From 932b60a12345aa2d97da7e0fa8ea237b5378b3d6 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Sat, 14 Aug 2010 21:15:44 +0000
Subject: [PATCH] Proper delta time computation in both the game and the
 editor.

---
 src/debugfps.cpp   | 20 +++++++++++++++++++-
 src/gtk/editor.cpp | 20 ++++++++++++++------
 src/test-map.cpp   | 15 ++++++---------
 3 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/src/debugfps.cpp b/src/debugfps.cpp
index 9a1414f9..a0325403 100644
--- a/src/debugfps.cpp
+++ b/src/debugfps.cpp
@@ -20,7 +20,10 @@ class DebugFpsData
 {
     friend class DebugFps;
 
+    static int const HISTORY = 30;
+
 private:
+    float history[HISTORY];
     Font *font;
     int frame;
 };
@@ -33,6 +36,8 @@ DebugFps::DebugFps()
 {
     data = new DebugFpsData();
 
+    for (int i = 0; i < DebugFpsData::HISTORY; i++)
+        data->history[i] = 0.0f;
     data->font = Forge::GetFont("gfx/font/ascii.png");
     data->frame = 0;
 }
@@ -46,8 +51,21 @@ void DebugFps::TickRender(float delta_time)
 {
     Asset::TickGame(delta_time);
 
+    data->history[data->frame % DebugFpsData::HISTORY] = delta_time;
+    data->frame++;
+
+    float mean = 0.0f, max = 0.0f;
+    for (int i = 0; i < DebugFpsData::HISTORY; i++)
+    {
+        mean += data->history[i];
+        if (data->history[i] > max)
+            max = data->history[i];
+    }
+    mean /= DebugFpsData::HISTORY;
+
     char buf[1024];
-    sprintf(buf, "%3.2f fps (%i)", 1000.0f / delta_time, data->frame++);
+    sprintf(buf, "%3.2f ms (%3.2f fps) -- max %3.2f ms -- #%i",
+            mean, 1000.0f / mean, max, data->frame);
     data->font->Print(10, 10, buf);
     data->font->Print(11, 10, buf);
     data->font->Print(10, 11, buf);
diff --git a/src/gtk/editor.cpp b/src/gtk/editor.cpp
index 0af8eab8..2a784e8b 100644
--- a/src/gtk/editor.cpp
+++ b/src/gtk/editor.cpp
@@ -19,7 +19,11 @@
 #include "video.h"
 #include "game.h"
 
-volatile int quit = 0;
+static volatile int quit = 0;
+
+static GTimer *timer;
+static float delta_time;
+static int ticking = 0;
 
 static gint main_quit(GtkWidget *widget, GdkEventExpose *event)
 {
@@ -33,14 +37,16 @@ static gint main_quit(GtkWidget *widget, GdkEventExpose *event)
 
 static gboolean tick(void *widget)
 {
-    float const delta_time = 33.33333f;
-
     // FIXME: do not do anything if the previous tick was too recent?
+    delta_time = 1000.0f * g_timer_elapsed(timer, NULL);
+    g_timer_start(timer);
 
     // FIXME: only quit if all assets have been cleaned
     if (quit)
         return FALSE;
 
+    ticking = 1;
+
     /* Tick the game */
     Ticker::TickGame(delta_time);
 
@@ -70,10 +76,9 @@ static gint draw(GtkWidget *widget, GdkEventExpose *event)
         return TRUE;
 
     /* OpenGL functions can be called only if make_current returns true */
-    if (gtk_gl_area_make_current(GTK_GL_AREA(widget)))
+    if (ticking && gtk_gl_area_make_current(GTK_GL_AREA(widget)))
     {
-        // FIXME: do not do anything if the game tick wasn't called?
-        float const delta_time = 33.33333f;
+        ticking = 0;
 
         /* Clear the screen, tick the renderer, and show the frame */
         Video::Clear();
@@ -87,6 +92,7 @@ static gint draw(GtkWidget *widget, GdkEventExpose *event)
 int main(int argc, char **argv)
 {
     /* Initialize GTK */
+    g_thread_init(NULL);
     gtk_init(&argc, &argv);
 
     if (gdk_gl_query() == FALSE)
@@ -151,6 +157,8 @@ int main(int argc, char **argv)
 
     //gtk_idle_add(tick, glarea);
     gtk_timeout_add(33, tick, glarea);
+
+    timer = g_timer_new();
     gtk_main();
 
     return EXIT_SUCCESS;
diff --git a/src/test-map.cpp b/src/test-map.cpp
index 0481ad35..fcc868d1 100644
--- a/src/test-map.cpp
+++ b/src/test-map.cpp
@@ -40,9 +40,7 @@ int main(int argc, char **argv)
     SDL_WM_GrabInput(SDL_GRAB_ON);
 
     /* Initialise timer */
-    Uint32 start, ticks;
-    start = ticks = SDL_GetTicks();
-    int frames = 0;
+    Uint32 ticks = SDL_GetTicks();
 
     /* Initialise OpenGL */
     Video::Setup(video->w, video->h);
@@ -56,7 +54,10 @@ int main(int argc, char **argv)
 
     while (!game->Finished())
     {
-        float const delta_time = 33.33333f;
+        /* Compute delta time */
+        Uint32 newticks = SDL_GetTicks();
+        float delta_time = (float)(newticks - ticks);
+        ticks = newticks;
 
         /* Tick the game */
         Ticker::TickGame(delta_time);
@@ -67,14 +68,10 @@ int main(int argc, char **argv)
         SDL_GL_SwapBuffers();
 
         /* Clamp to desired framerate */
-        while (SDL_GetTicks() < ticks + (delta_time - 0.5f))
+        while (SDL_GetTicks() < ticks + (33.33333f - 0.5f))
             SDL_Delay(1);
-        ticks = SDL_GetTicks();
-        frames++;
     }
 
-    Uint32 total = SDL_GetTicks() - start;
-    printf("%f fps\n", 1000.0f * frames / total);
     SDL_Quit();
 
     return EXIT_SUCCESS;