Here is the source code to SampleDepth.p:

---

Program DepthSample(input,output);

Uses
    Toolbox, DepthLib;
	
Const
    kMillions   = 2;
    kThousands  = 3;
    k256        = 4;
    k16         = 5;
    k4          = 6;
    k2          = 7;
    kColor      = 8;
    kGray       = 9;

Procedure SetRadioItem(dlog: DialogPtr; itemNum: integer; on: boolean);

Var
    iType: integer;
    iHandle: Handle;
    iRect: Rect;

    begin
    GetDialogItem(dlog,itemNum,iType,iHandle,iRect);
    if on then
        SetControlValue(ControlHandle(iHandle),1)
    else
        SetControlValue(ControlHandle(iHandle),0);
    end;

Procedure DisableDItem(dlog: DialogPtr; itemNum: integer);

Var
    iType: integer;
    iHandle: handle;
    iRect: rect;

    begin
    GetDialogItem(dlog,itemNum,iType,iHandle,iRect);
    HiliteControl(ControlHandle(iHandle),255);
    end;

Procedure SampleWindow;

Var
    d: DialogPtr;
    g: GrafPtr;
    hit: integer;
    depthItem: integer;
    modeItem: integer;
	
Procedure ChangeDepth(newItem: integer;
                      dlg: dialogPtr;
                      depth: integer);
					  
    begin
    SetRadioItem(dlg,depthItem,FALSE);
    depthItem := newItem;
    SetRadioItem(dlg,depthItem,TRUE);
    SetScreenDepth(GetMainDevice,depth);
    end;

Procedure ChangeMode(newItem: integer;     
                     dlg: dialogPtr;
                     mode: integer);

    begin
    SetRadioItem(dlg,modeItem,FALSE);
    modeItem := newItem;
    SetRadioItem(dlg,modeItem,TRUE);
    SetScreenMode(GetMainDevice,mode);
    end;

    begin
    d := GetNewDialog(128, nil, WindowPtr(-1));
    if d = NIL then
        exit(SampleWindow);
    GetPort(g);
    SetPort(d);
    {-------------------------------------------------------------------}
    { find the maximum depth of main monitor, and disable radio items.  }
    { The C version had a strange bug... it showed my current depth as  }
    { 256, but only enabled a depth of 2.  To ensure that depths are    }
    { enabled properly, I examine each depth individually.              }
    {-------------------------------------------------------------------}
    if not SupportsDepth(GetMainDevice, k2Colors) then
        DisableDItem(d, k2);
    if not SupportsDepth(GetMainDevice, k4Colors) then
        DisableDItem(d, k4);
    if not SupportsDepth(GetMainDevice, k16Colors) then
        DisableDItem(d, k16);
    if not SupportsDepth(GetMainDevice, k256Colors) then
        DisableDItem(d, k256);
    if not SupportsDepth(GetMainDevice, kThousandsColors) then
        DisableDItem(d, kThousands);
    if not SupportsDepth(GetMainDevice, kMillionsColors) then
        DisableDItem(d, kMillions);
    {-----------------------------------------}
    { get the current depth and set the       }
    { appropriate radio item.                 }
    {-----------------------------------------}
    case GetScreenDepth(GetMainDevice) of
        k2Colors:         depthItem := k2;
        k4Colors:         depthItem := k4;
        k16Colors:        depthItem := k16;
        k256Colors:       depthItem := k256;
        kThousandsColors: depthItem := kThousands;
        kMillionsColors:  depthItem := kMillions;
    {CASE}                end;
    SetRadioItem(d,depthItem,TRUE);
    {-----------------------------------------}
    { figure out which modes are supported    }
    { and disable radio items                 }
    {-----------------------------------------}
    if not SupportsMode(GetMainDevice,kColorMode) then
        DisableDItem(d,kColor);
    if not SupportsMode(GetMainDevice,kGrayMode) then
        DisableDItem(d,kGray);
    {-----------------------------------------}
    { get current mode and set appropriate    }
    { radio item                              }
    {-----------------------------------------}
    case GetScreenMode(GetMainDevice) of
        kGrayMode:  modeItem := kGray;
        kColorMode: modeItem := kColor;
    {CASE}          end;
    SetRadioItem(d,modeItem,TRUE);
    ShowWindow(d);
    repeat
    ModalDialog(NIL, hit);
        case hit of
            k2:         ChangeDepth(k2,d,k2Colors);
            k4:         ChangeDepth(k4,d,k4Colors);
            k16:        ChangeDepth(k16,d,k16Colors);
            k256:       ChangeDepth(k256,d,k256Colors);
            kThousands: ChangeDepth(kThousands,d,kThousandsColors);
            kMillions:  ChangeDepth(kMillions,d,kMillionsColors);
            kGray:      ChangeMode(kGray,d,kGrayMode);
            kColor:     ChangeMode(kColor,d,kColorMode);
            otherwise;
        {CASE}          end;
    until hit = 1;
    SetPort(g);
    DisposeDialog(d);
    end;
	
{---------------}
{ Main Program  }
{---------------}
begin	
InitToolbox;
FlushEvents(everyEvent, 0);
SampleWindow;	
end.