Merging Faces

[Florian Beck <fb@fbeck.net>]

Hello everyone,

how do you add custom face properties to an org buffer?

I want to generate org buffers automatically (displaying verious entries 
and properties). Specifically, I want the resulting buffer in org mode 
to handle links, equations, and export. But I want also to add custom 
background or fonts to parts of the buffer.

The easiest way to see the problem is this:

(let ((entry
        (concat
         "any "
         (propertize "link" 'font-lock-face '(:family "DejaVu Sans Mono"))
         " like [[file:some-file]] or equations like 
\\(\\sqrt{\\frac{1}{(x+y)^2\\), but also /italics/ and *bold text* 
should be displayed correctly;")))
   (switch-to-buffer-other-window
    "*fb-merging-example")
   (erase-buffer)
   (insert (propertize (concat "1. " entry)
                       'font-lock-face '(:background "yellow")
                       'underline t))
   (insert "\n2. other font:")
   (insert (propertize entry 'font-lock-face '(:family "Symbola")))
   (org-mode))

Two problems:
1. "link" has not the right font. I guess `propertize' doesn't merge 
face. Is there a way to accomplish this?
2. Links and equations don't have the desired background.

Any help appreciated.