Windows api: wait until all keyboard keys are released system wide

问题

I have made an application in Delphi that handles some defined system wide hotkeys, works perfectly. However, for some hotkey functionality I have to trigger/simulate some keyboard strokes such as ALT+ENTER. This works great when the user releases the hotkey keys directly, but when the keys are still pressed by the user the keyboard simulation fail.

Is there a way (with windows API) to check if all keys are released before I process a keyboard simulation?

回答1:

Use GetAsyncKeyState as this API reflects the true current state of the keyboard, and not when your app last called GetMessage. Just write a loop that calls it for each value between 0 and 0xFF.

If the most significant bit is set, the key is down

回答2:

Thanks go to @David Ching and @David Heffernan (two Davids!) The solution is not only to test keyboard input but also mouse input or better, the state of input devices.

The mouse is also included because of:

  { Virtual Keys, Standard Set }
  VK_LBUTTON = 1;
  VK_RBUTTON = 2;
  VK_MBUTTON = 4;  { NOT contiguous with L & RBUTTON }

So, if don't want to test mousebuttons you have to exclude it from the loop. It's better to check these also because there are hotkeys that must be used with the mouse. It's better to check everything on input is idle.

function isUserInputDevicesInUse() : Boolean;  // Keyboard pressed / mouse pressed?
var
 i            : LongInt;

begin
 i:=256;
 Result:=FALSE;

 while( i > 0 ) and ( NOT Result ) do
 begin
  Dec( i );
  Result:=( GetAsyncKeyState(i) < 0 );
 end;
end;

function isUserInputDevicesIdle() : Boolean;
begin
 Result:=NOT isUserInputDevicesInUse();
end;

来源：https://stackoverflow.com/questions/32143747/windows-api-wait-until-all-keyboard-keys-are-released-system-wide