Prevent OS sleep and display blanking while SDR is running

Add PowerInhibit.pas with InhibitSleep/UninhibitSleep:
- Windows: SetThreadExecutionState (kernel32, no child process)
- macOS: caffeinate -d -i -s -w <PID> (auto-exits on crash via -w flag)
- Linux: systemd-inhibit with kill-0 poll loop (releases within 5s on crash)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

MainForm.pas

@@ -39,7 +39,8 @@ uses
   WinFirewall,
   BoardUtils, WisdomBuilder, UISync,
   FlatEdit, FMRepeater,
-  ChannelStore, ChannelsForm;
+  ChannelStore, ChannelsForm,
+  PowerInhibit;
 
 const
   CLR_BG         = TColor($00101010);
@@ -1464,6 +1465,7 @@ begin
       FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), 0, False, True, True);
       FNetwork.SetRunAndFreq(False, XvtrTranslate(FCenterFreq), XvtrTranslate(FCenterFreq), 0);
       FRunning      := False;
+      UninhibitSleep;
       FTransmitting := False;
       if FWDSPReady then FDSPEngine.SetTXRun(False);
     end;
@@ -3046,6 +3048,7 @@ begin
       BtnStartStop.Caption := 'START';
       StyleButton(BtnStartStop, False);
       FRunning := False;
+      UninhibitSleep;
       FNetwork.SetRunAndFreq(False, XvtrTranslate(FCenterFreq), XvtrTranslate(FCenterFreq), 0);
       SetRadioOfflineStatus('Hardware timeout');
       BtnMOX.Enabled := False;
@@ -3057,6 +3060,7 @@ begin
       BtnStartStop.Caption := 'START';
       StyleButton(BtnStartStop, False);
       FRunning := False;
+      UninhibitSleep;
       FNetwork.SetRunAndFreq(False, XvtrTranslate(FCenterFreq), XvtrTranslate(FCenterFreq), 0);
       SetRadioOfflineStatus('Connection lost');
       BtnMOX.Enabled := False;
@@ -3897,6 +3901,7 @@ begin
       FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), 0, False, True, True);
       FNetwork.SetRunAndFreq(False, XvtrTranslate(FCenterFreq), XvtrTranslate(FCenterFreq), 0);
       FRunning := False;
+      UninhibitSleep;
       FTransmitting := False;
       if FWDSPReady then FDSPEngine.SetTXRun(False);
       StyleButton(BtnMOX, False);
@@ -4220,6 +4225,7 @@ begin
   FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), FDriveLevel, False, True, True);
   FNetwork.SetRunAndFreq(True, XvtrTranslate(FCenterFreq), XvtrTranslate(FCenterFreq), FDriveLevel);
   FRunning       := True;
+  InhibitSleep;
   FRXStartTime   := GetTickCount64;
   FRXLastPktTime := 0;
   FRXPacketCount := 0;

PowerInhibit.pas

@@ -0,0 +1,109 @@
+unit PowerInhibit;
+
+{$IFDEF FPC}
+  {$MODE Delphi}
+{$ENDIF}
+
+{
+  Prevents OS idle sleep and display blanking while the SDR is running.
+
+  Windows : SetThreadExecutionState (kernel32) — one call, no child process.
+  macOS   : spawns /usr/bin/caffeinate -d -i -s -w <OurPID>
+              caffeinate exits automatically when our process exits (crash-safe).
+  Linux   : spawns systemd-inhibit in --mode=block with a shell loop that
+              polls kill -0 <OurPID> so the inhibitor is released within
+              ~5 s even on a crash (no orphan leak).
+}
+
+interface
+
+procedure InhibitSleep;
+procedure UninhibitSleep;
+
+implementation
+
+uses
+  SysUtils, Process
+  {$IFDEF WINDOWS}, Windows{$ENDIF};
+
+{$IFDEF WINDOWS}
+type
+  EXECUTION_STATE = DWORD;
+const
+  ES_CONTINUOUS       = DWORD($80000000);
+  ES_SYSTEM_REQUIRED  = DWORD($00000001);
+  ES_DISPLAY_REQUIRED = DWORD($00000002);
+function SetThreadExecutionState(esFlags: EXECUTION_STATE): EXECUTION_STATE; stdcall;
+  external 'kernel32.dll' name 'SetThreadExecutionState';
+{$ENDIF}
+
+var
+  FInhibitProc: TProcess = nil;
+
+procedure InhibitSleep;
+{$IF DEFINED(DARWIN) OR DEFINED(LINUX)}
+var
+  PidStr: string;
+{$ENDIF}
+begin
+{$IFDEF WINDOWS}
+  SetThreadExecutionState(ES_CONTINUOUS or ES_SYSTEM_REQUIRED or ES_DISPLAY_REQUIRED);
+{$ENDIF}
+
+{$IF DEFINED(DARWIN) OR DEFINED(LINUX)}
+  if FInhibitProc <> nil then Exit;
+  PidStr := IntToStr(GetProcessID);
+  FInhibitProc := TProcess.Create(nil);
+  try
+{$IFDEF DARWIN}
+    FInhibitProc.Executable := '/usr/bin/caffeinate';
+    FInhibitProc.Parameters.Add('-d');   // prevent display sleep
+    FInhibitProc.Parameters.Add('-i');   // prevent idle sleep
+    FInhibitProc.Parameters.Add('-s');   // prevent system sleep (AC power)
+    FInhibitProc.Parameters.Add('-w');   // watch our PID — caffeinate auto-exits with us
+    FInhibitProc.Parameters.Add(PidStr);
+{$ENDIF}
+{$IFDEF LINUX}
+    // systemd-inhibit holds the lock until the sh loop exits.
+    // The loop polls kill -0 <PID> every 5 s, so if we crash the
+    // inhibitor is released within 5 s (no orphan process leak).
+    FInhibitProc.Executable := 'systemd-inhibit';
+    FInhibitProc.Parameters.Add('--what=idle:sleep:handle-lid-switch');
+    FInhibitProc.Parameters.Add('--why=SDR running');
+    FInhibitProc.Parameters.Add('--who=ewsdr');
+    FInhibitProc.Parameters.Add('--mode=block');
+    FInhibitProc.Parameters.Add('sh');
+    FInhibitProc.Parameters.Add('-c');
+    FInhibitProc.Parameters.Add('while kill -0 ' + PidStr + ' 2>/dev/null; do sleep 5; done');
+{$ENDIF}
+    FInhibitProc.Options := [poNoConsole];
+    FInhibitProc.Execute;
+  except
+    FreeAndNil(FInhibitProc);
+  end;
+{$ENDIF}
+end;
+
+procedure UninhibitSleep;
+begin
+{$IFDEF WINDOWS}
+  SetThreadExecutionState(ES_CONTINUOUS);
+{$ENDIF}
+
+{$IF DEFINED(DARWIN) OR DEFINED(LINUX)}
+  if FInhibitProc <> nil then
+  begin
+    if FInhibitProc.Running then
+      FInhibitProc.Terminate(0);
+    FreeAndNil(FInhibitProc);
+  end;
+{$ENDIF}
+end;
+
+initialization
+  FInhibitProc := nil;
+
+finalization
+  UninhibitSleep;
+
+end.

ewsdr.lpi

@@ -229,6 +229,10 @@
         <Filename Value="PlatformUtils.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="PowerInhibit.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
       <Unit>
         <Filename Value="BoardUtils.pas"/>
         <IsPartOfProject Value="True"/>