is an undefined css class an error - and is there a detecrtion tool

stumped · 03-26-2020, 01:06 PM

some context. I have been trying to better understand why/when calibre introduces the css class pcalibre1 during a conversion.
I am asking here as sigil is my preferred investigation tool...

So, looking through various books, for usage of pcalibre1,
I find a book in my library which has the code
<p class="pcalibre2 pcalibre1"> for 1st line of each chapter

but there is no definition of pcalibre2 that I can find. Definitely not in the css sheet according to "find". Only pcalibre1 is defined, and there are no inline class definitions either
so I try all the various epub check type tools in sigil to see if the missing definition gets flagged as an error - but it doesn't- and the book renders normally.
I also tried the check/repair tools in the calibre editor and they do not report a missing definition either

so are undefined css classes generally safe to leave in?

[ just in case the definition is there, and I am just going blind, I then deliberately sabotaged the code by changing pcalibre2 to pcalibre3 - which for sure is not defined, and re ran all the checks. Every one passed OK ]

I am assuming for now that I must have accidentally deleted the definition somehow, because the alternative - that calibre adds undefined classes - seems very unlikely

this is the opposite of having an unused css class. its having an undefined css class

is there any tool which will flag up such cases that I can use- either in sigil, or outside of ?
will having undefined class(es) crash or confuse some renderers?

jhowell · 03-26-2020, 01:12 PM

Classes do not need to have associated CSS properties. They can be informational or used for other purposes.

stumped · 03-26-2020, 01:17 PM

Quote:

Originally Posted by jhowell

Classes do not need to have associated CSS properties. They can be informational or used for other purposes.

ok thanks , you are saying that code like <p class="randomgarbage"> is 100% valid and simply ignored by all readers/renderers , and that's why the checking tools do not flag it.

no need to reply if YES, but if I continue to misunderstand then please clarify

KevinH · 03-26-2020, 01:35 PM

Yes, and Sigil also uses them that way when marking words for inclusion in an index, marking potential headers, etc.

In fact, for spellchecking some html software adds a "spellerror" class (with an onhover menu) although it has a css definition to do a red squiggly underline) and added spans to mark potentially misspelled words and then uses javascript to remove that class when a user marks the word as ignore or correct. That way spellchecking can be external to the browser engine because some browser spellcheck dictionaries can leave a lot to be desired.

So the "misuse" of class names is one way to "mark" things in the DOM for a variety of reasons.

hobnail · 03-26-2020, 02:23 PM

It gets even more hairy when you include other attributes besides class. See for example a book from Standard Ebooks where they use the epub attributes. They do declare them in the namespaces (the '<html xmlns=' at the beginning of the file) but they make me nervous since my Kobo's renderer can be fragile.

carmenchu · 03-27-2020, 08:29 PM

However, I think that Sigil should show classes not in any css in the Reports: it would help to check for leftovers after a thorough (manual) re-format.

KevinH · 03-27-2020, 08:37 PM

We will consider it but it would be very low priority as they are perfectly legal and have many uses.

carmenchu · 03-27-2020, 09:25 PM

And so are most things in Reports. I look at Reports, for instance, to see if there are characters or external links that 'don't belong', however correct they might be.

stumped · 03-28-2020, 02:04 AM

Quote:

Originally Posted by KevinH

We will consider it but it would be very low priority as they are perfectly legal and have many uses.

i'd appreciate the ability to check. low priority is fine, so is a simple report + having to manually remove them still

KevinH · 03-28-2020, 09:04 AM

Perhaps a plugin approach might be easiest if this is something you feel is important.

03-26-2020, 01:06 PM	#1
stumped Wizard Posts: 3,305 Karma: 10259306 Join Date: May 2016 Device: kobo forma, Kobo Libra, Huawei media Tab, fire HD10, PW3 HDX8.9,	is an undefined css class an error - and is there a detecrtion tool some context. I have been trying to better understand why/when calibre introduces the css class pcalibre1 during a conversion. I am asking here as sigil is my preferred investigation tool... So, looking through various books, for usage of pcalibre1, I find a book in my library which has the code <p class="pcalibre2 pcalibre1"> for 1st line of each chapter but there is no definition of pcalibre2 that I can find. Definitely not in the css sheet according to "find". Only pcalibre1 is defined, and there are no inline class definitions either so I try all the various epub check type tools in sigil to see if the missing definition gets flagged as an error - but it doesn't- and the book renders normally. I also tried the check/repair tools in the calibre editor and they do not report a missing definition either so are undefined css classes generally safe to leave in? [ just in case the definition is there, and I am just going blind, I then deliberately sabotaged the code by changing pcalibre2 to pcalibre3 - which for sure is not defined, and re ran all the checks. Every one passed OK ] I am assuming for now that I must have accidentally deleted the definition somehow, because the alternative - that calibre adds undefined classes - seems very unlikely this is the opposite of having an unused css class. its having an undefined css class is there any tool which will flag up such cases that I can use- either in sigil, or outside of ? will having undefined class(es) crash or confuse some renderers?

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03-26-2020, 01:12 PM	#2
jhowell Grand Sorcerer Posts: 6,497 Karma: 84420419 Join Date: Nov 2011 Location: Tampa Bay, Florida Device: Kindles	Classes do not need to have associated CSS properties. They can be informational or used for other purposes.

03-26-2020, 01:35 PM	#4
KevinH Sigil Developer Posts: 7,645 Karma: 5433388 Join Date: Nov 2009 Device: many	Yes, and Sigil also uses them that way when marking words for inclusion in an index, marking potential headers, etc. In fact, for spellchecking some html software adds a "spellerror" class (with an onhover menu) although it has a css definition to do a red squiggly underline) and added spans to mark potentially misspelled words and then uses javascript to remove that class when a user marks the word as ignore or correct. That way spellchecking can be external to the browser engine because some browser spellcheck dictionaries can leave a lot to be desired. So the "misuse" of class names is one way to "mark" things in the DOM for a variety of reasons.

03-26-2020, 02:23 PM	#5
hobnail Running with scissors Posts: 1,552 Karma: 14325282 Join Date: Nov 2019 Device: none	It gets even more hairy when you include other attributes besides class. See for example a book from Standard Ebooks where they use the epub attributes. They do declare them in the namespaces (the '<html xmlns=' at the beginning of the file) but they make me nervous since my Kobo's renderer can be fragile.

03-27-2020, 08:29 PM	#6
carmenchu Groupie Posts: 183 Karma: 266070 Join Date: Dec 2010 Device: Win7,Win10,Lubuntu,smartphone	However, I think that Sigil should show classes not in any css in the Reports: it would help to check for leftovers after a thorough (manual) re-format.

03-27-2020, 08:37 PM	#7
KevinH Sigil Developer Posts: 7,645 Karma: 5433388 Join Date: Nov 2009 Device: many	We will consider it but it would be very low priority as they are perfectly legal and have many uses.

03-27-2020, 09:25 PM	#8
carmenchu Groupie Posts: 183 Karma: 266070 Join Date: Dec 2010 Device: Win7,Win10,Lubuntu,smartphone	And so are most things in Reports. I look at Reports, for instance, to see if there are characters or external links that 'don't belong', however correct they might be.

03-28-2020, 09:04 AM	#10
KevinH Sigil Developer Posts: 7,645 Karma: 5433388 Join Date: Nov 2009 Device: many	Perhaps a plugin approach might be easiest if this is something you feel is important.

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