Thread: Invalidaterect

Im trying to draw a rectangle around an arrow with InvalidateRect(hwnd, lpRect, FALSE)
It compiles without error but it keeps flashing and it invalidates the whole client area not only
the rectangle i want.
I guess the problem must be that InvalidateRect(hwnd, lpRect, FALSE) takes a CONST RECT* for rectangle
coordinates while the RECT structure is only of type RECT.
So i must be doing something wrong.
Thanks for any help.

Code:

#include<windows.h>
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("Invalidaterect") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;
if (!RegisterClass (&wndclass))
{
 
return 0 ;
}
 
hwnd = CreateWindow (szAppName, // window class name
TEXT ("The Hello Program"), // window caption
WS_OVERLAPPEDWINDOW, // window style
CW_USEDEFAULT, // initial x position
CW_USEDEFAULT, // initial y position
CW_USEDEFAULT, // initial x size
CW_USEDEFAULT, // initial y size
NULL, // parent window handle
NULL, // window menu handle
hInstance, // program instance handle
NULL) ; // creation parameters

ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;
 
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc ;
PAINTSTRUCT ps ;
RECT rect ;
HBRUSH hBrush, hOld ;
POINT points [7] = {{20, 50},{180, 50},{180, 20},{230, 70},
{180, 120},{180, 90},{20, 90}}; 
int cpt = 7 ;
CONST RECT* lpRect = 0 ;
rect.left = 10;
rect.top = 40;
rect.right = 200;
rect.bottom = 140;

switch (message)
{ 
case WM_PAINT: 
hdc = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &rect); 
hBrush = CreateSolidBrush (RGB(20,170,20)) ;
hOld = (HBRUSH) SelectObject (hdc,hBrush) ;
InvalidateRect(hwnd, lpRect, FALSE) ;
FillRect (hdc, &rect, hBrush) ;
 
hBrush = CreateHatchBrush (HS_FDIAGONAL, RGB(200,170,20)) ;
hOld = (HBRUSH) SelectObject (hdc,hBrush) ;
Polygon(hdc, points, cpt); 
SelectObject (hdc,hOld) ;
DeleteObject (hBrush) ;
EndPaint(hwnd, &ps);
return 0 ;
 
case WM_DESTROY:
PostQuitMessage (0) ; 
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}