防止RTL TListView镜像复选框和/或图形

Question

我试图使ListView的列从右到左显示。这个问题已经被提出并回答了。但问题是关于图标和复选框的。当我使用SetWindowLong使ListView RTL时，它也会镜像图形和复选框，这是不想要的。我可以使用编辑工具来镜像图形，虽然麻烦但可行，但我不知道如何处理复选框。

我认为它们的原因相同，所以我搜索了一篇关于RTL布局的完整文章Microsoft Docs。在激活每个设备上下文的镜像部分中，它指出了图形问题。建议使用LAYOUT_RTL和LAYOUT_BITMAPORIENTATIONPRESERVED标志更改DC的布局样式。

这是我实现的函数，结合了上述答案和文章中建议的方法：

const
  LAYOUT_RTL = 1;
  LAYOUT_BITMAPORIENTATIONPRESERVED = 8;

function GetLayout(DC: HDC): DWORD; stdcall; external 'gdi32.dll';
function SetLayout(DC: HDC; dwLayout: DWORD): DWORD; stdcall; external 'gdi32.dll';

procedure MakeRTL(const Handle: HWND);
var
  DC: HDC;
begin
  SetWindowLong(Handle, GWL_EXSTYLE,
    GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYOUTRTL);

  DC := GetWindowDC(Handle);
  if DC <> 0 then
    SetLayout(DC, GetLayout(DC) or LAYOUT_RTL or LAYOUT_ORIENTATIONMASK);

  InvalidateRect(Handle, nil, True);
end;

但这并没有改变什么。我尝试阻止它们中的任何一个，改变它们的顺序和调用不同的位置，但都没有成功。

现在的问题是，如何使ListView的列从右到左显示，而不需要镜像图形或复选框？

我正在使用Win10 x64和Delphi 2010。

如果您想重现问题，这里是我的Delphi代码：

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, ImgList, StdCtrls, CommCtrl, ShellAPI;

type
  TForm1 = class(TForm)
    ListView1: TListView;
    ImageList1: TImageList;
    ListView2: TListView;
    Button1: TButton;
    Label1: TLabel;
    procedure FormActivate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Label1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  LAYOUT_RTL = 1;
  LAYOUT_BTT = 2;
  LAYOUT_VBH = 4;
  LAYOUT_ORIENTATIONMASK = LAYOUT_RTL or LAYOUT_BTT or LAYOUT_VBH;
  LAYOUT_BITMAPORIENTATIONPRESERVED = 8;

function GetLayout(DC: HDC): DWORD; stdcall; external 'gdi32.dll';
function SetLayout(DC: HDC; dwLayout: DWORD): DWORD; stdcall; external 'gdi32.dll';

procedure MakeRTL(const Handle: HWND);
var
  DC: HDC;
begin
  SetWindowLong(Handle, GWL_EXSTYLE,
    GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYOUTRTL);

  DC := GetWindowDC(Handle);
  if DC <> 0 then
    SetLayout(DC, GetLayout(DC) or LAYOUT_RTL or LAYOUT_ORIENTATIONMASK);

  InvalidateRect(Handle, nil, True);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  MakeRTL(ListView_GetHeader(ListView1.Handle));
  MakeRTL(ListView1.Handle);
end;

procedure TForm1.FormActivate(Sender: TObject);
var
  I: Integer;
begin
  for I := 0 to ListView1.Items.Count - 1 do
  begin
    ListView1.Items[I].Checked := True;
    ListView2.Items[I].Checked := True;
  end;
end;

procedure TForm1.Label1Click(Sender: TObject);
begin
  ShellExecute(0, 'open', 'https://icons8.com/icons/set/check', '', '', SW_SHOWNORMAL);
end;

end.

