CEF4Delphi/demos/Lazarus_Windows/MediaRouter/uMediaRouterFrm.pas

// ************************************************************************
// ***************************** CEF4Delphi *******************************
// ************************************************************************
//
// CEF4Delphi is based on DCEF3 which uses CEF to embed a chromium-based
// browser in Delphi applications.
//
// The original license of DCEF3 still applies to CEF4Delphi.
//
// For more information about CEF4Delphi visit :
//         https://www.briskbard.com/index.php?lang=en&pageid=cef
//
//        Copyright © 2021 Salvador Diaz Fau. All rights reserved.
//
// ************************************************************************
// ************ vvvv Original license and comments below vvvv *************
// ************************************************************************
(*
 *                       Delphi Chromium Embedded 3
 *
 * Usage allowed under the restrictions of the Lesser GNU General Public License
 * or alternatively the restrictions of the Mozilla Public License 1.1
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
 * the specific language governing rights and limitations under the License.
 *
 * Unit owner : Henri Gourvest <hgourvest@gmail.com>
 * Web site   : http://www.progdigy.com
 * Repository : http://code.google.com/p/delphichromiumembedded/
 * Group      : http://groups.google.com/group/delphichromiumembedded
 *
 * Embarcadero Technologies, Inc is not permitted to use or redistribute
 * this source code without explicit permission.
 *
 *)

unit uMediaRouterFrm;

{$MODE Delphi}

{$I cef.inc}

interface

uses
  LCLIntf, LCLType, LMessages, Messages, SysUtils, Variants, Classes, Graphics, Menus,
  Controls, Forms, Dialogs, StdCtrls, ExtCtrls, Types, ComCtrls, ClipBrd,
  ActiveX, ShlObj, SyncObjs,
  uCEFChromium, uCEFWindowParent, uCEFInterfaces, uCEFApplication, uCEFTypes, uCEFConstants,
  uCEFWinControl, uCEFSentinel, uCEFChromiumCore;

const
  MEDIA_ROUTER_PENDING_LOG_LINES    = WM_APP + $B00;
  MEDIA_ROUTER_REFRESH_SINKS        = WM_APP + $B01;
  MEDIA_ROUTER_REFRESH_ROUTES       = WM_APP + $B02;
  MEDIA_ROUTER_UPDATE_BUTTONS       = WM_APP + $B03;

type
  TMediaRouterFrm = class(TForm)
    Chromium1: TChromium;
    CEFWindowParent1: TCEFWindowParent;
    Timer1: TTimer;
    MainPnl: TPanel;
    SinksGbx: TGroupBox;
    SinksLbx: TListBox;
    SinksButtonsPnl: TPanel;
    CreateRouteBtn: TButton;
    CentralPnl: TPanel;
    SourcePnl: TPanel;
    SourceLblPnl: TPanel;
    SourceURNLbl: TLabel;
    RoutesGbx: TGroupBox;
    RoutesLbx: TListBox;
    RoutesButtonPnl: TPanel;
    TerminateRouteBtn: TButton;
    MessageGbx: TGroupBox;
    SendMessagePnl: TPanel;
    SendMsgBtn: TButton;
    MessageMem: TMemo;
    LogGbx: TGroupBox;
    LogMem: TMemo;
    SpacerPnl: TPanel;
    NotifySinksBtn: TButton;
    NotifyRoutesBtn: TButton;
    ClearLogPnl: TPanel;
    ClearLogBtn: TButton;
    SourceURNCbx: TComboBox;

    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormShow(Sender: TObject);

    procedure Chromium1AfterCreated(Sender: TObject; const browser: ICefBrowser);
    procedure Chromium1BeforeClose(Sender: TObject; const browser: ICefBrowser);
    procedure Chromium1Close(Sender: TObject; const browser: ICefBrowser; var aAction: TCefCloseBrowserAction);
    procedure Chromium1Sinks(Sender: TObject; const sinks: TCefMediaSinkArray);
    procedure Chromium1Routes(Sender: TObject; const routes: TCefMediaRouteArray);
    procedure Chromium1RouteStateChanged(Sender: TObject; const route: ICefMediaRoute; state: TCefMediaRouteConnectionState);
    procedure Chromium1RouteMessageReceived(Sender: TObject; const route: ICefMediaRoute; const message_: ustring);
    procedure Chromium1MediaRouteCreateFinished(Sender: TObject; result: Integer; const error: ustring; const route: ICefMediaRoute);

