ios7 font size change when create nsattributedstring from html

15
votes

I have a UITextView where I'm managing an NSAttributedString, initially entered as normal via the keyboard. I save the attributed string as HTML, which looks fine. When I load it again, and convert it back to an attributed string from the HTML, the font size appears to change.

For example, the HTML on loading looks like this:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta http-equiv="Content-Style-Type" content="text/css">
<title></title>
<meta name="Generator" content="Cocoa HTML Writer">
<style type="text/css">
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 21.0px Helvetica; color: #000000; -webkit-text-        stroke: #000000}
span.s1 {font-family: 'Helvetica'; font-weight: normal; font-style: normal; font-size:     21.00pt;     font-kerning: none}
</style>
</head>
<body>
<p class="p1"><span class="s1">There is some text as usual lots of text</span></p>
</body>
</html>

I convert it and check the attributes with the following code:

    // convert to attributed string
    NSError *err;
    NSAttributedString *as = [[NSAttributedString alloc] initWithData:data3
                            options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
                                      NSCharacterEncodingDocumentAttribute: @(NSUTF8StringEncoding)}
                            documentAttributes:nil
                            error:&err] ;

    NSMutableAttributedString *res = [as mutableCopy];
    [res enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, res.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
        if (value) {
            UIFont *oldFont = (UIFont *)value;
            NSLog(@"On Loading: Font size %f, in range from %d length %d", oldFont.pointSize, range.location, range.length);
        }
    }];

The output shows that the font size has increased from 21 to 28:

On Loading: Font size 28.000000, in range from 0 length 40
On Loading: Font size 21.000000, in range from 40 length 1

Basically, each time I load the string, the font size increases. I need to store it as HTML rather than as NSData because it will also be used by other platforms.

Does anyone have any ideas why this is happening?

5
htmlfontsios7nsattributedstring

5 Answers

16
votes

I also faced this issue, I fixed it by iterating to the attributes and reseting the old font size as follows

NSMutableAttributedString *res = [attributedText mutableCopy];
[res beginEditing];
[res enumerateAttribute:NSFontAttributeName
                inRange:NSMakeRange(0, res.length)
                options:0
             usingBlock:^(id value, NSRange range, BOOL *stop) {
                 if (value) {
                     UIFont *oldFont = (UIFont *)value;
                     UIFont *newFont = [oldFont fontWithSize:15];
                     [res addAttribute:NSFontAttributeName value:newFont range:range];
                 }
             }];
[res endEditing];
[self.textFileInputView setAttributedText:res];
6
votes

Using <span> and css works for me, following Parsing HTML into NSAttributedText - how to set font?:

// HTML -> NSAttributedString
+ (NSAttributedString *)attributedStringFromHTML:(NSString *)html {
    NSError *error;
    NSDictionary *options = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithData:[html dataUsingEncoding:NSUTF8StringEncoding] options:options documentAttributes:nil error:&error];
    if(!attrString) {
        NSLog(@"creating attributed string from HTML failed: %@", error.debugDescription);
    }
    return attrString;
}

// force font thrugh <span> & css
+ (NSAttributedString *)attributedStringFromHTML:(NSString *)html withFont:(UIFont *)font    {
    return [Util attributedStringFromHTML:[NSString stringWithFormat:@"<span style=\"font-family: %@; font-size: %f\";>%@</span>", font.fontName, font.pointSize, html]];
}

This sets the font name and size but doesn't impact the styles.

4
votes

Fixed this magic Apple behaviour with following code:

static CGFloat const kListsLeading = 10.0;
static CGFloat const kListsAdditionalShift = 4.0;

//
// Fix Apple magic 4/3 koefficient
// http://stackoverflow.com/questions/20992950/ios7-font-size-change-when-create-nsattributedstring-from-html
//
static NSAttributedString *DecreaseFontSizeBecauseOfAppleMagic(NSAttributedString *astr) {
    NSMutableAttributedString *mastr = [astr mutableCopy];

    [mastr enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, astr.length) options:0 usingBlock:^(UIFont *_Nullable value, NSRange range, BOOL *_Nonnull stop) {
        if (value) {
            UIFont *font = [value fontWithSize:value.pointSize * 0.75];
            [mastr addAttribute:NSFontAttributeName value:font range:range];
        }
    }];

    [mastr enumerateAttribute:NSParagraphStyleAttributeName inRange:NSMakeRange(0, astr.length) options:0 usingBlock:^(NSParagraphStyle *_Nullable value, NSRange range, BOOL *_Nonnull stop) {
        if (value) {
            NSMutableParagraphStyle *style = [value mutableCopy];
            style.minimumLineHeight *= 0.75;
            if (style.firstLineHeadIndent == style.headIndent) {
                style.firstLineHeadIndent *= 0.75;
                style.headIndent *= 0.75;
            }
            else if (style.firstLineHeadIndent < kListsLeading) {
                CGFloat shift = (kListsLeading - style.firstLineHeadIndent);
                style.headIndent += shift + kListsAdditionalShift;
                style.firstLineHeadIndent = kListsLeading;
                NSMutableArray *tabs = [NSMutableArray array];
                NSInteger index = 0;
                for (NSTextTab *tab in style.tabStops) {
                    [tabs addObject:[[NSTextTab alloc] initWithTextAlignment:tab.alignment location:tab.location + shift + kListsAdditionalShift * (index ? 1 : 0) options:tab.options]];
                    index++;
                }
                style.tabStops = tabs;
            }
            style.tailIndent *= 0.75;
            [mastr addAttribute:NSParagraphStyleAttributeName value:style range:range];
        }
    }];

    return [mastr copy];
}
2
votes

Swift 3.0 Version

With 0.75 ratio

yourAttrStr.beginEditing()
yourAttrStr.enumerateAttribute(NSFontAttributeName, in: NSMakeRange(0, yourAttrStr.length), options: .init(rawValue: 0)) { 
        (value, range, stop) in
        if let font = value as? UIFont {
            let resizedFont = font.withSize(font.pointSize * 0.75)
            yourAttrStr.addAttribute(NSFontAttributeName, value: resizedFont, range: range)
        }
}
yourAttrStr.endEditing()//yourAttrStrwill be the same size as html string
1
votes

This is not entirely an answer, more an alternative and a comment on the various other answers given, so apologies.

The answers given @KishoreThindaak and @Danomatika are fine if you know what the font sizes should be - but my application has a Mac OS twin which can generate any size text, and therefore had to be general.

The answer given by @k06a works for simple text, but I found that it failed with embedded styles - particularly with multiple styles on a line which itself was embedded in an <li> tag.

After many hours of trying to fix this, I'm afraid I abandoned HTML altogether as the disk format and adopted RTF instead, which works fine, and provides an RTF file that is readable on all platforms. Simple code for getting RTF below...

extension NSAttributedString {
    func rtf(encoding: String.Encoding) -> Data? {
        let options: [NSAttributedString.DocumentAttributeKey : Any] = [
            NSAttributedString.DocumentAttributeKey.documentType: NSAttributedString.DocumentType.rtf,
            NSAttributedString.DocumentAttributeKey.characterEncoding: encoding.rawValue
        ]
        return try? self.data(from: NSMakeRange(0, self.length), documentAttributes: options)
    }
    class func from(rtfData data: Data, encoding: String.Encoding) -> NSAttributedString? {
        let options: [NSAttributedString.DocumentReadingOptionKey : Any] = [
            NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.rtf,
            NSAttributedString.DocumentReadingOptionKey.characterEncoding: encoding.rawValue
        ]
        return try? NSMutableAttributedString(data: data, options: options, documentAttributes: nil)
    }
}