WinAPI C语言创建RichEdit时修改行距及相关问题咨询

核心错误：误用普通EDIT控件而非RichEdit控件 #

你代码中创建的是普通EDIT控件（类名"EDIT"），而普通EDIT控件不支持PARAFORMAT2结构和EM_SETPARAFORMAT消息，这是行距修改无效的根本原因。必须将控件类名改为RichEdit对应的类名：

• ANSI版本："RichEdit20A"
• 宽字符版本："RichEdit20W"

LoadLibrary("riched20.dll")的必要性 #

是必要的。RichEdit控件的窗口类并非系统默认注册，必须先加载riched20.dll（或更高版本如riched32.dll、msftedit.dll）才能完成类注册，否则CreateWindowEx创建RichEdit控件会失败。建议保存模块句柄并在程序退出时释放，避免内存泄漏：

HMODULE hRichEdit = LoadLibrary("riched20.dll");
// ... 程序逻辑 ...
FreeLibrary(hRichEdit);

行距修改函数（LSpaceA、LSpaceB）修正 #

要正确设置行距，需结合bLineSpacingRule和dyLineSpacing，同时确保dwMask覆盖必要的格式位。建议先获取当前段落格式再修改，避免丢失原有设置：

修正后的LSpaceA（固定行距示例） #

void LSpaceA()
{
    PARAFORMAT2 pf2 = {0};
    pf2.cbSize = sizeof(PARAFORMAT2);
    // 先获取当前段落格式
    SendMessage(hEdit, EM_GETPARAFORMAT, 0, (LPARAM)&pf2);
    pf2.dwMask |= PFM_LINESPACING;
    // 设置为固定行距（LS_EXACT），dyLineSpacing为像素值
    pf2.bLineSpacingRule = LS_EXACT;
    pf2.dyLineSpacing = 40; // 固定40像素行距
    SendMessage(hEdit, EM_SETPARAFORMAT, 0, (LPARAM)&pf2);
}

修正后的LSpaceB（多倍行距示例） #

void LSpaceB(HWND hwnd, int spaceFactor)
{
    PARAFORMAT2 pf = {0};
    pf.cbSize = sizeof(PARAFORMAT2);
    SendMessage(hwnd, EM_GETPARAFORMAT, 0, (LPARAM)&pf);
    pf.dwMask |= PFM_LINESPACING;
    // 设置为多倍行距（LS_MULTIPLE），spaceFactor为1/20点的倍数（如40=2倍行距）
    pf.bLineSpacingRule = LS_MULTIPLE;
    pf.dyLineSpacing = spaceFactor;
    SendMessage(hwnd, EM_SETPARAFORMAT, 0, (LPARAM)&pf);
}

bLineSpacingRule常用取值说明：

• LS_SINGLE(0)：单倍行距
• LS_ONEHALF(1)：1.5倍行距
• LS_DOUBLE(2)：双倍行距
• LS_EXACT(4)：固定行距，dyLineSpacing为像素值
• LS_MULTIPLE(5)：多倍行距，dyLineSpacing为1/20点的倍数（例如20=1倍，30=1.5倍）

完整修正后的测试代码 #

#include <stdio.h>
#include <windows.h>
#include <richedit.h>

#define ID_EDIT 1
#define ID_BUTTON 2

HWND hEdit, hButton;
HINSTANCE hInstance;
HMODULE hRichEdit;

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);

char sbuf[900];
void MkBuf()
{
    char sta[300];
    int ii;
 
    _strcpy_s(sbuf, sizeof(sbuf), "");
    for(ii=0; ii<6; ii++){ 
        _snprintf_s(sta, sizeof(sta), _TRUNCATE, "%dth line Test WinApi Test WinApi Test WinApi Test WinApi Test WinApi\r\n", 1+ii);
        _strcat_s(sbuf, sizeof(sbuf), sta);
    }
}
void LSpaceA()
{
    PARAFORMAT2 pf2 = {0};
    pf2.cbSize = sizeof(PARAFORMAT2);
    SendMessage(hEdit, EM_GETPARAFORMAT, 0, (LPARAM)&pf2);
    pf2.dwMask |= PFM_LINESPACING;
    pf2.bLineSpacingRule = LS_EXACT;
    pf2.dyLineSpacing = 40;
    SendMessage(hEdit, EM_SETPARAFORMAT, 0, (LPARAM)&pf2);
}
void LSpaceB(HWND hwnd, int spaceFactor)
{
    PARAFORMAT2 pf = {0};
    pf.cbSize = sizeof(PARAFORMAT2);
    SendMessage(hwnd, EM_GETPARAFORMAT, 0, (LPARAM)&pf);
    pf.dwMask |= PFM_LINESPACING;
    pf.bLineSpacingRule = LS_MULTIPLE;
    pf.dyLineSpacing = spaceFactor;
    SendMessage(hwnd, EM_SETPARAFORMAT, 0, (LPARAM)&pf);
}

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {

    hRichEdit = LoadLibrary("riched20.dll");
    if (!hRichEdit) {
        MessageBox(NULL, "Failed to load riched20.dll", "Error", MB_ICONERROR);
        return 1;
    }

    WNDCLASSEX wc = {0};
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = "EditorWindowClass";
    RegisterClassEx(&wc);

    HWND hwnd = CreateWindowEx(0, "EditorWindowClass", "Text Editor", WS_OVERLAPPEDWINDOW, 
        CW_USEDEFAULT, CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL);

    // 创建RichEdit20A控件（ANSI版本）
    hEdit = CreateWindowEx(0, "RichEdit20A", "", WS_CHILD | WS_VISIBLE | WS_BORDER | ES_MULTILINE,
        0, 0, 800, 500, hwnd, (HMENU)ID_EDIT, hInstance, NULL);

    hButton = CreateWindowEx(0, "BUTTON", "Change Line Spacing", WS_CHILD | WS_VISIBLE,
        10, 510, 150, 30, hwnd, (HMENU)ID_BUTTON, hInstance, NULL);

    MkBuf();
    SetWindowText(hEdit, sbuf);
    LSpaceA();

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    FreeLibrary(hRichEdit);
    return (int)msg.wParam;
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    switch (uMsg) {
    case WM_COMMAND:
        if (LOWORD(wParam) == ID_BUTTON) {
            LSpaceB(hEdit, 40); // 设置2倍行距（40=2*20）
        }
        break;
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
    return 0;
}

VS编译兼容性说明 #

将strcpy、sprintf、strcat替换为安全版本_strcpy_s、_snprintf_s、_strcat_s，即可在Visual Studio中正常编译。

内容的提问来源于stack exchange，提问作者land cc