Windows 11 Drawing a border and background color with a handle to a window.

```
#include <Windows.h>
#include <Richedit.h>


HWND hwnd;
HWND panel;
HWND richEdit;
WNDPROC oldStaticProc;

int WINAPI WinMain(HINSTANCE, HINSTANCE, PSTR, int);
LRESULT CALLBACK WindowProcedure(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK StaticProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);

#if _DEBUG
#pragma comment( linker, "/subsystem:console" )
int main(int argc, const char** argv) {
return WinMain(GetModuleHandle(NULL), NULL, GetCommandLineA(), SW_SHOWDEFAULT);
}
#else
#pragma comment( linker, "/subsystem:windows" )
#endif
#pragma comment(lib, "opengl32.lib")

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) {
LoadLibrary(TEXT("Msftedit.dll"));
int width = 800;
int height = 600;

WNDCLASS wc = { };
const wchar_t* CLASS_NAME = L"OpenGL and RichEdit Message Processing";
wc.lpfnWndProc = WindowProcedure;
wc.hInstance = hInstance;
wc.lpszClassName = CLASS_NAME;

if (!RegisterClass(&wc))
{
MessageBox(NULL, L"Window Registration Failed!", L"Error!", MB_ICONEXCLAMATION | MB_OK);
}

hwnd = CreateWindowEx(
0,
CLASS_NAME,
L"OpenGL RichEdit Control",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, width, height,
NULL,
NULL,
hInstance,
NULL
);

if (hwnd == NULL)
{
MessageBox(NULL, L"Window Creation Failed!", L"Error!", MB_ICONEXCLAMATION | MB_OK);
}
if (hwnd != NULL)
{
ShowWindow(hwnd, SW_SHOW);
UpdateWindow(hwnd);
}
//GetClientRect(hwnd, &rect_hwnd);
panel = CreateWindowEx(
0,
L"STATIC",
NULL,
WS_CHILD | WS_VISIBLE,
0, height - 150, width, 150,
hwnd,
NULL,
hInstance,
NULL
);
InvalidateRect(panel, NULL, TRUE);
oldStaticProc = (WNDPROC)SetWindowLongPtr(panel, GWLP_WNDPROC, (LONG_PTR)StaticProc);

richEdit = CreateWindowEx(
WS_EX_CLIENTEDGE,
RICHEDIT_CLASS,
L"Type here...",
WS_CHILD | WS_VISIBLE | WS_VSCROLL | ES_MULTILINE | ES_AUTOVSCROLL,
0, 0, width, 150,
panel,
NULL,
hInstance,
NULL
);
MSG msg = { };
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

return 0;
}

LRESULT CALLBACK WindowProcedure(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static HBRUSH hBrush = CreateSolidBrush(RGB(0, 255, 0));

switch (msg)
{
case WM_PAINT:
{
if (hwnd == panel) // only draw border for the panel
{

}
break;
}
case WM_CTLCOLORSTATIC:
{
//HDC hdcStatic = (HDC)wParam;
//SetBkColor(hdcStatic, RGB(0, 255, 0));
//return (INT_PTR)hBrush;
}
case WM_SIZE:
{
int width = LOWORD(lParam);
int height = HIWORD(lParam);

SetWindowPos(panel, NULL, 0, height - 150, width, 150, SWP_NOZORDER);
SetWindowPos(richEdit, NULL, 0, 0, width, 150, SWP_NOZORDER);

break;
}
case WM_CLOSE:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}

LRESULT CALLBACK StaticProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_ERASEBKGND:
// Prevent the background from being erased
return TRUE;
case WM_PAINT:
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);

// Create a rectangle that is slightly smaller than the panel
RECT rect;
GetClientRect(hwnd, &rect);
rect.left += 2;
rect.top += 2;
rect.right -= 2;
rect.bottom -= 2;

// Create a pen (for drawing lines) that is red and 2 pixels wide
HPEN hPen = CreatePen(PS_SOLID, 2, RGB(255, 0, 0));

// Select the pen into the device context
HPEN hOldPen = (HPEN)SelectObject(hdc, hPen);

// Draw a rectangle that is the same size as the panel
Rectangle(hdc, rect.left, rect.top, rect.right, rect.bottom);

// Clean up: deselect the pen, delete it, and end the paint operation
SelectObject(hdc, hOldPen);
DeleteObject(hPen);
EndPaint(hwnd, &ps);
break;
default:
return CallWindowProc(oldStaticProc, hwnd, msg, wParam, lParam);
}
return 0;
}```


I would like to draw a border (1px black should be fine...) on the limits of panel and also I would like the background color of panel to be the color green. So far I have: ```
Severity Code Description Project File Line Suppression State Details
Warning C6387 'hwnd' could be '0': this does not adhere to the specification for the function 'UpdateWindow'. See line 58 for an earlier location where this can occur demo-win32 C:\Users\franc\source\repos\demo-win32\main.cpp 59```


What could be wrong here? How can I get the border and background color drawing in a way that is suitable to resizing of the window when maximized and also when the user drags the corner of the window or the side of the window with the mouse?