我为您准备了一个组件单元。
要使用此组件单元，请在主窗体上放置TApplication组件，并在OnModalBegin中调用_GrayForms，然后在OnModalEnd中调用_NormalForms方法。
这是一个非常简单的示例，可以很容易地使其更加复杂。检查多个调用级别等等......
对于像系统（打开，保存等）对话框之类的东西，您可以将对话框执行方法包装在try...finally块中，调用适当的函数以获得类似的反应。
这个组件单元应该能够在Win2k、WinXP、Vista上运行，甚至在Win7上也能运行。
Ryan。
unit GrayOut;
interface
procedure _GrayForms;
procedure _GrayDesktop;
procedure _NormalForms;
implementation
uses windows, classes, forms, Contnrs, Types, Graphics, sysutils;
var
gGrayForms : TComponentList;
procedure _GrayDesktop;
var
loop : integer;
wScrnFrm : TForm;
wForm : TForm;
wPoint : TPoint;
begin
if not assigned(gGrayForms) then
begin
gGrayForms := TComponentList.Create;
gGrayForms.OwnsObjects := true;
for loop := 0 to Screen.MonitorCount - 1 do
begin
wForm := TForm.Create(nil);
gGrayForms.Add(wForm);
wForm.Position := poDesigned;
wForm.AlphaBlend := true;
wForm.AlphaBlendValue := 64;
wForm.Color := clBlack;
wForm.BorderStyle := bsNone;
wForm.Enabled := false;
wForm.BoundsRect := Screen.Monitors[loop].BoundsRect;
SetWindowPos(wForm.handle, HWND_TOP, 0,0,0,0, SWP_NOSIZE or SWP_NOMOVE);
wForm.Visible := true;
end;
end;
end;
procedure _GrayForms;
var
loop : integer;
wScrnFrm : TForm;
wForm : TForm;
wPoint : TPoint;
wScreens : TList;
begin
if not assigned(gGrayForms) then
begin
gGrayForms := TComponentList.Create;
gGrayForms.OwnsObjects := true;
wScreens := TList.create;
try
for loop := 0 to Screen.FormCount - 1 do
wScreens.Add(Screen.Forms[loop]);
for loop := 0 to wScreens.Count - 1 do
begin
wScrnFrm := wScreens[loop];
if wScrnFrm.Visible then
begin
wForm := TForm.Create(wScrnFrm);
gGrayForms.Add(wForm);
wForm.Position := poOwnerFormCenter;
wForm.AlphaBlend := true;
wForm.AlphaBlendValue := 64;
wForm.Color := clBlack;
wForm.BorderStyle := bsNone;
wForm.Enabled := false;
wForm.BoundsRect := wScrnFrm.BoundsRect;
SetWindowLong(wForm.Handle, GWL_HWNDPARENT, wScrnFrm.Handle);
SetWindowPos(wForm.handle, wScrnFrm.handle, 0,0,0,0, SWP_NOSIZE or SWP_NOMOVE);
wForm.Visible := true;
end;
end;
finally
wScreens.free;
end;
end;
end;
procedure _NormalForms;
begin
FreeAndNil(gGrayForms);
end;
initialization
gGrayForms := nil;
end.
我曾经为显示模态表单做过类似的事情，尽可能保持实现简单。我不知道这是否符合您的需求，但是这里是代码：
function ShowModalDimmed(Form: TForm; Centered: Boolean = true): TModalResult;
var
Back: TForm;
begin
Back := TForm.Create(nil);
try
Back.Position := poDesigned;
Back.BorderStyle := bsNone;
Back.AlphaBlend := true;
Back.AlphaBlendValue := 192;
Back.Color := clBlack;
Back.SetBounds(0, 0, Screen.Width, Screen.Height);
Back.Show;
if Centered then begin
Form.Left := (Back.ClientWidth - Form.Width) div 2;
Form.Top := (Back.ClientHeight - Form.Height) div 2;
end;
result := Form.ShowModal;
finally
Back.Free;
end;
end;
我不确定做法是否“正确”，但为了实现“渐变至白”的效果，您可以将表单放置在另一个完全白色的表单中（白色背景色，没有控件）。
因此，当您的表单透明度为0％时，它将显示为常规表单，但当透明度为50％时，它将渐变至白色。您显然可以选择其他颜色作为背景。
我期待看到其他答案......
