Sigil’s Future Direction (Post 0.4.x)


With 0.4 my focus has been on getting the existing features in a stable state. I foresee 0.4 being around for quite some time as development shifts to accommodate new features. I wanted to be sure a relatively bug free version is available for people to use. If data loss is a constant then there wouldn’t be any point in using Sigil. Now that 0.4 is done it’s time to start working on what’s next.

Just what is next? For the time being I’ve marked a number of issues on the issue tracker as Milestone-0.5. My plan is to have 0.5 just implement the most commonly requested and most interesting features. 0.5 has no vision and is just a stop gap while I familiarize myself with Sigi’s code base. 0.5 is my short term plan. It’s not grand but it’s functional and sufficient.

Recently I posted the conclusion of my Sigil user study. The findings are Sigil is most used and most useful to power users and small professional ebook creating houses. Also, the overlap between the two is significant. Thus I want to target these two group and make Sigil even more useful for them. Keep this in mind because these two groups are who is going to shape my views of where I want to take Sigil.

Please realize that not everything I’m going to talk about is set in stone. A lot of it probably will never happend. Also, this is part plans, part what I want to do, and part rant about what Sigil does that I don’t like. This is what my ideal Sigil would look like and it is what I’m going to work toward. However, nothing is set in stone.


If you’ve ever used calibre or Firefox you will know that plugins are amazing. They allow for easy and quick changes and additions to be made without having to change the main application. Both calibre and Firefox have large third party plugin communities. I would like to bring this to Sigil and I want a framework where all book manipulation is available over a plugin interface.

My feelings with Sigil are plugins should make small self contained changes. Similar to calibre’s heuristic processing. For instance, italicize common cases, up / down shift headings, and normalize CSS. To make plugins really useful I want to have a system where multiple plugins can be chained together and run in sequence. This would be super basic internal script functionality.

For plugins themselves I’m undecided about how they should be implemented. I don’t mean API wise because that isn’t even a thought at this point. I’m talking about what languages they should be able to be written in. C++ as a shared library will of course be supported because Sigil is written in C++. However, I want to Sigil to be able to load plugins written in scripting languages.

My first thought is Python because I’m very familiar with it and love to work with it. I’m also thinking about Lua and QtScript (Javascript without DOM). I don’t support frameworks for every one of these languages due to the amount of maintenance required. So I want to support only one scripting language. Python is big and slow. Lua is small but doesn’t have the advanced text manipulation libraries Python offers. QtScript is Javascript with is an abomination of a language. Added size of Sigil’s install, execution speed, ease of supporting, knowledge by contributors and text manipulation support are all major considerations.


Currently Sigil does not respect the structure of existing files. When you open an EPUB in Sigil it restructures the file layout. It even goes as far as to rewrite each XHTML file by running it through Tidy. With 0.4.0 cleaning with Tidy can be disabled but pretty printing is still used and alters the XHTML. I absolutely hate this! If I want my XHTML or file structure changed I’ll do it myself.

I want to change Sigil to not be as automatic. Restructuring and cleaning of the XHTML should be moved to plugins and run when the user requests it. This way a user can open Sigil, change the metadata, save, and the only thing that changes is the OPF with the metadata changes. Not every single piece of the EPUB.

I also hate WYSIWYG editing because it inherently must make drastic changes to the underlying code. I don’t think it’s a good idea to remove it though. I would prefer to have the book view default to a preview mode that is read only. There wouldn’t be any changes made to the code by using book view. Read only is the default but the user should be able to have an edit toggle that will set the book view to edit mode which will work like it already does. This way a user can make changes that may not be valid or work, check them, see there is an error (say a missing </a> tag) without losing any work. They can see the issue fix it and still be able to use WYSIWYG editing when they want.

Data Store

Right now XML (XHTML included) data is stored as a Xerces DOMDocument. This is then loaded into the book or code view depending on which one is focused. The use of a DOMDocument often leads to data loss. Putting malformed XML into a DOMDocument can have unintended consequences. Especially when then loading that into a QWebView and getting back a string.

I want to replace the DOMDocument with a plain string as the data store. This will prevent a lot of data loss, especially combined with the book view defaulting to read only. Further, this combined with not making automatic changes to the code will make the well-formed error warning unnecessary.

Not auto processing with Tidy and checking for errors automatically will allow Sigil to produce invalid EPUBs. I really don’t care that this can happen. The tools (FlightCrew) will still be there to check that the file conforms to the spec. It’s up to the author to ensure they’re publishing valid EPUBs. An EPUB that is being actively edited doesn’t have to be valid at all times. I’d rather put the onus on the person using Sigil to ensure their EPUB is correct before publishing versus having Sigil force validity at every moment.


Undo is terrible right now. Some actions cannot be undone, some can. The book view’s undo is completely separate from the code view. You can’t undo a replacement when doing it across all HTML files on files that aren’t open in a tab. I want to see a unified single undo that allows for setting back out of any change.

Further along this line I would like some graphical display where you can look at the changes that have been made to make it easy to find exactly how far back to undo. Something like Apple’s Time Machine but for the state of the book.


Here is where I want to take Sigil: less hand holding, less automatic changes and more advanced text manipulation though a plugin interface. The big question is, should I skip putting out a 0.5.0 release with just the Milestone-0.5.0 marked changes and get started on the above now?

2 thoughts on “Sigil’s Future Direction (Post 0.4.x)

  1. John

    My thoughts:

    I would do all to make sure that data lost or corruption is at a minimum along with a few format additions to make life easier on us formatters(one who formats other writtings for the Kindle, etc.)

    I would then go about working on new features for some future release date.

  2. Sigil is an awesome program. I’ve used it to convert several large novels into .epub format, from html, and it’s worked beautifully. Thank you! …I’m recommending Sigil to other authors who need this virtually perfect program to convert their books for submission to Amazon Kindle Books. Between the html tidy, the .epub verifier, and the split screen text over/html under features, there’s almost no way to pull a final product out of Sigil with a flaw in it. I always preview my products in Calibre and I’m always floored when I see how lovely my books look.

Comments are closed.