如何在 Awesomium 中将 window.print() 事件处理为实际打印（不打印到 PDF）？我知道它会使用 WebView.PrintRequest 事件，但我不知道该怎么做
http://docs.awesomium.net/1_7_0/html/E_Awesomium_Core_WebView_PrintRequest.htm
【问题讨论】：
Awesomium 不支持打印到打印机设备。相反，Awesomium 支持打印到 PDF 文件。
我对在 Windows 中打印的有限理解是，您通常需要使用 GDI+ 绘图表面传递到您的打印事件的自定义事件处理程序中。 The MSDN documentation for the System.Drawing.Printing.PrintDocument class 很好地提供了示例实现。
我想人们可以使用 Awesomium .Net SDK 实现这种较低级别的打印，但是，这可能是一场没有支持的艰苦战斗 来自 Awesomium 的开发人员。
一个不错的“hack”可能是将 Awesomium 的打印到 PDF 功能与打印 PDF 文件粘合在一起。我能想到至少 3 种从 C# 打印 PDF 文件的方法：
在最终用户的计算机上使用 Acrobat Reader 来处理打印，其中包含 Acrobat 的 COM 自动化对象周围的 .Net 运行时可调用包装 (RCW)。见an example of using an Acrobat RCW in VB.NET。
使用用户机器上的任何 PDF 阅读器来处理打印。见an example of using the .Net ProcessStartInfo with the print verb to use the default PDF application on the user's machine。
使用 Windows 常用对话框选择打印机，然后将 PDF 发送到打印机进行原始（直接）打印。 （这类似于将 PostScript [.ps] 文件直接发送到打印机）。这仅适用于直接接受 PDF 文件的打印机。
下面是解决方法选项 #3 的示例，使用将 Awesomium PDF 文件直接发送到最终用户选择的打印机。
此答案结合了两个现有示例：Microsoft KB on raw printing with .Net 和 Awesomium answer for printing。
运行演示会加载 Microsoft KB 的 URL，其中包括调用 window.print() 的“打印”UI 按钮。
using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Printing;
using System.IO;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using Awesomium.Core;
namespace Demo
{
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new PrinterDemo());
}
}
public class PrinterDemo : Form
{
private Awesomium.Windows.Forms.WebControl webControl;
private PrinterSettings printerSettings;
private string printerName;
public PrinterDemo()
{
InitializeComponent();
WindowState = FormWindowState.Maximized;
}
private void InitializeComponent()
{
this.webControl = new Awesomium.Windows.Forms.WebControl();
this.SuspendLayout();
//
// webControl1
//
this.webControl.Dock = System.Windows.Forms.DockStyle.Fill;
this.webControl.Location = new System.Drawing.Point(0, 0);
this.webControl.Size = new System.Drawing.Size(784, 562);
this.webControl.Source = new System.Uri("http://support.microsoft.com/kb/322091", System.UriKind.Absolute);
this.webControl.TabIndex = 0;
this.webControl.PrintRequest += WebControl_PrintRequest;
this.webControl.PrintComplete += WebControl_PrintComplete;
this.webControl.PrintFailed += WebControl_PrintFailed;
//
// PrinterDemo
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(784, 562);
this.Controls.Add(this.webControl);
this.Name = "PrinterDemo";
this.Text = "PrinterDemo";
this.ResumeLayout(false);
}
/// <summary>Handle `window.print()` events</summary>
private void WebControl_PrintRequest(object sender, PrintRequestEventArgs e)
{
this.Print();
e.Handled = true;
}
/// <summary>Event handler for successful printing</summary>
private void WebControl_PrintComplete(object sender, PrintCompleteEventArgs e)
{
// Print the file to the printer.
