Why does NSPrintOperation create an empty PDF when I try to save a WebView to a PDF?

Question

I'm trying to convert HTML to a PDF file on OS X. After lots of digging, I found that the best way to do it is by using an NSPrintOperation. This is the code I'm using to convert an HTML string to a PDF:

WebView *webview = [[WebView alloc] init];
[webview.mainFrame loadHTMLString:htmlString baseURL:nil];

NSDictionary *printOpts = @{
                            NSPrintJobDisposition: NSPrintSaveJob,
                            NSPrintSavePath: outputFilePath
                            };
NSPrintInfo *printInfo = [[NSPrintInfo alloc] initWithDictionary:printOpts];
printInfo.horizontalPagination = NSAutoPagination;
printInfo.verticalPagination = NSAutoPagination;
NSPrintOperation *printOp = [NSPrintOperation 
                             printOperationWithView:webview.mainFrame.frameView.documentView
                                          printInfo:printInfo];
printOp.showsPrintPanel = NO;
printOp.showsProgressPanel = NO;

[printOp runOperation];

This code does produce a PDF file, but the PDF file is empty. Is it because the WebView doesn't have a frame? I've tried using dataWithPDFInsideRect:, but that doesn't work either.

Should I initialise the webview with a frame the size of an A4 sheet? Or is the problem somewhere else?

Answer 1

I know this is an old thread but I wanted to post the solution I came up with today. Since WebViews load asynchronously, the key is to set a frame load delegate callback then run through the run loop until the frame is finished loading.

My code below creates a fresh WebView then loads an HTML file into it:

// Clear the loaded flag
_webViewIsLoaded = NO;

// Fetch the default paper size and init print settings
NSPrintInfo * sharedInfo = [NSPrintInfo sharedPrintInfo];
NSMutableDictionary * sharedDict = [sharedInfo dictionary];
NSMutableDictionary * printInfoDict = [NSMutableDictionary dictionaryWithDictionary:sharedDict];
NSRect printRect = NSZeroRect;
printRect.size = [sharedInfo paperSize];

// Create a new web view
WebView * printView = [[WebView alloc] initWithFrame:printRect];
[printView setFrameLoadDelegate:self];

// Configure the WebView
WebPreferences * preferences = [[WebPreferences alloc] initWithIdentifier:@"com.id.here"];
[preferences setShouldPrintBackgrounds:YES];
[preferences setAllowsAnimatedImageLooping:NO];
[preferences setJavaScriptCanOpenWindowsAutomatically:NO];
[preferences setAutosaves:NO];
[preferences setJavaEnabled:NO];
[preferences setJavaScriptEnabled:NO];
[preferences setCacheModel:WebCacheModelDocumentViewer];        // most memory-efficient setting
[preferences setPlugInsEnabled:NO];                             // disable plugins
[printView setPreferences:preferences];

// Load the HTML file
NSURL * url = [NSURL fileURLWithPath:htmlPath];
NSURLRequest * request = [NSURLRequest requestWithURL:url];
[[printView mainFrame] loadRequest:request];

[printInfoDict setObject:NSPrintSaveJob
                  forKey:NSPrintJobDisposition];
[printInfoDict setObject:saveUrl forKey:NSPrintJobSavingURL];

NSPrintInfo * printInfo = [[NSPrintInfo alloc] initWithDictionary:printInfoDict];
[printInfo setHorizontalPagination:NSFitPagination];
[printInfo setVerticalPagination:NSAutoPagination];
[printInfo setVerticallyCentered:NO];
[printInfo setHorizontallyCentered:YES];

// Wait for the frame to finish loading
while(!_webViewIsLoaded)
{
    @autoreleasepool
    {
        [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.005]];
    }
}

NSPrintOperation * printOp = [NSPrintOperation printOperationWithView:[[[printView mainFrame] frameView] documentView]
                                                            printInfo:printInfo];
[printOp setShowsProgressPanel:YES];
[printOp setShowsPrintPanel:NO];
[printOp runOperation];

Next, my frame load delegate method sets a flag once the frame is fully loaded and also resizes the height of the frame to match that of the contents:

-(void)webView:(WebView *)sender didFinishLoadForFrame:(WebFrame *)webFrame
{
    _webViewIsLoaded = YES;

    NSRect webFrameRect = [[[webFrame frameView] documentView] frame];
    NSRect webViewRect = [webView frame];

    // Resize the webview so it fits all of its contents
    NSRect newWebViewRect = NSMakeRect(webViewRect.origin.x,
                                   webViewRect.origin.y - (NSHeight(webFrameRect) - NSHeight(webViewRect)),
                                   NSWidth(webViewRect),
                                   NSHeight(webFrameRect));
    [webView setFrame:newWebViewRect];
}

This should work well for saving HTML documents to PDF.

Answer 2

Try this:

 NSPrintOperation *printOp = [NSPrintOperation
                             printOperationWithView:[[[webview mainFrame] frameView] documentView] printInfo:printInfo];

Instead of:

NSPrintOperation *printOp = [NSPrintOperation printOperationWithView:webview.mainFrame.frameView.documentView
                             printInfo:printInfo];

This should work :)

EDIT: This is the full code that I used

NSString *htmlString = @"<html><head></head><body><h1>Hello, World</h1></body></html>";

WebView *webview = [[WebView alloc] init];
[webview.mainFrame loadHTMLString:htmlString baseURL:nil];

NSString* outputFilePath = @"/Users/YOUR-USERNAME/Documents/MyAwesomePDF.pdf";
NSURL *url = [[NSURL alloc] initWithString:outputFilePath];

NSDictionary *printOpts = @{
                            NSPrintJobDisposition: NSPrintSaveJob,
                            NSPrintSaveJob: url
                            };
NSPrintInfo *printInfo = [[NSPrintInfo alloc] initWithDictionary:printOpts];
printInfo.horizontalPagination = NSAutoPagination;
printInfo.verticalPagination = NSAutoPagination;



NSPrintOperation *printOp = [NSPrintOperation
                             printOperationWithView:[[[webview mainFrame] frameView] documentView] printInfo:printInfo];
printOp.showsPrintPanel = NO;
printOp.showsProgressPanel = NO;

[printOp runOperation];