How to change the face of a long line without affecting other font-lock customizations in Emacs?

Question

I have some code that I borrowed from a long while ago that sets a long-line face when the line is too long:

 (add-hook 'font-lock-mode-hook
           (function
            (lambda ()
              (setq font-lock-keywords
                    (append font-lock-keywords
                            '( ("^.\\{133,\\}$" (0 'my-long-line-face t))
                              )
                            )
                    )
              )
            ))

(I know about font-lock-add-keywords now, BTW; like I said, this is kind of old.)

The problem is that this changes the face of the entire line. So if I indicate that long-line-face is bold, I lose all the contextual customization of the line, and it appears in the default face, but bold.

How would I get it to keep the contextual colouring but make everything bold?

Answer 1

You are overriding the fontification with the t in your font-lock spec. Try changing the (0 'my-long-line-face t) to either (0 'my-long-line-face prepend) or (0 'my-long-line-face append).