Use select on x11 display instead of sleeping and use xdamage again

project.conf

@@ -18,7 +18,7 @@ libavformat = ">=58"
 libavutil = ">=56.2"
 x11 = ">=1"
 xcomposite = ">=0.2"
-#xdamage = "1"
+xdamage = "1"
 
 # TODO: Remove this dependency, this is needed right now for glfwMakeContextCurrent
 glfw3 = "3"

src/main.cpp

@@ -37,6 +37,7 @@
 #include <GLFW/glfw3.h>
 
 #include <X11/extensions/Xcomposite.h>
+#include <X11/extensions/Xdamage.h>
 
 extern "C" {
 #include <libavcodec/avcodec.h>
@@ -839,6 +840,16 @@ int main(int argc, char **argv) {
 
     XSelectInput(dpy, src_window_id, StructureNotifyMask);
 
+    int damage_event;
+    int damage_error;
+    if (!XDamageQueryExtension(dpy, &damage_event, &damage_error)) {
+        fprintf(stderr, "Error: XDamage is not supported by your X11 server\n");
+        return 1;
+    }
+
+    Damage damage = XDamageCreate(dpy, src_window_id, XDamageReportNonEmpty);
+    XDamageSubtract(dpy, damage,None,None);
+
     int frame_count = 0;
 
     CUresult res;
@@ -975,15 +986,34 @@ int main(int argc, char **argv) {
         }, av_format_context, audio_stream, audio_frame_buf, &sound_device, audio_frame, &write_output_mutex);
     }
 
+    int x11_fd = ConnectionNumber(dpy);
+    fd_set in_fds;
+    struct timeval tv;
+
     bool redraw = true;
     XEvent e;
     while (running) {
-        double frame_start = glfwGetTime();
-
-        /*glClear(GL_COLOR_BUFFER_BIT);*/
         glfwPollEvents();
 
-        if (XCheckTypedWindowEvent(dpy, src_window_id, ConfigureNotify, &e) && e.xconfigure.window == src_window_id) {
+        FD_ZERO(&in_fds);
+        FD_SET(x11_fd, &in_fds);
+
+        /* Wake up thread every frame even if no events are received */
+        tv.tv_usec = 1000 * (1000.0 / (double)fps);
+        tv.tv_sec = 0;
+
+        int num_ready_fds = select(x11_fd + 1, &in_fds, NULL, NULL, &tv);
+        if (num_ready_fds < 0) {
+            //fprintf(stderr, "Window manager error: select failed on display file descriptor!\n");
+            continue;
+        }
+
+        /*glClear(GL_COLOR_BUFFER_BIT);*/
+
+        while(num_ready_fds > 0 && XPending(dpy)) {
+            XNextEvent(dpy, &e);
+
+            if (e.type == ConfigureNotify && e.xconfigure.window == src_window_id) {
                 // Window resize
                 if(e.xconfigure.width != window_width || e.xconfigure.height != window_height) {
                     window_width = e.xconfigure.width;
@@ -993,7 +1023,19 @@ int main(int argc, char **argv) {
                 }
             }
 
+            if (e.type == damage_event + XDamageNotify) {
+                // fprintf(stderr, "Redraw!\n");
+                XDamageNotifyEvent *de = (XDamageNotifyEvent *)&e;
+                // de->drawable is the window ID of the damaged window
+                XserverRegion region = XFixesCreateRegion(dpy, nullptr, 0);
+                // Subtract all the damage, repairing the window
+                XDamageSubtract(dpy, de->damage, None, region);
+                XFixesDestroyRegion(dpy, region);
+
+                ++fps_counter;
                 redraw = true;
+            }
+        }
 
         const double window_resize_timeout = 1.0; // 1 second
         if(window_resized && glfwGetTime() - window_resize_timer >= window_resize_timeout) {
@@ -1030,8 +1072,6 @@ int main(int argc, char **argv) {
             }
         }
 
-        ++fps_counter;
-
         double time_now = glfwGetTime();
         double frame_timer_elapsed = time_now - frame_timer_start;
         double elapsed = time_now - start_time;
@@ -1087,12 +1127,6 @@ int main(int argc, char **argv) {
         }
 
         // av_frame_free(&frame);
-
-        double frame_end = glfwGetTime();
-        double frame_sleep_fps = 1.0 / 250.0;
-        double sleep_time = frame_sleep_fps - (frame_end - frame_start);
-        if(sleep_time > 0.0)
-            usleep(sleep_time * 1000.0 * 1000.0);
     }
 
 	running = 0;