Fix status bar and tab bar flicker when updated

Add double buffering for status bar and tab bar to avoid flickering.

Fix #15260, close #15296

PowerEditor/src/WinControls/DoubleBuffer.h

@@ -0,0 +1,101 @@
+// This file is part of Notepad++ project
+// Copyright (C) 2024 Jiri Hruska <jirka@fud.cz>
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// at your option any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+#include <windows.h>
+#include <cassert>
+
+class DoubleBuffer final
+{
+private:
+	SIZE _size{};
+	HDC _hMemoryDC = nullptr;
+	HBITMAP _hDefaultBitmap = nullptr;
+	HBITMAP _hBufferBitmap = nullptr;
+
+public:
+	DoubleBuffer() {}
+	DoubleBuffer(const DoubleBuffer&) = delete;
+	DoubleBuffer& operator=(const DoubleBuffer&) = delete;
+
+	~DoubleBuffer()
+	{
+		if (_hBufferBitmap)
+		{
+			::SelectObject(_hMemoryDC, _hDefaultBitmap);
+			::DeleteObject(_hBufferBitmap);
+		}
+
+		if (_hMemoryDC)
+		{
+			::DeleteDC(_hMemoryDC);
+		}
+	}
+
+	HDC beginPaint(HWND hWnd, PAINTSTRUCT* ps)
+	{
+		if (!::BeginPaint(hWnd, ps))
+		{
+			return nullptr;
+		}
+
+		if (!_hMemoryDC)
+		{
+			_hMemoryDC = ::CreateCompatibleDC(ps->hdc);
+		}
+
+		RECT clientRc{};
+		::GetClientRect(hWnd, &clientRc);
+		if (clientRc.right != _size.cx || clientRc.bottom != _size.cy || !_hBufferBitmap)
+		{
+			_size = { clientRc.right, clientRc.bottom };
+
+			if (_hBufferBitmap)
+			{
+				::SelectObject(_hMemoryDC, _hDefaultBitmap);
+				::DeleteObject(_hBufferBitmap);
+			}
+
+			_hBufferBitmap = ::CreateCompatibleBitmap(ps->hdc, _size.cx, _size.cy);
+			_hDefaultBitmap = static_cast<HBITMAP>(::SelectObject(_hMemoryDC, _hBufferBitmap));
+		}
+
+		assert(ps->rcPaint.left  <  _size.cx && ps->rcPaint.top    <  _size.cy);
+		assert(ps->rcPaint.right <= _size.cx && ps->rcPaint.bottom <= _size.cy);
+
+		return _hMemoryDC;
+	}
+
+	void endPaint(HWND hWnd, PAINTSTRUCT* ps)
+	{
+		::BitBlt(
+			ps->hdc, ps->rcPaint.left, ps->rcPaint.top, ps->rcPaint.right - ps->rcPaint.left, ps->rcPaint.bottom - ps->rcPaint.top,
+			_hMemoryDC, ps->rcPaint.left, ps->rcPaint.top,
+			SRCCOPY);
+
+		::EndPaint(hWnd, ps);
+	}
+
+	int getWidth() const
+	{
+		return _size.cx;
+	}
+
+	int getHeight() const
+	{
+		return _size.cy;
+	}
+};

PowerEditor/src/WinControls/StatusBar/StatusBar.cpp

@@ -24,6 +24,7 @@
 #include "NppDarkMode.h"
 #include <uxtheme.h>
 #include <vssym32.h>
+#include "DoubleBuffer.h"
 
 //#define IDC_STATUSBAR 789
 
@@ -50,6 +51,7 @@ struct StatusBarSubclassInfo
 {
 	HTHEME hTheme = nullptr;
 	HFONT _hFont = nullptr;
+	DoubleBuffer _dblBuf;
 
