Issues converting NSAttributedString to HTML and back again - html

Question

I know that this issue is pretty much the same issue as the one reported by Konstantin Heinrich here but since there was no satisfactory solution given, I thought I'd bring this up again.
I'm basically trying to apply some rich formatting to text in a standard UITextView, convert it to HTML, convert it back to an NSAttributedString and display it in a UITextView again. Below you can find the methods I'm using to convert to and from NSAttributedString.
- (NSString *)htmlStringFromAttributedString:(NSAttributedString *)attributedString {
NSError *error;
NSData *htmlData = [attributedString dataFromRange:NSMakeRange(0, attributedString.length)
documentAttributes:#{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType}
error:&error];
if (error) {
NSLog(#"%#", error);
return nil;
}
NSString *htmlString = [[NSString alloc] initWithData:htmlData encoding:NSUTF8StringEncoding];
return htmlString;
}
- (NSAttributedString *)attributedStringFromHTMLString:(NSString *)htmlString {
NSError *error;
NSAttributedString *attributedString = [[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUTF8StringEncoding]
options:#{NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType}
documentAttributes:nil
error:&error];
if (error) {
NSLog(#"%#", error);
return nil;
}
return attributedString;
}
Now everything works smoothly with the exception that the font size for the NSAttributedString which has been generated from the HTML string is bigger than the original one. If I use RTF instead of HTML (i.e. simply replacing NSHTMLTextDocumentType with NSRTFTextDocumentType) everything works as expected as you can see in the screenshot.
To be perfectly honest, I'm tempted to believe that we're looking at a bug in the Foundation framework here. Especially given the console output of the NSAttributedString generated from HTML. See how only the last chunk of attributes (the one that does not even affect any text anymore) contains the correct font size?
Some {
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde3919b70> font-family: \"Avenir-Light\"; font-weight: normal; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}simple{
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde39172f0> font-family: \"Avenir-Heavy\"; font-weight: bold; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
} text {
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde3919b70> font-family: \"Avenir-Light\"; font-weight: normal; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}with{
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde3919b70> font-family: \"Avenir-Light\"; font-weight: normal; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
NSUnderline = 1;
} {
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde3919b70> font-family: \"Avenir-Light\"; font-weight: normal; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}formatting{
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde1f43a20> font-family: \"Avenir-HeavyOblique\"; font-weight: bold; font-style: italic; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}.{
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde3919b70> font-family: \"Avenir-Light\"; font-weight: normal; font-style: normal; font-size: 20.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 28/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}
{
NSColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSFont = "<UICTFont: 0x7fdde1f75740> font-family: \"Avenir-Book\"; font-weight: normal; font-style: normal; font-size: 15.00pt";
NSKern = 0;
NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 21/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n), DefaultTabInterval 36, Blocks (\n), Lists (\n), BaseWritingDirection 0, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0";
NSStrokeColor = "UIDeviceRGBColorSpace 0 0 0 1";
NSStrokeWidth = 0;
}
Bug or not, does anybody have any idea how to overcome this issue? Preferably without having to manually reset font sizes in the resulting string as suggested for the question referenced at the top? Any help would be appreciated.