When I try to get offsetHeight or of any DOM element with Javascript when printing with wkhtmltopdf library, the height is never determined and is always equal to 0. When I execute the same JS code in any browser it works correctly and results in a specific height of element.
I googled for a long time and I found out that it might be related with wkhtmltopdf in which the width and height of document and window are equal to 0. I tried to override the size of the body tag with CSS and override the viewport size with wkhtmltopdf configuration parameters, but the offsetHeight still results in 0.
Is there any known walkaround to receive height of DOM element when printing with wkhtmltopdf?
I use the latest stable version of the printing library (0.12.6)
I have used wkHtml2Pdf in the past.
My advice is to stop right now, because wkhtmltopdf uses a very old browser version, and you're likely to run into problems anyway. Also, wkHtmlToPdf doesn't work properly (and performance is crap).
Instead, you can use a much better option.
That option is to use the Chrome DevTools with the remote-debugging-protocol:
https://chromedevtools.github.io/devtools-protocol/
Which basically runs Chrome like this
chrome.exe --remote-debugging-port=9222
With optional
$"--user-data-dir=\"{directoryInfo.FullName}\"";
and
"--headless --disable-gpu";
Here's how I start the Chrome process on the server (C# Code)
public IChromeProcess Create(int port, bool headless)
{
string path = System.IO.Path.GetRandomFileName();
System.IO.DirectoryInfo directoryInfo = System.IO.Directory.CreateDirectory(
System.IO.Path.Combine(
System.IO.Path.GetTempPath(), path)
);
string remoteDebuggingArg = $"--remote-debugging-port={port}";
string userDirectoryArg = $"--user-data-dir=\"{directoryInfo.FullName}\"";
const string headlessArg = "--headless --disable-gpu";
// https://peter.sh/experiments/chromium-command-line-switches/
System.Collections.Generic.List<string> chromeProcessArgs =
new System.Collections.Generic.List<string>
{
remoteDebuggingArg,
userDirectoryArg,
// Indicates that the browser is in "browse without sign-in" (Guest session) mode.
// Should completely disable extensions, sync and bookmarks.
"--bwsi",
"--no-first-run"
};
if (false)
{
string proxyProtocol = "socks5";
proxyProtocol = "http";
proxyProtocol = "https";
string proxyIP = "68.183.233.181";
string proxyPort = "3128";
string proxyArg = "--proxy-server=\"" + proxyProtocol + "://" + proxyIP + ":" + proxyPort + "\"";
chromeProcessArgs.Add(proxyArg);
}
if (headless)
chromeProcessArgs.Add(headlessArg);
if(IsRoot)
chromeProcessArgs.Add("--no-sandbox");
string args = string.Join(" ", chromeProcessArgs);
System.Diagnostics.ProcessStartInfo processStartInfo = new System.Diagnostics.ProcessStartInfo(ChromePath, args);
System.Diagnostics.Process chromeProcess = System.Diagnostics.Process.Start(processStartInfo);
string remoteDebuggingUrl = "http://localhost:" + port;
return new LocalChromeProcess(new System.Uri(remoteDebuggingUrl), () => DirectoryCleaner.Delete(directoryInfo), chromeProcess);
}
I used this C# library here to interface with the DevTools (via WebSockets):
https://github.com/MasterDevs/ChromeDevTools
If you use NodeJS on the server, you could use this:
https://github.com/cyrus-and/chrome-remote-interface
or for TypeScript:
https://github.com/TracerBench/chrome-debugging-client
In order to generate a PDF, you need to issue the PrintToPDF-Command:
Dim cm2inch As UnitConversion_t = Function(ByVal centimeters As Double) centimeters * 0.393701
Dim mm2inch As UnitConversion_t = Function(ByVal milimeters As Double) milimeters * 0.0393701
Dim printCommand2 As PrintToPDFCommand = New PrintToPDFCommand() With {
.Scale = 1,
.MarginTop = 0,
.MarginLeft = 0,
.MarginRight = 0,
.MarginBottom = 0,
.PrintBackground = True,
.Landscape = False,
.PaperWidth = mm2inch(conversionData.PageWidth),
.PaperHeight = mm2inch(conversionData.PageHeight) '
}
And to create a raster graphic, you need to issue the CaptureScreenshot-Command :
Dim screenshot As MasterDevs.ChromeDevTools.CommandResponse(Of CaptureScreenshotCommandResponse) = Await chromeSession.SendAsync(New CaptureScreenshotCommand With {
.Format = "png"
})
System.Diagnostics.Debug.WriteLine("Screenshot taken.")
