Delphi 11.3：GDI缩放+bsNone边框样式多显示器坐标异常问题

问题概述 #

在Delphi 11.3项目中，将DPI Awareness模式设置为GDI Scaling时，若二级窗体的BorderStyle设为bsNone，且主窗体位于不同DPI缩放的显示器上，二级窗体在主显示器（Monitor 1）的坐标会完全错误。

设备配置（Windows 11） #

• Monitor 1：1920×1080，100%缩放（DPI）
• Monitor 3：4K电视，与Monitor 1克隆显示
• Monitor 2：1920×1200，150%缩放（DPI），位于Monitor 1右侧

测试场景 #

1. Form2设为bsSizeable，Form1在任意显示器，修改Form2位置→正常
2. Form2设为bsNone，Form1在Monitor 1，修改Form2位置→正常
3. Form2设为bsNone，将Form1移至Monitor 2后修改Form2位置→坐标完全错误

其他模式验证 #

• Per Monitor v2模式下所有情况正常（存在其他无关问题）
• GDI Scaling+Form2为bsSizeable→正常
• GDI Scaling+Form2为bsNone→坐标错误

复现代码 #

Project1.dpr #

program Project1;

uses
  Vcl.Forms,
  Unit1 in 'Unit1.pas' {Form1},
  Unit2 in 'Unit2.pas' {Form2},
  Vcl.Themes,
  Vcl.Styles;

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

Unit1.pas #

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Unit2;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Form2 := TForm2.Create(Application);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Form2.Left := Screen.PrimaryMonitor.WorkareaRect.Left + 300;
  Form2.Top  := Screen.PrimaryMonitor.WorkareaRect.Top  + 300;
  Form1.Caption := Form2.Left.ToString + ' - ' + Form2.Top.ToString;
end;

end.

Form1.dfm #

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 312
  ClientWidth = 296
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -12
  Font.Name = 'Segoe UI'
  Font.Style = []
  Position = poScreenCenter
  TextHeight = 15
  object Button1: TButton
    Left = 8
    Top = 8
    Width = 185
    Height = 121
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 8
    Top = 135
    Width = 185
    Height = 114
    Caption = 'Button2'
    TabOrder = 1
    OnClick = Button2Click
  end
end

Unit2.pas #

unit Unit2;

interface

uses
  Winapi.Windows, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, ShellApi,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls;
type
  TForm2 = class(TForm)
    Label1: TLabel;
  private
    procedure CreateParams(var Params : TCreateParams);  override;
  public
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.CreateParams(var Params : TCreateParams);
begin
  inherited CreateParams(Params);
  With Params do begin
    ExStyle   := ExStyle or WS_EX_TOPMOST;
    WndParent := GetDesktopwindow;
  end;
end;

end.

Form2.dfm #

object Form2: TForm2
  Left = 100
  Top = 100
  AlphaBlendValue = 200
  BorderStyle = bsNone
  Caption = 'Form2'
  ClientHeight = 95
  ClientWidth = 201
  Color = 4227327
  TransparentColorValue = clGreen
  DefaultMonitor = dmPrimary
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -12
  Font.Name = 'Segoe UI'
  Font.Style = []
  FormStyle = fsStayOnTop
  Position = poScreenCenter
  Visible = True
  TextHeight = 15
  object Label1: TLabel
    Left = 8
    Top = 8
    Width = 142
    Height = 37
    Caption = 'Hello World'
    Font.Charset = DEFAULT_CHARSET
    Font.Color = clWindowText
    Font.Height = -27
    Font.Name = 'Segoe UI'
    Font.Style = []
    ParentFont = False
  end
end

内容的提问来源于stack exchange，提问作者hikari