wsMaximized形式不显示为最大化 [英] wsMaximized forms do not appear maximized

问题描述

将表单设置为 WindowState = wsMaximized 有时会导致表单最大化，但不会：

< img src = https://i.stack.imgur.com/L3L5l.png alt =在此处输入图片描述>

长期错误：此是我在2003年在Borland新闻组中首次提出的问题：

• 例如：

   程序TForm1.FormActivate（Sender：TObject）; 
   begin 
   //仅在第一次激活表单时才最大化一次
  ，如果未进行FMaxsimized，则
  开始
   FMaxsimized：= True; 
   ShowWindow（Handle，SW_MAXIMIZE）; 
  结尾； 
  结尾； 
    

  此方法在 OnShow 。

  
  
  

  更好的解决方法： 使用 ShowWindowAsync 在 OnShow 或 OnCreate 期间，例如：

   过程TForm1.FormCreate（Sender：TObject）; 
   begin 
   ShowWindowAsync（Handle，SW_MAXIMIZE）; 
  结尾； 
    

  这将设置窗口的显示状态，而无需等待操作完成。

  
  

  Setting a form to WindowState = wsMaximized will sometimes cause the form to be maximized but not:

  Long-time bug: this is a question I first asked in the Borland newsgroups in 2003:

  • Accepted fix for WindowState = wsMaximized?

  and then again in 2006:

  • wsMaximized breaks it, NOT caused by Position=poScreenCenter, reproducible dfm

  and then again in 2008:

  • Forms not starting maximized

  Someone asked it on the Embarcadero forums in 2012:

  • Thread: Application not starting with maximized window

  Now it's time to port the 18 year old bug to Stackoverflow. Maybe someone's finally figured out a workaround.

  Steps to reproduce:

  My posts contained half a dozen failure modes, but the easiest is:

  • Drop a Label and an Edit on a form:

  • Add an OnEnter event for the TEdit:

    procedure TForm1.Edit1Enter(Sender: TObject);
    begin
       Label1.Font.Style := Label1.Font.Style + [fsBold];
    end;
    

  • and set the form:

    • WindowState to wsMaximized
    • AutoScroll to False

  And bazinga, fails.

  One of the other set of steps from the 2008 post:

  1. Create a new app and a form.
  2. Set the form to maximized (WindowState = wsMaximized) at design time.
  3. Drop a ListView control on the form

  4. During OnShow, add 20 empty items to the list view:

     procedure TForm1.FormShow(Sender: TObject);
     var
          i: Integer;
     begin
          for i := 1 to 20 do
               ListView1.Items.Add;
     
     end;
     

  5. Set the form's AutoScroll property to false (AutoScroll = False) at design time

  Of course what I'm not after is "fixed in version n of RadStudio. Just use that". I'm looking for an actual fix (if there is one); which could include quoting relevant changes to the VCL source when CodeGear finally did fix it. (If it is even fixed).

  Note: Changing Position from poDesigned to anything else doesn't fix it.

  Workaround

  A horrible, ugly, awful, disgusting, workaround I had been using was to start a timer during OnShow, and then when the timer fires, maximize the form:

  procedure TForm1.tmrVclMaximizeHackTimer(Sender: TObject);
  begin
     Self.WindowState := wsMaximized;
  end;
  

  I later improved this hack to post a message during OnShow; which is essentially the same as a timer message, without having to use a timer:

  const
    WM_MaximizeWindow = WM_APP + $03;
  
  procedure TForm1.FormShow(Sender: TObject);
  begin
    if (Self.WindowState = wsMaximized) then
    begin
       Self.WindowState := wsNormal;
       PostMessage(Self.Handle, WM_MaximizeWindow , 0, 0);
    end;
  end;
  
  private
     procedure WMMaximizeWindow(var Message: TMessage); message WM_MaximizeWindow;
  
  procedure TForm1.WMMaximizeWindow(var Message: TMessage);
  begin
     Self.WindowState := wsMaximized;
  end;
  

  Sometimes I invent the OnAfterShow event that Delphi never did:

  const
    WM_AfterShow = WM_APP + $02;
  
  procedure TForm1.FormShow(Sender: TObject);
  begin
    PostMessage(Self.Handle, WM_AfterShow, 0, 0);
    if (Self.WindowState = wsMaximized) then
    begin
       Self.WindowState := wsNormal;
       FMaximizeNeeded := True;
    end;
  end;
  
  private
     procedure WMAfterShow(var Message: TMessage); message WM_AfterShow;
  
  procedure TForm1.WMAfterShow(var Message: TMessage);
  begin
     if FMaximizeNeeded then
     begin    
        FMaximizeNeeded := False;
        Self.WindowState := wsMaximized;
     end;
  end;
  

  But no hacks are better than hacks.

  解决方案

  I Can reproduce with D7/Win7.

  I don't use wsMaximized at all (similar random problems as you describe).

  Workaround: use OnActivate -> ShowWindow(Handle, SW_MAXIMIZE) e.g.:

  procedure TForm1.FormActivate(Sender: TObject);
  begin
    // Maximize only once when the Form is first activated
    if not FMaxsimized then
    begin
      FMaxsimized := True;
      ShowWindow(Handle, SW_MAXIMIZE);
    end;
  end;
  

  This method will not work during OnShow.

  Better Workaround: use ShowWindowAsync during OnShow or OnCreate e.g:

  procedure TForm1.FormCreate(Sender: TObject);
  begin
    ShowWindowAsync(Handle, SW_MAXIMIZE);
  end;
  

  This sets the show state of a window without waiting for the operation to complete.

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