I am building a new theme, so I created a new folder under 'themes'.
Then I changed the _config.php file to point to the new theme. That all worked perfect.
They I was having a 'light blue' background but I never set that background.
I looked at the source code of the resulting HTML page and I found that there are 2 lines that are included there but I didn't write them:
ok, found the problem, but I still don't understand why is developed that way.
When I create a new theme the files layout.css and typography.css are kind of mandatory.
If they are there, it takes the new files automatically.
If they are not there, it takes the one from Silverstripe admin page.
For me that doesn't make sense since the idea was to create a totally new theme.
first, the files layout.css, typography.css and form.css are mandatory to standardize the creation of themes.
What's more, the CMS uses the typography.css file to display the content correctly during the edition.
If these files are not detected, the default ones are used - in fact, it's not about the css files but about the whole themes.
It shouldn't be a problem to name your files layout.css and typography.css to make things easier, but if it is, just create empty files with such names and then no default styling will be used.
Nothings fixed in the 'core' apart from editor.css - if you want to control the fonts / colors in the cms then you have to use a editor.css.
In the current theme editor.css just @imports the typography css so we can have styles for the CMS only in editor.css. Styles for the CMS and front end in typography.css and styles for the front end in layout.css.
But you have full control over how ever you want to do it in your theme!. You can even choose not to include the CSS as we have - Via a PHP method (Requirements::css()) - you could hard code them in the theme if you wanted to or call them style.css and mysite.css or whatever - just remember to edit the Requirements call in the page.php file
Why not just comment out or delete the requirements call in Page.php to ensure they aren't included? If you started your site theme by copying the blackcandy one and changing it to fit your design, the Page.php file will have the typography and layout requirement calls inside it already.