 	StatusBarSubclassInfo() = default;
 	StatusBarSubclassInfo(const HFONT& hFont)
@@ -107,22 +109,24 @@ static LRESULT CALLBACK StatusBarSubclass(HWND hWnd, UINT uMsg, WPARAM wParam, L
 	{
 		case WM_ERASEBKGND:
 		{
-			if (!NppDarkMode::isEnabled())
-			{
-				break;
-			}
-
-			RECT rc{};
-			GetClientRect(hWnd, &rc);
-			FillRect((HDC)wParam, &rc, NppDarkMode::getBackgroundBrush());
-			return TRUE;
+			// Skip background erasing and set fErase in PAINTSTRUCT instead,
+			// WM_PAINT does all the painting in all cases
+			return FALSE;
 		}
 
 		case WM_PAINT:
 		{
+			PAINTSTRUCT ps{};
+			HDC hdc = pStatusBarInfo->_dblBuf.beginPaint(hWnd, &ps);
+
 			if (!NppDarkMode::isEnabled())
 			{
-				break;
+				// Even if the standard status bar common control is used directly in non-dark mode,
+				// it suffers from flickering during updates, so let it paint into a back buffer
+				DefSubclassProc(hWnd, WM_ERASEBKGND, reinterpret_cast<WPARAM>(hdc), 0);
+				DefSubclassProc(hWnd, WM_PRINTCLIENT, reinterpret_cast<WPARAM>(hdc), PRF_NONCLIENT | PRF_CLIENT);
+				pStatusBarInfo->_dblBuf.endPaint(hWnd, &ps);
+				return 0;
 			}
 
 			struct {
@@ -136,16 +140,10 @@ static LRESULT CALLBACK StatusBarSubclass(HWND hWnd, UINT uMsg, WPARAM wParam, L
 			const auto style = ::GetWindowLongPtr(hWnd, GWL_STYLE);
 			bool isSizeGrip = style & SBARS_SIZEGRIP;
 
-			PAINTSTRUCT ps{};
-			HDC hdc = BeginPaint(hWnd, &ps);
-
 			auto holdPen = static_cast<HPEN>(::SelectObject(hdc, NppDarkMode::getEdgePen()));
 
 			auto holdFont = static_cast<HFONT>(::SelectObject(hdc, pStatusBarInfo->_hFont));
 
-			RECT rcClient{};
-			GetClientRect(hWnd, &rcClient);
-
 			FillRect(hdc, &ps.rcPaint, NppDarkMode::getBackgroundBrush());
 
 			int nParts = static_cast<int>(SendMessage(hWnd, SB_GETPARTS, 0, 0));
@@ -220,8 +218,8 @@ static LRESULT CALLBACK StatusBarSubclass(HWND hWnd, UINT uMsg, WPARAM wParam, L
 			{
 				pStatusBarInfo->ensureTheme(hWnd);
 				SIZE gripSize{};
-				GetThemePartSize(pStatusBarInfo->hTheme, hdc, SP_GRIPPER, 0, &rcClient, TS_DRAW, &gripSize);
-				RECT rc = rcClient;
+				RECT rc = { 0, 0, pStatusBarInfo->_dblBuf.getWidth(), pStatusBarInfo->_dblBuf.getHeight() };
+				GetThemePartSize(pStatusBarInfo->hTheme, hdc, SP_GRIPPER, 0, &rc, TS_DRAW, &gripSize);
 				rc.left = rc.right - gripSize.cx;
 				rc.top = rc.bottom - gripSize.cy;
 				DrawThemeBackground(pStatusBarInfo->hTheme, hdc, SP_GRIPPER, 0, &rc, nullptr);
@@ -230,7 +228,7 @@ static LRESULT CALLBACK StatusBarSubclass(HWND hWnd, UINT uMsg, WPARAM wParam, L
 			::SelectObject(hdc, holdFont);
 			::SelectObject(hdc, holdPen);
 
-			EndPaint(hWnd, &ps);
+			pStatusBarInfo->_dblBuf.endPaint(hWnd, &ps);
 			return 0;
 		}
 

