From af9412b01999bc5918c04e3cdd0e661e23cb3ae6 Mon Sep 17 00:00:00 2001
From: Bart <9132501-flyingsheep@users.noreply.gitlab.com>
Date: Fri, 5 Jan 2024 17:59:21 +0100
Subject: [PATCH] TCustomListView: trying to implement OnChanging (Win32): *
 according to Delph docs
 (https://docwiki.embarcadero.com/Libraries/Alexandria/en/Vcl.ComCtrls.TCustomListView.CanChange)
 the function CanClose calls the OnChanging event. It's result indicates
 wether changing will be allowed.

---
 lcl/comctrls.pp                               |  2 +-
 lcl/include/customlistview.inc                | 16 +++++---------
 .../win32/win32wscustomlistview.inc           | 22 +++++++++----------
 3 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/lcl/comctrls.pp b/lcl/comctrls.pp
index b6b7eac5d5..d843facbea 100644
--- a/lcl/comctrls.pp
+++ b/lcl/comctrls.pp
@@ -1525,7 +1525,7 @@ type
     function CreateListItems: TListItems; virtual;
     function CanEdit(Item: TListItem): Boolean; virtual;
     procedure Change(AItem: TListItem; AChange: Integer); virtual;
-    procedure DoChanging(AItem: TListItem; AChange: Integer; var AllowChange: Boolean);
+    function CanChange(AItem: TListItem; AChange: Integer): Boolean;
     procedure ColClick(AColumn: TListColumn); virtual;
 
     procedure Delete(AItem : TListItem); virtual;
diff --git a/lcl/include/customlistview.inc b/lcl/include/customlistview.inc
index aea7ae2f9c..a4d855f216 100644
--- a/lcl/include/customlistview.inc
+++ b/lcl/include/customlistview.inc
@@ -205,10 +205,11 @@ begin
   then FOnChange(Self, AItem, ItemChange);
 end;
 
-procedure TCustomListView.DoChanging(AItem: TListItem; AChange: Integer; var AllowChange: Boolean);
+function TCustomListView.CanChange(AItem: TListItem; AChange: Integer): Boolean;
 var
   ItemChange: TItemChange;
 begin
+  Result := True;
   case AChange of
     LVIF_TEXT: ItemChange := ctText;
     LVIF_IMAGE: ItemChange := ctImage;
@@ -217,14 +218,7 @@ begin
     Exit;
   end;
   if Assigned(FOnChanging) then
-  begin
-    FOnChanging(Self, AItem, ItemChange, AllowChange);
-    if not AllowChange then
-    begin
-      //ToDo
-    end;
-  end;
-
+    FOnChanging(Self, AItem, ItemChange, Result);
 end;
 
 {------------------------------------------------------------------------------}
@@ -335,7 +329,7 @@ begin
     LVN_ITEMCHANGING: begin
       //Check
       debugln('TCustomListView.CNNotify: LVN_ITEMCHANGING');
-      AMessage.Result:=1;
+      //AMessage.Result:=1;  //1=disallow changing
       //if nm^.iItem < 0 then
       //  Item := nil
       //else
@@ -344,7 +338,7 @@ begin
       //if Assigned(Item) then
       //begin
       //  AllowChange := True;
-      //  DoChanging(Item, nm^.uChanged, AllowChange);
+      //  CanChange(Item, nm^.uChanged, AllowChange);
       //  if not AllowChange then
       //    AMessage.Result := 1;
       //end;
diff --git a/lcl/interfaces/win32/win32wscustomlistview.inc b/lcl/interfaces/win32/win32wscustomlistview.inc
index 8053b447dc..a4c5dec818 100644
--- a/lcl/interfaces/win32/win32wscustomlistview.inc
+++ b/lcl/interfaces/win32/win32wscustomlistview.inc
@@ -300,11 +300,9 @@ var
   var
     nm: PNMListView;
     Item: TListItem;
-    AllowChange: Boolean;
   begin
-    debugln(['HandleListChanging: HandleAllocated=',ALV.HandleAllocated]);
-    MsgResult := LResult(1);
-    EXIT;
+    debugln(['HandleListChanging: HandleAllocated=',ALV.HandleAllocated,', (wcfInitializing in FWinControlFlags)=',Dbgs(wcfInitializing in ALV.FWinControlFlags)]);
+    if (wcfInitializing in ALV.FWinControlFlags) then Exit;
     nm := PNMListView(NMHdr);
     if nm^.iItem < 0 then
       Item := nil
@@ -313,12 +311,11 @@ var
 
     if Assigned(Item) then
     begin
-      AllowChange := True;
-      ALV.DoChanging(Item, nm^.uChanged, AllowChange);
-      //if not AllowChange then
-        MsgResult := 0;
+      if ALV.CanChange(Item, nm^.uChanged) then
+        MsgResult := 0
+      else
+        MsgResult := 1;
     end;
-
   end;
 
   procedure HandleListViewOwnerDataHint(ALV: TCustomListViewAccess);
@@ -350,10 +347,11 @@ begin
           HandleListViewFindItem(TCustomListViewAccess(AWinControl));
         LVN_ITEMCHANGING:
         begin
-          debugln('ListViewParentMsgHandler: LVN_ITEMCHANGING');
-          MsgResult := LResult(-1);
-          //HandleListChanging(TCustomListViewAccess(AWinControl));
+          //debugln('ListViewParentMsgHandler: LVN_ITEMCHANGING');
+          //MsgResult := LResult(-1);
+          HandleListChanging(TCustomListViewAccess(AWinControl));
         end;
+        //LVN_ITEMCHANGED: debugln('ListViewParentMsgHandler: LVN_ITEMCHANGed');
         LVN_ODCACHEHINT:
           HandleListViewOwnerDataHint(TCustomListViewAccess(AWinControl));
       end;