From 531bef28d8b4da18bb442f7dbdf2b5a552295a8a Mon Sep 17 00:00:00 2001
From: Ashfaaq18 <ashfaaq.riphque@gmail.com>
Date: Tue, 21 Sep 2021 22:04:27 +0530
Subject: [PATCH] Fix docked window sizing direction problem in RTL mode

Fix #10536, close #10576
---
 PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp | 4 +++-
 PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h   | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
index daeee1263..0c46ce93b 100644
--- a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
+++ b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.cpp
@@ -31,6 +31,8 @@ void DockingSplitter::init(HINSTANCE hInst, HWND hWnd, HWND hMessage, UINT flags
 	_flags = flags;
 
 	WNDCLASS wc;
+	DWORD hwndExStyle = (DWORD)GetWindowLongPtr(hWnd, GWL_EXSTYLE);
+	isRTL = hwndExStyle & WS_EX_LAYOUTRTL;
 
 	if (flags & DMS_HORIZONTAL)
 	{
@@ -137,7 +139,7 @@ LRESULT DockingSplitter::runProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM
 				}
 				else if (_ptOldPos.x != pt.x)
 				{
-					::SendMessage(_hMessage, DMM_MOVE_SPLITTER, _ptOldPos.x - pt.x, reinterpret_cast<LPARAM>(_hSelf));
+					::SendMessage(_hMessage, DMM_MOVE_SPLITTER, isRTL ? pt.x - _ptOldPos.x : _ptOldPos.x - pt.x, reinterpret_cast<LPARAM>(_hSelf));
 				}
 				_ptOldPos = pt;
 			}
diff --git a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
index 901c15db9..b1085ce5a 100644
--- a/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
+++ b/PowerEditor/src/WinControls/DockingWnd/DockingSplitter.h
@@ -49,5 +49,8 @@ private:
 
 	static BOOL _isVertReg;
 	static BOOL _isHoriReg;
+
+	// get layout direction
+	bool isRTL;
 };