Можно ли изменить вид текстового курсора (каретки) edit'а или другого элемента?

Можно! В примере показано как создать два цветных "bitmap'а": "улыбчивый" и "хмурый" и присвоить их курсору edit'а. Для этого нужно перехватить оконную процедуру edit'а. Чтобы сделать это заменим адрес оконной процедуры Edit'а нашим собственным, а старую оконную процедуру будем вызывать по необходимости. Пример показывает "улыбчивый" курсор при наборе текста и "хмурый" при забое клавишей backspace.

unit caret1;
 
interface
 
{$IFDEF WIN32}
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls;
{$ELSE}
uses
  WinTypes, WinProcs, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
{$ENDIF}
 
type
  TForm1 = class(TForm)
    Edit1: TEdit;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
  {Private declarations}
  public
  {Public declarations}
    CaretBm: TBitmap;
    CaretBmBk: TBitmap;
    OldEditsWindowProc: Pointer;
  end;
 
var
  Form1: TForm1;
 
implementation
{$R *.DFM}
 
type
{$IFDEF WIN32}
  WParameter = LongInt;
{$ELSE}
  WParameter = Word;
{$ENDIF}
  LParameter = LongInt;
 
{New windows procedure for the edit control}
 
function NewWindowProc(WindowHandle: hWnd; TheMessage: WParameter; ParamW: WParameter;
  ParamL: LParameter): LongInt
{$IFDEF WIN32} stdcall; {$ELSE}; export; {$ENDIF}
begin
{Call the old edit controls windows procedure}
  NewWindowProc := CallWindowProc(Form1.OldEditsWindowProc, WindowHandle,
    TheMessage, ParamW, ParamL);
  if TheMessage = WM_SETFOCUS then
    begin
      CreateCaret(WindowHandle, Form1.CaretBm.Handle, 0, 0);
      ShowCaret(WindowHandle);
    end;
  if TheMessage = WM_KILLFOCUS then
    begin
      HideCaret(WindowHandle);
      DestroyCaret;
    end;
  if TheMessage = WM_KEYDOWN then
    begin
      if ParamW = VK_BACK then
        CreateCaret(WindowHandle, Form1.CaretBmBk.Handle, 0, 0)
      else
        CreateCaret(WindowHandle, Form1.CaretBm.Handle, 0, 0);
      ShowCaret(WindowHandle);
    end;
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
{Create a smiling bitmap using the wingdings font}
  CaretBm := TBitmap.Create;
  CaretBm.Canvas.Font.Name := 'WingDings';
  CaretBm.Canvas.Font.Height := Edit1.Font.Height;
  CaretBm.Canvas.Font.Color := clWhite;
  CaretBm.Width := CaretBm.Canvas.TextWidth('J') + 2;
  CaretBm.Height := CaretBm.Canvas.TextHeight('J') + 2;
  CaretBm.Canvas.Brush.Color := clBlue;
  CaretBm.Canvas.FillRect(Rect(0, 0, CaretBm.Width, CaretBm.Height));
  CaretBm.Canvas.TextOut(1, 1, 'J');
{Create a frowming bitmap using the wingdings font}
  CaretBmBk := TBitmap.Create;
  CaretBmBk.Canvas.Font.Name := 'WingDings';
  CaretBmBk.Canvas.Font.Height := Edit1.Font.Height;
  CaretBmBk.Canvas.Font.Color := clWhite;
  CaretBmBk.Width := CaretBmBk.Canvas.TextWidth('L') + 2;
  CaretBmBk.Height := CaretBmBk.Canvas.TextHeight('L') + 2;
  CaretBmBk.Canvas.Brush.Color := clBlue;
  CaretBmBk.Canvas.FillRect(Rect(0, 0, CaretBmBk.Width, CaretBmBk.Height));
  CaretBmBk.Canvas.TextOut(1, 1, 'L');
{Hook the edit controls window procedure}
  OldEditsWindowProc := Pointer(SetWindowLong(Edit1.Handle, GWL_WNDPROC,
    LongInt(@NewWindowProc)));
end;
 
procedure TForm1.FormDestroy(Sender: TObject);
begin
{Unhook the edit controls window procedure and clean up}
  SetWindowLong(Edit1.Handle, GWL_WNDPROC, LongInt(OldEditsWindowProc));
  CaretBm.Free;
  CaretBmBk.Free;
end;

