internal/egl: replace glFinish with eglWaitClient

glFinish depends on package gl which is about to require a function
pointer loader. eglWaitClient is in the EGL API and always available.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

internal/egl/egl.go

@@ -11,12 +11,10 @@ import (
 	"strings"
 
 	"gioui.org/gpu"
-	"gioui.org/internal/gl"
 	"gioui.org/internal/srgb"
 )
 
 type Context struct {
-	c             *gl.Functions
 	disp          _EGLDisplay
 	eglCtx        *eglContext
 	eglSurf       _EGLSurface
@@ -105,14 +103,9 @@ func NewContext(disp NativeDisplayType) (*Context, error) {
 	if err != nil {
 		return nil, err
 	}
-	f, err := gl.NewFunctions(nil)
-	if err != nil {
-		return nil, err
-	}
 	c := &Context{
 		disp:   eglDisp,
 		eglCtx: eglCtx,
-		c:      f,
 	}
 	return c, nil
 }
@@ -126,7 +119,7 @@ func (c *Context) ReleaseSurface() {
 		return
 	}
 	// Make sure any in-flight GL commands are complete.
-	c.c.Finish()
+	eglWaitClient()
 	c.ReleaseCurrent()
 	eglDestroySurface(c.disp, c.eglSurf)
 	c.eglSurf = nilEGLSurface

internal/egl/egl_unix.go

@@ -102,3 +102,7 @@ func eglCreateWindowSurface(disp _EGLDisplay, conf _EGLConfig, win NativeWindowT
 	eglSurf := C.eglCreateWindowSurface(disp, conf, win, &attribs[0])
 	return eglSurf
 }
+
+func eglWaitClient() bool {
+	return C.eglWaitClient() == C.EGL_TRUE
+}

internal/egl/egl_windows.go

@@ -40,6 +40,7 @@ var (
 	_eglSwapBuffers         = libEGL.NewProc("eglSwapBuffers")
 	_eglTerminate           = libEGL.NewProc("eglTerminate")
 	_eglQueryString         = libEGL.NewProc("eglQueryString")
+	_eglWaitClient          = libEGL.NewProc("eglWaitClient")
 )
 
 var loadOnce sync.Once
@@ -156,6 +157,11 @@ func eglQueryString(disp _EGLDisplay, name _EGLint) string {
 	return syscall.BytePtrToString((*byte)(unsafe.Pointer(r)))
 }
 
+func eglWaitClient() bool {
+	r, _, _ := _eglWaitClient.Call()
+	return r != 0
+}
+
 // issue34474KeepAlive calls runtime.KeepAlive as a
 // workaround for golang.org/issue/34474.
 func issue34474KeepAlive(v interface{}) {