Linux: Fix a regression in 0.14.0 that caused the event loop to tick continuously, wasting CPU even when idle

Fixes #1782

docs/changelog.rst

@@ -43,6 +43,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 
 - macOS: Fix a rare deadlock causing kitty to hang (:iss:`1779`)
 
+- Linux: Fix a regression in 0.14.0 that caused the event loop to tick
+  continuously, wasting CPU even when idle (:iss:`1782`)
+
 
 0.14.2 [2019-06-09]
 ---------------------

glfw/backend_utils.c

@@ -278,6 +278,7 @@ int
 pollForEvents(EventLoopData *eld, double timeout) {
     int read_ok = 0;
     timeout = prepareForPoll(eld, timeout);
+    EVDBG("pollForEvents final timeout: %.3f", timeout);
     int result;
     double end_time = monotonic() + timeout;
 

kitty/child-monitor.c

@@ -471,8 +471,6 @@ pyset_iutf8(ChildMonitor *self, PyObject *args) {
 #undef INCREF_CHILD
 #undef DECREF_CHILD
 
-static double last_render_at = -DBL_MAX;
-
 extern void cocoa_update_title(PyObject*);
 
 static inline void
@@ -631,6 +629,7 @@ no_render_frame_received_recently(OSWindow *w, double now, double max_wait) {
 
 static inline void
 render(double now) {
+    static double last_render_at = -DBL_MAX;
     double time_since_last_render = now - last_render_at;
     if (time_since_last_render < OPT(repaint_delay)) {
         set_maximum_wait(OPT(repaint_delay) - time_since_last_render);
@@ -884,9 +883,13 @@ set_cocoa_pending_action(CocoaPendingAction action, const char *wd) {
 static void process_global_state(void *data);
 
 static void
-do_state_check(id_type timer_id UNUSED, void *data) {
-    ChildMonitor *self = data;
-    process_global_state(self);
+do_state_check(id_type timer_id UNUSED, void *data UNUSED) {
+#ifdef __APPLE__
+    process_global_state(data);
+#endif
+    // We don't actually do anything here as process_global_state
+    // will be called when the loop ticks on Linux
+
 }
 
 static id_type state_check_timer = 0;