Thread: InvalidateRect

Im trying to refresh one part of the window with InvalidateRect but it wont get refreshed right away. It will be if you move another window over it.

What am I doing wrong?

Code:

#include <windows.h>
#include <iostream>
using namespace std;

#pragma comment(linker,"/subsystem:\"console\" /entry:\"WinMainCRTStartup\"")

#define IDB_SOURCE    1008

const RECT rText={20,100,420,25};
char buf[260]="aaaaaaaaaaaaa";
HWND hwnd;
LRESULT CALLBACK WindowFunc(HWND,UINT,WPARAM,LPARAM);

int WINAPI WinMain(HINSTANCE hThisInst,
                   HINSTANCE hPrevInst,
                   LPSTR Args,int WinMode)
{
    MSG Message;
    WNDCLASS WinClass={0};

    char * Class="Find Files";

    WinClass.hInstance    =hThisInst;
    WinClass.lpszClassName=Class;
    WinClass.lpfnWndProc  =WindowFunc;
    WinClass.style        =0;
    WinClass.hIcon        =LoadIcon(NULL,IDI_APPLICATION);
    WinClass.hCursor      =LoadCursor(NULL,IDC_ARROW);
    WinClass.lpszMenuName =NULL;
    WinClass.cbClsExtra   =0;
    WinClass.cbWndExtra   =0;
    WinClass.hbrBackground=(HBRUSH) GetStockObject(LTGRAY_BRUSH);

    if(!RegisterClass(&WinClass)) return 0;

    DWORD dwStyle=(WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU |
                   WS_MINIMIZEBOX | WS_VISIBLE);
    hwnd=CreateWindow(Class,
                        TEXT("Search"),
                        dwStyle,
                        100,100,
                        600,400,
                        NULL,
                        NULL,
                        hThisInst,
                        NULL);
    if(hwnd==NULL)
    {
        //ReportError("CreateWindow");
        return 0;
    }

    while(GetMessage(&Message,NULL,0,0))
    {
        TranslateMessage(&Message);
        DispatchMessage(&Message);
    }
    return Message.wParam;
}
/// ////////////////////////////////////////////////////
///
LRESULT CALLBACK WindowFunc(HWND hwnd,UINT Message,WPARAM wParam,LPARAM lParam)
{
    HDC hdc=0;
    PAINTSTRUCT ps;

    switch(Message)
    {
    case WM_CREATE:
    {
        CreateWindowEx(0,TEXT("button"),
                       TEXT("Clickme"),
                       WS_VISIBLE | WS_CHILD,
                       20,140,60,20,
                       hwnd,(HMENU)IDB_SOURCE,0,NULL);

        return 0;
    }

    case WM_COMMAND:
        switch(wParam)
        {
        case IDB_SOURCE:
            sprintf(buf, "bbbbbbbbbbbbbb");
            InvalidateRect(hwnd, &rText, TRUE);
            UpdateWindow(hwnd);
            break;
        }
        return 0;

    case WM_PAINT:
    {
        cout << " WM PAINT.\n";
        hdc=BeginPaint(hwnd,&ps);
        TextOut(hdc, 20, 100, buf, strlen(buf));
        EndPaint(hwnd,&ps);
    }
    return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    default:
        return DefWindowProc(hwnd,Message,wParam,lParam);
    }
    return 0;
}

Your paint is working, you have just asked for no area to be redrawn.

Code:

const RECT rText={20,100,420,25}

the TOP of this rect is 100 but the bottom is 25, so it has a negative height.

As you cannot draw to a rect with a negative height (or any area outside the rect you invalidated) your paint fails to show any change.

Try;

Code:

const RECT rText={20,100,420,250};

OR

InvalidateRect(hwnd, NULL, TRUE);

Thanks, that was it!