Add AppCreateForm wrapper function.

Author: jordanrussell

Projects/Setup.dpr

@@ -2,7 +2,7 @@ program Setup;
 
 {
   Inno Setup
-  Copyright (C) 1997-2024 Jordan Russell
+  Copyright (C) 1997-2025 Jordan Russell
   Portions by Martijn Laan
   For conditions of distribution and use, see LICENSE.TXT.
 
@@ -300,7 +300,6 @@ begin
     Application.MainFormOnTaskBar := True;
     InitializeSetup;
     MainForm := TMainForm.Create(Application);
-    Application.CreateForm(TWizardForm, WizardForm);
     MainForm.InitializeWizard;
   except
     { Halt on any exception }

Projects/Src/Setup.MainForm.pas

@@ -107,6 +107,7 @@ procedure TMainForm.SetStep(const AStep: TSetupStep; const HandleExceptions: Boo
 
 procedure TMainForm.InitializeWizard;
 begin
+  WizardForm := AppCreateForm(TWizardForm) as TWizardForm;
   if CodeRunner <> nil then begin
     try
       CodeRunner.RunProcedures('InitializeWizard', [''], False);

Projects/Src/Setup.SelectLanguageForm.pas

@@ -2,7 +2,7 @@
 
 {
   Inno Setup
-  Copyright (C) 1997-2019 Jordan Russell
+  Copyright (C) 1997-2025 Jordan Russell
   Portions by Martijn Laan
   For conditions of distribution and use, see LICENSE.TXT.
 
@@ -36,7 +36,8 @@ function AskForLanguage: Boolean;
 implementation
 
 uses
-  Shared.Struct, SetupLdrAndSetup.Messages, Shared.SetupMessageIDs, Setup.MainFunc;
+  Shared.Struct, SetupLdrAndSetup.Messages, Shared.SetupMessageIDs,
+  Setup.MainFunc, Shared.CommonFunc.Vcl;
 
 {$R *.DFM}
 
@@ -48,7 +49,7 @@ function AskForLanguage: Boolean;
   I, J: Integer;
   LangEntry: PSetupLanguageEntry;
 begin
-  Application.CreateForm(TSelectLanguageForm, LangForm);
+  LangForm := AppCreateForm(TSelectLanguageForm) as TSelectLanguageForm;
   try
     for I := 0 to Entries[seLanguage].Count-1 do begin
       LangEntry := Entries[seLanguage][I];

Projects/Src/Setup.Uninstall.pas

@@ -2,7 +2,7 @@
 
 {
   Inno Setup
-  Copyright (C) 1997-2024 Jordan Russell
+  Copyright (C) 1997-2025 Jordan Russell
   Portions by Martijn Laan
   For conditions of distribution and use, see LICENSE.TXT.
 
@@ -91,7 +91,7 @@ function TExtUninstallLog.ShouldRemoveSharedFile(const Filename: String): Boolea
 
 procedure InitializeUninstallProgressForm;
 begin
-  Application.CreateForm(TUninstallProgressForm, UninstallProgressForm);
+  UninstallProgressForm := AppCreateForm(TUninstallProgressForm) as TUninstallProgressForm;
   UninstallProgressForm.Initialize(Title, UninstLog.AppName, ufModernStyle in UninstLog.Flags);
   if CodeRunner <> nil then begin
     try

Projects/Src/Shared.CommonFunc.Vcl.pas

@@ -2,7 +2,7 @@
 
 {
   Inno Setup
-  Copyright (C) 1997-2024 Jordan Russell
+  Copyright (C) 1997-2025 Jordan Russell
   Portions by Martijn Laan
   For conditions of distribution and use, see LICENSE.TXT.
 
@@ -37,6 +37,7 @@   TWindowDisabler = class
 const
   EnableColor: array[Boolean] of TColor = (clBtnFace, clWindow);
 
+function AppCreateForm(const AClass: TCustomFormClass): TCustomForm;
 procedure UpdateHorizontalExtent(const ListBox: TCustomListBox);
 function MinimizePathName(const Filename: String; const Font: TFont;
   MaxLen: Integer): String;
@@ -68,6 +69,22 @@ implementation
   MessageBoxCallbackParam: LongInt;
   MessageBoxCallbackActive: Boolean;
 
+function AppCreateForm(const AClass: TCustomFormClass): TCustomForm;
+{ Creates a form, making it the main form if there isn't one already.
+  Usage: AppCreateForm(TMyForm) as TMyForm
+  This is a wrapper around Application.CreateForm, but with these advantages:
+  - Safety: Returns a typed value instead of writing to an untyped parameter.
+  - Safety: When used in an assignment statement: MyForm := AppCreateForm(...)
+    the variable isn't modified until the form is fully constructed and the
+    function exits. Application.CreateForm writes to its parameter, making the
+    value public, before the form's constructor is executed, which could allow
+    code outside the form to access the form before it's fully constructed.
+  - When the result is casted with "as", it works with type inference.
+  - When used in the .dpr, the Delphi IDE will never touch it. }
+begin
+  Application.CreateForm(AClass, Result);
+end;
+
 type
   TListBoxAccess = class(TCustomListBox);