Delphi 調用 WinAPI：自訂輸入光標形狀與顏色（三）

動態切換光標外觀：標準、灰階與自訂點陣圖

本篇示範如何使用 CreateCaret 的 hBitmap 參數，配合 RadioGroup 讓使用者即時切換三種光標樣式：預設黑色閃爍線、灰階方塊、以及自訂的星號 (★) 點陣圖。同時展示 SetCaretBlinkTime 在表單銷毀時還原系統預設閃爍速度 (530 ms) 的良好習慣。

關鍵技術點

• hBitmap = 0：標準垂直線光標，寬度由 nWidth 決定。
• hBitmap = 1：灰階光標（系統內建）。
• hBitmap = TBitmap.Handle：使用自訂點陣圖作為光標形狀，尺寸需與點陣圖實際大小一致。

完整程式碼

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    RadioGroup1: TRadioGroup;
    procedure FormCreate(Sender: TObject);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure RadioGroup1Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  bit: TBitmap;

procedure TForm1.FormCreate(Sender: TObject);
const
  c = '★';
begin
  RadioGroup1.Caption := '光標形色';
  RadioGroup1.Items.CommaText := '黑色,灰度,自定義';
  RadioGroup1.ItemIndex := 0;

  bit := TBitmap.Create;
  bit.Canvas.Font.Size := 16;
  bit.Width := bit.Canvas.TextWidth(c);
  bit.Height := bit.Canvas.TextHeight(c);
  bit.Canvas.TextOut(0, 0, c);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  SetCaretBlinkTime(530); // 還原系統預設值
  bit.Free;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  h: HBITMAP;
begin
  DestroyCaret;
  h := 0;
  case RadioGroup1.ItemIndex of
    1: h := 1;          // 灰度
    2: h := bit.Handle; // 自訂點陣圖
  end;
  CreateCaret(Handle, h, 4, 32);
  SetCaretPos(X, Y);
  ShowCaret(Handle);
end;

procedure TForm1.RadioGroup1Click(Sender: TObject);
var
  h: HBITMAP;
  pt: TPoint;
begin
  GetCaretPos(pt);
  DestroyCaret;
  h := 0;
  case RadioGroup1.ItemIndex of
    1: h := 1;
    2: h := bit.Handle;
  end;
  CreateCaret(Handle, h, 4, 32);
  SetCaretPos(pt.X, pt.Y);
  ShowCaret(Handle);
end;

end.

表單定義 (DFM)

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 137
  ClientWidth = 228
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  OnMouseUp = FormMouseUp
  PixelsPerInch = 96
  TextHeight = 13
  object RadioGroup1: TRadioGroup
    Left = 137
    Top = 16
    Width = 80
    Height = 113
    Caption = 'RadioGroup1'
    TabOrder = 0
    OnClick = RadioGroup1Click
  end
end

透過簡單的位圖操作即可打造專屬光標，為應用程式增添獨特視覺識別。