您能指出与组合框（WinAPI）（C 源代码）相关的代码中的错误吗

Question

当我将鼠标指针悬停/单击组合框显示的选项上时，我的组合框不会突出显示/选择文本，甚至当我按键盘上的 TAB 时，项目选择也不会突出显示组合框。谁能看出下面的代码片段有什么错误吗？

PS：组合框在主窗口中可见，下拉列表按预期工作。

#include <windows.h>
#include <windowsx.h>
#include <CommCtrl.h>
#include <wingdi.h>
#include <WinUser.h>
#include <stdbool.h>

#define APP_CLASS_NAME_W        L"Test GUI Class"
#define APP_NAME_CAPTION_W      L"My Test GUI"
#define APP_DEFAULT_WIDTH       640
#define APP_DEFAULT_HEIGHT      480
#define APP_BACKGROUND_COLOR    (RGB(225, 229, 180))

enum e_TestGUIObjectIndices
{
    e_TEST_GUI_COMBOBOX     = 1
};

typedef struct s_TestGUIWindowsParams
{
    int X;
    int Y;
    int Width;
    int Height;
} t_TestGUIWindowsParams;

LRESULT CALLBACK TestGUI_Process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR pCmdLine, int nCmdShow)
{
    MSG message = {0};
    WNDCLASSW window_class = {0};
    HWND main_window = {0};
    t_TestGUIWindowsParams main_window_size = {0};
    ATOM result = 0;

    /* Initialization Main Window Class Structure */
    window_class.lpszClassName = APP_CLASS_NAME_W;
    window_class.style = CS_HREDRAW | CS_VREDRAW;
    window_class.hInstance = hInstance;
    window_class.hbrBackground = CreateSolidBrush(APP_BACKGROUND_COLOR);
    window_class.lpfnWndProc = TestGUI_Process;
    window_class.hCursor = LoadCursor(0, IDC_ARROW);
    window_class.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    window_class.lpszMenuName = NULL;
    window_class.cbClsExtra = 0;
    window_class.cbWndExtra = 0;

    result = RegisterClassW(&window_class);

    // Center aligned main window parameters
    main_window_size.X = (GetSystemMetrics(SM_CXSCREEN) >> 1)-(APP_DEFAULT_WIDTH >> 1);
    main_window_size.Y = (GetSystemMetrics(SM_CYSCREEN) >> 1)-(APP_DEFAULT_HEIGHT  >> 1);
    main_window_size.Width = APP_DEFAULT_WIDTH;
    main_window_size.Height = APP_DEFAULT_HEIGHT;

    /* Creation of Main Window */
    main_window = CreateWindowExW(WS_EX_COMPOSITED, window_class.lpszClassName,
                                APP_NAME_CAPTION_W, (WS_OVERLAPPEDWINDOW | WS_VISIBLE | WS_TABSTOP | WS_BORDER),
                                main_window_size.X, main_window_size.Y, main_window_size.Width, main_window_size.Height,
                                NULL, NULL, window_class.hInstance, NULL);
    
    if(main_window == NULL)
    {
        MessageBoxW(NULL, L"CreateWindowExW Failed", L"Anything", MB_OK | MB_ICONERROR);
        return 0;
    }

    EnableWindow(main_window, TRUE);

    ShowWindow(main_window, nCmdShow);
    UpdateWindow(main_window);
    
    while(GetMessageW(&message, main_window, 0, 0) > 0)
    {
        TranslateMessage(&message);
        DispatchMessageW(&message);
    }

    return(int)message.wParam;
}

LRESULT CALLBACK TestGUI_Process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static TITLEBARINFO main_window_titlebar = {0};
    static HWND main_window_combobox = {0};
    HINSTANCE main_window_instance = (HINSTANCE)GetWindowLongPtrW(hwnd, GWLP_HINSTANCE);
    static const WCHAR item_text[3][7] = {  { L"Item 1\000" },
                                            { L"Item 2\000" },
                                            { L"Item 3\000" } };

    switch(message)
    {
        case WM_CREATE:
            main_window_titlebar.cbSize = sizeof(TITLEBARINFO);
            GetTitleBarInfo(hwnd, &main_window_titlebar);
            main_window_combobox = CreateWindowExW(0, WC_COMBOBOXW, L"",
                                WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST | WS_VSCROLL | WS_TABSTOP,
                                10, main_window_titlebar.rcTitleBar.bottom - main_window_titlebar.rcTitleBar.top + 25,
                                200, 500, // Position and size
                                hwnd, (HMENU)e_TEST_GUI_COMBOBOX, main_window_instance, NULL);
            UpdateWindow(hwnd);
            SendMessageW(main_window_combobox, CB_ADDSTRING, 0, (LPARAM)item_text[0]);
            SendMessageW(main_window_combobox, CB_ADDSTRING, 0, (LPARAM)item_text[1]);
            SendMessageW(main_window_combobox, CB_ADDSTRING, 0, (LPARAM)item_text[2]);
            SendMessageW(main_window_combobox, CB_SETCURSEL, (WPARAM)2, 0);
            break;
        
        case WM_GETMINMAXINFO:
            LPMINMAXINFO lpMMI = (LPMINMAXINFO)lParam;
            lpMMI->ptMinTrackSize.x = APP_DEFAULT_WIDTH;
            lpMMI->ptMinTrackSize.y = APP_DEFAULT_HEIGHT;
            break;
        
        case WM_SIZE:
            break;
        
        case WM_COMMAND: 
            switch(LOWORD(wParam))
            {
                case e_TEST_GUI_COMBOBOX:
                {
                    switch(HIWORD(wParam))
                    {                      
                        case CBN_SELCHANGE:
                            WCHAR get_string[12];
                            int index = SendMessageW(main_window_combobox, CB_GETCURSEL, 0, 0);
                            SendMessageW(main_window_combobox, CB_GETLBTEXT, (WPARAM)index, (LPARAM)get_string);
                            break;
                        
                        default:
                            break;
                    }
                }
                break;
            }
            break;
        
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
    }

    return DefWindowProcW(hwnd, message, wParam, lParam);
}

我一直在努力完成这项工作。

我什至尝试通过 ChatGPT 搜索代码，它给了我类似的代码，当然变量名不同。代码片段是相同的。甚至 WinAPI 文档中的示例代码也类似。

Answer 1

GetMessage的第二个参数必须为NULL，否则只能获取主窗口的消息，而无法获取ComboBox的消息。

while(GetMessageW(&message, NULL, 0, 0) > 0)