GLFW_LOSE_CONTEXT_ON_RESET` |
+| `GLFW_CONTEXT_RELEASE_BEHAVIOR` | `GLFW_ANY_RELEASE_BEHAVIOR` | `GLFW_ANY_RELEASE_BEHAVIOR`, `GLFW_RELEASE_BEHAVIOR_FLUSH` or `GLFW_RELEASE_BEHAVIOR_NONE` |
 | `GLFW_OPENGL_FORWARD_COMPAT`    | `GL_FALSE`                  | `GL_TRUE` or `GL_FALSE` |
 | `GLFW_OPENGL_DEBUG_CONTEXT`     | `GL_FALSE`                  | `GL_TRUE` or `GL_FALSE` |
 | `GLFW_OPENGL_PROFILE`           | `GLFW_OPENGL_ANY_PROFILE`   | `GLFW_OPENGL_ANY_PROFILE`, `GLFW_OPENGL_COMPAT_PROFILE` or `GLFW_OPENGL_CORE_PROFILE` |

include/GLFW/glfw3.h

@@ -525,6 +525,7 @@ extern "C" {
 #define GLFW_OPENGL_FORWARD_COMPAT  0x00022006
 #define GLFW_OPENGL_DEBUG_CONTEXT   0x00022007
 #define GLFW_OPENGL_PROFILE         0x00022008
+#define GLFW_CONTEXT_RELEASE_BEHAVIOR 0x00022009
 
 #define GLFW_OPENGL_API             0x00030001
 #define GLFW_OPENGL_ES_API          0x00030002
@@ -545,6 +546,10 @@ extern "C" {
 #define GLFW_CURSOR_HIDDEN          0x00034002
 #define GLFW_CURSOR_DISABLED        0x00034003
 
+#define GLFW_ANY_RELEASE_BEHAVIOR            0
+#define GLFW_RELEASE_BEHAVIOR_FLUSH 0x00035001
+#define GLFW_RELEASE_BEHAVIOR_NONE  0x00035002
+
 #define GLFW_CONNECTED              0x00040001
 #define GLFW_DISCONNECTED           0x00040002
 

src/context.c

@@ -198,6 +198,17 @@ GLboolean _glfwIsValidContextConfig(const _GLFWctxconfig* ctxconfig)
         }
     }
 
+    if (ctxconfig->release)
+    {
+        if (ctxconfig->release != GLFW_RELEASE_BEHAVIOR_NONE &&
+            ctxconfig->release != GLFW_RELEASE_BEHAVIOR_FLUSH)
+        {
+            _glfwInputError(GLFW_INVALID_VALUE,
+                            "Invalid context release behavior requested");
+            return GL_FALSE;
+        }
+    }
+
     return GL_TRUE;
 }
 
@@ -468,6 +479,17 @@ GLboolean _glfwRefreshContextAttribs(const _GLFWctxconfig* ctxconfig)
                 window->context.robustness = GLFW_NO_RESET_NOTIFICATION;
         }
     }
+
+    if (glfwExtensionSupported("GL_KHR_context_flush_control"))
+    {
+        GLint behavior;
+        glGetIntegerv(GL_CONTEXT_RELEASE_BEHAVIOR, &behavior);
+
+        if (behavior == GL_NONE)
+            window->context.release = GLFW_RELEASE_BEHAVIOR_NONE;
+        else if (behavior == GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH)
+            window->context.release = GLFW_RELEASE_BEHAVIOR_FLUSH;
+    }
 #endif // _GLFW_USE_OPENGL
 
     return GL_TRUE;

src/egl_context.c

@@ -381,6 +381,9 @@ int _glfwCreateContext(_GLFWwindow* window,
         setEGLattrib(EGL_NONE, EGL_NONE);
     }
 
+    // Context release behaviors (GL_KHR_context_flush_control) are not yet
+    // supported on EGL but are not a hard constraint, so ignore and continue
+
     window->egl.context = eglCreateContext(_glfw.egl.display,
                                            config, share, attribs);
 

src/glx_context.c

@@ -255,6 +255,9 @@ int _glfwInitContextAPI(void)
     if (_glfwPlatformExtensionSupported("GLX_EXT_create_context_es2_profile"))
         _glfw.glx.EXT_create_context_es2_profile = GL_TRUE;
 
+    if (_glfwPlatformExtensionSupported("GLX_ARB_context_flush_control"))
+        _glfw.glx.ARB_context_flush_control = GL_TRUE;
+
     return GL_TRUE;
 }
 
@@ -384,6 +387,23 @@ int _glfwCreateContext(_GLFWwindow* window,
             }
         }
 
