C++ WinAPI TextOut()更新文本

Question

我正在使用WinAPI创建一个Windows应用程序。在处理窗口的WM_PAINT消息时，我使用TextOut()函数向用户显示更新后的文本。

case WM_PAINT:
{
     PAINTSTRUCT ps;
     HDC hdc;
     hdc = BeginPaint(hwnd, &ps);
     SelectObject(hdc, hfDefault);

     // display the user data in the window
     TextOut(hdc,10,70, "Points: 0", 9);
     TextOut(hdc,10,85, "Level: 0", 8);

     // ...
     EndPaint(hwnd, &ps);
}
break;

如何在调用函数后更改TextOut()打印的文本以及决定打印文本长度的最后一个参数？

我找到的关于使用TextOut()的一切都是关于文本字体的。

Answer 1

也许是这样的.

// I'll assume hwnd is global
void OnSomeActionToRefreshValues()
{
    HDC hdc = ::GetDc(hwnd);
    DrawValues(hdc, 88, 99);
    ReleaseDC(hdc);
}

void DrawValues(HDC hdc, int points, int level)
{
    // Might need a rectangle here to overwrite old text
    SelectObject(hdc, hfDefault);    // I assume hfDefault is global
    TCHAR text[256];
    swprintf_s(text, 256, L"Points: %d", points);
    TextOut(hdc, 10, 70, text, wcslen(text));
    swprintf_s(text, 256, L"Level: %d", level);
    TextOut(hdc, 10, 85, text, wcslen(text));
}

在你赢的过程中：

case WM_PAINT:
    PAINTSTRUCT ps;
    HDC hdc;
    hdc = BeginPaint(hwnd,&ps);
    DrawValues(hdc, 88, 99);
    EndPaint(hwnd,&ps);
    break;

Answer 2

为了在处理WM_PAINT消息时更新窗口中显示的文本，您需要为要显示的文本字符串提供一些源。

由于你最初的帖子有点旧，Windows API已经随着Windows的新版本发生了变化，当前版本的Windows 10和Windows 11已经处于测试阶段。

由于Windows XP是用于WinAPI的16位UNICODE，因此人们大多使用wchar_t文本字符。这要求文本字符串常量需要L修饰符，就像在L"wchar_t text"中一样。

使用Visual Studio2019，我组合了一个运行在Windows10上的简单示例。这是一个简单的Windows WinAPI桌面图形用户界面应用程序。我从Visual Studio中的一个新项目开始，让集成开发环境使用wWinMain()、MyRegisterClass()、InitInstance()和WndProc()为Windows Desktop GUI应用程序生成框架。

然后，我修改了生成的源代码以执行以下操作：

在主窗口中提供了四个按钮，允许使用

• 两个文本字符串，这些文本字符串会随着按钮点击次数的更新而更新

我选择使用默认字体，所以没有对用于显示文本的字体进行任何修改。如果需要修改字体，则需要添加代码以创建所需的字体，在用于绘制文本的HDC中选择新字体，然后使用TextOut()使用新字体绘制文本。使用该字体后，您需要将其换回，然后将其删除。

​

​

第一步是创建一个用于管理按钮和按钮点击的数据区。我选择在InitInstance()中创建按钮。

static struct {
    const wchar_t* txt;    // pointer to text to display on button face
    int      iCount;       // count of number of times button clicked
    HWND     hwnd;         // button window handle which identifies the button
} myButtons[] = {
    {L"Points up", 0, 0},
    {L"Points dwn", 0, 0},
    {L"Level up", 0, 0},
    {L"Level dwn", 0, 0}
};

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   hInst = hInstance; // Store instance handle in our global variable

   HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);

   if (!hWnd)
   {
      return FALSE;
   }

   // create the displayed window along with the buttons.
   // the buttons are in a single row at the top of the window.

   POINT myPoint = { 10, 10 };  // x, y

   for (auto &a : myButtons) {
       a.hwnd = CreateWindow(
           L"BUTTON",  // Predefined class; Unicode assumed 
           a.txt,      // Button text 
           WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
           myPoint.x,  // x position 
           myPoint.y,  // y position 
           100,        // Button width
           50,         // Button height
           hWnd,       // Parent window
           NULL,       // No menu.
           (HINSTANCE)GetWindowLongPtr(hWnd, GWLP_HINSTANCE),
           NULL);      // Pointer not needed.

       myPoint.x += 100 + 20;    // button width plus a separation distance
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

更新显示窗口的源代码如下。我们有两个函数，一个是按钮单击处理程序，用于确定哪个按钮被单击了；另一个是带有WM_PAINT消息处理程序的WndProc()，用于修改显示的窗口。

// process a button click event and return an indication
// whether the button handle matches one we are managing (1)
// or not managing (0).
int buttonClick(HWND hWnd, HWND hButton)
{
    // look through the list of buttons to see if the window handle
    // of the button event matches one of our buttons.
    for (auto &a : myButtons) {
        if (a.hwnd == hButton) {
            // this is one of our buttons so we increment button click count.
            // then invalidate the window area and update to trigger WM_PAINT message.
            a.iCount++;
            InvalidateRect(hWnd, NULL, TRUE);
            UpdateWindow(hWnd);
            return 1;    // indicate we processed this event.
        }
    }
    return 0;    // indicate we did not process this event
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_COMMAND:
        {
            int wmId = LOWORD(wParam);
            int wmCode = HIWORD(wParam);
            // Parse the menu selections:
            switch (wmId)
            {
            case IDM_ABOUT:
                DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                break;
            case IDM_EXIT:
                DestroyWindow(hWnd);
                break;
            default:
                // not a menu event so see if it is a button click or not.
                if (wmCode == BN_CLICKED) {
                    // if we are managing this button then we skip
                    // the DefWindowProc() otherwise it is called.
                    if (buttonClick(hWnd, (HWND)lParam))
                        break;
                }
                return DefWindowProc(hWnd, message, wParam, lParam);
            }
        }
        break;
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);

            // TODO: Add any drawing code that uses hdc here...

            // create the text strings we are going to display/update

            wchar_t myText[2][64];
            // following swprintf_s() works because template
            // generates the proper call with the additional buffer
            // size argument.
            swprintf_s(myText[0], L"Points: %d", myButtons[0].iCount - myButtons[1].iCount);
            swprintf_s(myText[1], L"Level: %d", myButtons[2].iCount - myButtons[3].iCount);

            // get the text metrics of the font we are using to draw the text so
            // that we can find out how tall the letters are and can adjust the
            // distance for each line of text properly.
            TEXTMETRIC myTextMetric = { 0 };
            GetTextMetrics(hdc , &myTextMetric);

            // we will use a POINT struct for maintaining the point at which
            // the text output will start. x coordinate is horizontal position
            // and y coordinate is the vertical position.
            POINT myPoint = { 10, 150 };  // x, y
            int   myMargin = 5;

            // iterate over the list of strings we are displaying and
            // display each one on a separate line.
            for (auto &a : myText) {
                TextOut(hdc, myPoint.x, myPoint.y, a, wcslen(a));
                myPoint.y += myTextMetric.tmHeight + myMargin;
            }

            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}