added windowGetDeltaTime

main.c

@@ -19,11 +19,15 @@ int main(void)
 {
     Window * w = openWindow("Window", 800, 600);
 
+    windowSetFps(w, 300);
+
     while (!windowKeyPressed(w, WINDOW_KEY_ESC)) {
         windowHandleEvents(w);
 
         handleInput(w);
 
+        printf("fps: %lf\n", 1 / windowGetDeltaTime(w));
+
         glClearColor(0.1, 0.2, 0.3, 1);
         glClear(GL_COLOR_BUFFER_BIT);
         glViewport(0, 0, 800, 600);

src/openwindow.c

@@ -3,7 +3,9 @@
 #include "openwindow.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 int initOpenGL() {
     if (getOpenGLProcs() == 0) return -1;
@@ -175,12 +177,20 @@ int init(Window * window, const char * name, size_t width, size_t height) {
     XSync(window->x.display, False);
     glXMakeCurrent(window->x.display, window->x.window, window->glx.context);
 
+    //TODO: Check for errors
+    PFNGLXSWAPINTERVALEXTPROC glXSwapIntervalEXT = (PFNGLXSWAPINTERVALEXTPROC)
+                     glXGetProcAddress((const GLubyte *)"glXSwapIntervalEXT");
+
+    if (glXSwapIntervalEXT) glXSwapIntervalEXT(window->x.display, window->x.window, 0);
+
     return 0;
 }
 
 Window * openWindow(const char * name, size_t width, size_t height) {
     Window * w = calloc(1, sizeof(Window));
     w->fps = WINDOW_DEFAULT_FPS;
+    w->dt.t1  = calloc(1, sizeof(struct timespec));
+    w->dt.t2  = calloc(1, sizeof(struct timespec));
 
     if (init(w, name, width, height) < 0) {
         fprintf(stderr, "Failed to initialize window: X11 error!\n");
@@ -199,9 +209,19 @@ void windowSetFps(Window * window, uint32_t fps) {
     window->fps = fps;
 }
 
+double windowGetDeltaTime(Window *window) {
+    return window->dt.dt;
+}
+
 void windowDraw(Window * window) {
     glXSwapBuffers(window->x.display, window->x.window);
-    usleep(1 / window->fps);
+
+    usleep(((float)1 / (window->fps + 1)) * 1e6);
+    clock_gettime(CLOCK_MONOTONIC, window->dt.t2);
+
+    window->dt.dt = (double) (window->dt.t2->tv_sec - window->dt.t1->tv_sec) + (window->dt.t2->tv_nsec - window->dt.t1->tv_nsec) / 1e9;
+
+    clock_gettime(CLOCK_MONOTONIC, window->dt.t1);
 }
 
 void resetIOState(Window * window) {
@@ -209,6 +229,7 @@ void resetIOState(Window * window) {
 }
 
 void windowHandleEvents(Window * window) {
+
     XEvent xev = {0};
 
     resetIOState(window);
@@ -227,6 +248,10 @@ void closeWindow(Window * window) {
     XFreeColormap(window->x.display, window->x.cmap);
     XDestroyWindow(window->x.display, window->x.window);
     XCloseDisplay(window->x.display);
+
+    free(window->dt.t1);
+    free(window->dt.t2);
+
     free(window);
 }
 
@@ -414,6 +439,10 @@ int init(Window * window, const char * title, size_t width, size_t height) {
 
     SetTimer(window->wgl.window, 1, (1 / window->fps) * 1000, NULL);
 
+    //TODO: Check for errors
+    PFNWGLSWAPINTERVALEXTPROC wglSwapIntervalEXT = (void *)wglGetProcAddress("wglSwapIntervalEXT");
+    if (wglSwapIntervalEXT) wglSwapIntervalEXT(0);
+
     return 0;
 }
 
@@ -434,8 +463,25 @@ Window * openWindow(const char * name, size_t width, size_t height) {
     return w;
 }
 
+void windowSetFps(Window * window, uint32_t fps) {
+    window->fps = fps;
+}
+
+double windowGetDeltaTime(Window * window) {
+    return window->dt.dt;
+}
+
 void windowDraw(Window * window) {
     SwapBuffers(window->wgl.display);
+
+    Sleep((uint32_t)(((double)1 / (window->fps + 1)) * 1e3));
+
+    QueryPerformanceFrequency(&window->dt.freq);
+    QueryPerformanceCounter(&window->dt.t2);
+
+    window->dt.dt = (double) (window->dt.t2.QuadPart - window->dt.t1.QuadPart) / window->dt.freq.QuadPart;
+
+    QueryPerformanceCounter(&window->dt.t1);
 }
 
 void resetIOState(Window * window) {

src/openwindow.h

@@ -9,6 +9,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <time.h>
 
 int gladLoadGL(void);
 
@@ -40,12 +41,19 @@ typedef struct {
     char last[WINDOW_KEY_COUNT];
 } WindowIOState;
 
+typedef struct {
+    struct timespec * t1;
+    struct timespec * t2;
+    double dt;
+} WindowDeltaTime;
+
 typedef struct Window Window;
 
 typedef struct Window {
     WindowIOState io;
     GLX glx;
     X11 x;         
+    WindowDeltaTime dt;
     uint32_t fps;
 } Window;
 
@@ -114,11 +122,19 @@ typedef struct {
     BYTE last[WINDOW_KEY_COUNT];
 } WindowIOState;
 
+typedef struct {
+    LARGE_INTEGER t1;
+    LARGE_INTEGER t2;
+    LARGE_INTEGER freq;
+    double dt;
+} WindowDeltaTime;
+
 typedef struct Window Window;
 
 typedef struct Window {
     WindowIOState io;
     WGL wgl;
+    WindowDeltaTime dt;
     uint32_t fps;
 } Window;
 
@@ -175,6 +191,7 @@ bool windowKeyAlt(Window * window);
 
 Window * openWindow(const char * name, size_t width, size_t height);
 void windowSetFps(Window * window, uint32_t fps);
+double windowGetDeltaTime(Window * window);
 void windowDraw(Window * window);
 void windowHandleEvents(Window * window);
 void closeWindow(Window * window);