+        if (ctxconfig->release)
+        {
+            if (_glfw.glx.ARB_context_flush_control)
+            {
+                if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_NONE)
+                {
+                    setGLXattrib(GLX_CONTEXT_RELEASE_BEHAVIOR_ARB,
+                                 GLX_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB);
+                }
+                else if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_FLUSH)
+                {
+                    setGLXattrib(GLX_CONTEXT_RELEASE_BEHAVIOR_ARB,
+                                 GLX_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB);
+                }
+            }
+        }
+
         if (ctxconfig->major != 1 || ctxconfig->minor != 0)
         {
             // NOTE: Only request an explicitly versioned context when

src/glx_context.h

@@ -105,6 +105,7 @@ typedef struct _GLFWlibraryGLX
     GLboolean       ARB_create_context_profile;
     GLboolean       ARB_create_context_robustness;
     GLboolean       EXT_create_context_es2_profile;
+    GLboolean       ARB_context_flush_control;
 
 #if defined(_GLFW_DLOPEN_LIBGL)
     void*           libGL;  // dlopen handle for libGL.so

src/internal.h

@@ -173,6 +173,7 @@ struct _GLFWctxconfig
     GLboolean     debug;
     int           profile;
     int           robustness;
+    int           release;
     _GLFWwindow*  share;
 };
 
@@ -242,6 +243,7 @@ struct _GLFWwindow
         GLboolean       forward, debug;
         int             profile;
         int             robustness;
+        int             release;
     } context;
 
 #if defined(_GLFW_USE_OPENGL)
@@ -338,6 +340,7 @@ struct _GLFWlibrary
         int         debug;
         int         profile;
         int         robustness;
+        int         release;
     } hints;
 
     double          cursorPosX, cursorPosY;

src/nsgl_context.m

@@ -115,6 +115,9 @@ int _glfwCreateContext(_GLFWwindow* window,
     // Context robustness modes (GL_KHR_robustness) are not yet supported on
     // OS X but are not a hard constraint, so ignore and continue
 
+    // Context release behaviors (GL_KHR_context_flush_control) are not yet
+    // supported on OS X but are not a hard constraint, so ignore and continue
+
 #define ADD_ATTR(x) { attributes[attributeCount++] = x; }
 #define ADD_ATTR2(x, y) { ADD_ATTR(x); ADD_ATTR(y); }
 

src/wgl_context.c

@@ -57,6 +57,7 @@ static void initWGLExtensions(_GLFWwindow* window)
     window->wgl.ARB_create_context_robustness = GL_FALSE;
     window->wgl.EXT_swap_control = GL_FALSE;
     window->wgl.ARB_pixel_format = GL_FALSE;
+    window->wgl.ARB_context_flush_control = GL_FALSE;
 
     window->wgl.GetExtensionsStringEXT = (PFNWGLGETEXTENSIONSSTRINGEXTPROC)
         wglGetProcAddress("wglGetExtensionsStringEXT");
@@ -119,6 +120,9 @@ static void initWGLExtensions(_GLFWwindow* window)
         if (window->wgl.GetPixelFormatAttribivARB)
             window->wgl.ARB_pixel_format = GL_TRUE;
     }
+
+    if (_glfwPlatformExtensionSupported("WGL_ARB_context_flush_control"))
+        window->wgl.ARB_context_flush_control = GL_TRUE;
 }
 
 // Returns the specified attribute of the specified pixel format
@@ -421,6 +425,23 @@ int _glfwCreateContext(_GLFWwindow* window,
             }
         }
 
+        if (ctxconfig->release)
+        {
+            if (window->wgl.ARB_context_flush_control)
+            {
+                if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_NONE)
+                {
+                    setWGLattrib(WGL_CONTEXT_RELEASE_BEHAVIOR_ARB,
+                                 WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB);
+                }
+                else if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_FLUSH)
+                {
+                    setWGLattrib(WGL_CONTEXT_RELEASE_BEHAVIOR_ARB,
+                                 WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB);
+                }
+            }
+        }
+
         if (ctxconfig->major != 1 || ctxconfig->minor != 0)
         {
             // NOTE: Only request an explicitly versioned context when
@@ -535,6 +556,12 @@ int _glfwAnalyzeContext(const _GLFWwindow* window,
 
             required = GL_TRUE;
         }
+
+        if (ctxconfig->release)
+        {
+            if (window->wgl.ARB_context_flush_control)
+                required = GL_TRUE;
+        }
     }
     else
     {

src/wgl_context.h

@@ -65,6 +65,7 @@ typedef struct _GLFWcontextWGL
     GLboolean                           ARB_create_context_profile;
     GLboolean                           EXT_create_context_es2_profile;
     GLboolean                           ARB_create_context_robustness;
+    GLboolean                           ARB_context_flush_control;
 } _GLFWcontextWGL;
 
 

src/window.c

@@ -178,6 +178,7 @@ GLFWAPI GLFWwindow* glfwCreateWindow(int width, int height,
     ctxconfig.debug         = _glfw.hints.debug ? GL_TRUE : GL_FALSE;
     ctxconfig.profile       = _glfw.hints.profile;
     ctxconfig.robustness    = _glfw.hints.robustness;
+    ctxconfig.release       = _glfw.hints.release;
     ctxconfig.share         = (_GLFWwindow*) share;
 
