大家知道 TreeView 上的节点如果显示不完全，鼠标移上去会出现一提示，这就是 In-place Tooltips。下面这段代码在 Listbox 上实现这一功能(下面代码只是在标准 Listbox 上测试，如果是自画的，则要修改)：
{直接将下面代码拷贝到新建工程中Form1的Unit1.pas文件即可运行，不需添加任何控件}
//------------------------------------------------------------------------------
// 在 ListBox 上实现 In-place Tooltips
// 原创作者：Joe Huang Email：Happyjoe@21cn.com
//
//------------------------------------------------------------------------------
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, CommCtrl;
type
//改写 TListBox 拦截 CM_MOUSELEAVE 消息
TNewListBox = class(TListBox)
protected
{ Protected declarations }
procedure WndProc(var Message: TMessage); override;
end;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
GHWND: HWND;
TipVisable: Boolean;
OldIndex, CurrentIndex: Integer;
ti: TOOLINFO;
ListBox1: TListBox;
procedure InitListBox; //动态生成 ListBox1
procedure CreateTipsWindow; //生成 Tooltip Window
procedure HideTipsWindow; //隐藏 Tooltip Window
//拦截 WM_NOTIFY 消息，动态改变 Tooltip Window 显示的内容
procedure WMNotify(var Msg: TMessage); message WM_NOTIFY;
procedure ListBox_MouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
procedure ListBox_MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TNewListBox }
procedure TNewListBox.WndProc(var Message: TMessage);
begin
case Message.Msg of
CM_MOUSELEAVE: Form1.HideTipsWindow;
end;
inherited WndProc(Message);
end;
{ TForm1 }
procedure TForm1.InitListBox;
begin
ListBox1 := TNewListBox.Create(Self);
ListBox1.Parent := Self;
ListBox1.Left := 50;
ListBox1.Top := 50;
ListBox1.Width := 200;
ListBox1.Height := 200;
//添加几项，以供测试用
ListBox1.Items.Append('happyjoe');
ListBox1.Items.Append('Please send me email: happyjoe@21cn.com');
ListBox1.Items.Append('Delphi 5 开发人员指南');
ListBox1.Items.Append('Delphi 5.X ADO/MTS/COM+ 高级程序设计篇');
ListBox1.OnMouseMove := ListBox_MouseMove;
ListBox1.OnMouseDown := ListBox_MouseDown;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Self.Font.Name := 'Tahoma';
InitListBox;
CreateTipsWindow;
end;
procedure TForm1.CreateTipsWindow;
var
iccex: tagINITCOMMONCONTROLSEX;
begin
// Load the ToolTip class from the DLL.
iccex.dwSize := sizeof(tagINITCOMMONCONTROLSEX);
iccex.dwICC := ICC_BAR_CLASSES;
InitCommonControlsEx(iccex);
// Create the ToolTip control.
GHWND := CreateWindow(TOOLTIPS_CLASS, '',
WS_POPUP,
Integer(CW_USEDEFAULT), Integer(CW_USEDEFAULT),
Integer(CW_USEDEFAULT), Integer(CW_USEDEFAULT),
0, 0, hInstance,
nil);
// Prepare TOOLINFO structure for use as tracking ToolTip.
ti.cbSize := sizeof(ti);
ti.uFlags := TTF_IDISHWND + TTF_TRACK + TTF_ABSOLUTE + TTF_TRANSPARENT;
ti.hwnd := Self.Handle;
ti.uId := ListBox1.Handle;
ti.hinst := hInstance;
ti.lpszText := LPSTR_TEXTCALLBACK;
ti.rect.left := 0;
ti.rect.top := 0;
ti.rect.bottom := 0;
ti.rect.right := 0;
SendMessage(GHWND, WM_SETFONT, ListBox1.Font.Handle, Integer(LongBool(false)));
SendMessage(GHWND,TTM_ADDTOOL,0,Integer(@ti));
end;
procedure TForm1.WMNotify(var Msg: TMessage);
var
phd :PHDNotify;
NMTTDISPINFO: PNMTTDispInfo;
begin
phd := PHDNotify(Msg.lParam);
if phd.Hdr.hwndFrom = GHWND then
begin
if phd.Hdr.code = TTN_NEEDTEXT then
begin
NMTTDISPINFO := PNMTTDispInfo(phd);
NMTTDISPINFO.lpszText := PChar(ListBox1.Items[CurrentIndex]);
end;
end;
end;
procedure TForm1.ListBox_MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if TipVisable then //当鼠标按下，将显示的 Tooltip Window 隐藏
begin
SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
TipVisable := false;
end;
end;
procedure TForm1.ListBox_MouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
var
Index: Integer;
APoint: TPoint;
ARect: TRect;
ScreenRect: TRect;
begin
Index := ListBox1.ItemAtPos(Point(X, Y), true);
if Index = -1 then //如果鼠标下没有 Item，将 Tooltip Window 隐藏
begin
SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
OldIndex := -1;
TipVisable := false;
exit;
end;
CurrentIndex := Index;
if Index = OldIndex then exit; //如果鼠标在同一 Item 上移动，退出处理
if TipVisable then //先将显示的 Tooltip Window 隐藏
begin
SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
OldIndex := -1;
TipVisable := false;
end else
begin
ARect := ListBox1.ItemRect(Index);
//判断该 Item 是否完全显示
if (ARect.Right - ARect.Left - 2) >= ListBox1.Canvas.TextWidth(ListBox1.Items[Index]) then
begin
OldIndex := -1;
exit;
end;
APoint := ListBox1.ClientToScreen(ARect.TopLeft);
windows.GetClientRect(GetDesktopWindow, ScreenRect);
//判断 Tooltip Window 显示后是否会超出屏幕范围，这里只判断了右边界
if ListBox1.Canvas.TextWidth(ListBox1.Items[Index]) + APoint.X > ScreenRect.Right then
APoint.X := ScreenRect.Right - ListBox1.Canvas.TextWidth(ListBox1.Items[Index]) - 5;
SendMessage(GHWND,
TTM_TRACKPOSITION,
0,
MAKELPARAM(APoint.x - 1, APoint.y - 2));
SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(true)), Integer(@ti));
OldIndex := Index;
TipVisable := true;
end;
end;
procedure TForm1.HideTipsWindow;
begin
if TipVisable then
begin
SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
OldIndex := -1;
TipVisable := false;
end;
end;
end.