Richedit redraw issue. Windows 8 specific.

Question

Hi,
Source code for demo application is pasted at the end of the message. Just add it to a blank Win32 project in Visual Studio and run on Windows 8. When compiled as is on my system the main window looks like this after the startup. 
If I change n_lines_in_edit at the first source code line to 20, Richedits redraws correctly.
I need help figuring out how to make sure Richedit redraws correctly for any reasonable number of lines. 
const int n_lines_in_edit = 200;
#include <stdlib.h>
#include <tchar.h>
#include <windows.h>
#include <WindowsX.h>
#include <Richedit.h>
#include <memory>
#define MAX_LOADSTRING 255
using namespace std;
// Global Variables
HINSTANCE hInstGlobal; // current instance
TCHAR szTitle[MAX_LOADSTRING]; // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING]; // the main window class name
TCHAR szChildClass[MAX_LOADSTRING]; // the child window class name
HWND m_hWnd;
HWND hWndFrame;
HWND hWndClient;
// Forward declarations of functions
ATOM FrameRegisterClass(HINSTANCE hInstance);
ATOM ChildRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK ChildWndProc(HWND, UINT, WPARAM, LPARAM);
HWND CreateChildWindow();
int APIENTRY _tWinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPTSTR lpCmdLine,
int nCmdShow)
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
MSG msg;
// Initialize global strings
wcscpy_s(szTitle, _T("Main window"));
wcscpy_s(szWindowClass, _T("FrameClass"));
wcscpy_s(szChildClass, _T("ChildClass"));
FrameRegisterClass(hInstance);
ChildRegisterClass(hInstance);
// Perform application initialization
if (!InitInstance (hInstance, nCmdShow))
return FALSE;
// Main message loop
while (GetMessage(&msg, NULL, 0, 0))
TranslateMessage(&msg);
DispatchMessage(&msg);
return (int) msg.wParam;
ATOM FrameRegisterClass(HINSTANCE hInstance)
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = 0;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = sizeof(LONG_PTR);
wcex.hInstance = hInstance;
wcex.hIcon = 0;
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_BACKGROUND);
wcex.lpszMenuName = szTitle;
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = 0;
return RegisterClassEx(&wcex);
ATOM ChildRegisterClass(HINSTANCE hInstance)
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = 0;
wcex.lpfnWndProc = ChildWndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = sizeof(LONG_PTR);
wcex.hInstance = hInstance;
wcex.hIcon = 0;
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH) (COLOR_3DFACE + 1);
wcex.lpszMenuName = 0;
wcex.lpszClassName = szChildClass;
wcex.hIconSm = 0;
return RegisterClassEx(&wcex);
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
hInstGlobal = hInstance;
m_hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);
if (!m_hWnd)
return FALSE;
hWndFrame = m_hWnd;
ShowWindow(m_hWnd, nCmdShow);
UpdateWindow(m_hWnd);
CreateChildWindow();
return TRUE;
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
switch (message) {
case WM_CREATE:
CLIENTCREATESTRUCT ccs;
hWndClient = CreateWindow(_T("MDICLIENT"), _T(""),
WS_CHILD | WS_CLIPCHILDREN | WS_VSCROLL | WS_HSCROLL,
0, 0, 0, 0, hWnd, (HMENU)0, hInstGlobal, &ccs);
if (!hWndClient)
DestroyWindow(hWnd);
break;
ShowWindow(hWndClient, SW_SHOW);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefFrameProc(hWnd, hWndClient, message, wParam, lParam);
return 0;
HWND CreateChildWindow()
RECT r;
GetClientRect(hWndFrame, &r);
HWND hWnd = CreateWindowExW(WS_EX_MDICHILD, szChildClass, _T("Sample title"),
WS_CLIPCHILDREN | WS_CHILD, CW_USEDEFAULT, CW_USEDEFAULT, r.right / 2, CW_USEDEFAULT,
hWndClient, nullptr, hInstGlobal, ChildWndProc);
if (hWnd != nullptr)
ShowWindow(hWnd, SW_SHOW);
else
PostQuitMessage(0);
return hWnd;
LRESULT CALLBACK ChildWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
switch (message)
case WM_CREATE:
LoadLibrary(TEXT("Msftedit.dll"));
HWND hEdit = CreateWindow(_T("RICHEDIT50W"),_T(""), WS_BORDER | WS_VSCROLL |
WS_HSCROLL | WS_GROUP | WS_TABSTOP | WS_CHILD | WS_CLIPCHILDREN | WS_VISIBLE |
ES_READONLY | ES_AUTOVSCROLL | ES_AUTOHSCROLL | ES_MULTILINE | ES_NOHIDESEL | ES_SAVESEL,
0, 0, 300, 200, hWnd, nullptr, hInstGlobal, nullptr);
SETTEXTEX stEX;
stEX.flags = ST_SELECTION;
stEX.codepage = -1;
char text[250];
for(int j = 1; j < n_lines_in_edit; j++)
sprintf(text, "Sample string #%d\r\n", j);
SendMessage(hEdit, EM_SETTEXTEX, (WPARAM)&stEX, (LPARAM) text);
Edit_SetSel(hEdit, -1, 0);
Edit_ScrollCaret(hEdit);
ShowWindow(hWnd, SW_SHOW);
return 0;
case WM_SETFOCUS:
SetFocus(GetWindow(hWnd, GW_CHILD));
return 0;
case WM_MOUSEACTIVATE:
BringWindowToTop(hWnd);
return MA_ACTIVATE;
case WM_DESTROY:
break;
default:
return DefMDIChildProc(hWnd, message, wParam, lParam);
return 0;
O.Z.

Answer 1

Hi O.Z,
I find this issue only happens on RICHEDIT50W, if you use RICHEDIT20W instead, this issue is gone.
Then I try send EN_REQUESTRESIZE notification code to notifies the rich edit control's parent window that the control's contents are larger than the control's window size.
SendMessage(hEdit, EM_SETEVENTMASK, 0, ENM_REQUESTRESIZE);
I find the issue is gone with RICHEDIT50W, maybe this can be a workaround for this issue, hope this helps some.
Best regards,
Shu
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