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            "Delphi X-Files" <www.DelphiXFiles.narod.ru"
                       "Изменение громкости"
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Данный пример уж очень расширен. Зато все очень выглядит красиво. Если
Вы хотите посмотреть на программу, которая хорошо применяет данный код,
то заходите в раздел сайта "Примеры" (www.DelphiXFiles.narod.ru/Samples.htm)
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unit svol;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ComCtrls, MMsystem, Buttons;

type
  TSetVol = class(TForm)
    VolBar: TProgressBar;
    SpeedButton1: TSpeedButton;
    SpeedButton2: TSpeedButton;
    procedure FormCreate(Sender: TObject);
    procedure VolBarMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormDestroy(Sender: TObject);
    procedure SpeedButton1Click(Sender: TObject);
    procedure SpeedButton2Click(Sender: TObject);
  private
    { Private declarations }
    procedure MixCtrlChange(var mess : TMessage); message MM_MIXM_CONTROL_CHANGE;

  public
    { Public declarations }
  end;

var
  SetVol: TSetVol;
  hmix:integer;
  mixcaps:TMixerCaps;
  volumeID,volmin,volmax:integer;
  details:TMixerControlDetails;
  mixctrl:TMixerControl;
  valdets:TMixerControlDetailsUnsigned;
  curvolume:dword;
  svEnable : boolean;

implementation

{$R *.DFM}

procedure TSetVol.MixCtrlChange(var mess : TMessage);
begin
  if not svEnable then exit;
  if SetVol.WindowState=wsMinimized then exit;
  details.cbStruct:=sizeof(details);
  details.dwControlID:=VolumeID;
  details.cChannels:=1;
  details.cMultipleItems:=0;
  details.cbDetails:=sizeof(valdets);
  details.paDetails:=@valdets;
  mixerGetControlDetails(hmix,@details,MIXER_GETCONTROLDETAILSF_VALUE);
  curvolume:=valdets.dwValue;
  SetVol.VolBar.Position:=curvolume;
end;

procedure TSetVol.FormCreate(Sender: TObject);
var
  i:integer;
  mixline:TMixerLine;
  mixlinectrl:TMixerLineControls;
  mixctrl:TMixerControl;
begin
  inherited;
  hVolForm:=Handle;
  Left:=80;
  Top:=TBHeight+2;
  mixerOpen(@hmix,0,Handle,0,MIXER_OBJECTF_MIXER or CALLBACK_WINDOW);
  mixerGetDevCaps(0,@mixcaps,sizeof(mixcaps))
  for i:=0 to mixcaps.cDestinations-1 do
   begin
     mixline.dwDestination:=i;
     mixline.cbStruct:=sizeof(mixline);
     mixerGetLineInfo(hmix,@mixline,MIXER_GETLINEINFOF_DESTINATION);
     if mixline.dwComponentType=MIXERLINE_COMPONENTTYPE_DST_SPEAKERS then
break;
   end;
  if mixline.dwComponentType<>MIXERLINE_COMPONENTTYPE_DST_SPEAKERSthen
   begin
     ShowMessage('Hет миксера!!!');
     svEnable:=False;
     exit;
   end
  else
    svEnable:=true;
  mixlinectrl.cbStruct:=sizeof(mixlinectrl);
  mixlinectrl.dwControlType:=MIXERCONTROL_CONTROLTYPE_VOLUME;
  mixlinectrl.dwLineID:=mixline.dwLineID;
  mixlinectrl.cControls:=2;
  mixlinectrl.cbmxctrl:=sizeof(mixctrl);
  mixctrl.dwControlType:=MIXERCONTROL_CONTROLTYPE_VOLUME;
  mixlinectrl.pamxctrl:=@mixctrl;
  mixerGetLineControls(hmix,@mixlinectrl,MIXER_GETLINECONTROLSF_ONEBYTYPE);

  VolumeID:=mixctrl.dwControlID;
  volmin:=mixctrl.Bounds.dwMinimum;
  volmax:=mixctrl.Bounds.dwMaximum;

  details.cbStruct:=sizeof(details);
  details.dwControlID:=VolumeID;
  details.cChannels:=1;
  details.cMultipleItems:=0;
  details.cbDetails:=sizeof(valdets);
  details.paDetails:=@valdets;
  mixerGetControlDetails(hmix,@details,MIXER_GETCONTROLDETAILSF_VALUE);

  curvolume:=valdets.dwValue;
  VolBar.Min:=volmin;
  VolBar.Max:=volmax;
  VolBar.Position:=curvolume;
end;

procedure TSetVol.VolBarMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if not svEnable then exit;
  X:=Round(X/VolBar.Width*(VolBar.Max-VolBar.Min)+VolBar.Min);
  VolBar.Position:=X;
  details.cbStruct:=sizeof(details);
  details.dwControlID:=VolumeID;
  details.cChannels:=1;
  details.cMultipleItems:=0;
  details.cbDetails:=sizeof(valdets);
  details.paDetails:=@valdets;
  if X>4000 then
    valdets.dwValue:=VolBar.Position
  else
    valdets.dwValue:=0;
  mixerSetControlDetails(hmix,@details,MIXER_SETCONTROLDETAILSF_VALUE);
end;

procedure TSetVol.FormDestroy(Sender: TObject);
begin
  hVolForm:=0;
  if not svEnable then exit;
  mixerClose(hmix);
  inherited;
end;

procedure TSetVol.SpeedButton1Click(Sender: TObject);
begin
  if not svEnable then exit;
  VolBar.Position:=VolBar.Position-(VolBar.Max-VolBar.Min)div 10;
  if VolBar.Position<VolBar.Minthen VolBar.Position:=VolBar.Min;
  details.cbStruct:=sizeof(details);
  details.dwControlID:=VolumeID;
  details.cChannels:=1;
  details.cMultipleItems:=0;
  details.cbDetails:=sizeof(valdets);
  details.paDetails:=@valdets;
  if VolBar.Position>4000then
    valdets.dwValue:=VolBar.Position
  else
    valdets.dwValue:=0;
  mixerSetControlDetails(hmix,@details,MIXER_SETCONTROLDETAILSF_VALUE);
end;

procedure TSetVol.SpeedButton2Click(Sender: TObject);
begin
  if not svEnable then exit;
  VolBar.Position:=VolBar.Position+(VolBar.Max-VolBar.Min)div 10;
  if VolBar.Position>VolBar.Maxthen VolBar.Position:=VolBar.Max;
  details.cbStruct:=sizeof(details);
  details.dwControlID:=VolumeID;
  details.cChannels:=1;
  details.cMultipleItems:=0;
  details.cbDetails:=sizeof(valdets);
  details.paDetails:=@valdets;
  if VolBar.Position>4000then
    valdets.dwValue:=VolBar.Position
  else
    valdets.dwValue:=0;
  mixerSetControlDetails(hmix,@details,MIXER_SETCONTROLDETAILSF_VALUE);
end;

end. 
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