how to clear a text box in Win32 C++ - c++

Question

I am making a notepad in C++, and I want to clear the text box when a certain button is clicked. I can't take the text box from the WinMain() function from the LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {...} where my text box is. This is the code for my text box
HWND hWndEdit = CreateWindow(TEXT("EDIT"), TEXT(""), WS_CHILD | WS_VISIBLE | WS_BORDER | WB_LEFT | ES_AUTOVSCROLL | ES_MULTILINE, 0, 0, 1366, 768, hWnd, NULL, NULL, NULL);
I've tried googling to no avail, mulled over many forums, and even placed the text box inside the LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {...}, and using SetWindowText(hWndEdit, _T("")), which causes my program to freeze. I am not sure on what to do. Putting the text box code back in the WinMain function stops it from freezing, but then I can't clear it anymore. What can I do?
If you need all my code here it is.
// compile with: /D_UNICODE /DUNICODE /DWIN32 /D_WINDOWS /c
#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <tchar.h>
// Global variables
HMENU menuStrip;
// The main window class name.
static TCHAR szWindowClass[] = _T("DesktopApp");
// The string that appears in the application's title bar.
static TCHAR szTitle[] = _T("NoteRecorder");
HINSTANCE hInst;
// Forward declarations of functions included in this code module:
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void AddMenuStrip(HWND hWnd);
int WINAPI WinMain(
_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPSTR lpCmdLine,
_In_ int nCmdShow
)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(wcex.hInstance, L"");
wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);
if (!RegisterClassEx(&wcex))
{
MessageBox(NULL,
_T("Call to RegisterClassEx failed!"),
_T("Windows Desktop Guided Tour"),
NULL);
return 1;
}
hInst = hInstance;
// Height and width
int x = 1366;
int y = 768;
HWND hWnd = CreateWindowEx(
WS_EX_OVERLAPPEDWINDOW,
szWindowClass,
szTitle,
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
x, y,
NULL,
NULL,
hInstance,
NULL
);
if (!hWnd)
{
MessageBox(NULL,
_T("Call to CreateWindow failed!"),
_T("NoteRecorder"),
NULL);
return 1;
}
// The parameters to ShowWindow explained:
// hWnd: the value returned from CreateWindow
// nCmdShow: the fourth parameter from WinMain
ShowWindow(hWnd,
nCmdShow);
UpdateWindow(hWnd);
// Main message loop:
MSG msg;
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int)msg.wParam;
}
// FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
// PURPOSE: Processes messages for the main window.
//
// WM_PAINT - Paint the main window
// WM_DESTROY - post a quit message and return
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HWND hWndEdit = CreateWindow(TEXT("EDIT"), TEXT(""), WS_CHILD | WS_VISIBLE | WS_BORDER | WB_LEFT | ES_AUTOVSCROLL | ES_MULTILINE, 0, 0, 1366, 768, hWnd, NULL, NULL, NULL);
switch (message)
{
case WM_COMMAND:
switch (wParam)
{
case 11:
SetWindowText(hWndEdit, _T(""));
MessageBox(NULL,
_T("The function has executed successfully."),
_T("NoteRecorder"),
MB_ICONASTERISK);
break;
case 12:
break;
case 13:
break;
case 14:
break;
case 15:
break;
case 21:
break;
case 22:
break;
case 23:
break;
case 24:
break;
case 25:
break;
case 26:
break;
case 31:
break;
case 41:
break;
case 42:
break;
}
break;
case WM_CREATE:
AddMenuStrip(hWnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
break;
}
return 0;
}
void AddMenuStrip(HWND hWnd)
{
menuStrip = CreateMenu();
HMENU fileMenu = CreateMenu();
AppendMenu(fileMenu, MF_STRING, 11, L"New");
AppendMenu(fileMenu, MF_STRING, 12, L"Open");
AppendMenu(fileMenu, MF_STRING, 13, L"Save");
AppendMenu(fileMenu, MF_STRING, 14, L"Save As");
AppendMenu(fileMenu, MF_SEPARATOR, NULL, NULL);
AppendMenu(fileMenu, MF_STRING, 15, L"Exit");
HMENU editMenu = CreateMenu();
AppendMenu(editMenu, MF_STRING, 21, L"Undo");
AppendMenu(editMenu, MF_STRING, 22, L"Redo");
AppendMenu(editMenu, MF_SEPARATOR, NULL, NULL);
AppendMenu(editMenu, MF_STRING, 23, L"Cut");
AppendMenu(editMenu, MF_STRING, 24, L"Copy");
AppendMenu(editMenu, MF_STRING, 25, L"Paste");
AppendMenu(editMenu, MF_SEPARATOR, NULL, NULL);
AppendMenu(editMenu, MF_STRING, 26, L"Select All");
HMENU formatMenu = CreateMenu();
AppendMenu(formatMenu, MF_BYCOMMAND, 31, L"Font...");
HMENU helpMenu = CreateMenu();
AppendMenu(helpMenu, MF_STRING, 41, L"Get Help");
AppendMenu(helpMenu, MF_SEPARATOR, NULL, NULL);
AppendMenu(helpMenu, MF_STRING, 42, L"About WorkPlace 247...");
// Menu Items for the MenuStrip
AppendMenu(menuStrip, MF_POPUP, (UINT_PTR)fileMenu, L"File");
AppendMenu(menuStrip, MF_POPUP, (UINT_PTR)editMenu, L"Edit");
AppendMenu(menuStrip, MF_POPUP, (UINT_PTR)formatMenu, L"Format");
AppendMenu(menuStrip, MF_POPUP, (UINT_PTR)helpMenu, L"Help");
SetMenu(hWnd, menuStrip);
}
I am using VS2019 MSVC, with Win32.
I'm also really bad at C++, and I want to learn. Thanks in advance.

Answer 1

Here is your problem:
HWND hWndEdit = CreateWindow(TEXT("EDIT"), TEXT(""), WS_CHILD | WS_VISIBLE | WS_BORDER | WB_LEFT | ES_AUTOVSCROLL | ES_MULTILINE, 0, 0, 1366, 768, hWnd, NULL, NULL, NULL);
That edit control will be created every time your main window gets ANY message, quickly running out of resources.
You only need to create it once (for example, in response to WM_CREATE message), and save that window handle in some static (or global) variable, so that you can use it later.
One way: add this to your "Global" section
// Global variables
HMENU menuStrip;
HWND hWndEdit = 0; // <- new line
then move a call to create that control into WM_CREATE handler:
case WM_CREATE:
AddMenuStrip(hWnd);
hWndEdit = CreateWindow(TEXT("EDIT"), TEXT(""), WS_CHILD | WS_VISIBLE | WS_BORDER | ES_AUTOVSCROLL | ES_MULTILINE, 0, 0, 1366, 768, hWnd, NULL, NULL, NULL);
break;

Answer 2

WndProc is called everytime event occures like (mouse move, click, size, paint...)
so an hWndEdit is created every message, that's the problem
you can do this:
you can keep it there but make it static
create hWndEdit in WinMain, give it ID, then in WM_COMMAND call hWndEdit = GetDlgItem(hWnd, ID)
create hWndEdit in WM_CREATE and do the same as in step two
make hWndEdit global and create it in WinMain, WM_CREATE or at any stage