PowerEditor/src/WinControls/TabBar/TabBar.cpp

@@ -915,35 +915,29 @@ LRESULT TabBarPlus::runProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lPara
 
 		case WM_ERASEBKGND:
 		{
-			if (!NppDarkMode::isEnabled())
-			{
-				break;
-			}
-
-			RECT rc{};
-			GetClientRect(hwnd, &rc);
-			FillRect((HDC)wParam, &rc, NppDarkMode::getDarkerBackgroundBrush());
-
-			return 1;
+			// Skip background erasing and set fErase in PAINTSTRUCT instead,
+			// WM_PAINT does all the painting in all cases
+			return FALSE;
 		}
 
 		case WM_PAINT:
 		{
-			if (!NppDarkMode::isEnabled())
-			{
-				break;
-			}
+			PAINTSTRUCT ps{};
+			HDC hdc = _dblBuf.beginPaint(hwnd, &ps);
 
 			LONG_PTR dwStyle = GetWindowLongPtr(hwnd, GWL_STYLE);
-			if (!(dwStyle & TCS_OWNERDRAWFIXED))
+			if (!NppDarkMode::isEnabled() || !(dwStyle & TCS_OWNERDRAWFIXED))
 			{
-				break;
+				// Even if the tab bar common control is used directly, e.g. in non-dark mode,
+				// it suffers from flickering during updates, so let it paint into a back buffer
+				::CallWindowProc(_tabBarDefaultProc, hwnd, WM_ERASEBKGND, reinterpret_cast<WPARAM>(hdc), 0);
+				::CallWindowProc(_tabBarDefaultProc, hwnd, WM_PRINTCLIENT, reinterpret_cast<WPARAM>(hdc), PRF_NONCLIENT | PRF_CLIENT);
+				_dblBuf.endPaint(hwnd, &ps);
+				return 0;
 			}
 
 			const bool hasMultipleLines = ((dwStyle & TCS_BUTTONS) == TCS_BUTTONS);
 
-			PAINTSTRUCT ps{};
-			HDC hdc = BeginPaint(hwnd, &ps);
 			FillRect(hdc, &ps.rcPaint, NppDarkMode::getDarkerBackgroundBrush());
 
 			UINT id = ::GetDlgCtrlID(hwnd);
@@ -1072,7 +1066,7 @@ LRESULT TabBarPlus::runProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lPara
 
 			SelectObject(hdc, holdPen);
 
-			EndPaint(hwnd, &ps);
+			_dblBuf.endPaint(hwnd, &ps);
 			return 0;
 		}
 

PowerEditor/src/WinControls/TabBar/TabBar.h

@@ -28,6 +28,7 @@
 #include <commctrl.h>
 #include "Window.h"
 #include "dpiManagerV2.h"
+#include "DoubleBuffer.h"
 
 //Notification message
 #define TCN_TABDROPPED (TCN_FIRST - 10)
@@ -241,6 +242,7 @@ protected:
 	int _previousTabSwapped = -1;
 	POINT _draggingPoint{}; // coordinate of Screen
 	WNDPROC _tabBarDefaultProc = nullptr;
+	DoubleBuffer _dblBuf;
 
 	RECT _currentHoverTabRect{};
 	int _currentHoverTabItem = -1; // -1 : no mouse on any tab

PowerEditor/visual.net/notepadPlus.vcxproj

@@ -298,6 +298,7 @@
     <ClInclude Include="..\src\WinControls\DockingWnd\DockingSplitter.h" />
     <ClInclude Include="..\src\ScintillaComponent\DocTabView.h" />
     <ClInclude Include="..\src\WinControls\DocumentMap\documentMap.h" />
+    <ClInclude Include="..\src\WinControls\DoubleBuffer.h" />
     <ClInclude Include="..\src\EncodingMapper.h" />
     <ClInclude Include="..\src\MISC\FileNameStringSplitter.h" />
     <ClInclude Include="..\src\WinControls\FindCharsInRange\FindCharsInRange.h" />