About DevExpress skinning and custom skins

Here is the thing. DevExpress WinForms components support custom skinning. Out of the box there are plenty of skins you might use just by assigning a simple property with a name of the skin. Every DevExpress WinForms control will follow the skin settings and will look fancy and so will your application. That’s great. But if you want more advanced skinning you are in for troubles.

Let’s see my case. An application I am building for a customer of mine supports skinning. However I had to slightly modify out of the box skins with some adjustments and I’ve added few new glyphs which I use in my custom controls (they follow skinning UI as well since entire application does). Here is how I started. I’ve opened SkinEditor, a tool provided by DevExpress and created new skins based on their skins, i.e. MyCaramel from Caramel, etc. Once I had “my” skins I’ve adjusted some properties still using SkinEditor. Finally I’ve created a “skin resource” assembly. That’s all easily done via SkinEditor. So far so good. But there are problems ahead.

First problem – adding custom glyphs to skin

Since I have custom controls that have custom glyphs I had to add those glyphs to skins. After all they belong in the skin assembly since they will be also changed when skin changes. I could add them somewhere else, but that would be asking for troubles – better to have “grouped” resources in one place. But there is no way to add custom glyphs to my skin via SkinEditor. By design. Obviously nobody at DevExpress ever supposed that custom skins might be used for custom controls.

Second problem – updating the custom skin

Next, much more annoying problem, is updating custom skin to a newer DevExpress version. Even when a minor DevExpress version is released the out of the box skin definition might change a bit - here and there. So, the template you have built your custom skin from has changed but your custom skin still “sits” on the top of the old template version. It might even result in a runtime exception if you don’t upgrade the skin while application uses newer version of DevExpress components. And go wonder, SkinEditor doesn’t have an “upgrade custom skin” option. You have to recreate the original project (what a fun when you are dealing with 20+ skins – you have to add separately) and reapply all changes you might to out of the box skins. Eeek.

Third problem – skin size

If you use a lot of custom skins they will use a lot of space (each skin is about 500KB) even though you might not be using all of DevExpress controls and thus you don’t require full skins. The relatively big size might be a problem if you distribute your application via internet and even if you don’t your application uses more memory without any apparent benefit. SkinEditor doesn’t support removing of skin elements and even if you modify skin.xml definition (by removing unnecessary nodes) SkinEditor will add them again when you open the project next time.

Fourth problem – nor skin nor its assembly can’t be unloaded

Once the skin assembly is loaded to your application (main AppDomain) it can’t be unloaded. And once skin is registered it creates a hash table of all resources (a ton of Images – I am not 100% about this but it pretty much looks like it) and you can’t unloaded any of them. So, when you register a skin assembly it will remain loaded until the application is closed and all resources will be loaded to hash table in the form of images (souds like a sort of duplication to me). There is no way to load a skin from a custom AppDomain.

Solutions to problems

The first problem can be solved “manually”. I say manually, but you can pretty easily create some XML manipulation and file copy code. While SkinEditor doesn’t support adding custom glyphs you can still add them manually in two steps – save the graphics to the proper folder of the SkinEditor project and modify skin.xml file by adding proper XML nodes pointing to newly added glyphs. After some trial and error I was able to accomplish this task.

I’ll write about the solution to the second problem in a later post. I’ll also provide an utility that does a part of the job.

I have an idea how to solve the third problem but didn’t solve it yet nor I am sure whether it will work.

The fourth problem is the most hard to solve due to the current implementation. I am not sure whether it is even possible or whether does it make sense to invest much energy into this.

Conclusion

While skinning works pretty nicely in DevExpress controls its implementation is not the best one. Specially support for custom skinning isn’t very well thought and SkinEditor can be enhanced with these problems in mind.

The good news is that with little effort I’ve managed the overcome the most important issue – how to create slightly modified out of the box skins and how to update them to new versions (automatically). I’ll talk more about this solution in a later post.

What do you think? Do you use DevExpress skinning feature? Did you create your own skins?