win32: Convert the API to being based on function pointers, like Linux.

For performance, I want to be able to make single-context (well,
single-pixel-format-and-device) apps be able to directly call GL
functions through function pointers.  Bake that into the ABI now so I
can get a release out the door and fix this up later.

This also fixes the lack of __stdcall annotation on the
PFNWHATEVERPROC typedefs.

README.md

@@ -119,3 +119,13 @@ pixel format.  If ```wglMakeCurrent()``` is called from outside of
 epoxy (in a way that might change the device or pixel format), then
 epoxy needs to be notified of the change using
 ```epoxy_handle_external_wglMakeCurrent()```.
+
+The win32 dispatch layer is currently slower than it should be in the
+single-context (or multi-context, but same device and pixel format)
+case.  We need to switch to using the linux-like function pointer
+stubs, and detect when transitioning to multi-device/format and hook
+in the per-thread dispatch table at that point.
+
+The win32 wglMakeCurrent () variants are slower than they should be,
+because they should be caching the resolved dispatch tables instead of
+resetting an entire thread-local dispatch table every time.

include/epoxy/gl.h

@@ -59,7 +59,7 @@ extern "C" {
 #endif
 
 #ifndef EPOXYAPIENTRY
-#define EPOXYAPIENTRY __declspec(dllimport)
+#define EPOXYAPIENTRY __declspec(dllimport) __stdcall
 #endif
 
 #ifndef GLAPI

src/dispatch_common.c

@@ -503,7 +503,5 @@ WRAPPER(epoxy_glEnd)(void)
 #endif
 }
 
-#ifndef _WIN32
 PUBLIC PFNGLBEGINPROC epoxy_glBegin = epoxy_glBegin_wrapped;
 PUBLIC PFNGLENDPROC epoxy_glEnd = epoxy_glEnd_wrapped;
-#endif

src/dispatch_common.h

@@ -27,7 +27,7 @@
 #define PLATFORM_HAS_EGL 0
 #define PLATFORM_HAS_GLX 0
 #define PLATFORM_HAS_WGL 1
-#define EPOXYAPIENTRY __declspec(dllexport)
+#define EPOXYAPIENTRY __declspec(dllexport) __stdcall
 #elif defined(__APPLE__)
 #define PLATFORM_HAS_EGL 0
 #define PLATFORM_HAS_GLX 1
@@ -65,16 +65,14 @@
  */
 #if defined(_WIN32)
 #define USING_DISPATCH_TABLE 1
-#define UNWRAPPED_PROTO(x) x
-#define WRAPPER_VISIBILITY PUBLIC
-#define WRAPPER(x) x
 #else
 #define USING_DISPATCH_TABLE 0
-#define UNWRAPPED_PROTO(x) (*x)
-#define WRAPPER_VISIBILITY static
-#define WRAPPER(x) x ## _wrapped
 #endif
 
+#define UNWRAPPED_PROTO(x) (GLAPIENTRY *x)
+#define WRAPPER_VISIBILITY static GLAPIENTRY
+#define WRAPPER(x) x ## _wrapped
+
 void *epoxy_egl_dlsym(const char *name);
 void *epoxy_glx_dlsym(const char *name);
 void *epoxy_gl_dlsym(const char *name);

src/dispatch_wgl.c

@@ -176,3 +176,7 @@ WRAPPER(epoxy_wglMakeAssociatedContextCurrentAMD)(HGLRC hglrc)
     return ret;
 }
 
+PUBLIC PFNWGLMAKECURRENTPROC epoxy_wglMakeCurrent = epoxy_wglMakeCurrent_wrapped;
+PUBLIC PFNWGLMAKECONTEXTCURRENTEXTPROC epoxy_wglMakeContextCurrentEXT = epoxy_wglMakeContextCurrentEXT_wrapped;
+PUBLIC PFNWGLMAKECONTEXTCURRENTARBPROC epoxy_wglMakeContextCurrentARB = epoxy_wglMakeContextCurrentARB_wrapped;
+PUBLIC PFNWGLMAKEASSOCIATEDCONTEXTCURRENTAMDPROC epoxy_wglMakeAssociatedContextCurrentEXT = epoxy_wglMakeAssociatedContextCurrentAMD_wrapped;

src/gen_dispatch.py

@@ -451,8 +451,9 @@ class Generator(object):
 
     def write_function_ptr_typedefs(self):
         for func in self.sorted_functions:
-            self.outln('typedef {0} (*{1})({2});'.format(func.ret_type, func.ptr_type,
+            self.outln('typedef {0} (GLAPIENTRY *{1})({2});'.format(func.ret_type,
-                                                         func.args_decl))
+                                                                    func.ptr_type,
+                                                                    func.args_decl))
 