    procedure Timer1Timer(Sender: TObject);
    procedure SourceURNEdtChange(Sender: TObject);
    procedure SinksLbxClick(Sender: TObject);
    procedure CreateRouteBtnClick(Sender: TObject);
    procedure TerminateRouteBtnClick(Sender: TObject);
    procedure SendMsgBtnClick(Sender: TObject);
    procedure NotifySinksBtnClick(Sender: TObject);
    procedure NotifyRoutesBtnClick(Sender: TObject);
    procedure ClearLogBtnClick(Sender: TObject);
    procedure MessageMemChange(Sender: TObject);
    procedure RoutesLbxClick(Sender: TObject);

  protected
    // Variables to control when can we destroy the form safely
    FCanClose : boolean;  // Set to True in TChromium.OnBeforeClose
    FClosing  : boolean;  // Set to True in the CloseQuery event.

    FMediaCS  : TCriticalSection;
    FLog      : TStringList;
    FSinks    : TCefMediaSinkInfoArray;
    FRoutes   : TCefMediaRouteInfoArray;

    procedure BrowserDestroyMsg(var aMessage : TMessage); message CEF_DESTROY;
    procedure PendingLogLinesMsg(var aMessage : TMessage); message MEDIA_ROUTER_PENDING_LOG_LINES;
    procedure RefreshSinksMsg(var aMessage : TMessage); message MEDIA_ROUTER_REFRESH_SINKS;
    procedure RefreshRoutesMsg(var aMessage : TMessage); message MEDIA_ROUTER_REFRESH_ROUTES;
    procedure UpdateButtonsMsg(var aMessage : TMessage); message MEDIA_ROUTER_UPDATE_BUTTONS;

    procedure DestroySinksArray;
    procedure DestroyRoutesArray;
    procedure DestroyAllArrays;
    procedure CopySinksArray(const aSinks : TCefMediaSinkArray);
    procedure CopyRoutesArray(const aRoutes : TCefMediaRouteArray);
    procedure UpdateAvailableSinks;
    procedure UpdateAvailableRoutes;
    procedure UpdateButtons;
    procedure AppendPendingLogStrings;
    procedure AddLogEntry(const aMessage1, aMessage2 : string; aRec : boolean); overload;
    procedure AddLogEntry(const aMessage1 : string; const aMessage2 : string = ''); overload;
  end;

var
  MediaRouterFrm: TMediaRouterFrm;

procedure CreateGlobalCEFApp;

implementation

{$R *.lfm}

uses
  {$IFDEF DELPHI16_UP}
  System.Math,
  {$ELSE}
  Math,
  {$ENDIF}
  uCEFMiscFunctions;

// This demo can use a MediaRouter to communicate with devices on the local
// network via the CAST and DIAL protocols.

// TChromium exposes all the ICefMediaObserver events and the ICefMediaRouter
// methods to show the available devices, to established communication routes
// and to send messages to those devices.

// Follow these steps to test this demo :

// STEP 1
// ------
// Turn on your ChromeCast receiver. It can be an Android TV or similar device
// like a Xiaomi MiBox. It must be on the same local network as the computer
// running this demo.

// STEP 2
// ------
// Run this demo and wait a few seconds. It will show all the available devices
// in the local network and the protocol used to communicate with them.
// In the case of the MiBox device it shows a DIAL and a CAST "sink" but after
// a couple of secods the list is updated and it only shows the CAST sink.

// STEP 3
// ------
// Select the CAST sink and click on the "Create route" button. This button will
// use the "Source URN" value to create the route and that value has a CAST URN
// with the "Application ID" of the "Default Media Receiver", which is CC1AD845.
// This ID can be used for tests.

// STEP 4
// ------
// The "Established routes" box will show the routes that you created.

// STEP 5
// ------
// Select the route, type the message and click on the "Send message" button.

// STEP 6
// ------
// Click on the "Terminate route" button.

// WARNING
// =======
// This demo has a known bug when you close the form and it will crash.

