app,app/internal/wm: fold context MakeCurrent/ReleaseCurrent into Lock/Unlock

While here, make context Refresh useful and remove the redundant
MakeCurrent from the window loop.

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

app/internal/wm/gl_macos.go

@@ -68,11 +68,14 @@ func (c *context) Present() error {
 	return nil
 }
 
-func (c *context) Lock() {
+func (c *context) Lock() error {
 	C.gio_lockContext(c.ctx)
+	C.gio_makeCurrentContext(c.ctx)
+	return nil
 }
 
 func (c *context) Unlock() {
+	C.gio_clearCurrentContext()
 	C.gio_unlockContext(c.ctx)
 }
 
@@ -83,17 +86,6 @@ func (c *context) Refresh() error {
 	return nil
 }
 
-func (c *context) MakeCurrent() error {
-	c.Lock()
-	defer c.Unlock()
-	C.gio_makeCurrentContext(c.ctx)
-	return nil
-}
-
-func (c *context) ReleaseCurrent() {
-	C.gio_clearCurrentContext()
-}
-
 func (w *window) NewContext() (Context, error) {
 	return newContext(w)
 }