Remove window requirement for all event functions

This lets an application wait for non-window events without needing to
create a window.

Fixes #1317.

README.md

@@ -189,6 +189,8 @@ information on what to include when reporting a bug.
 - Removed `GLFW_USE_RETINA` compile-time option
 - Removed `GLFW_USE_CHDIR` compile-time option
 - Removed `GLFW_USE_MENUBAR` compile-time option
+- Removed requirement of at least one window for `glfwWaitEvents` and
+  `glfwPostEmptyEvent` (#1317)
 - Bugfix: Calling `glfwMaximizeWindow` on a full screen window was not ignored
 - Bugfix: `GLFW_INCLUDE_VULKAN` could not be combined with the corresponding
           OpenGL and OpenGL ES header macros

docs/input.dox

@@ -57,8 +57,7 @@ glfwWaitEvents();
 
 It puts the thread to sleep until at least one event has been received and then
 processes all received events.  This saves a great deal of CPU cycles and is
-useful for, for example, editing tools.  There must be at least one GLFW window
-for this function to sleep.
+useful for, for example, editing tools.
 
 If you want to wait for events but have UI elements or other tasks that need
 periodic updates, @ref glfwWaitEventsTimeout lets you specify a timeout.

include/GLFW/glfw3.h

@@ -3718,10 +3718,6 @@ GLFWAPI void glfwPollEvents(void);
  *  GLFW will pass those events on to the application callbacks before
  *  returning.
  *
- *  If no windows exist, this function returns immediately.  For synchronization
- *  of threads in applications that do not create windows, use your threading
- *  library of choice.
- *
  *  Event processing is not required for joystick input to work.
  *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
@@ -3769,10 +3765,6 @@ GLFWAPI void glfwWaitEvents(void);
  *  GLFW will pass those events on to the application callbacks before
  *  returning.
  *
- *  If no windows exist, this function returns immediately.  For synchronization
- *  of threads in applications that do not create windows, use your threading
- *  library of choice.
- *
  *  Event processing is not required for joystick input to work.
  *
  *  @param[in] timeout The maximum amount of time, in seconds, to wait.
@@ -3799,10 +3791,6 @@ GLFWAPI void glfwWaitEventsTimeout(double timeout);
  *  This function posts an empty event from the current thread to the event
  *  queue, causing @ref glfwWaitEvents or @ref glfwWaitEventsTimeout to return.
  *
- *  If no windows exist, this function returns immediately.  For synchronization
- *  of threads in applications that do not create windows, use your threading
- *  library of choice.
- *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
  *  GLFW_PLATFORM_ERROR.
  *

src/window.c

@@ -1078,10 +1078,6 @@ GLFWAPI void glfwPollEvents(void)
 GLFWAPI void glfwWaitEvents(void)
 {
     _GLFW_REQUIRE_INIT();
-
-    if (!_glfw.windowListHead)
-        return;
-
     _glfwPlatformWaitEvents();
 }
 
@@ -1104,10 +1100,6 @@ GLFWAPI void glfwWaitEventsTimeout(double timeout)
 GLFWAPI void glfwPostEmptyEvent(void)
 {
     _GLFW_REQUIRE_INIT();
-
-    if (!_glfw.windowListHead)
-        return;
-
     _glfwPlatformPostEmptyEvent();
 }