engine: Fix rendering under 1FPS

Refactor a bit, add Period to optimize FPS division

It was also tested in Ubuntu-Core on Pi3 at 0.30 FPS
Using VC4 V3D 2.1 backend from GL 2.1 Mesa 20.2.6.

While Ubuntu classic on weston is way faster,
I'll may check again with Mir on next classic Release.

Relate-to: #21
Signed-off-by: Philippe Coval <[email protected]>
Change-Id: I544a7407d0cec5eb3def99c1353a7eb27193de9f

base/Engine.cpp

@@ -11,6 +11,8 @@
 #include <cstring>
 #include <ctime>
 
+#include <iostream>
+
 #if EM_THREADS
 #include <sched.h>
 #endif
@@ -45,7 +47,7 @@
 #endif
 #endif
 
-volatile int g_iStartTime = -1;
+volatile unsigned int g_iStartTime = 0;
 //volatile int g_iDesiredTime = -1;
 volatile int g_iLastRender = 0;
 
@@ -71,7 +73,7 @@ extern "C" {
 #endif
 
 #if EM_USE_SDL
-#define GET_TIME (signed)SDL_GetTicks()
+#define GET_TIME ((unsigned int) SDL_GetTicks())
 #endif
 
 #if EM_USE_ALLEGRO
@@ -82,7 +84,10 @@ float Engine::m_fFps = 0.0f;
 
 Engine * Engine::p_Engine = NULL;
 
-Engine::Engine(int & argc, char *argv[]) {
+Engine::Engine(int & argc, char *argv[])
+  : Group{},
+    m_iPeriod(1000/50)
+{
   Config * config = Config::getInstance();
   config->loadArgs(argc, argv);
 
@@ -339,17 +344,25 @@ void Engine::delay(int ms) {
 #endif
 }
 
-bool Engine::nextTickFPS(int fps) {
-  // default 100 FPS
-  int delay = 10;
-  if (fps > 0) {
-    delay = 1000/fps;
+void Engine::setSpeed(int fps) {
+  m_iPeriod = 1000/fps;
+}
+
+bool Engine::nextTick() {
+  if (GET_TIME >= g_iStartTime + 1000) {
+#ifdef EM_DEBUG
+    cerr << "warning: Too slow (less than 1FPS) :"
+	 << g_iStartTime << " " << GET_TIME << " +" << m_iPeriod << endl;
+#endif
+    tick(); // Animate world once before rendering
+    g_iStartTime = GET_TIME; // Trying to catch up
+    return false;
   }
-  if ((g_iStartTime + delay) <= GET_TIME) {
-    g_iStartTime += delay;
-    return true;
+  if (GET_TIME <= (g_iStartTime + m_iPeriod)) {
+    return false;
   }
-  return false;
+  g_iStartTime += m_iPeriod;
+  return true;
 }
 
 void Engine::resetTick() {

base/Engine.h

@@ -50,9 +50,10 @@ class Engine : public Group {
   void setLightning(float diffuse, float ambient);
   void addLight(Light*);
   /** Use this function to limit the main loop to a desired frame rate.
-   * @return false if the thread is behind schedule else true. 
-   ** Available FPS: 100, 50, 40, 33, 25, 20 */
-  bool nextTickFPS(int fps);
+   * @return false if the thread is behind schedule else true. see limitFPS */
+  bool nextTick();
+  /** Available FPS: 100, 50, 40, 33, 25, 20 */
+  void setSpeed(int fps=25*4);
   void resetTick();
   //  bool limitFPS(int fps);
   void delay(int ms);
@@ -68,9 +69,11 @@ class Engine : public Group {
   void resumeTickThread();
   void endTickThread();
 #endif
- private:
+protected:
+  unsigned int m_iPeriod; ///<  Allocated time for tick
+private:
   static float m_fFps;
-	static Engine * p_Engine;
+  static Engine * p_Engine;
 };
 
 #endif // ENGINE_H

src/Pinball.cpp

@@ -825,6 +825,7 @@ int Pinball::setup(int argc, char *argv[])
   // cerr<<"log: pinball: Draw to the screen"<<endl;
   miCount = 0;
 
+  mpEngine->setSpeed(25*8);
   mpEngine->resetTick();
   mpEngine->swap();
 
@@ -889,7 +890,7 @@ int Pinball::loop()
   if (Keyboard::isKeyDown(SDLK_r)) {
     SendSignal(PBL_SIG_RESET_ALL, 0, mpEngine, NULL);
   }
-  if (mpEngine->nextTickFPS(200)) {
+  if (mpEngine->nextTick()) {
     mpEngine->tick();
   } else {
     mpEngine->render();

test/explode.cpp

@@ -73,7 +73,7 @@ int main(int argc, char *argv[]) {
 
 	engine->resetTick();
 	while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-	  if (engine->nextTickFPS(50)) {
+	  if (engine->nextTick()) {
 	    engine->tick();
 	  } else {
 	    engine->render();

test/load.cpp

@@ -55,7 +55,7 @@ int main(int argc, char *argv[]) {
 	engine->resetTick();
 	bool keydown = false;
 	while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-	  if (engine->nextTickFPS(50)) {
+	  if (engine->nextTick()) {
 	    engine->tick();
 			Group * g = engine->getGroup(1);
 			if (g != NULL) {

test/menu.cpp

@@ -90,7 +90,7 @@ int main(int argc, char *argv[]) {
   bool done = false;
   engine->resetTick();
   while (!Keyboard::isKeyDown(SDLK_SPACE) && !done) {
-    if (engine->nextTickFPS(50)) {
+    if (engine->nextTick()) {
       engine->tick();
     } else {
       engine->render();

test/misc.cpp

@@ -72,8 +72,9 @@ int main(int argc, char *argv[]) {
   Vertex3D vtx = {0.0f, 0.0f, 0.0f};
   Vertex3D vtxDist;
   engine->resetTick();
+  engine->setSpeed(10);
   while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-    if (engine->nextTickFPS(10)) {
+    if (engine->nextTick()) {
       engine->tick();
       float sqrdist = CollisionVisitor::getInstance()->
 	vtxPolySqrDist(vtx, tri->getPolygon(0), vtxDist);

test/scale.cpp

@@ -59,8 +59,8 @@ int main(int argc, char *argv[]) {
   float x=0, y=0, z=0;
   float dx=-1, dy=-1, dz=-1;
   engine->resetTick();
-	while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-    if (engine->nextTickFPS(50)) {
+  while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
+    if (engine->nextTick()) {
       if (x > 2) dx=-0.012;
       if (y > 2) dy=-0.021;
       if (z > 2) dz=-0.027;

test/signal.cpp

@@ -74,7 +74,7 @@ int main(int argc, char *argv[]) {
       // multicast a signal with delay
       SendSignal(2, 50, engine, NULL);
     }
-    if (engine->nextTickFPS(50)) {
+    if (engine->nextTick()) {
       engine->tick();
     } else {
       engine->render();

test/texture.cpp

@@ -73,7 +73,7 @@ int main(int argc, char *argv[]) {
 
 	engine->resetTick();
 	while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-	  if (engine->nextTickFPS(50)) {
+	  if (engine->nextTick()) {
 	    engine->tick();
 	  } else {
 	    engine->render();

test/trans.cpp

@@ -52,7 +52,7 @@ int main(int argc, char *argv[]) {
 
   engine->resetTick();
   while (!Keyboard::isKeyDown(SDLK_ESCAPE)) {
-    if (engine->nextTickFPS(50)) {
+    if (engine->nextTick()) {
       engine->tick();
     } else {
       engine->render();