From 7d4a36a290d0ca71c05a9a5f44661335c7b94055 Mon Sep 17 00:00:00 2001
From: Bart <9132501-flyingsheep@users.noreply.gitlab.com>
Date: Wed, 30 Aug 2023 23:23:17 +0200
Subject: [PATCH] LCL: TOpenDialog: set ofExtensionDifferent if (DefaultExt <>
 '') and (Extension <> DefExt) for all WS. Our docs about ofExtensionDifferent
 wrongfully states: "Allows a file name with an extension which does not match
 the filters or default extension in a file dialog." This is not how Delphi
 defines it, and also not how it's implemented in pre-Vista dialogs (using
 OPENFILE structure, the OS sets the corresponding flag). (Since there have
 been no bugreports about this, it's doubtfull anybody cares, but
 nevertheless...)

---
 lcl/include/filedialog.inc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lcl/include/filedialog.inc b/lcl/include/filedialog.inc
index 24ee1fb16d..ad21a05e08 100644
--- a/lcl/include/filedialog.inc
+++ b/lcl/include/filedialog.inc
@@ -352,6 +352,9 @@ begin
     else
       AFilename:=AFilename+DefaultExt;
   end;
+  if (not {already} (ofExtensionDifferent in FOptions)) and (DefaultExt <> '')
+      and (CompareFileNames(DefaultExt,ExtractFileExt(AFilename)) <> 0) then
+      Include(FOptions, ofExtensionDifferent);
   //ofOverwritePrompt -> is done in the interface
   if (ofPathMustExist in Options)
   and (not DirPathExists(ExtractFileDir(AFilename))) then begin
@@ -430,6 +433,7 @@ end;
  ------------------------------------------------------------------------------}
 function TOpenDialog.DoExecute: boolean;
 begin
+  Options := Options - [ofExtensionDifferent]; //clear, it'll be set by WS or in CheckFile
   Result:=inherited DoExecute;
   if not (ofNoResolveLinks in Options) then
     ResolveLinks;