CODEWITHSUNDEEP
windowswinapirect
Tomay
Tomay

Reputation: 55

How to get the client rect offsets of a window relative to the non-client rect of that window?

I need to get the client rect offsets of a window relative to the non-client rect of that window.

I have tried GetClientRect but this only gets the client rect relative to the client rect itself, meaning: rect.left = 0, rect.top = 0, rect.right = clientWidth and rect.bottom = clientHeight.

So, how to do it?

Thanks in advance.

Upvotes: 2

Views: 1583

Answers (2)

byteptr
byteptr

Reputation: 1385

It sounds like you want the non-client offsets from the edges of the Window into the client rectangle. That is, the left and top internal leading pixels along with the right and bottom trailing pixels. Within these offsets (sizes), you could have the title bar, menu bar and edges that adorn your client rectangle if you were doing this for a top-level window such as a dialog. Windows doesn't calculate this for you, but it provides everything you need to calculate it yourself. Here is some sample code that you might use to perform this calculation from a given window handle:

RECT rcNonCli = {0,0,0,0}; //calculate non-client offsets here
RECT rcWin = {0,0,0,0};
RECT rcClient = {0,0};
POINT ptClient = {0,0};
if (GetWindowRect(hwnd,&rcWin) && GetClientRect(hwnd,&rcClient) && ClientToScreen(hwnd,&ptClient))
{
    rcNonCli.left = ptClient.x - rcWin.left;
    rcNonCli.top = ptClient.y - rcWin.top;
    rcNonCli.right = rcWin.right - ptClient.x - rcClient.right;
    rcNonCli.bottom = rcWin.bottom - ptClient.y - rcClient.bottom;

    printf("nonclient offsets={%d,%d,%d,%d}\n",rcNonCli.left,rcNonCli.top,rcNonCli.right,rcNonCli.bottom);
}

EXPLANATION: ClientToScreen() gives us the beginning coordinate of the client area providing the top and left offsets. Once we know this, we can subtract from the complete Window size (from GetWindowRect()), the client size (from GetClientRect()) and the non-client top and left offsets to give us what remains which would be the bottom and right offsets.

Upvotes: 2

Zeus
Zeus

Reputation: 3880

As Jonathan Potter commented, I recommend you to use MapWindowPoints.

You can pass the rect obtained by GetClientRect into MapWindowPoints, and set the cPoints parameter to 2, to get the coordinates relative to the window you want.

Here is the sample:

#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("hello windows");
    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(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;
    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
    }

    hwnd = CreateWindow(szAppName,
        TEXT("the hello program"),
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while (GetMessageW(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessageW(&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    switch (message)
    {
    case WM_CREATE:
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        GetClientRect(hwnd, &rect);
        DrawTextW(hdc, (L"Hello,Windows"), -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
        MapWindowPoints(hwnd, HWND_DESKTOP, (LPPOINT)&rect, 2);
        EndPaint(hwnd, &ps);
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

You can observe the result of rect after calling the MapWindowPoints. It converts the original coordinates to the coordinates relative to the desktop.

Upvotes: 1

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