// References :
// ============
// https://bitbucket.org/chromiumembedded/cef/issues/2900/add-mediarouter-support-for-cast-receiver
// https://blog.oakbits.com/google-cast-protocol-overview.html
// https://developers.google.com/cast/docs/developers
// https://gist.github.com/jloutsenhizer/8855258

procedure CreateGlobalCEFApp;
begin
  GlobalCEFApp             := TCefApplication.Create;
  GlobalCEFApp.LogFile     := 'debug.log';
  GlobalCEFApp.LogSeverity := LOGSEVERITY_INFO;
end;

procedure TMediaRouterFrm.Chromium1AfterCreated(Sender: TObject;
  const browser: ICefBrowser);
begin
  AddLogEntry('Browser initialized.');
end;

procedure TMediaRouterFrm.Chromium1BeforeClose(Sender: TObject; const browser: ICefBrowser);
begin
  FCanClose := True;
  PostMessage(Handle, WM_CLOSE, 0, 0);
end;

procedure TMediaRouterFrm.Chromium1Close(Sender: TObject;
  const browser: ICefBrowser; var aAction: TCefCloseBrowserAction);
begin
  PostMessage(Handle, CEF_DESTROY, 0, 0);
  aAction := cbaDelay;
end;

procedure TMediaRouterFrm.Chromium1MediaRouteCreateFinished(Sender: TObject;
  result: Integer; const error: ustring; const route: ICefMediaRoute);
var
  TempMsg, TempID : string;
begin
  TempMsg := '';

  try
    FMediaCS.Acquire;

    if (result = CEF_MRCR_OK) then
      begin
        TempMsg := 'Route created';
        if (route <> nil) then TempID := 'Route ID : ' + route.ID;
      end
     else
      TempMsg := error;
  finally
    FMediaCS.Release;
    if (length(TempMsg) > 0) then AddLogEntry(TempID, TempMsg);
    PostMessage(Handle, MEDIA_ROUTER_UPDATE_BUTTONS, 0, 0);
  end;
end;

procedure TMediaRouterFrm.Chromium1RouteMessageReceived(Sender: TObject;
  const route: ICefMediaRoute; const message_: ustring);
var
  TempID : string;
begin
  if (route <> nil) then
    TempID := 'Route ID : ' + route.ID;

  AddLogEntry(TempID, 'Message contents : ' + message_, True);
end;

procedure TMediaRouterFrm.Chromium1Routes(Sender: TObject;
  const routes: TCefMediaRouteArray);
begin
  CopyRoutesArray(routes);
end;

procedure TMediaRouterFrm.Chromium1RouteStateChanged(Sender: TObject;
  const route: ICefMediaRoute; state: TCefMediaRouteConnectionState);
var
  TempMsg, TempID : string;
begin
  if (route <> nil) then TempID := 'Route ID : ' + route.ID;

  case state of
    CEF_MRCS_CONNECTING : TempMsg := 'Route state : Connecting.';
    CEF_MRCS_CONNECTED  : TempMsg := 'Route state : Connected.';
    CEF_MRCS_CLOSED     : TempMsg := 'Route state : Closed.';
    CEF_MRCS_TERMINATED : TempMsg := 'Route state : Terminated.';
    else                  TempMsg := 'Route state : Unknown.';
  end;

  TempMsg := TempMsg + ' ' + dateTimeToStr(now);

  AddLogEntry(TempID, TempMsg);
end;

procedure TMediaRouterFrm.Chromium1Sinks(Sender: TObject;
  const sinks: TCefMediaSinkArray);
begin
  CopySinksArray(sinks);
end;

procedure TMediaRouterFrm.ClearLogBtnClick(Sender: TObject);
begin
  LogMem.Lines.Clear;
end;

procedure TMediaRouterFrm.FormCloseQuery(Sender: TObject;
  var CanClose: Boolean);
begin
  CanClose := FCanClose;

  if not(FClosing) then
    begin
      FClosing := True;
      Visible  := False;
      DestroyAllArrays;
      Chromium1.CloseBrowser(True);
    end;
end;

procedure TMediaRouterFrm.FormCreate(Sender: TObject);
begin
  FCanClose := False;
  FClosing  := False;
  FSinks    := nil;
  FRoutes   := nil;
  FMediaCS  := TCriticalSection.Create;
  FLog      := TStringList.Create;
end;

procedure TMediaRouterFrm.FormDestroy(Sender: TObject);
begin
  FLog.Free;
  FMediaCS.Free;
end;

procedure TMediaRouterFrm.FormShow(Sender: TObject);
begin
  UpdateButtons;

  if not(Chromium1.CreateBrowser(CEFWindowParent1)) then
    Timer1.Enabled := True;
end;