     def write_header_header(self, file):
         self.out_file = open(file, 'w')
@@ -503,18 +504,8 @@ class Generator(object):
         self.outln('')
         self.write_function_ptr_typedefs()
 
-        self.outln('/* The library ABI is a set of functions on win32 (where')
-        self.outln(' * we have to use per-thread dispatch tables) and a set')
-        self.outln(' * of function pointers, otherwise.')
-        self.outln(' */')
-        self.outln('#ifdef _WIN32')
-        self.outln('#define EPOXY_FPTR(x) x')
-        self.outln('#else')
-        self.outln('#define EPOXY_FPTR(x) (*x)')
-        self.outln('#endif')
-
         for func in self.sorted_functions:
-            self.outln('extern EPOXYAPIENTRY {0} EPOXY_FPTR(epoxy_{1})({2});'.format(func.ret_type,
+            self.outln('extern EPOXYAPIENTRY {0} (*epoxy_{1})({2});'.format(func.ret_type,
                                                                                      func.name,
                                                                                      func.args_decl))
             self.outln('')
@@ -582,8 +573,8 @@ class Generator(object):
 
         dispatch_table_entry = 'dispatch_table->p{0}'.format(func.alias_name)
 
-        self.outln('{0}{1}'.format(func.public, func.ret_type))
+        self.outln('static __stdcall {0}'.format(func.ret_type))
-        self.outln('epoxy_{0}({1})'.format(func.wrapped_name, func.args_decl))
+        self.outln('epoxy_{0}_dispatch_table_thunk({1})'.format(func.wrapped_name, func.args_decl))
         self.outln('{')
         self.outln('    struct dispatch_table *dispatch_table = get_dispatch_table();')
         self.outln('')
@@ -601,7 +592,7 @@ class Generator(object):
 
         dispatch_table_entry = 'dispatch_table->p{0}'.format(func.name)
 
-        self.outln('static {0}'.format(func.ret_type))
+        self.outln('static GLAPIENTRY {0}'.format(func.ret_type))
         self.outln('epoxy_{0}_rewrite_stub({1})'.format(func.name, func.args_decl))
         self.outln('{')
         self.outln('    struct dispatch_table *dispatch_table = get_dispatch_table();')
@@ -616,7 +607,7 @@ class Generator(object):
         self.outln('}')
         self.outln('')
 
-    def write_function_pointer(self, func):
+    def write_linux_function_pointer(self, func):
         # Writes out the function for resolving and updating the
         # global function pointer, plus the actual global function
         # pointer initializer.
@@ -642,6 +633,12 @@ class Generator(object):
                                                                       func.wrapped_name))
         self.outln('')
 
+    def write_win32_function_pointer(self, func):
+        self.outln('{0}{1} epoxy_{2} = epoxy_{2}_dispatch_table_thunk;'.format(func.public,
+                                                                               func.ptr_type,
+                                                                               func.wrapped_name))
+        self.outln('')
+
     def write_provider_enums(self):
         # Writes the enum declaration for the list of providers
         # supported by gl_provider_resolver()
@@ -816,10 +813,13 @@ class Generator(object):
         self.outln('}')
         self.outln('')
 
+        for func in self.sorted_functions:
+            self.write_win32_function_pointer(func)
+
         self.outln('#else /* !USING_DISPATCH_TABLE */')
 
         for func in self.sorted_functions:
-            self.write_function_pointer(func)
+            self.write_linux_function_pointer(func)
 
         self.outln('#endif /* !USING_DISPATCH_TABLE */')