Add gl_proc_resolver to resolve GL procs within the GLFW context

flutter/flutter_helper.c

@@ -9,6 +9,7 @@ bool proxy_clear_current(void *v);
 bool proxy_present(void *v);
 uint32_t proxy_fbo_callback(void *v);
 bool proxy_make_resource_current(void *v);
+void *proxy_gl_proc_resolver(void *v, const char *procname);
 
 bool proxy_on_platform_message(FlutterPlatformMessage *message,
                              void *window);
@@ -27,6 +28,7 @@ FlutterResult runFlutter(uintptr_t window, FlutterEngine *engine, FlutterProject
   config.open_gl.present = proxy_present;
   config.open_gl.fbo_callback = proxy_fbo_callback;
   config.open_gl.make_resource_current = proxy_make_resource_current;
+  config.open_gl.gl_proc_resolver = proxy_gl_proc_resolver;
 
 	Args->command_line_argc = nVmAgrs;
 	Args->command_line_argv = vmArgs;

flutter/flutter_proxy_glfw.go

@@ -70,3 +70,8 @@ func proxy_make_resource_current(v unsafe.Pointer) C.bool {
 	index := *(*C.int)(w.GetUserPointer())
 	return C.bool(flutterEngines[index].FMakeResourceCurrent(v))
 }
+
+//export proxy_gl_proc_resolver
+func proxy_gl_proc_resolver(v unsafe.Pointer, procname *C.char) unsafe.Pointer {
+	return glfw.GetProcAddress(C.GoString(procname))
+}

flutter/library/flutter_embedder.h

@@ -31,8 +31,31 @@ typedef enum {
 
 typedef struct _FlutterEngine* FlutterEngine;
 
+typedef struct {
+  //   horizontal scale factor
+  double scaleX;
+  //    horizontal skew factor
+  double skewX;
+  //   horizontal translation
+  double transX;
+  //    vertical skew factor
+  double skewY;
+  //   vertical scale factor
+  double scaleY;
+  //   vertical translation
+  double transY;
+  //    input x-axis perspective factor
+  double pers0;
+  //    input y-axis perspective factor
+  double pers1;
+  //    perspective scale factor
+  double pers2;
+} FlutterTransformation;
+
 typedef bool (*BoolCallback)(void* /* user data */);
+typedef FlutterTransformation (*TransformationCallback)(void* /* user data */);
 typedef uint32_t (*UIntCallback)(void* /* user data */);
+typedef void* (*ProcResolver)(void* /* user data */, const char* /* name */);
 
 typedef struct {
   // The size of this struct. Must be sizeof(FlutterOpenGLRendererConfig).
@@ -41,7 +64,22 @@ typedef struct {
   BoolCallback clear_current;
   BoolCallback present;
   UIntCallback fbo_callback;
+  // This is an optional callback. Flutter will ask the emebdder to create a GL
+  // context current on a background thread. If the embedder is able to do so,
+  // Flutter will assume that this context is in the same sharegroup as the main
+  // rendering context and use this context for asynchronous texture uploads.
+  // Though optional, it is recommended that all embedders set this callback as
+  // it will lead to better performance in texture handling.
   BoolCallback make_resource_current;
+  // By default, the renderer config assumes that the FBO does not change for
+  // the duration of the engine run. If this argument is true, the
+  // engine will ask the embedder for an updated FBO target (via an fbo_callback
+  // invocation) after a present call.
+  bool fbo_reset_after_present;
+  // The transformation to apply to the render target before any rendering
+  // operations. This callback is optional.
+  TransformationCallback surface_transformation;
+  ProcResolver gl_proc_resolver;
 } FlutterOpenGLRendererConfig;
 
 typedef struct {