From 3986f667cb0f3fffeaee637dcee097b582e240ca Mon Sep 17 00:00:00 2001
From: George Hazan <ghazan@miranda.im>
Date: Tue, 28 Mar 2023 14:14:31 +0300
Subject: CCtrlTreeView: OnBeginDrag / OnEndDrag callbacks became boolean

---
 include/m_gui.h                            |  2 ++
 include/m_system.h                         | 26 +++++++++++++++++++++++---
 src/mir_app/src/menu_options.cpp           |  6 ++++--
 src/mir_core/src/Windows/CCtrlTreeView.cpp | 22 +++++++++++++---------
 4 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/include/m_gui.h b/include/m_gui.h
index 17b544ef61..0d13d5974a 100644
--- a/include/m_gui.h
+++ b/include/m_gui.h
@@ -1306,6 +1306,7 @@ public:
 			NMTVGETINFOTIP *nmtvit;
 			NMTVCUSTOMDRAW *nmcd;
 			HTREEITEM hItem; // for OnItemChanged
+			TVHITTESTINFO *ntvhi; // for OnEndDrag
 		};
 	};
 
@@ -1314,6 +1315,7 @@ public:
 	CCallback<TEventInfo> OnBeginRDrag;
 	CCallback<TEventInfo> OnCustomDraw;
 	CCallback<TEventInfo> OnDeleteItem;
+	CCallback<TEventInfo> OnEndDrag;
 	CCallback<TEventInfo> OnEndLabelEdit;
 	CCallback<TEventInfo> OnGetDispInfo;
 	CCallback<TEventInfo> OnGetInfoTip;
diff --git a/include/m_system.h b/include/m_system.h
index 2d36a47bcd..f5003a2585 100644
--- a/include/m_system.h
+++ b/include/m_system.h
@@ -604,19 +604,29 @@ class CCallbackImp
 	};
 
 	typedef void (CDummy:: *TFnCallback)(void *argument);
+	typedef bool (CDummy:: *TFnBCallback)(void *argument);
 
 	CDummy *m_object;
-	TFnCallback m_func;
+	union {
+		TFnCallback m_func;
+		TFnBCallback m_bfunc;
+	};
 
 protected:
 	template<typename TClass, typename TArgument>
 	__inline CCallbackImp(TClass *object, void (TClass:: *func)(TArgument *argument)) :
 		m_object((CDummy *)object),
 		m_func((TFnCallback)func)
-	{
-	}
+	{}
+
+	template<typename TClass, typename TArgument>
+	__inline CCallbackImp(TClass *object, bool (TClass:: *func)(TArgument *argument)) :
+		m_object((CDummy *)object),
+		m_bfunc((TFnBCallback)func)
+	{}
 
 	__inline void Invoke(void *argument) const { if (m_func && m_object) (m_object->*m_func)(argument); }
+	__inline bool BInvoke(void *argument) const { return (m_bfunc && m_object) ? (m_object->*m_bfunc)(argument) : true; }
 
 public:
 	__inline CCallbackImp() : m_object(nullptr), m_func(nullptr) {}
@@ -641,9 +651,13 @@ public:
 	template<typename TClass>
 	__inline CCallback(TClass *object, void (TClass:: *func)(TArgument *argument)) : CCallbackImp(object, func) {}
 
+	template<typename TClass>
+	__inline CCallback(TClass *object, bool (TClass:: *func)(TArgument *argument)) : CCallbackImp(object, func) {}
+
 	__inline CCallback &operator=(const CCallbackImp &x) { CSuper::operator =(x); return *this; }
 
 	__inline void operator()(TArgument *argument) const { Invoke((void *)argument); }
+	__inline bool Check(TArgument *argument) const { return BInvoke((void *)argument); }
 };
 
 template<typename TClass, typename TArgument>
@@ -652,6 +666,12 @@ __inline CCallback<TArgument> Callback(TClass *object, void (TClass:: *func)(TAr
 	return CCallback<TArgument>(object, func);
 }
 
+template<typename TClass, typename TArgument>
+__inline CCallback<TArgument> Callback(TClass *object, bool (TClass:: *func)(TArgument *argument))
+{
+	return CCallback<TArgument>(object, func);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // http support
 
diff --git a/src/mir_app/src/menu_options.cpp b/src/mir_app/src/menu_options.cpp
index c2dfae7c87..3c6ce3cf55 100644
--- a/src/mir_app/src/menu_options.cpp
+++ b/src/mir_app/src/menu_options.cpp
@@ -572,12 +572,14 @@ public:
 		m_customName.Enable(true);
 	}
 
-	void onMenuItemBeginDrag(CCtrlTreeView::TEventInfo *evt)
+	bool onMenuItemBeginDrag(CCtrlTreeView::TEventInfo *evt)
 	{
 		MenuItemOptData *p = (MenuItemOptData*)evt->nmtv->itemNew.lParam;
 		if (p->pimi != nullptr)
 			if (p->pimi->mi.flags & CMIF_UNMOVABLE)
-				evt->nmhdr->code = 0; // reject an attempt to change item's position
+				return false; // reject an attempt to change item's position
+
+		return true;
 	}
 };
 
diff --git a/src/mir_core/src/Windows/CCtrlTreeView.cpp b/src/mir_core/src/Windows/CCtrlTreeView.cpp
index 92ad166f91..4f4aeabf2f 100644
--- a/src/mir_core/src/Windows/CCtrlTreeView.cpp
+++ b/src/mir_core/src/Windows/CCtrlTreeView.cpp
@@ -161,12 +161,16 @@ LRESULT CCtrlTreeView::CustomWndProc(UINT msg, WPARAM wParam, LPARAM lParam)
 			m_bDragging = false;
 			ReleaseCapture();
 
-			hti.pt.x = (short)LOWORD(lParam);
-			hti.pt.y = (short)HIWORD(lParam) - GetItemHeight() / 2;
+			hti.pt.x = GET_X_LPARAM(lParam);
+			hti.pt.y = GET_Y_LPARAM(lParam) - GetItemHeight() / 2;
 			HitTest(&hti);
 			if (m_hDragItem == hti.hItem)
 				break;
 
+			TEventInfo evt = { this, (LPNMHDR)&hti};
+			if (!OnEndDrag.Check(&evt))
+				break;
+
 			if (hti.flags & TVHT_ABOVE)
 				hti.hItem = TVI_FIRST;
 			else if (hti.flags & TVHT_BELOW)
@@ -288,14 +292,14 @@ BOOL CCtrlTreeView::OnNotify(int, NMHDR *pnmh)
 	case TVN_SINGLEEXPAND:   OnSingleExpand(&evt);    return TRUE;
 
 	case TVN_BEGINDRAG:
-		OnBeginDrag(&evt);
-
 		// user-defined can clear the event code to disable dragging
-		if (m_bDndEnabled && pnmh->code) {
-			::SetCapture(m_hwnd);
-			m_bDragging = true;
-			m_hDragItem = evt.nmtv->itemNew.hItem;
-			SelectItem(m_hDragItem);
+		if (m_bDndEnabled) {
+			if (OnBeginDrag.Check(&evt)) {
+				::SetCapture(m_hwnd);
+				m_bDragging = true;
+				m_hDragItem = evt.nmtv->itemNew.hItem;
+				SelectItem(m_hDragItem);
+			}
 		}
 		return TRUE;
 
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