SDL/src/video/windows/SDL_windowsevents.h
Francesco Abbate 0dd7024d55 Modifies WaitEvent and WaitEventTimeout to actually wait instead of polling
When possible use native os functions to make a blocking call waiting for
an incoming event. Previous behavior was to continuously poll the event
queue with a small delay between each poll.

The blocking call uses a new optional video driver event,
WaitEventTimeout, if available. It is called only if an window
already shown is available. If present the window is designated
using the variable wakeup_window to receive a wakeup event if
needed.

The WaitEventTimeout function accept a timeout parameter. If
positive the call will wait for an event or return if the timeout
expired without any event. If the timeout is zero it will
implement a polling behavior. If the timeout is negative the
function will block indefinetely waiting for an event.

To let the main thread sees events sent form a different thread
a "wake-up" signal is sent to the main thread if the main thread
is in a blocking state. The wake-up event is sent to the designated
wakeup_window if present.

The wake-up event is sent only if the PushEvent call is coming
from a different thread. Before sending the wake-up event
the ID of the thread making the blocking call is saved using the
variable blocking_thread_id and it is compared to the current
thread's id to decide if the wake-up event should be sent.

Two new optional video device methods are introduced:

WaitEventTimeout
SendWakeupEvent

in addition the mutex

wakeup_lock

which is defined and initialized but only for the drivers supporting the
methods above.

If the methods are not present the system behaves as previously
performing a periodic polling of the events queue.

The blocking call is disabled if a joystick or sensor is detected
and falls back to previous behavior.
2021-06-04 13:50:50 -07:00

40 lines
1.5 KiB
C

/*
Simple DirectMedia Layer
Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"
#ifndef SDL_windowsevents_h_
#define SDL_windowsevents_h_
extern LPTSTR SDL_Appname;
extern Uint32 SDL_Appstyle;
extern HINSTANCE SDL_Instance;
extern LRESULT CALLBACK WIN_KeyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam);
extern LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam,
LPARAM lParam);
extern void WIN_PumpEvents(_THIS);
extern void WIN_SendWakeupEvent(_THIS, SDL_Window *window);
extern int WIN_WaitEventTimeout(_THIS, int timeout);
#endif /* SDL_windowsevents_h_ */
/* vi: set ts=4 sw=4 expandtab: */