conversionData.PngData = System.Convert.FromBase64String(screenshot.Result.Data)
Note that for the screenshot to work properly, you need to set the width and the height via the SetDeviceMetricsOverride-Command:
Await chromeSession.SendAsync(New SetDeviceMetricsOverrideCommand With {
.Width = conversionData.ViewPortWidth,
.Height = conversionData.ViewPortHeight,
.Scale = 1
})
You might have to put overflow:hidden on the HTML, or some sub-elements just so you don't screenshot the scrollbars ;)
By the way, if you need a specific version of Chrome for Windows (Chromium, because old Chrome versions are not available for security reasons), you can get them from the Chocolatey-Repository: https://chocolatey.org/packages/chromium/#versionhistory
Here's my full test-code for reference (minus some classes)
Imports MasterDevs.ChromeDevTools
Imports MasterDevs.ChromeDevTools.Protocol.Chrome.Browser
Imports MasterDevs.ChromeDevTools.Protocol.Chrome.Page
Imports MasterDevs.ChromeDevTools.Protocol.Chrome.Target
Namespace Portal_Convert.CdpConverter
Public Class ChromiumBasedConverter
Private Delegate Function UnitConversion_t(ByVal value As Double) As Double
Public Shared Sub KillHeadlessChromes(ByVal writer As System.IO.TextWriter)
Dim allProcesses As System.Diagnostics.Process() = System.Diagnostics.Process.GetProcesses()
Dim exeName As String = "\chrome.exe"
If System.Environment.OSVersion.Platform = System.PlatformID.Unix Then
exeName = "/chrome"
End If
For i As Integer = 0 To allProcesses.Length - 1
Dim proc As System.Diagnostics.Process = allProcesses(i)
Dim commandLine As String = ProcessUtils.GetCommandLine(proc)
If String.IsNullOrEmpty(commandLine) Then Continue For
commandLine = commandLine.ToLowerInvariant()
If commandLine.IndexOf(exeName, System.StringComparison.InvariantCultureIgnoreCase) = -1 Then Continue For
If commandLine.IndexOf("--headless", System.StringComparison.InvariantCultureIgnoreCase) <> -1 Then
writer.WriteLine($"Killing process {proc.Id} with command line ""{commandLine}""")
ProcessUtils.KillProcessAndChildren(proc.Id)
End If
Next
writer.WriteLine($"Finished killing headless chromes")
End Sub
Public Shared Sub KillHeadlessChromes()
KillHeadlessChromes(System.Console.Out)
End Sub
Private Shared Function __Assign(Of T)(ByRef target As T, value As T) As T
target = value
Return value
End Function
Public Shared Function KillHeadlessChromesWeb() As System.Collections.Generic.List(Of String)
Dim ls As System.Collections.Generic.List(Of String) = New System.Collections.Generic.List(Of String)()
Dim sb As System.Text.StringBuilder = New System.Text.StringBuilder()
Using sw As System.IO.StringWriter = New System.IO.StringWriter(sb)
KillHeadlessChromes(sw)
End Using
Using tr As System.IO.TextReader = New System.IO.StringReader(sb.ToString())
Dim thisLine As String = Nothing
While (__Assign(thisLine, tr.ReadLine())) IsNot Nothing
ls.Add(thisLine)
End While
End Using
sb.Length = 0
sb = Nothing
Return ls
End Function
Private Shared Async Function InternalConnect(ByVal ci As ConnectionInfo, ByVal remoteDebuggingUri As String) As System.Threading.Tasks.Task
ci.ChromeProcess = New RemoteChromeProcess(remoteDebuggingUri)
ci.SessionInfo = Await ci.ChromeProcess.StartNewSession()
End Function
Private Shared Async Function ConnectToChrome(ByVal chromePath As String, ByVal remoteDebuggingUri As String) As System.Threading.Tasks.Task(Of ConnectionInfo)
Dim ci As ConnectionInfo = New ConnectionInfo()
Try
Await InternalConnect(ci, remoteDebuggingUri)
Catch ex As System.Exception
If ex.InnerException IsNot Nothing AndAlso Object.ReferenceEquals(ex.InnerException.[GetType](), GetType(System.Net.WebException)) Then
If (CType(ex.InnerException, System.Net.WebException)).Status = System.Net.WebExceptionStatus.ConnectFailure Then
Dim chromeProcessFactory As MasterDevs.ChromeDevTools.IChromeProcessFactory = New MasterDevs.ChromeDevTools.ChromeProcessFactory(New FastStubbornDirectoryCleaner(), chromePath)
Dim persistentChromeProcess As MasterDevs.ChromeDevTools.IChromeProcess = chromeProcessFactory.Create(9222, True)
' await cannot be used inside catch ...
