subsurfaces: fix rendering problem with cairo-glesv2
when using cairo-glesv2 subsurface rendering code
implicitly calls eglMakeCurrent(dpy, NULL, NULL, ctx)
(since EGL_KHR_surfaceless_context is used), thus,
triangle_frame_callback:eglSwapBuffers returns EGL_BAD_SURFACE
error for all invocations other that the first one
diff --git a/clients/subsurfaces.c b/clients/subsurfaces.c
index 51b07a2..101ff17 100644
--- a/clients/subsurfaces.c
+++ b/clients/subsurfaces.c
@@ -398,6 +398,9 @@
if (callback)
wl_callback_destroy(callback);
+ eglMakeCurrent(tri->egl->dpy, tri->egl_surface,
+ tri->egl_surface, tri->egl->ctx);
+
glViewport(0, 0, tri->width, tri->height);
triangle_draw(&tri->gl, tri->time);