procedure TMediaRouterFrm.MessageMemChange(Sender: TObject);
begin
  UpdateButtons;
end;

procedure TMediaRouterFrm.NotifyRoutesBtnClick(Sender: TObject);
begin
  Chromium1.NotifyCurrentRoutes;
end;

procedure TMediaRouterFrm.NotifySinksBtnClick(Sender: TObject);
begin
  Chromium1.NotifyCurrentSinks;
end;

procedure TMediaRouterFrm.SendMsgBtnClick(Sender: TObject);
var
  TempMsg, TempID : string;
begin
  TempMsg := '';

  try
    FMediaCS.Acquire;

    if (RoutesLbx.Items.Count > 0) and
       (FRoutes <> nil) and
       (RoutesLbx.ItemIndex >= 0) and
       (RoutesLbx.ItemIndex < length(FRoutes)) and
       (MessageMem.Lines.Count > 0) then
      begin
        TempMsg := trim(MessageMem.Lines.Text);

        if (length(TempMsg) > 0) and
           (FRoutes[RoutesLbx.ItemIndex].RouteIntf <> nil) then
          try
            TempID := 'Route ID : ' + FRoutes[RoutesLbx.ItemIndex].RouteIntf.ID;
            FRoutes[RoutesLbx.ItemIndex].RouteIntf.SendRouteMessage(TempMsg);
            TempMsg := 'Message contents : ' + TempMsg;
          except
            on e : exception do
              if CustomExceptionHandler('TMediaRouterFrm.SendMsgBtnClick', e) then raise;
          end;
      end;
  finally
    FMediaCS.Release;
    if (length(TempMsg) > 0) then AddLogEntry(TempID, TempMsg, False);
  end;
end;

procedure TMediaRouterFrm.SinksLbxClick(Sender: TObject);
begin
  UpdateButtons;
end;

procedure TMediaRouterFrm.SourceURNEdtChange(Sender: TObject);
begin
  UpdateButtons;
end;

procedure TMediaRouterFrm.TerminateRouteBtnClick(Sender: TObject);
begin
  try
    FMediaCS.Acquire;

    if (RoutesLbx.Items.Count > 0) and
       (FRoutes <> nil) and
       (RoutesLbx.ItemIndex >= 0) and
       (RoutesLbx.ItemIndex < length(FRoutes)) and
       (FRoutes[RoutesLbx.ItemIndex].RouteIntf <> nil) then
      try
        FRoutes[RoutesLbx.ItemIndex].RouteIntf.Terminate;
      except
        on e : exception do
          if CustomExceptionHandler('TMediaRouterFrm.TerminateRouteBtnClick', e) then raise;
      end;
  finally
    FMediaCS.Release;
    UpdateButtons;
  end;
end;

procedure TMediaRouterFrm.Timer1Timer(Sender: TObject);
begin
  Timer1.Enabled := False;
  if not(Chromium1.CreateBrowser(CEFWindowParent1)) and not(Chromium1.Initialized) then
    Timer1.Enabled := True;
end;

procedure TMediaRouterFrm.BrowserDestroyMsg(var aMessage : TMessage);
begin
  CEFWindowParent1.Free;
end;

procedure TMediaRouterFrm.PendingLogLinesMsg(var aMessage : TMessage);
begin
  if FClosing then exit;

  AppendPendingLogStrings;
end;

procedure TMediaRouterFrm.AppendPendingLogStrings;
begin
  try
    FMediaCS.Acquire;

    if (FLog <> nil) and (FLog.Count > 0) then
      begin
        LogMem.Lines.AddStrings(FLog);
        LogMem.SelLength := 0;
        LogMem.SelStart  := Length(LogMem.Text);
        FLog.Clear;
      end;
  finally
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.RefreshSinksMsg(var aMessage : TMessage);
begin
  if FClosing then exit;

  UpdateAvailableSinks;
  AppendPendingLogStrings;
  UpdateButtons;
end;

procedure TMediaRouterFrm.RoutesLbxClick(Sender: TObject);
begin
  UpdateButtons;
end;

procedure TMediaRouterFrm.RefreshRoutesMsg(var aMessage : TMessage);
begin
  if FClosing then exit;

  UpdateAvailableRoutes;
  AppendPendingLogStrings;
  UpdateButtons;
end;

procedure TMediaRouterFrm.UpdateButtonsMsg(var aMessage : TMessage);
begin
  if FClosing then exit;