' Await InternalConnect(ci, remoteDebuggingUri)
InternalConnect(ci, remoteDebuggingUri).Wait()
Return ci
End If
End If
System.Console.WriteLine(chromePath)
System.Console.WriteLine(ex.Message)
System.Console.WriteLine(ex.StackTrace)
If ex.InnerException IsNot Nothing Then
System.Console.WriteLine(ex.InnerException.Message)
System.Console.WriteLine(ex.InnerException.StackTrace)
End If
System.Console.WriteLine(ex.[GetType]().FullName)
Throw
End Try
Return ci
End Function
Private Shared Async Function ClosePage(ByVal chromeSession As MasterDevs.ChromeDevTools.IChromeSession, ByVal frameId As String, ByVal headLess As Boolean) As System.Threading.Tasks.Task
Dim closeTargetTask As System.Threading.Tasks.Task(Of MasterDevs.ChromeDevTools.CommandResponse(Of CloseTargetCommandResponse)) = chromeSession.SendAsync(New CloseTargetCommand() With {
.TargetId = frameId
})
' await will block forever if headless
If Not headLess Then
Dim closeTargetResponse As MasterDevs.ChromeDevTools.CommandResponse(Of CloseTargetCommandResponse) = Await closeTargetTask
System.Console.WriteLine(closeTargetResponse)
Else
System.Console.WriteLine(closeTargetTask)
End If
End Function
Public Shared Async Function ConvertDataAsync(ByVal conversionData As ConversionData) As System.Threading.Tasks.Task
Dim chromeSessionFactory As MasterDevs.ChromeDevTools.IChromeSessionFactory = New MasterDevs.ChromeDevTools.ChromeSessionFactory()
Using connectionInfo As ConnectionInfo = Await ConnectToChrome(conversionData.ChromePath, conversionData.RemoteDebuggingUri)
Dim chromeSession As MasterDevs.ChromeDevTools.IChromeSession = chromeSessionFactory.Create(connectionInfo.SessionInfo.WebSocketDebuggerUrl)
Await chromeSession.SendAsync(New SetDeviceMetricsOverrideCommand With {
.Width = conversionData.ViewPortWidth,
.Height = conversionData.ViewPortHeight,
.Scale = 1
})
Dim navigateResponse As MasterDevs.ChromeDevTools.CommandResponse(Of NavigateCommandResponse) = Await chromeSession.SendAsync(New NavigateCommand With {
.Url = "about:blank"
})
System.Console.WriteLine("NavigateResponse: " & navigateResponse.Id)
Dim setContentResponse As MasterDevs.ChromeDevTools.CommandResponse(Of SetDocumentContentCommandResponse) = Await chromeSession.SendAsync(New SetDocumentContentCommand() With {
.FrameId = navigateResponse.Result.FrameId,
.Html = conversionData.Html
})
Dim cm2inch As UnitConversion_t = Function(ByVal centimeters As Double) centimeters * 0.393701
Dim mm2inch As UnitConversion_t = Function(ByVal milimeters As Double) milimeters * 0.0393701
Dim printCommand2 As PrintToPDFCommand = New PrintToPDFCommand() With {
.Scale = 1,
.MarginTop = 0,
.MarginLeft = 0,
.MarginRight = 0,
.MarginBottom = 0,
.PrintBackground = True,
.Landscape = False,
.PaperWidth = mm2inch(conversionData.PageWidth),
.PaperHeight = mm2inch(conversionData.PageHeight) '
}
'.PaperWidth = cm2inch(conversionData.PageWidth),
'.PaperHeight = cm2inch(conversionData.PageHeight)
If conversionData.ChromiumActions.HasFlag(ChromiumActions_t.GetVersion) Then
Try
System.Diagnostics.Debug.WriteLine("Getting browser-version")
Dim version As MasterDevs.ChromeDevTools.CommandResponse(Of GetVersionCommandResponse) = Await chromeSession.SendAsync(New GetVersionCommand())
System.Diagnostics.Debug.WriteLine("Got browser-version")
conversionData.Version = version.Result
Catch ex As System.Exception
conversionData.Exception = ex
System.Diagnostics.Debug.WriteLine(ex.Message)
End Try
End If
If conversionData.ChromiumActions.HasFlag(ChromiumActions_t.ConvertToImage) Then
Try
System.Diagnostics.Debug.WriteLine("Taking screenshot")
Dim screenshot As MasterDevs.ChromeDevTools.CommandResponse(Of CaptureScreenshotCommandResponse) = Await chromeSession.SendAsync(New CaptureScreenshotCommand With {
.Format = "png"
})
System.Diagnostics.Debug.WriteLine("Screenshot taken.")
conversionData.PngData = System.Convert.FromBase64String(screenshot.Result.Data)
Catch ex As System.Exception
conversionData.Exception = ex
System.Diagnostics.Debug.WriteLine(ex.Message)
End Try
End If
If conversionData.ChromiumActions.HasFlag(ChromiumActions_t.ConvertToPdf) Then
Try
System.Diagnostics.Debug.WriteLine("Printing PDF")
Dim pdf As MasterDevs.ChromeDevTools.CommandResponse(Of PrintToPDFCommandResponse) = Await chromeSession.SendAsync(printCommand2)
System.Diagnostics.Debug.WriteLine("PDF printed.")
conversionData.PdfData = System.Convert.FromBase64String(pdf.Result.Data)
Catch ex As System.Exception
conversionData.Exception = ex
System.Diagnostics.Debug.WriteLine(ex.Message)
End Try
End If
System.Console.WriteLine("Closing page")
Await ClosePage(chromeSession, navigateResponse.Result.FrameId, True)
System.Console.WriteLine("Page closed")
End Using ' connectionInfo
End Function ' ConvertDataAsync
Public Shared Sub ConvertData(ByVal conversionData As ConversionData)
ConvertDataAsync(conversionData).Wait()
End Sub
End Class
End Namespace
Note that if anyone is using C#, it's better to use this library:
https://github.com/BaristaLabs/chrome-dev-tools-runtime
which uses less external depencencies, and is NetCore. I used the other only because I had to backport it to an old framework version...