如何在delphi中使用笔压力属性？

Question

我将此代码用于获取压力属性，但不起作用。为什么GetPointerPenInfo函数返回false？ LastError函数返回87（参数错误）

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
  private
    { Private declarations }
  public
    { Public declarations }
    procedure PenEvent(var msg: TWMPointerUpdate); message WM_POINTERUPDATE;
  end;

var
  Form1: TForm1;

implementation


{$R *.dfm}
{ TForm1 }


{ TForm1 }

procedure TForm1.PenEvent(var msg: TWMPointerUpdate);
var
  pInfo: PPointerPenInfo;
begin
  if GetPointerPenInfo(msg.pointerId, pInfo) then
    Label1.Caption := inttostr(pInfo.pressure);
end;

end.

Answer 1

您正在将未初始化的指针传递给GetPointerPenInfo()。尝试以下方法：

procedure TForm1.PenEvent(var msg: TWMPointerUpdate);
var
  Info: TPointerPenInfo;
begin
  if not GetPointerPenInfo(msg.pointerId, @Info) then RaiseLastOSError;
  Label1.Caption := IntToStr(Info.pressure);
end;