From 3b0270c3e44c4a9e0f95ac43069883df9eab6d01 Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Fri, 20 Sep 2013 15:29:03 -0700
Subject: [PATCH] Initial import of libglfps demo for glaze

This first implementation is a simple FPS-counter for OpenGL
implemented via a library suitable for use with LD_PRELOAD.
---
 .gitignore |  1 +
 Makefile   |  8 ++++++++
 glfps.c    | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 glfps.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..916f458
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+libglfps.so
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..3e7e390
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,8 @@
+CC ?= gcc
+CFLAGS ?= -g -Wall -Wextra -Wmissing-declarations
+
+libglfps.so: glfps.c
+	$(CC) $(CFLAGS) -fPIC -shared -Wl,-Bsymbolic -o $@ $<
+
+clean:
+	rm -f libglfps.so
diff --git a/glfps.c b/glfps.c
new file mode 100644
index 0000000..68d389a
--- /dev/null
+++ b/glfps.c
@@ -0,0 +1,48 @@
+#define _GNU_SOURCE /* For RTLD_NEXT */
+#include <dlfcn.h>
+
+#include <stdio.h>
+
+#include <X11/Xlib.h>
+#include <GL/gl.h>
+#include <GL/glx.h>
+
+#include <sys/time.h>
+
+/* How many frames between reports. */
+#define REPORT_FREQ 60
+
+static void
+on_each_frame (void)
+{
+	static int count = 0;
+	static struct timeval tv_last;
+	struct timeval tv_now;
+
+	if ((count % REPORT_FREQ) == 0) {
+		gettimeofday (&tv_now, NULL);
+		if (count == 0) {
+			printf ("glfps: Initializing FPS timer\n");
+		} else {
+			double elapsed = ((tv_now.tv_sec - tv_last.tv_sec) +
+					  (tv_now.tv_usec - tv_last.tv_usec) / 1e6);
+			printf ("FPS: %.3f\n", ((double) REPORT_FREQ) / elapsed);
+		}
+		tv_last = tv_now;
+	}
+
+	count++;
+}
+
+void
+glXSwapBuffers (Display *dpy, GLXDrawable drawable)
+{
+	static typeof(&glXSwapBuffers) real_glXSwapBuffers = NULL;
+
+	if (real_glXSwapBuffers == NULL)
+		real_glXSwapBuffers = dlsym (RTLD_NEXT, "glXSwapBuffers");
+
+	on_each_frame ();
+
+	real_glXSwapBuffers (dpy, drawable);
+}
-- 
2.43.0