编辑：在看到您的“Jedi Concentrate”链接后，似乎深灰色背景会更好地模仿Expose效果。
我使用一个大小与屏幕工作区相同的窗体，颜色为clBlack，BorderStyle为bsNone，创建了类似Jedi Concentrate的效果。
我发现设置AlphaBlendValue速度太慢，无法流畅地进行动画，因此我使用了SetLayeredWindowAttributes()。
该单元的代码：
unit frmConcentrate;
{$WARN SYMBOL_PLATFORM OFF}
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TFadeThread = class(TThread)
private
fForm: TForm;
public
constructor Create(frm: TForm);
procedure Execute; override;
end;
TConcentrateFrm = class(TForm)
procedure FormDestroy(Sender: TObject);
procedure FormClick(Sender: TObject);
private
{ Private declarations }
fThread: TFadeThread;
public
{ Public declarations }
end;
procedure StartConcentrate(aForm: TForm = nil);
var
ConcentrateFrm: TConcentrateFrm;
implementation
{$R *.dfm}
procedure StartConcentrate(aForm: TForm = nil);
var
Hnd: HWND;
begin
try
if not Assigned(ConcentrateFrm) then
ConcentrateFrm := TConcentrateFrm.Create(nil)
else
Exit;
ConcentrateFrm.Top := Screen.WorkAreaTop;
ConcentrateFrm.Left := Screen.WorkAreaLeft;
ConcentrateFrm.Width := Screen.WorkAreaWidth;
ConcentrateFrm.Height := Screen.WorkAreaHeight;
Hnd := GetForegroundWindow;
SetWindowLong(ConcentrateFrm.Handle, GWL_EXSTYLE,
GetWindowLong(ConcentrateFrm.Handle, GWL_EXSTYLE) or WS_EX_LAYERED
);
SetLayeredWindowAttributes(
ConcentrateFrm.Handle,
ColorToRGB(clBlack),
0,
LWA_ALPHA
);
ConcentrateFrm.Show;
if Assigned(aForm) then
aForm.BringToFront
else
SetForegroundWindow(Hnd);
ConcentrateFrm.fThread := TFadeThread.Create(ConcentrateFrm);
Application.ProcessMessages;
ConcentrateFrm.fThread.Resume;
except
FreeAndNil(ConcentrateFrm);
end;
end;
procedure TConcentrateFrm.FormClick(Sender: TObject);
var
p: TPoint;
hnd: HWND;
begin
GetCursorPos(p);
ConcentrateFrm.Hide;
hnd := WindowFromPoint(p);
while GetParent(hnd) 0 do
hnd := GetParent(hnd);
SetForegroundWindow(hnd);
Release;
end;
procedure TConcentrateFrm.FormDestroy(Sender: TObject);
begin
ConcentrateFrm := nil;
end;
{ TFadeThread }
constructor TFadeThread.Create(frm: TForm);
begin
inherited Create(true);
FreeOnTerminate := true;
Priority := tpIdle;
fForm := frm;
end;
procedure TFadeThread.Execute;
var
i: Integer;
begin
try
// let the main form open before doing this intensive process.
Sleep(300);
i := 0;
while i < 180 do
begin
if not Win32Check(
SetLayeredWindowAttributes(
fForm.Handle,
ColorToRGB(clBlack),
i,
LWA_ALPHA
)
) then
begin
RaiseLastOSError;
end;
Sleep(10);
Inc(i, 4);
end;
except
end;
end;
end.