X11 event loop polling

dev/CMakeLists.txt

@@ -45,7 +45,8 @@ else()
 endif()
 
 add_custom_target(CopyHeader
-    COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_BINARY_DIR}/olcPixelGameEngine3.h ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
+    BYPRODUCTS ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different ${CMAKE_BINARY_DIR}/olcPixelGameEngine3.h ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
     DEPENDS olcPixelGameEngine3.h
 )
 

dev/src/host_lin_x11.cpp

@@ -131,6 +131,10 @@ namespace olc::host
             return nullptr;
         };
 
+        // Create a pollfd that we will use later to wait for events to appear on the queue
+        // preventing the event loop from becoming a busy loop
+        pollfd x11_connection_fd {.fd = ConnectionNumber(olc_Display), .events = POLLIN};
+
         X11::XEvent xev;
         while(systemActive){
             while (XPending(olc_Display))
@@ -297,6 +301,9 @@ namespace olc::host
                     }
                 }
             }
+
+            // Wait until an event appears on the x11 event queue file descriptor
+            poll(&x11_connection_fd, 1, -1);
         }
 
         systemActive = false;

dev/src/host_lin_x11.h

@@ -16,6 +16,7 @@
 
 //! START DECLARATION
 #include <GL/gl.h>
+#include <poll.h>
 namespace X11
 {
 #include <X11/X.h>

olcPixelGameEngine3.h

@@ -5965,6 +5965,7 @@ namespace olc
 #if OLC_HOST == OLC_HOST_LINUX_X11
 
 #include <GL/gl.h>
+#include <poll.h>
 namespace X11
 {
 #include <X11/X.h>
@@ -12365,6 +12366,10 @@ namespace olc::host
             return nullptr;
         };
 
+        // Create a pollfd that we will use later to wait for events to appear on the queue
+        // preventing the event loop from becoming a busy loop
+        pollfd x11_connection_fd {.fd = ConnectionNumber(olc_Display), .events = POLLIN};
+
         X11::XEvent xev;
         while(systemActive){
             while (XPending(olc_Display))
@@ -12531,6 +12536,9 @@ namespace olc::host
                     }
                 }
             }
+
+            // Wait until an event appears on the x11 event queue file descriptor
+            poll(&x11_connection_fd, 1, -1);
         }
 
         systemActive = false;