dfm：

object Form1: TForm1
  Left = 0
  Top = 0
  BiDiMode = bdLeftToRight
  Caption = 'Form1'
  ClientHeight = 169
  ClientWidth = 353
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  ParentBiDiMode = False
  OnActivate = FormActivate
  PixelsPerInch = 96
  TextHeight = 13
  object Label1: TLabel
    Left = 277
    Top = 128
    Width = 47
    Height = 26
    Cursor = crHandPoint
    Alignment = taCenter
    Caption = 'graphics by Icons8'
    Font.Charset = DEFAULT_CHARSET
    Font.Color = clBlue
    Font.Height = -11
    Font.Name = 'Tahoma'
    Font.Style = [fsUnderline]
    ParentFont = False
    WordWrap = True
    OnClick = Label1Click
  end
  object ListView1: TListView
    Left = 8
    Top = 8
    Width = 250
    Height = 73
    Checkboxes = True
    Columns = <
      item
        Caption = 'Cap'
        Width = 100
      end
      item
        Caption = 'Sub1'
        Width = 100
      end>
    Items.ItemData = {
      03620000000200000000000000FFFFFFFFFFFFFFFF01000000FFFFFFFF000000
      00054900740065006D00310005500072006F007000310001000000FFFFFFFFFF
      FFFFFF01000000FFFFFFFF00000000054900740065006D00320005500072006F
      0070003200FFFFFFFF}
    LargeImages = ImageList1
    SmallImages = ImageList1
    TabOrder = 0
    ViewStyle = vsReport
  end
  object ListView2: TListView
    Left = 8
    Top = 87
    Width = 250
    Height = 73
    Checkboxes = True
    Columns = <
      item
        Caption = 'Cap'
        Width = 100
      end
      item
        Caption = 'Sub1'
        Width = 100
      end>
    Items.ItemData = {
      03620000000200000000000000FFFFFFFFFFFFFFFF01000000FFFFFFFF000000
      00054900740065006D00310005500072006F007000310001000000FFFFFFFFFF
      FFFFFF01000000FFFFFFFF00000000054900740065006D00320005500072006F
      0070003200FFFFFFFF}
    SmallImages = ImageList1
    TabOrder = 1
    ViewStyle = vsReport
  end
  object Button1: TButton
    Left = 264
    Top = 8
    Width = 75
    Height = 25
    Caption = 'RTL'
    TabOrder = 2
    OnClick = Button1Click
  end
  object ImageList1: TImageList
    ColorDepth = cd32Bit
    DrawingStyle = dsTransparent
    Left = 272
    Top = 40
    Bitmap = {
      494C0101020008003C0010001000FFFFFFFF2110FFFFFFFFFFFFFFFF424D3600
      0000000000003600000028000000400000001000000001002000000000000010
      0000000000000000000000000000000000000000000000000000000000000000
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  end
end

- saastn

Answer 1

你的调用没有效果的原因是你所检索到的设备上下文根本没有被使用。从你当前的设计中可以怀疑这一点，因为你甚至不能调用ReleaseDC，导致设备上下文泄漏。

所有的绘制都在绘制循环中完成，当系统发送绘制消息时会触发它。你可以拦截该消息以修改要使用的设备上下文的布局 - VCL设计允许你首先检索上下文。

下面是你完整的示例代码相应地进行了修改，使用一个interposer类来修改listview的消息处理。

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, ImgList, StdCtrls, CommCtrl, ShellAPI;

type
  TListView = class(comctrls.TListView)
  protected
    procedure WMPaint(var Message: TWMPaint); message WM_PAINT;

  end;

  TForm1 = class(TForm)
    ListView1: TListView;
    ImageList1: TImageList;
    ListView2: TListView;
    Button1: TButton;
    Label1: TLabel;
    procedure FormActivate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Label1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function GetLayout(DC: HDC): DWORD; stdcall; external 'gdi32.dll';
function SetLayout(DC: HDC; dwLayout: DWORD): DWORD; stdcall; external 'gdi32.dll';

procedure MakeRTL(const Handle: HWND);
begin
  SetWindowLong(Handle, GWL_EXSTYLE,
    GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYOUTRTL);
  InvalidateRect(Handle, nil, True);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  MakeRTL(ListView_GetHeader(ListView1.Handle));
  MakeRTL(ListView1.Handle);
end;

procedure TForm1.FormActivate(Sender: TObject);
var
  I: Integer;
begin
  for I := 0 to ListView1.Items.Count - 1 do
  begin
    ListView1.Items[I].Checked := True;
    ListView2.Items[I].Checked := True;
  end;
end;

procedure TForm1.Label1Click(Sender: TObject);
begin
  ShellExecute(0, 'open', 'https://icons8.com/icons/set/check', '', '', SW_SHOWNORMAL);
end;

{ TListView }

const
  LAYOUT_RTL = 1;
  LAYOUT_BITMAPORIENTATIONPRESERVED = 8;

procedure TListView.WMPaint(var Message: TWMPaint);
var
  Layout: DWORD;
  PS: TPaintStruct;
begin
  Message.DC := BeginPaint(Handle, PS);
  Layout := GetLayout(Message.DC);
  if (Layout and LAYOUT_RTL) <> 0 then
    SetLayout(Message.DC, Layout or LAYOUT_BITMAPORIENTATIONPRESERVED);
  inherited;
  EndPaint(Handle, PS);
end;

end.

- Sertac Akyuz

---

谢谢Sertac。阅读那篇文章，我真的不认为每次绘制都需要这样做！完全将应用程序变成RTL是一件很麻烦的事情。 - saastn