使用WinSpool API对接ESC/POS热敏打印机时如何设置自定义页尺寸

核心实现步骤 #

你可以通过修改Winspool的DevMode结构体实现自定义页尺寸配置，操作需要放在OpenPrinter执行完成后、StartDocPrinter调用前执行。

步骤1：获取打印机默认DevMode #

首先调用DocumentProperties接口获取打印机当前的DevMode数据，需要先查询所需内存大小再分配空间，避免遗漏驱动私有数据：

// 查询DevMode需要的内存大小
int devModeSize = NativeMethods.DocumentProperties(IntPtr.Zero, _hPrinter, 你的打印机名称, IntPtr.Zero, IntPtr.Zero, 0);
IntPtr pDevMode = Marshal.AllocHGlobal(devModeSize);
// 填充默认DevMode数据
NativeMethods.DocumentProperties(IntPtr.Zero, _hPrinter, 你的打印机名称, pDevMode, IntPtr.Zero, NativeMethods.DM_OUT_BUFFER);
// 转换为托管结构体
DevMode devMode = (DevMode)Marshal.PtrToStructure(pDevMode, typeof(DevMode));

步骤2：配置自定义页尺寸参数 #

DevMode中纸张尺寸的单位为0.1毫米，你需要的50mm高度对应数值为500，宽度根据你使用的是58mm还是80mm纸填入对应值即可：

// 标记要修改的字段
devMode.dmFields |= NativeMethods.DM_PAPERSIZE | NativeMethods.DM_PAPERWIDTH | NativeMethods.DM_PAPERLENGTH;
// 固定值，标识使用自定义纸张尺寸
devMode.dmPaperSize = NativeMethods.DMPAPER_USER;
// 宽度：58mm填580，80mm填800
devMode.dmPaperWidth = 580;
// 高度：按需调整，50mm对应500
devMode.dmPaperLength = 500;
// 将修改后的结构体写回内存
Marshal.StructureToPtr(devMode, pDevMode, true);

步骤3：应用配置到打印机 #

调用SetPrinter接口将修改后的配置应用到当前打印机句柄，之后再执行你原有的文档创建逻辑即可：

// 应用配置
NativeMethods.SetPrinter(_hPrinter, 8, pDevMode, 0);
// 释放内存
Marshal.FreeHGlobal(pDevMode);

依赖的结构体与常量声明 #

你需要补充以下声明到你的代码中：

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public struct DevMode
{
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string dmDeviceName;
    public short dmSpecVersion;
    public short dmDriverVersion;
    public short dmSize;
    public short dmDriverExtra;
    public int dmFields;
    public short dmOrientation;
    public short dmPaperSize;
    public short dmPaperLength;
    public short dmPaperWidth;
    public short dmScale;
    public short dmCopies;
    public short dmDefaultSource;
    public short dmPrintQuality;
    public short dmColor;
    public short dmDuplex;
    public short dmYResolution;
    public short dmTTOption;
    public short dmCollate;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string dmFormName;
    public short dmLogPixels;
    public int dmBitsPerPel;
    public int dmPelsWidth;
    public int dmPelsHeight;
    public int dmDisplayFlags;
    public int dmDisplayFrequency;
    public int dmICMMethod;
    public int dmICMIntent;
    public int dmMediaType;
    public int dmDitherType;
    public int dmReserved1;
    public int dmReserved2;
    public int dmPanningWidth;
    public int dmPanningHeight;
    public int dmDisplayOrientation;
    public int dmDisplayFixedOutput;
}

public class NativeMethods
{
    public const int DM_OUT_BUFFER = 2;
    public const int DM_PAPERSIZE = 0x00000002;
    public const int DM_PAPERWIDTH = 0x00000008;
    public const int DM_PAPERLENGTH = 0x00000010;
    public const int DMPAPER_USER = 256;

    [DllImport("winspool.drv", CharSet = CharSet.Auto)]
    public static extern int DocumentProperties(IntPtr hwnd, IntPtr hPrinter, string pDeviceName, IntPtr pDevModeOutput, IntPtr pDevModeInput, int fMode);

    [DllImport("winspool.drv", CharSet = CharSet.Auto)]
    public static extern bool SetPrinter(IntPtr hPrinter, int Level, IntPtr pPrinter, int Command);
}

适配兼容性优化 #

部分厂商的热敏打印机驱动在RAW模式下会优先使用驱动内置的页尺寸配置，忽略ESC/POS的打印区域设置指令，用上述DevMode配置可以覆盖驱动默认参数。如果仍有个别驱动出现走纸异常，可以在切纸指令后追加3~5个LF走纸指令，避免最后部分内容被截断。 #

内容的提问来源于stack exchange，提问作者jstuardo