[client] ds: refactor common EGL swap with damage logic

This commit creates a new utility library, eglutil.h, which contains code
to detect and use EGL_KHR_swap_buffers_with_damage or its EXT equivalent.

This logic used to be duplicated between the X11 and Wayland display servers,
which is not ideal.

client/include/eglutil.h

@@ -0,0 +1,41 @@
+/**
+ * Looking Glass
+ * Copyright (C) 2017-2021 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _H_LG_GLUTIL_
+#define _H_LG_GLUTIL_
+
+#include <stdbool.h>
+#include <EGL/egl.h>
+
+#include "common/types.h"
+#include "egl_dynprocs.h"
+
+struct SwapWithDamageData
+{
+  bool init;
+  eglSwapBuffersWithDamageKHR_t func;
+};
+
+void swapWithDamageInit(struct SwapWithDamageData * data, EGLDisplay display);
+void swapWithDamageDisable(struct SwapWithDamageData * data);
+void swapWithDamage(struct SwapWithDamageData * data, EGLDisplay display, EGLSurface surface,
+    const struct Rect * damage, int count);
+
+#endif