App crash on close when windows style = windows

[Gary 17]

Hello all,

 

I have an app that dynamically changes the style. On close it saves style to ini and reloads on startup.

Changing style and closing is fine with any style except if the app has changed style to windows. App crashes after writing to ini, so if app starts with windows style and closes without changing all is fine. I logged the OnClose of the Main form and get no errors.

Debug shows the problem in the TStyleEngine.DoUnregisterStyleHook call and jumps to System here:

 

function _IsClass(const Child: TObject; Parent: TClass): Boolean;
begin
  Result := (Child <> nil) and Child.InheritsFrom(Parent);
end;

 

I have included the EurekaLog file.

 

Any help?

Gary

EurekaLog.txt

[aehimself 388]

I had issues like this when I used a combo box to change the style of the application in the OnChange handler. I suppose it had to do something with the dropdown window still visible.

 

On the other hand don't be surprised, VCL themes are quite unstable. Since upgrading to 11.2 my main application started to throw similar AVs upon closure, but coming from DBGrid's style hook.

[FPiette 367]

37 minutes ago, aehimself said:

Since upgrading to 11.2 my main application started to throw similar AVs upon closure, but coming from DBGrid's style hook.

You should file a bug report at https://quality.embarcadero.com You should write the smalest possible test application demonstrating the issue.

 

[GPRSNerd 11]

Hi,

 

did you find a fix for your problem?

I've exactly the same problem with one application, exception logged with madExcept:

 

exception number   : 1
exception class    : EAccessViolation
exception message  : Zugriffsverletzung bei Adresse 004090BC in Modul 'NikonDecoder.exe'. Lesen von Adresse 0030FFF0.

main thread ($4cd0):
004090bc +04 NikonDecoder.exe System          67 +0 TObject.InheritsFrom
00408fa6 +0e NikonDecoder.exe System          67 +0 @IsClass
007104bf +43 NikonDecoder.exe Vcl.Styles            TStyleEngine.DoUnregisterStyleHook
00710716 +1a NikonDecoder.exe Vcl.Styles            TStyleEngine.Notification
00667aef +f3 NikonDecoder.exe Vcl.Themes            TCustomStyleEngine.UnRegisterStyleHook

 

[GPRSNerd 11]

Here are two bug reports that seem to describe the issue above:

https://quality.embarcadero.com/browse/RSP-38114

https://quality.embarcadero.com/browse/RSP-39197

 

Both may have been fixed in Delphi 11.3 released today.

I will check that after installation.

[Dave Nottage 493]

19 minutes ago, GPRSNerd said:

Both may have been fixed in Delphi 11.3 released today

Both are in the list of fixes: https://docwiki.embarcadero.com/RADStudio/Alexandria/en/New_features_and_customer_reported_issues_fixed_in_RAD_Studio_11.3

[KodeZwerg 54]

For me this works flawless:

unit uMain;

interface

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

type
  TfrmMain = class(TForm)
    mmMain: TMainMenu;
    miVcl: TMenuItem;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormCreate(Sender: TObject);
  strict private
    FMenuItem: TMenuItem;
  private
    procedure AddNativeStyle(const AMenuItem: TMenuItem);
  public
    procedure NativeStyleClick(Sender: TObject);
  end;

var
  frmMain: TfrmMain;

implementation

{$R *.dfm}

procedure TfrmMain.FormCreate(Sender: TObject);
var
  ini: TIniFile;
  fn: string;
  Stylename: string;
  i: Integer;
begin
  AddNativeStyle(miVcl);
  fn := ChangeFileExt(ParamStr(0), '.ini');
  ini := TIniFile.Create(fn);
  try
    Stylename := ini.ReadString('Options', 'Theme', 'Windows');
    for i := 0 to Pred(miVcl.Count) do
      if StripHotkey(miVcl.Items[i].Caption) <> Stylename then
        miVcl.Items[i].Checked := False
        else
        miVcl.Items[i].Checked := True;
    TStyleManager.TrySetStyle(StyleName, True);
  finally
    ini.Free;
  end;
end;

procedure TfrmMain.FormClose(Sender: TObject; var Action: TCloseAction);
var
  ini: TIniFile;
  fn: string;
  i: Integer;
  StyleName: String;
begin
  fn := ChangeFileExt(ParamStr(0), '.ini');
  ini := TIniFile.Create(fn);
  try
    for i := 0 to Pred(miVcl.Count) do
      if miVcl.Items[i].Checked then
        begin
          StyleName := StripHotkey(miVcl.Items[i].Caption);
          Break;
        end;
    ini.WriteString('Options', 'Theme', StyleName);
  finally
    ini.Free;
  end;
end;

procedure TfrmMain.AddNativeStyle(const AMenuItem: TMenuItem);
  procedure AddMenuEntry(const ACaption: string; const AValue: Integer);
  var
    Item: TMenuItem;
  begin
    Item := TMenuItem.Create(FMenuItem);
    Item.Caption := ACaption;
    Item.OnClick := NativeStyleClick;
    Item.AutoCheck := False;
    Item.RadioItem := False;
    Item.Checked :=  TStyleManager.ActiveStyle.Name = ACaption;
    if ((AValue) mod 50) = 0 then
      Item.Break := mbBarBreak;
    FMenuItem.Add(Item);
  end;
var
  Arr: TArray<string>;
  SystemStyle: string;
  FoundStyle: String;
  i: Integer;
begin
  FMenuItem := AMenuItem;
  FMenuItem.Clear;
  FMenuItem.AutoLineReduction := maAutomatic;
  Arr := TStyleManager.StyleNames;
  SystemStyle := TStyleManager.SystemStyle.Name;
  AddMenuEntry(SystemStyle, 0);
  i := 1;
  for FoundStyle in Arr do
  begin
    if FoundStyle <> SystemStyle then
    begin
      AddMenuEntry(FoundStyle, i);
      Inc(i);
    end;
  end;
end;

procedure TfrmMain.NativeStyleClick(Sender: TObject);
var
  StyleName: String;
  i: Integer;
begin
  StyleName := StripHotkey((Sender as TMenuItem).Caption);
  TStyleManager.TrySetStyle(StyleName, True);
  (Sender as TMenuItem).Checked := True;
  for i := 0 to Pred(FMenuItem.Count) do
    if (not FMenuItem.Items[i].Equals(Sender)) then
      FMenuItem.Items[i].Checked := False;
end;

end.

Tested with Alexandria 11.2

[aehimself 388]

Fyi, D11.3 (in theory) solved some issues with UnregisterStyleHook.

Can not confirm, though.

[GPRSNerd 11]

I can confirm that Delphi 11.3 has the issue fixed.

No more exception on close when the default style "Windows" was used/changed during runtime.

[aehimself 388]

51 minutes ago, GPRSNerd said:

I can confirm that Delphi 11.3 has the issue fixed.

No more exception on close when the default style "Windows" was used/changed during runtime.

Did you manage to consistently reproduce the issue?

At me it seemed random, popped up once or twice before disappearing for days.

[GPRSNerd 11]

Yeah, it was reproducible.

I added a functionality to switch the embedded styles in my app on runtime.

When I start the app and switch styles and in this procedure once the default Windows style was set, then the app throws the exception on close.

It is not necessarily the "Windows" style which has to be set last before closing.

Edited March 3, 2023 by GPRSNerd