  AppendPendingLogStrings;
  UpdateButtons;
end;

procedure TMediaRouterFrm.DestroyAllArrays;
begin
  try
    FMediaCS.Acquire;
    DestroyRoutesArray;
    DestroySinksArray;
  finally
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.DestroySinksArray;
var
  i : integer;
begin
  if (FSinks <> nil) then
    begin
      i := pred(length(FSinks));
      while (i >= 0) do
        begin
          FSinks[i].SinkIntf := nil;
          dec(i);
        end;

      Finalize(FSinks);
      FSinks := nil;
    end;
end;

procedure TMediaRouterFrm.DestroyRoutesArray;
var
  i : integer;
begin
  if (FRoutes <> nil) then
    begin
      i := pred(length(FRoutes));
      while (i >= 0) do
        begin
          FRoutes[i].RouteIntf := nil;
          dec(i);
        end;

      Finalize(FRoutes);
      FRoutes := nil;
    end;
end;

procedure TMediaRouterFrm.CopySinksArray(const aSinks : TCefMediaSinkArray);
var
  i, TempLen : integer;
begin
  try
    FMediaCS.Acquire;

    FLog.Add('Sinks available : ' + inttostr(length(aSinks)));
    FLog.Add('------------------------------------------');

    DestroySinksArray;

    if (aSinks <> nil) then
      begin
        TempLen := length(aSinks);
        SetLength(FSinks, TempLen);

        i := 0;
        while (i < TempLen) do
          begin
            FSinks[i].ID          := aSinks[i].ID;
            FSinks[i].Name        := aSinks[i].Name;
            FSinks[i].Description := aSinks[i].Description;
            FSinks[i].IconType    := aSinks[i].IconType;
            FSinks[i].SinkIntf    := aSinks[i];

            if aSinks[i].IsCastSink then
              FSinks[i].SinkType := mtCast
             else
              if aSinks[i].IsDialSink then
                FSinks[i].SinkType := mtDial
               else
                FSinks[i].SinkType := mtUnknown;

            inc(i);
          end;
      end;
  finally
    PostMessage(Handle, MEDIA_ROUTER_REFRESH_SINKS, 0, 0);
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.CopyRoutesArray(const aRoutes : TCefMediaRouteArray);
var
  i, TempLen : integer;
begin
  try
    FMediaCS.Acquire;

    FLog.Add('Routes available : ' + inttostr(length(aRoutes)));
    FLog.Add('------------------------------------------');

    DestroyRoutesArray;

    if (aRoutes <> nil) then
      begin
        TempLen := length(aRoutes);
        SetLength(FRoutes, TempLen);

        i := 0;
        while (i < TempLen) do
          begin
            FRoutes[i].ID        := aRoutes[i].ID;
            FRoutes[i].SourceID  := aRoutes[i].GetSource.ID;
            FRoutes[i].SinkID    := aRoutes[i].GetSink.ID;
            FRoutes[i].RouteIntf := aRoutes[i];
            inc(i);
          end;
      end;
  finally
    PostMessage(Handle, MEDIA_ROUTER_REFRESH_ROUTES, 0, 0);
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.CreateRouteBtnClick(Sender: TObject);
var
  TempURN, TempErrorMsg : string;
  TempSource : ICefMediaSource;
begin
  TempURN := trim(SourceURNCbx.Text);

  if (length(TempURN) = 0) then
    begin
      AddLogEntry('Invalid URN');
      exit;
    end;

  TempErrorMsg := '';

  try
    try
      FMediaCS.Acquire;

      if (FSinks <> nil) and
         (SinksLbx.Items.Count > 0) and
         (SinksLbx.ItemIndex >= 0) and
         (SinksLbx.ItemIndex < length(FSinks)) then
        begin
          TempSource := Chromium1.GetSource(TempURN);

