swift - usedRectForTextContainer size bug with NSAttributedString? -

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i attempting calculate minimum height needed nstextview's content @ set width through following process (where self instance of nstextview):

let currentwidth = self.frame.width let textstorage = nstextstorage(attributedstring: self.attributedstring()) let textcontainer = nstextcontainer(containersize: nsmakesize(currentwidth, cgfloat.max)) let layoutmanager = nslayoutmanager() layoutmanager.addtextcontainer(textcontainer) textstorage.addlayoutmanager(layoutmanager) layoutmanager.glyphrangefortextcontainer(textcontainer) let newsize = layoutmanager.usedrectfortextcontainer(textcontainer) heightconstraint.constant = newsize.height

the string created through conversion markdown nsattributedstring:

let data = styledhtml.datausingencoding(nsutf8stringencoding, allowlossyconversion: false) let attributed = try! nsattributedstring(data: data!, options: [     nsdocumenttypedocumentattribute: nshtmltextdocumenttype ], documentattributes: nil) self.textstorage?.setattributedstring(attributed)

the issue, however, minimum height calculated off 20px (the grey area indicates text, red indicates view):

enter image description here

i figured issue usedrectfortextcontainer(), when set string value of nstextview instance else, i.e.:

self.string = "random string...\ntwo lines" let currentwidth = self.frame.width ...

i correct height:

enter image description here

i haven't found useful on google, other this question has similar issue no solution.

it might worth noting setting grey background through inline style sheet pretty barebones:

*{     margin:0 !important;     padding:0 !important;     line-height:20px;     /*default_font*/     /*default_font_size*/     background:grey; } em{     font-style:italic; }

where /*default_font*/ , /*default_font_size*/ swapped default nsfont values prior being added html.

edit: it's not html generated causes discrepancy, both have exact same format/styling:

original string:

<!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"> <meta name="cocoaversion" content="1404.11"> <style type="text/css"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 20.0px; font: 13.0px 'helvetica neue'; color: #0000ee; -webkit-text-stroke: #0000ee; background-color: #808080} span.s1 {text-decoration: underline ; font-kerning: none} </style> </head> <body> <p class="p1"><span class="s1"><a href="http://www.native-languages.org/houses.htm">http://www.native-languages.org/houses.htm</a></span></p> <p class="p1"><span class="s1"><a href="https://www.youtube.com/watch?v=1ou6__m8to4">https://www.youtube.com/watch?v=1ou6__m8to4</a></span></p> </body> </html>

random string:

<!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"> <meta name="cocoaversion" content="1404.11"> <style type="text/css"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 20.0px; font: 13.0px 'helvetica neue'; color: #0000ee; -webkit-text-stroke: #0000ee; background-color: #808080} span.s1 {text-decoration: underline ; font-kerning: none} </style> </head> <body> <p class="p1"><span class="s1"><a href="http://www.native-languages.org/houses.htm">f</a></span></p> </body> </html>

well embarrassing! after testing further, noticed self.attributedstring().string value had trailing line break \n, must've been created during conversion html nsattributedstring. remedied so:

let data = styledhtml.datausingencoding(nsutf8stringencoding, allowlossyconversion: false) let attributed = try! nsmutableattributedstring(data: data!, options: [     nsdocumenttypedocumentattribute: nshtmltextdocumenttype ], documentattributes: nil) let lastcharacterrange = nsmakerange(commentstring.length - 1, 1)        let lastcharacter = self.attributedsubstringfromrange(lastcharacterrange) if lastcharacter.string == "\n" {     self.deletecharactersinrange(lastcharacterrange) }

basically, changed nsattributedstring nsmutableattributedstring, allowing me remove last character through deletecharactersinrange.


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