我有带渐变背景的窗口。组合框具有自己的背景画笔。
如何删除组合框中的白角？如何更改画笔或其他方式。
在图片的白色角上标有红色框。



我将组合框创建为:

DWORD dwStyle = WS_CHILD | CBS_DROPDOWNLIST;
if (m_bVisible) dwStyle |= WS_VISIBLE;
m_hWnd = CreateWindow(WC_COMBOBOX, NULL, dwStyle,
    m_posX, m_posY, m_width, m_height, m_hParent, (HMENU)m_id, m_hInstance, NULL);

case WM_CTLCOLOREDIT:
    if ((HWND)lParam == m_hSrcListBox)
    {
        return (LRESULT)m_hBrush;
    }
break;

case WM_CTLCOLORSTATIC:
    if ((HWND)lParam == m_hSrcListBox)
    {
        return (LRESULT)m_pSrcListBox->GetHbrush();
    }
break;

//
// CListBox::GetHbrush().
//
// Get brush.
//
HBRUSH CListBox::GetHbrush()
{
    if (!m_hBrush)
    {
        m_hBrush = CreateTransparentBackgroundBrush(m_hParent, m_hWnd);
    }
    return m_hBrush;
}

//
// CListBox::CreateTransparentBackgroundBrush().
//
// Create transparent background for element.
//
HBRUSH CListBox::CreateTransparentBackgroundBrush(HWND parent, HWND client)
{
    RECT rct;
    POINT p1;
    POINT p2;
    GetWindowRect(client, &rct);
    p1.x = rct.left;
    p1.y = rct.top;
    ScreenToClient(parent, &p1);
    p2.x = rct.right;
    p2.y = rct.bottom;
    ScreenToClient(parent, &p2);

    HDC hdcParent = GetDC(parent);
    HDC hdcClient = GetDC(client);

    HDC hdcmem = CreateCompatibleDC(hdcClient);
    HBITMAP hbitmap = CreateCompatibleBitmap(hdcClient, p2.x - p1.x, p2.y - p1.y);
    SelectObject(hdcmem, hbitmap);
    BitBlt(hdcmem, 0, 0, p2.x - p1.x, p2.y - p1.y, hdcParent, p1.x, p1.y, SRCCOPY);

    HBRUSH pattern = CreatePatternBrush(hbitmap);

    DeleteDC(hdcmem);
    DeleteObject(hbitmap);
    ReleaseDC(client, hdcClient);
    ReleaseDC(parent, hdcParent);

    return pattern;
}

case WM_ERASEBKGND:
    m_hdc = (HDC)wParam;

    // draw background.

    return TRUE;
break;

最佳答案

对于对话框，处理WM_CTLCOLORDLG并为组合框返回背景画笔
如果要在对话框中显示此组合框，则技巧实际上是在对话框的窗口过程中处理WM_CTLCOLORDLG消息。响应此消息，您将画笔的句柄返回到对话框将用于绘制其背景的画笔。

case WM_CTLCOLORDLG:
{
   // NOTE: This code is wrong because it creates a new brush object each time it processes
   //       the message, which it promptly leaks. It is merely for demonstration purposes.
   //       Normally, you would create the brush once, in response to WM_INITDIALOG,
   //       cache it away, and return that same cached handle each time, finally destroying
   //       the brush in response to WM_NCDESTROY.
   HBRUSH hBrush = CreateSolidBrush(RGB(255, 120, 0));
   return reinterpret_cast<INT_PTR>(hBrush);
}

WNDCLASSEX wcex;
wcex.cbSize        = sizeof(WNDCLASSEX);
wcex.style         = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc   = WndProc;
wcex.cbClsExtra    = 0;
wcex.cbWndExtra    = 0;
wcex.hInstance     = hInstance;
wcex.hIcon         = LoadIcon(hInstance, MAKEINTRESOURCE(IDR_APPLICATION));
wcex.hIconSm       = LoadIcon(hInstance, MAKEINTRESOURCE(IDR_APPLICATION_SMALL));
wcex.hCursor       = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = reinterpret_cast<HBRUSH>(COLOR_3DDKSHADOW + 1);  // background brush
wcex.lpszMenuName  = NULL;
wcex.lpszClassName = TEXT("My Colored Window Class");
RegisterClassEx(&wcex);

case WM_CTLCOLORSTATIC:
{
  // NOTE: No leak here because we're using a system brush in this example.
  return reinterpret_cast<LRESULT>(GetSysColorBrush(COLOR_3DDKSHADOW)); // background brush
}

关于c++ - 渐变父窗口上的背景组合框？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37640434/