如何同步2个TTreeviews的滚动？

Question

我有 2 个 TTreeviews。他们两个都有相同数量的项目。 我希望能够同步他们的滚动条...如果我移动其中一个，其他的也会移动...

对于水平，它按我的预期工作...... 对于垂直，如果我使用滚动条的箭头，它会起作用，但如果我拖动拇指或如果我使用鼠标滚轮，它就不起作用...

这是我为说明我的问题而编写的示例：

unit main;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ComCtrls, StrUtils;

type
  TForm1 = class(TForm)
    tv1: TTreeView;
    tv2: TTreeView;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    originalTv1WindowProc : TWndMethod;
    originalTv2WindowProc : TWndMethod;
    procedure Tv1WindowProc (var Msg : TMessage);
    procedure Tv2WindowProc (var Msg : TMessage);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to 10 do
  begin
    tv1.Items.AddChild(nil, DupeString('A', 20) + IntToStr(i));
    tv2.Items.AddChild(nil, DupeString('B', 20) + IntToStr(i));
  end;

  originalTv1WindowProc := tv1.WindowProc;
  tv1.WindowProc        := Tv1WindowProc;
  originalTv2WindowProc := tv2.WindowProc;
  tv2.WindowProc        := Tv2WindowProc;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  tv1.WindowProc := originalTv1WindowProc;
  tv2.WindowProc := originalTv2WindowProc;

  originalTv1WindowProc := nil;
  originalTv2WindowProc := nil;
end;

procedure TForm1.Tv1WindowProc(var Msg: TMessage);
begin
  originalTv1WindowProc(Msg);
  if ((Msg.Msg = WM_VSCROLL)
   or (Msg.Msg = WM_HSCROLL)
   or (Msg.msg = WM_Mousewheel)) then
  begin
//    tv2.Perform(Msg.Msg, Msg.wparam, Msg.lparam);
    originalTv2WindowProc(Msg);
  end;
end;

procedure TForm1.Tv2WindowProc(var Msg: TMessage);
begin
  originalTv2WindowProc(Msg);
  if ((Msg.Msg = WM_VSCROLL)
   or (Msg.Msg = WM_HSCROLL)
   or (Msg.msg = WM_Mousewheel)) then
  begin
//    tv1.Perform(Msg.Msg, Msg.wparam, Msg.lparam);
    originalTv1WindowProc(Msg);
  end;
end;

end.

DFM：

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 113
  ClientWidth = 274
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object tv1: TTreeView
    Left = 8
    Top = 8
    Width = 121
    Height = 97
    Indent = 19
    TabOrder = 0
  end
  object tv2: TTreeView
    Left = 144
    Top = 8
    Width = 121
    Height = 97
    Indent = 19
    TabOrder = 1
  end
end

我也尝试从 TTreeview 创建一个子类，但没有成功（相同的行为）... 我尝试了一个 TMemo，它按预期工作......

我错过了什么？

干杯，

W.

Answer 1

首先，一个有趣的测试：取消选中项目选项中的“启用运行时主题”，您将看到两个树视图将同步滚动。这向我们展示了树视图控件的默认窗口过程在不同版本的 comctl32.dll 中实现不同。看来，comctl32 v6 中的实现在垂直滚动时特别不同。

无论如何，看起来，仅对于垂直滚动，控件会查找拇指位置，然后相应地调整窗口内容。当您将WM_VSCROLL 路由到相邻的树视图时，它会查看其拇指的位置，并且由于它没有更改，因此决定无事可做（我们只更改了我们正在拖动的那个的拇指位置）。

因此，要使其正常工作，请在发送WM_VSCROLL 之前调整树视图的拇指位置。 tv1 的修改过程如下所示：

procedure TForm1.Tv1WindowProc(var Msg: TMessage);
begin
  originalTv1WindowProc(Msg);

  if Msg.Msg = WM_VSCROLL then begin
    if Msg.WParamLo = SB_THUMBTRACK then
      SetScrollPos(tv2.Handle, SB_VERT, Msg.WParamHi, False);
  end;

  if ((Msg.Msg = WM_VSCROLL)
   or (Msg.Msg = WM_HSCROLL)
   or (Msg.msg = WM_Mousewheel)) then
  begin
//    tv2.Perform(Msg.Msg, Msg.wparam, Msg.lparam);
    originalTv2WindowProc(Msg);
  end;
end;

Answer 2

更新：

我在French forum 上得到了另一个答案，来自ShaiLeTroll：

此解决方案完美运行。我始终保持同步：箭头、拇指、水平、垂直、鼠标滚轮！

这是更新后的代码（混合了两种解决方案：拇指和鼠标滚轮）：

unit main;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ComCtrls, StrUtils;

type
  TForm1 = class(TForm)
    tv1: TTreeView;
    tv2: TTreeView;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    originalTv1WindowProc : TWndMethod;
    originalTv2WindowProc : TWndMethod;

    sender: TTreeView;

    procedure Tv1WindowProc (var Msg : TMessage);
    procedure Tv2WindowProc (var Msg : TMessage);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
  tn: TTreeNode;
begin
  for i := 0 to 20 do
  begin
    tn := tv1.Items.AddChild(nil, DupeString('A', 20) + IntToStr(i));
    tv1.Items.AddChild(tn, DupeString('C', 20) + IntToStr(i));
    tv1.Items.AddChild(tn, DupeString('C', 20) + IntToStr(i));
    tn := tv2.Items.AddChild(nil, DupeString('B', 20) + IntToStr(i));
    tv2.Items.AddChild(tn, DupeString('D', 20) + IntToStr(i));
    tv2.Items.AddChild(tn, DupeString('D', 20) + IntToStr(i));
  end;

  originalTv1WindowProc := tv1.WindowProc;
  tv1.WindowProc        := Tv1WindowProc;
  originalTv2WindowProc := tv2.WindowProc;
  tv2.WindowProc        := Tv2WindowProc;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  tv1.WindowProc        := originalTv1WindowProc;
  tv2.WindowProc        := originalTv2WindowProc;
  originalTv1WindowProc := nil;
  originalTv2WindowProc := nil;
end;

procedure TForm1.Tv1WindowProc(var Msg: TMessage);
begin
  originalTv1WindowProc(Msg);

  if Msg.Msg = WM_VSCROLL then
  begin
    if Msg.WParamLo = SB_THUMBTRACK then
    begin
      SetScrollPos(tv2.Handle, SB_VERT, Msg.WParamHi, False);
    end;
  end;

  if (sender <> tv2) and
    ((Msg.Msg = WM_VSCROLL) or (Msg.Msg = WM_HSCROLL) or (Msg.Msg = WM_MOUSEWHEEL)) then
  begin
    sender := tv1;
    tv2.Perform(Msg.Msg, Msg.wparam, Msg.lparam);
    sender := nil;
  end;
end;

procedure TForm1.Tv2WindowProc(var Msg: TMessage);
begin
  originalTv2WindowProc(Msg);

  if Msg.Msg = WM_VSCROLL then
  begin
    if Msg.WParamLo = SB_THUMBTRACK then
    begin
      SetScrollPos(tv1.Handle, SB_VERT, Msg.WParamHi, False);
    end;
  end;

  if (sender <> tv1) and ((Msg.Msg = WM_VSCROLL) or (Msg.Msg = WM_HSCROLL) or (Msg.Msg = WM_MOUSEWHEEL)) then
  begin
    sender := tv2;
    tv1.Perform(Msg.Msg, Msg.wparam, Msg.lparam);
    sender := nil;
  end;
end;

end.