better FPS calculation

1 files changed, 15 insertions, 25 deletions

diff --git a/progs/demos/fire.c b/progs/demos/fire.c
index f4c45219d05..52ea8683021 100644
--- a/progs/demos/fire.c
+++ b/progs/demos/fire.c
@@ -71,7 +71,9 @@ static int fullscreen = 1;
 static int WIDTH = 640;
 static int HEIGHT = 480;
 
-#define FRAME 50
+static GLint T0 = 0;
+static GLint Frames = 0;
+
 #define DIMP 20.0
 #define DIMTP 16.0
 
@@ -137,21 +139,6 @@ static float alpha = -90.0;
 static float beta = 90.0;
 
 static float
-gettime(void)
-{
-   static clock_t told = 0;
-   clock_t tnew, ris;
-
-   tnew = clock();
-
-   ris = tnew - told;
-
-   told = tnew;
-
-   return (ris / (float) CLOCKS_PER_SEC);
-}
-
-static float
 vrnd(void)
 {
    return (((float) rand()) / RAND_MAX);
@@ -387,10 +374,8 @@ dojoy(void)
 static void
 drawfire(void)
 {
-   static int count = 0;
-   static char frbuf[80];
+   static char frbuf[80] = "";
    int j;
-   float fr;
 
    dojoy();
 
@@ -468,11 +453,6 @@ drawfire(void)
    }
    glEnd();
 
-   if ((count % FRAME) == 0) {
-      fr = gettime();
-      sprintf(frbuf, "Frame rate: %f", FRAME / fr);
-   }
-
    glDisable(GL_TEXTURE_2D);
    glDisable(GL_ALPHA_TEST);
    glDisable(GL_DEPTH_TEST);
@@ -499,7 +479,17 @@ drawfire(void)
 
    glutSwapBuffers();
 
-   count++;
+   Frames++;
+   {
+      GLint t = glutGet(GLUT_ELAPSED_TIME);
+      if (t - T0 >= 2000) {
+         GLfloat seconds = (t - T0) / 1000.0;
+         GLfloat fps = Frames / seconds;
+         sprintf(frbuf, "Frame rate: %f", fps);
+         T0 = t;
+         Frames = 0;
+      }
+   }
 }