{
  The example below demonstrates creating custom caret:
}
 
unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls, StdCtrls;
 
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Image1: TImage;
    Edit1: TEdit;
    procedure Memo1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Edit1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.DFM}
 
procedure TForm1.Memo1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  CreateCaret(Memo1.Handle, Image1.Picture.Bitmap.Handle, 0, 0);
  ShowCaret(Memo1.Handle);
end;
 
procedure TForm1.Edit1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  CreateCaret(Edit1.Handle, 0, 10, 4);
  ShowCaret(Edit1.Handle);
end;
 
end.

{The form file source (*.dfm) }
 
  object Form1: TForm1
    Left = 192
    Top = 107
    Width = 544
    Height = 375
    Caption = 'Form1'
    Color = clBtnFace
    Font.Charset = DEFAULT_CHARSET
    Font.Color = clWindowText
    Font.Height = -11
    Font.Name = 'MS Sans Serif'
    Font.Style = []
    OldCreateOrder = False
    PixelsPerInch = 96
    TextHeight = 13
    object Image1: TImage
      Left = 12
      Top = 4
      Width = 16
      Height = 16
      AutoSize = True
      Picture.Data = {  
      07544269746D6170B6020000424DB602000000000000B6000000280000001000  
      0000100000000100100000000000000200000000000000000000100000000000  
      000000000000000080000080000000808000800000008000800080800000C0C0  
      C000808080000000FF0000FF000000FFFF00FF000000FF00FF00FFFF0000FFFF  
      FF00000000000000000000000000000000000000000000000000000000000000  
      0000000000000000000000000000000000000000000000000000000000000000  
      000000000000FF7FFF7FFF7FFF7F000000000000FF7FFF7FFF7FFF7FFF7FFF7F  
      00000000FF7FFF7FFF7FFF7F000000000000FF7FFF7FFF7FFF7FFF7FFF7F0000  
      0000FF7FFF7FFF7FFF7FFF7F00000000FF7FFF7FFF7FFF7FFF7FFF7FFF7F0000  
      000000000000FF7FFF7FFF7F0000000000000000FF7FFF7FFF7FFF7F00000000  
      0000000000000000FF7FFF7FFF7FFF7FFF7FFF7FFF7FFF7FFF7FFF7F00000000  
      0000000000000000FF7FFF7FFF7FFF7FFF7FFF7FFF7FFF7FFF7F000000000000  
      0000000000000000FF7FFF7FFF7F00000000FF7FFF7FFF7FFF7F000000000000  
      00000000000000000000FF7FFF7FFF7FFF7FFF7FFF7FFF7F0000000000000000  
      00000000000000000000FF7FFF7FFF7FFF7FFF7FFF7FFF7F0000000000000000  
      000000000000000000000000FF7FFF7FFF7FFF7FFF7FFF7F0000000000000000  
      000000000000000000000000FF7FFF7FFF7FFF7FFF7F00000000000000000000  
      0000000000000000000000000000FF7FFF7FFF7FFF7F00000000000000000000  
      0000000000000000000000000000FF7FFF7FFF7F000000000000000000000000  
      00000000000000000000000000000000FF7F0000000000000000000000000000  
      0000}
    end
    object Memo1: TMemo
      Left = 12
      Top = 36
      Width = 149
      Height = 149
      Lines.Strings = ('Memo1')
      TabOrder = 0
      OnMouseDown = Memo1MouseDown
    end
    object Edit1: TEdit
      Left = 220
      Top = 60
      Width = 121
      Height = 21
      TabOrder = 1
      Text = 'Edit1'
      OnMouseDown = Edit1MouseDown
    end
  end
 

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