How to Detect Forward and Back Mouse Button Events in Delphi?

If a mouse has other buttons in addition to the standard left/right/middle (e.g. forward/back), how can we detect those button clicks in Delphi?

An example of how this is used is the Intern开发者_如何学Pythonet Explorer, where the forward/back button on the side of a Logitech or MS mouse cycles forward and back between any loaded web pages. This seems to replicate the Backspace/CTRL+Backspace on the keyboard but I tried to detect that using KeyPreview and the KeyPress event but it does not pick it up.

Any idea how to detect clicks on these extended mouse buttons?

You need to capture the WM_APPCOMMAND message and then extract the specific command request using GET_APPCOMMAND_LPARAM. Basically, something like this:

type
  TMyForm = class(TForm)
  private
    procedure WMAppCommand(var Msg: TMessage); message WM_APPCOMMAND;
  end;

procedure TMyForm.WMAppCommand(var Msg: TMessage);
begin
  case GET_APPCOMMAND_LPARAM(Msg.LParam) of
    APPCOMMAND_BROWSER_BACKWARD:
    begin
      // Do "go back" code
      Msg.Result := 1;
    end;
  end;
end;

Here's the relevant header translation:

unit AppCommand;

{$RANGECHECKS OFF}

interface

uses
  Windows;

const
  WM_APPCOMMAND = $0319;

const
  // Windows 2000, ME, and above
  APPCOMMAND_BROWSER_BACKWARD                   = 1;
  APPCOMMAND_BROWSER_FORWARD                    = 2;
  APPCOMMAND_BROWSER_REFRESH                    = 3;
  APPCOMMAND_BROWSER_STOP                       = 4;
  APPCOMMAND_BROWSER_SEARCH                     = 5;
  APPCOMMAND_BROWSER_FAVORITES                  = 6;
  APPCOMMAND_BROWSER_HOME                       = 7;
  APPCOMMAND_VOLUME_MUTE                        = 8;
  APPCOMMAND_VOLUME_DOWN                        = 9;
  APPCOMMAND_VOLUME_UP                          = 10;
  APPCOMMAND_MEDIA_NEXTTRACK                    = 11;
  APPCOMMAND_MEDIA_PREVIOUSTRACK                = 12;
  APPCOMMAND_MEDIA_STOP                         = 13;
  APPCOMMAND_MEDIA_PLAY_PAUSE                   = 14;
  APPCOMMAND_LAUNCH_MAIL                        = 15;
  APPCOMMAND_LAUNCH_MEDIA_SELECT                = 16;
  APPCOMMAND_LAUNCH_APP1                        = 17;
  APPCOMMAND_LAUNCH_APP2                        = 18;
  APPCOMMAND_BASS_DOWN                          = 19;
  APPCOMMAND_BASS_BOOST                         = 20;
  APPCOMMAND_BASS_UP                            = 21;
  APPCOMMAND_TREBLE_DOWN                        = 22;
  APPCOMMAND_TREBLE_UP                          = 23;
  // Windows XP and above
  APPCOMMAND_MICROPHONE_VOLUME_MUTE             = 24;
  APPCOMMAND_MICROPHONE_VOLUME_DOWN             = 25;
  APPCOMMAND_MICROPHONE_VOLUME_UP               = 26;
  APPCOMMAND_HELP                               = 27;
  APPCOMMAND_FIND                               = 28;
  APPCOMMAND_NEW                                = 29;
  APPCOMMAND_OPEN                               = 30;
  APPCOMMAND_CLOSE                              = 31;
  APPCOMMAND_SAVE                               = 32;
  APPCOMMAND_PRINT                              = 33;
  APPCOMMAND_UNDO                               = 34;
  APPCOMMAND_REDO                               = 35;
  APPCOMMAND_COPY                               = 36;
  APPCOMMAND_CUT                                = 37;
  APPCOMMAND_PASTE                              = 38;
  APPCOMMAND_REPLY_TO_MAIL                      = 39;
  APPCOMMAND_FORWARD_MAIL                       = 40;
  APPCOMMAND_SEND_MAIL                          = 41;
  APPCOMMAND_SPELL_CHECK                        = 42;
  APPCOMMAND_DICTATE_OR_COMMAND_CONTROL_TOGGLE  = 43;
  APPCOMMAND_MIC_ON_OFF_TOGGLE                  = 44;
  APPCOMMAND_CORRECTION_LIST                    = 45;
  // Windows XP SP1 and above
  APPCOMMAND_MEDIA_PLAY                         = 46;
  APPCOMMAND_MEDIA_PAUSE                        = 47;
  APPCOMMAND_MEDIA_RECORD                       = 48;
  APPCOMMAND_MEDIA_FAST_FORWARD                 = 49;
  APPCOMMAND_MEDIA_REWIND                       = 50;
  APPCOMMAND_MEDIA_CHANNEL_UP                   = 51;
  APPCOMMAND_MEDIA_CHANNEL_DOWN                 = 52;

  FAPPCOMMAND_MOUSE = $8000;
  FAPPCOMMAND_KEY   = 0;
  FAPPCOMMAND_OEM   = $1000;
  FAPPCOMMAND_MASK  = $F000;

  // Mouse buttons;  remaining ones are declared in Windows.pas
  MK_XBUTTON1 = $20;
  MK_XBUTTON2 = $40;

function GET_APPCOMMAND_LPARAM(lParam: LPARAM): Short;
function GET_DEVICE_LPARAM(lParam: LPARAM): Word;
function GET_KEYSTATE_LPARAM(lParam: LPARAM): Word;


implementation

function GET_APPCOMMAND_LPARAM(lParam: LPARAM): Short;
begin
  Result := HiWord(lParam) and not FAPPCOMMAND_MASK;
end;

function GET_DEVICE_LPARAM(lParam: LPARAM): Word;
begin
  Result := HiWord(lParam) and FAPPCOMMAND_MASK;
end;

function GET_KEYSTATE_LPARAM(lParam: LPARAM): Word;
begin
  Result := LoWord(lParam);
end;

end.