Prevent RTL TListView from mirroring check boxes a

2020-04-11 03:58发布

问题:

I'm trying to make columns of a ListView appear from right to left. This has already been asked and answered. But the problem is about icons and check boxes. When I make a ListView RTL using SetWindowLong, it mirrors graphics and checkboxes as well, wich is not wanted. I can mirror graphics using editing tools, bothering but doable, but I don't know how to handle check boxes.

I think both of them have same reason, so I searched about it and found an entire article about RTL layout in Microsoft Docs. In Activating Mirroring per Device Context section it points out the graphics problem. It suggests to change layout style of DC with LAYOUT_RTL and LAYOUT_BITMAPORIENTATIONPRESERVED flags.

This is the function I implemented with combining methods suggested in the article and the answer mentioned above:

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;

But it doesn't change anything. I tried blocking either of them, changing order of them and changing different places to call it, but no success.

Now the question is, how to make columns of a ListView appear from right to left, without mirroring graphics or checkboxes?

I'm using Win10 x64 and Delphi 2010.

here is my delphi codes if you want to reproduce the problem:

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

回答1:

The reason your calls doesn't have an effect is that the device context you retrieved is not used in any way at all. You should suspect this since, in your current design, you can't even call ReleaseDC and the DC leaks.

All painting is done in a painting cycle when the system triggers it by sending a paint message. You can intercept the message to modify the layout of the device context to be used - VCL design allows that you retrieve the context first.

Below is your full example code accordingly modified, using an interposer class to modify listview's message handling.

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.