Hi.
I'm completely new to SilverStripe, but I like what I've seen so far. I've started a new job and had to take over the previous guys development.

The content editor in the admin area isn't like the default one. It looks more like sublime text and has Edit, Add Link, Add Image, Expand and Markdown cheatsheet buttons along the top.

I've decided to start from scratch with a fresh SilverStripe installation so I can get to know their website inside and out. My question is. How do you change the default content editor? I've added modules such as axllent/silverstripe-gfmarkdown but I can only add new fields, not change the content field.

Thanks.

This will need you to actually take each instance and use http://api.silverstripe.org/3.1/class-FieldList.html#_replaceField to replace it.
There are some classes that I think replace the TextareaField and TextField - but as there is so much going on with the HTMLField in terms of integration I don't think it has an equivalent.

I do agree with you that personally I'd prefer markdown, textile or something as an option over TinyMCE - but I'm not holding my breath.

Something may also be possible with Injector, or by specifying some other implementation of the appropriate superclass. IIRC the editor field was engineered in a way where it was supposed to be easily swappable, however ended up ... not quite getting there.
It's still possible, just requires more work I think. You'd have to really look into it though, this is all old memory I'm recalling without checking anything.

Otherwise basically what Swaiba has said. Probably in something like the Page::getCMSFields() superclass replacing all Content field instances in pages easily.

According to this description this new module should do exactly as required...

http://addons.silverstripe.org/add-ons/mademedia/silverstripe-markdown

Thanks Swaiba. That sent me in the right direction :)