          if (TempSource <> nil) then
            begin
              if (FSinks[SinksLbx.ItemIndex].SinkIntf <> nil) then
                begin
                  if FSinks[SinksLbx.ItemIndex].SinkIntf.IsCompatibleWith(TempSource) then
                    Chromium1.CreateRoute(TempSource, FSinks[SinksLbx.ItemIndex].SinkIntf)
                   else
                    TempErrorMsg := 'The selected Sink is not compatible with the Media Source.';
                end
               else
                TempErrorMsg := 'The selected Sink is not valid.';
            end
           else
            TempErrorMsg := 'The Media Source is not valid.';
        end
       else
        TempErrorMsg := 'The sinks list is outdated.';
    except
      on e : exception do
        begin
          TempErrorMsg := e.Message;
          if CustomExceptionHandler('TMediaRouterFrm.CreateRouteBtnClick', e) then raise;
        end;
    end;
  finally
    TempSource := nil;
    FMediaCS.Release;
    if (length(TempErrorMsg) > 0) then AddLogEntry(TempErrorMsg);
  end;
end;

procedure TMediaRouterFrm.UpdateAvailableSinks;
var
  i : integer;
  TempItem : string;
begin
  try
    FMediaCS.Acquire;
    SinksLbx.Items.Clear;

    if (FSinks <> nil) then
      begin
        i := 0;
        while (i < length(FSinks)) do
          begin
            TempItem := FSinks[i].Name;

            case FSinks[i].SinkType of
              mtCast : TempItem := TempItem + ' (CAST';
              mtDial : TempItem := TempItem + ' (DIAL';
              else     TempItem := TempItem + ' (UNKNOWN';
            end;

            case FSinks[i].IconType of
              CEF_MSIT_CAST             : TempItem := TempItem + ', CAST)';
              CEF_MSIT_CAST_AUDIO_GROUP : TempItem := TempItem + ', CAST_AUDIO_GROUP)';
              CEF_MSIT_CAST_AUDIO       : TempItem := TempItem + ', CAST_AUDIO)';
              CEF_MSIT_MEETING          : TempItem := TempItem + ', MEETING)';
              CEF_MSIT_HANGOUT          : TempItem := TempItem + ', HANGOUT)';
              CEF_MSIT_EDUCATION        : TempItem := TempItem + ', EDUCATION)';
              CEF_MSIT_WIRED_DISPLAY    : TempItem := TempItem + ', WIRED_DISPLAY)';
              CEF_MSIT_GENERIC          : TempItem := TempItem + ', GENERIC)';
              else                        TempItem := TempItem + ', UNKNOWN)';
            end;

            SinksLbx.Items.Add(TempItem);
            inc(i);
          end;
      end;
  finally
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.UpdateAvailableRoutes;
var
  i : integer;
begin
  try
    FMediaCS.Acquire;
    RoutesLbx.Items.Clear;

    if (FRoutes <> nil) then
      begin
        i := 0;
        while (i < length(FRoutes)) do
          begin
            RoutesLbx.Items.Add('ID : ' + quotedstr(FRoutes[i].ID));
            inc(i);
          end;
      end;
  finally
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.UpdateButtons;
begin
  TerminateRouteBtn.Enabled := (RoutesLbx.ItemIndex >= 0) and
                               (RoutesLbx.Items.Count > 0);

  SendMsgBtn.Enabled := TerminateRouteBtn.Enabled and
                        (length(trim(MessageMem.Lines.Text)) > 0);

  CreateRouteBtn.Enabled := not(TerminateRouteBtn.Enabled) and
                            (length(trim(SourceURNCbx.Text)) > 0) and
                            (SinksLbx.ItemIndex >= 0) and
                            (SinksLbx.Items.Count > 0);
end;

procedure TMediaRouterFrm.AddLogEntry(const aMessage1, aMessage2 : string; aRec : boolean);
begin
  try
    FMediaCS.Acquire;

    if aRec then
      FLog.Add('Message received ' + dateTimeToStr(now))
     else
      FLog.Add('Message sent ' + dateTimeToStr(now));

    FLog.Add(aMessage1);
    if (length(aMessage2) > 0) then FLog.Add(aMessage2);
    FLog.Add('------------------------------------------');
  finally
    PostMessage(Handle, MEDIA_ROUTER_PENDING_LOG_LINES, 0, 0);
    FMediaCS.Release;
  end;
end;

procedure TMediaRouterFrm.AddLogEntry(const aMessage1, aMessage2 : string);
begin
  try
    FMediaCS.Acquire;
    FLog.Add(aMessage1);
    if (length(aMessage2) > 0) then FLog.Add(aMessage2);
    FLog.Add('------------------------------------------');
  finally
    PostMessage(Handle, MEDIA_ROUTER_PENDING_LOG_LINES, 0, 0);
    FMediaCS.Release;
  end;
end;

end.