     // Check the OpenGL bits of the window config
@@ -383,6 +384,9 @@ GLFWAPI void glfwWindowHint(int target, int hint)
         case GLFW_OPENGL_PROFILE:
             _glfw.hints.profile = hint;
             break;
+        case GLFW_CONTEXT_RELEASE_BEHAVIOR:
+            _glfw.hints.release = hint;
+            break;
         default:
             _glfwInputError(GLFW_INVALID_ENUM, NULL);
             break;
@@ -623,6 +627,8 @@ GLFWAPI int glfwGetWindowAttrib(GLFWwindow* handle, int attrib)
             return window->context.debug;
         case GLFW_OPENGL_PROFILE:
             return window->context.profile;
+        case GLFW_CONTEXT_RELEASE_BEHAVIOR:
+            return window->context.release;
     }
 
     _glfwInputError(GLFW_INVALID_ENUM, NULL);

tests/glfwinfo.c

@@ -51,11 +51,15 @@
 #define STRATEGY_NAME_NONE  "none"
 #define STRATEGY_NAME_LOSE  "lose"
 
+#define BEHAVIOR_NAME_NONE  "none"
+#define BEHAVIOR_NAME_FLUSH "flush"
+
 static void usage(void)
 {
-    printf("Usage: glfwinfo [-h] [-a API] [-m MAJOR] [-n MINOR] [-d] [-l] [-f] [-p PROFILE] [-r STRATEGY]\n");
+    printf("Usage: glfwinfo [-h] [-a API] [-m MAJOR] [-n MINOR] [-d] [-l] [-f] [-p PROFILE] [-s STRATEGY] [-b BEHAVIOR]\n");
     printf("Options:\n");
     printf("  -a the client API to use (" API_OPENGL " or " API_OPENGL_ES ")\n");
+    printf("  -b the release behavior to use (" BEHAVIOR_NAME_NONE " or " BEHAVIOR_NAME_FLUSH ")\n");
     printf("  -d request a debug context\n");
     printf("  -f require a forward-compatible context\n");
     printf("  -h show this help\n");
@@ -63,7 +67,7 @@ static void usage(void)
     printf("  -m the major number of the requred client API version\n");
     printf("  -n the minor number of the requred client API version\n");
     printf("  -p the OpenGL profile to use (" PROFILE_NAME_CORE " or " PROFILE_NAME_COMPAT ")\n");
-    printf("  -r the robustness strategy to use (" STRATEGY_NAME_NONE " or " STRATEGY_NAME_LOSE ")\n");
+    printf("  -s the robustness strategy to use (" STRATEGY_NAME_NONE " or " STRATEGY_NAME_LOSE ")\n");
 }
 
 static void error_callback(int error, const char* description)
@@ -188,12 +192,12 @@ static GLboolean valid_version(void)
 
 int main(int argc, char** argv)
 {
-    int ch, api = 0, profile = 0, strategy = 0, major = 1, minor = 0, revision;
+    int ch, api = 0, profile = 0, strategy = 0, behavior = 0, major = 1, minor = 0, revision;
     GLboolean debug = GL_FALSE, forward = GL_FALSE, list = GL_FALSE;
     GLint flags, mask;
     GLFWwindow* window;
 
-    while ((ch = getopt(argc, argv, "a:dfhlm:n:p:r:")) != -1)
+    while ((ch = getopt(argc, argv, "a:b:dfhlm:n:p:s:")) != -1)
     {
         switch (ch)
         {
@@ -208,6 +212,17 @@ int main(int argc, char** argv)
                     exit(EXIT_FAILURE);
                 }
                 break;
+            case 'b':
+                if (strcasecmp(optarg, BEHAVIOR_NAME_NONE) == 0)
+                    behavior = GLFW_RELEASE_BEHAVIOR_NONE;
+                else if (strcasecmp(optarg, BEHAVIOR_NAME_FLUSH) == 0)
+                    behavior = GLFW_RELEASE_BEHAVIOR_FLUSH;
+                else
+                {
+                    usage();
+                    exit(EXIT_FAILURE);
+                }
+                break;
             case 'd':
                 debug = GL_TRUE;
                 break;
@@ -237,7 +252,7 @@ int main(int argc, char** argv)
                     exit(EXIT_FAILURE);
                 }
                 break;
-            case 'r':
+            case 's':
                 if (strcasecmp(optarg, STRATEGY_NAME_NONE) == 0)
                     strategy = GLFW_NO_RESET_NOTIFICATION;
                 else if (strcasecmp(optarg, STRATEGY_NAME_LOSE) == 0)
@@ -285,6 +300,9 @@ int main(int argc, char** argv)
     if (strategy)
         glfwWindowHint(GLFW_CONTEXT_ROBUSTNESS, strategy);
 
+    if (behavior)
+        glfwWindowHint(GLFW_CONTEXT_RELEASE_BEHAVIOR, behavior);
+
     glfwWindowHint(GLFW_RED_BITS, GLFW_DONT_CARE);
     glfwWindowHint(GLFW_GREEN_BITS, GLFW_DONT_CARE);
     glfwWindowHint(GLFW_BLUE_BITS, GLFW_DONT_CARE);