if (String.IsNullOrWhiteSpace(printerName))
{
return;
}
foreach (string file in e.Files)
{
System.Diagnostics.Debug.Print("Printing file {0}", file);
RawPrinterHelper.SendFileToPrinter(printerName, file);
}
}
/// <summary>Event handler for unsuccessful printing</summary>
private void WebControl_PrintFailed(object sender, PrintOperationEventArgs e)
{
MessageBox.Show("MyApp", "Printing failed", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
/// <summary>Sends a PDF file to the printer</summary>
private void Print()
{
PrintDialog printerDialog;
int requestId;
string path = System.IO.Path.GetTempPath();
if (!webControl.IsLive)
return;
printerDialog = new PrintDialog();
printerSettings = new PrinterSettings();
printerDialog.PrinterSettings = printerSettings;
if (DialogResult.OK == printerDialog.ShowDialog(this))
{
printerName = printerDialog.PrinterSettings.PrinterName;
requestId = webControl.PrintToFile(path, PrintConfig.Default);
}
}
}
public class RawPrinterHelper
{
// Structure and API declarions:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class DOCINFOA
{
[MarshalAs(UnmanagedType.LPStr)]
public string pDocName;
[MarshalAs(UnmanagedType.LPStr)]
public string pOutputFile;
[MarshalAs(UnmanagedType.LPStr)]
public string pDataType;
}
[DllImport("winspool.Drv", EntryPoint = "OpenPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);
[DllImport("winspool.Drv", EntryPoint = "ClosePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool ClosePrinter(IntPtr hPrinter);
[DllImport("winspool.Drv", EntryPoint = "StartDocPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool StartDocPrinter(IntPtr hPrinter, Int32 level, [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);
[DllImport("winspool.Drv", EntryPoint = "EndDocPrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool EndDocPrinter(IntPtr hPrinter);
[DllImport("winspool.Drv", EntryPoint = "StartPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool StartPagePrinter(IntPtr hPrinter);
[DllImport("winspool.Drv", EntryPoint = "EndPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool EndPagePrinter(IntPtr hPrinter);
[DllImport("winspool.Drv", EntryPoint = "WritePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, Int32 dwCount, out Int32 dwWritten);
// SendBytesToPrinter()
// When the function is given a printer name and an unmanaged array
// of bytes, the function sends those bytes to the print queue.
// Returns true on success, false on failure.
public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, Int32 dwCount)
{
Int32 dwError = 0, dwWritten = 0;
IntPtr hPrinter = new IntPtr(0);
DOCINFOA di = new DOCINFOA();
bool bSuccess = false; // Assume failure unless you specifically succeed.
di.pDocName = "My C#.NET RAW Document";
di.pDataType = "RAW";
// Open the printer.
if (OpenPrinter(szPrinterName.Normalize(), out hPrinter, IntPtr.Zero))
{
// Start a document.
if (StartDocPrinter(hPrinter, 1, di))
{
// Start a page.
if (StartPagePrinter(hPrinter))
{
// Write your bytes.
bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
EndPagePrinter(hPrinter);
}
EndDocPrinter(hPrinter);
}
ClosePrinter(hPrinter);
}
// If you did not succeed, GetLastError may give more information
// about why not.
if (bSuccess == false)
{
dwError = Marshal.GetLastWin32Error();
}
return bSuccess;
}
public static bool SendFileToPrinter(string szPrinterName, string szFileName)
{
// Open the file.
FileStream fs = new FileStream(szFileName, FileMode.Open);
// Create a BinaryReader on the file.
BinaryReader br = new BinaryReader(fs);
// Dim an array of bytes big enough to hold the file's contents.
Byte[] bytes = new Byte[fs.Length];
bool bSuccess = false;
// Your unmanaged pointer.
IntPtr pUnmanagedBytes = new IntPtr(0);
int nLength;
nLength = Convert.ToInt32(fs.Length);
// Read the contents of the file into the array.
bytes = br.ReadBytes(nLength);
// Allocate some unmanaged memory for those bytes.
pUnmanagedBytes = Marshal.AllocCoTaskMem(nLength);
// Copy the managed byte array into the unmanaged array.
Marshal.Copy(bytes, 0, pUnmanagedBytes, nLength);
// Send the unmanaged bytes to the printer.
bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, nLength);
// Free the unmanaged memory that you allocated earlier.
Marshal.FreeCoTaskMem(pUnmanagedBytes);
return bSuccess;
}
public static bool SendStringToPrinter(string szPrinterName, string szString)
{
IntPtr pBytes;
Int32 dwCount;
// How many characters are in the string?
dwCount = szString.Length;
// Assume that the printer is expecting ANSI text, and then convert
// the string to ANSI text.
pBytes = Marshal.StringToCoTaskMemAnsi(szString);
// Send the converted ANSI string to the printer.
SendBytesToPrinter(szPrinterName, pBytes, dwCount);
Marshal.FreeCoTaskMem(pBytes);
return true;
}
}
}
我能够使用以下命令行将该示例编译并运行为一个名为 demo.cs 的单个文件：
SETLOCAL
PATH C:\Windows\Microsoft.NET\Framework\v4.0.30319\;%PATH%
IF EXIST demo.exe DEL demo.exe
csc.exe /target:winexe /lib:"%ProgramFiles%\Awesomium Technologies LLC\Awesomium SDK\1.7.3.0\wrappers\Awesomium.NET\Assemblies" /reference:Awesomium.Core.dll,Awesomium.Windows.Forms.dll demo.cs
demo.exe
ENDLOCAL
【讨论】：