broguyman broguyman - 1 year ago 291
C# Question

Letting the Javascript finish before rendering pdf in ABC pdf

I'm trying to make a pdf of a web page that is displaying locations on Google Maps. The only problem is that the Javascript isn't quite completing by the time that ABCpdf renders the pdf. It's incomplete. How can I make ABDpdf wait until the javascript is 100% complete before the pdf is rendered. Here is what I've tried so far.

Doc theDoc = new Doc();
string theURL = url;
// Set HTML options
theDoc.HtmlOptions.AddLinks = true;
theDoc.HtmlOptions.UseScript = true;
theDoc.HtmlOptions.PageCacheEnabled = false;
//theDoc.HtmlOptions.Engine = EngineType.Gecko;
// JavaScript is used to extract all links from the page

theDoc.HtmlOptions.OnLoadScript = "var hrefCollection = document.all.tags(\"a\");" +
"var allLinks = \"\";" +
"for(i = 0; i < hrefCollection.length; ++i) {" +
"if (i > 0)" +
" allLinks += \",\";" +
"allLinks += hrefCollection.item(i).href;" +
"};" +
"document.documentElement.abcpdf = allLinks;";
// Array of links - start with base URL
theDoc.HtmlOptions.OnLoadScript = "(function(){window.ABCpdf_go = false; setTimeout(function(){window.ABCpdf_go = true;}, 1000);})();";
ArrayList links = new ArrayList();
for (int i = 0; i < links.Count; i++)
// Stop if we render more than 20 pages
if (theDoc.PageCount > 20)
// Add page
theDoc.Page = theDoc.AddPage();
int theID = theDoc.AddImageUrl(links[i] as string);
// Links from the rendered page
string allLinks = theDoc.HtmlOptions.GetScriptReturn(theID);
string[] newLinks = allLinks.Split(new char[] { ',' });
foreach (string link in newLinks)
// Check to see if we allready rendered this page
if (links.BinarySearch(link) < 0)
// Skip links inside the page
int pos = link.IndexOf("#");
if (!(pos > 0 && links.BinarySearch(link.Substring(0, pos)) >= 0))
if (link.StartsWith(theURL))
// Add other pages
while (true)
if (!theDoc.Chainable(theID))
theDoc.Page = theDoc.AddPage();
theID = theDoc.AddImageToChain(theID);
// Link pages together
// Flatten all pages
for (int i = 1; i <= theDoc.PageCount; i++)
theDoc.PageNumber = i;

byte[] theData = theDoc.GetData();

Response.Buffer = false; //new
//Response.ContentEncoding = Encoding.Default;
Response.ClearContent(); //new
Response.ClearHeaders(); //new
Response.ContentType = "application/pdf"; //new
Response.AddHeader("Content-Disposition", "attachment; filename=farts");

Response.AddHeader("content-length", theData.Length.ToString());
//Response.ContentType = "application/pdf";


Answer Source

I had a very similar problem (rendering Google Visualization as PDF) and here's the trick that I used to partially solve it:

First of all, your JavaScript needs to be executed on DOMContentLoaded rather than on load (you will understand why just in a moment). Next create an empty page that will serve content by a timer (you can just use System.Threading.Thread.Sleep to make the page "wait" for a certain amount of time).

Then place a hidden image on the page that you want to render as PDF and that contains JavaScript that needs to be executed before the PDF can be produced. The "src" attribute of an image must have a URL pointing to your timer page (in the following example I specify the delay in milliseconds via query-string):

<img src="Timer.aspx?Delay=1000" style="width: 1px; height: 1px; visibility: hidden" />

Notice that I use visibility: hidden instead of display: none to hide the image. The reason is that some browsers might not start loading the image until it's visible.

Now what will happen is that ABCpdf will wait until the image is loaded while your JavaScript will be executing already (because the DOMContentLoaded is fired before load which waits until all images are loaded).

Of course you cannot predict how much time exactly do you need to execute your JavaScript. Another thing is that if ABCpdf is unable to load page within 15 seconds (default value but I think you can change it) it will throw an exception so be careful when choosing the delay.

Hope this helps.

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