Lazarus实现TEdit组件的文本垂直居中

在Lazarus中要实现TEdit组件的文本垂直居中，可以通过自定义TEdit组件并重写其CreateParams方法来设置编辑框的样式为多行，然后通过SetCenter方法来调整文本的垂直位置。
在需要的unit添加EditCenter单元。
注意：EditCenter单元一定要放StdCtrls后面，否则无效果。

unit EditCenter;

{$mode ObjFPC}{$H+}

interface

uses
 Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, Messages, LCLType, LCLIntf;

Type

  TEdit = class(StdCtrls.TEdit)
  protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure KeyPress(var Key: Char); override;
    procedure WMSize(var msg: TWMSize); message WM_SIZE;
    procedure SetParent(AParent: TWinControl); override;
    procedure SetCenter;
  end;

implementation

procedure TEdit.CreateParams(var Params: TCreateParams);
begin
  inherited;
  Params.Style := Params.Style or ES_MULTILINE;
end;

procedure TEdit.KeyPress(var Key: Char);
begin
  inherited;
  if Key = #13 then
    key := #0;
end;

procedure TEdit.WMSize(var msg: TWMSize);
begin
  inherited;
  SetCenter;
end;

procedure TEdit.SetParent(AParent: TWinControl);
begin
  inherited;
  if Parent <> nil then
  begin
    SetCenter;
  end;
end;

procedure TEdit.SetCenter;
var
  DC: HDC;
  SaveFont: HFont;
  Sin: Integer;
  SysMetrics, Metrics: TTextMetric;
  Rct: TRect;
begin
  DC := GetDC(0);
  GetTextMetrics(DC, SysMetrics);
  SaveFont := SelectObject(DC, Font.Handle);
  GetTextMetrics(DC, Metrics);
  SelectObject(DC, SaveFont);
  ReleaseDC(0, DC);
  Rct := ClientRect;
  Sin := Height - Metrics.tmHeight - Sin;
  Rct.Top := Sin div 2;
  SendMessage(Handle, 180, 0, Integer(@Rct));
end;

end.

使用范例：

unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls,  EditCenter;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
  private

  public
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}
           

 编译运行的效果：

 这个方面windows和linux都有效。
注意：要设置控件的AutoSize:=false;