Current status for mailrendering in kube & kmail

In my last entry I introduced libotp. But this name has some problems, that people thought, that it is a library for one-time-passwords, so we renamed it to libmimetreeparser.

Over the the last months I cleanup and refactored the whole mimetreeparser to turn it into a self-contained library.

Usage Dependencies

As a gerneral rule we wanted to make sure, that we only have dependecies in mimetreeparser, where we we can easily tell, why we need them. We end up with:

  • KF5::Libkleo is the dependecy we are not happy with, because it pulls in many widget related dependencies, that we want avoid. But there is light at the end of the tunnel and we will be hopefully switch in the next weeks to GpgME directly. GpgME is planning to have a Qt interface, that fulfills our need for decrypting and verifying mails. The source of the Qt interface of GpgME is libkleo, that's why the patch will be get quite small. At KDEPIM sprint in Toulouse in spring this year, I already give the Qt interface a try and made sure, that your tests are still passing.
  • KF5::Codecs to translate between different codes, that can occur in a mail
  • KF5::I18n for translations of error messages. If we want consistent translations of error messages we need to handle them in libmimetreeparser.
  • KF5::Mime because the input mail is a mimetree.

Rendering in Kube

In Kube we have decided to use QML to render mails for the user, that's made it easy to switch all html rendering specific parts away. So we end up with just triggering the ObjectTreeParser and create a model out of the resulting tree. The model is than the input for QML. QML now loads different code for different parts in the mail. For example for plain text it just shows the plain text, for html it loads this part in a WebEngine. But as a matter of fact, the interface we use is quite new and it is currently still under development (T2308). For sure there will be changes, until we are happy with it. I will describe the interface in detail if we are happy with it. Just as sidenote, we don't want a separate interface for kube and kdepim. The new interface should be suitable for all clients. To not break the clients constently, we keep the current interface and develop the new interface from scratch and than switch we are happy with the interface.

Rendering in Kmail

As before we use html as rendering output, but with the rise of libmimtreeparser, kmail uses also the messageparttree as input and translate this into html. So we also have here a clear seperation between the parsing step ( handled in libmimetreeparser) and the rendering step, that is happening in messageviewer. Kmail has additional support for different mime-types like iTip (invitations) ind vCard. The problem with these parts are, that they need to interact directly with Akonadi to load informations. So we can actually detect if a event is already known in Akonadi or if we have the vCard already saved, which than changes the visible representation of that part. This all works because libmimetreeparser has an interface to add additional mime-type handlers ( called BodyPartFormatters).

And additionally messageviewer now using grantlee for creating the html, that is very handy and makes it now easy to change the visual presentation of mails, just by changing the theme files. That should help a lot if we want to change the look-and-feel of email presentation to the user. And allow us additionally to think about different themes for emailpresentation. We also thought about the implications of the easy changeable themes and came up with the problem, that it shouldn't be that easy to change the theme files, because malicious users, could fake good cryptomails. That's why the theme files are shipped inside resource files.

Meanwhile I was implementing this, Laurent Montel added javascript/jQuery support to the messageviewer. So I sat down and created a example to switch the alterantivepart ( html and textpart, that can be switched) with jQuery. Okay we came to the conclusion that this is not a good idea (D1991). But maybe others came up with good ideas, where we can use the power of jQuery inside the messageviewer.