Capture Minimize event for Firemonkey form?

Question

I'm trying to do a very simple task... Detect when my form has been minimized. But it seems Firemonkey has absolutely no way of handling this. I've tried to use AllocateHWnd to intercept WM_SYSCOMMAND messages, but all I get is WM_ACTIVATEAPP messages and nothing else.

CreateForm:

AllocateHWnd(WndProcHandler);

WndProcHandler:

procedure TfrmMain.WndProcHandler(var Message: TMessage);
begin
  if Message.msg = WM_SYSCOMMAND then
    OutputDebugStringA('got command');
end;

Answer 1

Got it working with the following code. Looks for the WM_SIZE command and SIZE_MINIMIZED parameter to detect all minimising events.

uses
  Winapi.Windows, Winapi.Messages;

var
  WndProcHook: THandle;

function WndProc(Code: integer; WParam, LParam: LongInt): LRESULT; stdcall;
var
  msg: TCWPRetStruct;
begin;
  if (Code >= HC_ACTION) and (LParam > 0) then begin
    msg := PCWPRetStruct(LParam)^;
    if (msg.Message = WM_SIZE) and (msg.WParam = SIZE_MINIMIZED) then begin
      // Application has been minimized
      // Check msg.wnd = WindowHandleToPlatform(Form1.Handle).wnd if necessary
    end;
  end;
  result := CallNextHookEx(WndProcHook, Code, WParam, LParam)
end;

initialization
  WndProcHook := SetWindowsHookEx(WH_CALLWNDPROCRET, @WndProc, 0, GetCurrentThreadId);

finalization
  UnhookWindowsHookEx(WndProcHook);