Reduce cpu usage when ui is not visible

include/Overlay.hpp

@@ -39,7 +39,8 @@ namespace gsr {
 
         void handle_events();
         void on_event(mgl::Event &event);
-        void draw();
+        // Returns false if not visible
+        bool draw();
 
         void show();
         void hide();

src/Overlay.cpp

@@ -279,20 +279,20 @@ namespace gsr {
         process_key_bindings(event);
     }
 
-    void Overlay::draw() {
+    bool Overlay::draw() {
         update_notification_process_status();
         update_gsr_process_status();
 
         if(!visible)
-            return;
+            return false;
 
         if(page_stack.empty()) {
             hide();
-            return;
+            return false;
         }
 
         if(!window)
-            return;
+            return false;
 
         window->clear();
 
@@ -312,6 +312,8 @@ namespace gsr {
         page_stack.draw(*window, mgl::vec2f(0.0f, 0.0f));
 
         window->display();
+
+        return true;
     }
 
     void Overlay::show() {

src/main.cpp

@@ -7,6 +7,7 @@
 
 #include <unistd.h>
 #include <signal.h>
+#include <thread>
 
 #include <X11/keysym.h>
 #include <mglpp/mglpp.hpp>
@@ -160,7 +161,8 @@ int main(int argc, char **argv) {
 
         global_hotkeys.poll_events();
         overlay->handle_events();
-        overlay->draw();
+        if(!overlay->draw())
+            std::this_thread::sleep_for(std::chrono::milliseconds(50));
     }
 
     fprintf(stderr, "info: shutting down!\n");