PrintWindow function makes mistake in notepad.exe

Question

PrintWindow function in Win32API could capture the image of a program. By the following code we can get the copy of the screenshot in clipboard.

#define _WIN32_WINNT    0x0501        
#include <windows.h>
#include <iostream>
using namespace std;

WCHAR programName[] = L"Notepad";

int main()
{
    HWND hwnd = FindWindow(programName, NULL);
    if (hwnd == NULL)
    {
        cerr << "Cannot find window" << endl;
        return -1;
    }

    WINDOWINFO wi;
    wi.cbSize = sizeof(WINDOWINFO);
    GetWindowInfo(hwnd, &wi);

    RECT rc = {
        wi.rcClient.left - wi.rcWindow.left,
        wi.rcClient.top - wi.rcWindow.top,
        wi.rcClient.right - wi.rcWindow.left,
        wi.rcClient.bottom - wi.rcWindow.top
    };

    HDC hdcScreen = GetDC(NULL);
    HDC hdc = CreateCompatibleDC(hdcScreen);
    HBITMAP hbmp = CreateCompatibleBitmap(hdcScreen,
        wi.rcWindow.right - wi.rcWindow.left,
        wi.rcWindow.bottom - wi.rcWindow.top);
    SelectObject(hdc, hbmp);

    HBITMAP hbmp2 = CreateCompatibleBitmap(hdcScreen,
        wi.rcClient.right - wi.rcClient.left,
        wi.rcClient.bottom - wi.rcClient.top);
    HDC hdc2 = CreateCompatibleDC(hdcScreen);
    SelectObject(hdc2, hbmp2);

    PrintWindow(hwnd, hdc, 0);

    BitBlt(hdc2,
        0, 0, rc.right - rc.left, rc.bottom - rc.top,
        hdc,
        rc.left, rc.top,
        SRCCOPY);

    OpenClipboard(NULL);
    EmptyClipboard();
    SetClipboardData(CF_BITMAP, hbmp2);
    CloseClipboard();

    DeleteDC(hdc);
    DeleteObject(hbmp);

    DeleteDC(hdc2);
    DeleteObject(hbmp2);

    ReleaseDC(NULL, hdcScreen);

    cout << "Success" << endl;

    return 0;
}

When I use the code to capture a screenshot, it works but returns a wrong picture into my clipboard. Like this: My screenshot of notepad.exe

It seems like part of the notepad program. But why it is just the part of the program. I tried other programs and they works well. Is there any bugs in notepad or win32api?

My system is Windows 10 1909(18363.592) 64-bit and my compiler is visual studio 2019. — Lyronx L, Feb 17 '20 at 13:44

score 0 · Accepted Answer · answered Feb 17 '20 at 14:34

You only get the client area. This code gets the whole window:

HWND hwnd = FindWindow(programName, nullptr);
if (hwnd == nullptr)
    return -1;

WINDOWINFO wi;
wi.cbSize = sizeof(WINDOWINFO);
GetWindowInfo(hwnd, &wi);

const LONG w = wi.rcWindow.right - wi.rcWindow.left;
const LONG h = wi.rcWindow.bottom - wi.rcWindow.top;

HDC hdcScreen = GetDC(nullptr);
HDC hdc = CreateCompatibleDC(hdcScreen);
HBITMAP hbmp = CreateCompatibleBitmap(hdcScreen, w, h);
SelectObject(hdc, hbmp);

PrintWindow(hwnd, hdc, 0); // or use PW_RENDERFULLCONTENT
BitBlt(hdc, 0, 0, w, h, hdc, 0, 0, SRCCOPY);

OpenClipboard(nullptr);
EmptyClipboard();
SetClipboardData(CF_BITMAP, hbmp);
CloseClipboard();

DeleteDC(hdc);
DeleteObject(hbmp);

ReleaseDC(nullptr, hdcScreen);
return 0;

It would be good to explain which parts of the code you changed — M.M, Feb 17 '20 at 19:48
@M.M - it's pretty obvious. As I said in the introduction, I changed client coordinates by window coordinates. The rest is purely cosmetic. — Simon Mourier, Feb 17 '20 at 22:18

PrintWindow function makes mistake in notepad.exe

1 Answers1