I have just managed to create an overlay being a small image (the Emacs logo) which purpose is to be shown instead of a special single character in the buffer text:
I would like to place this image so that it enqueues itself perfectly into the line of small text letters, but haven't found (yet) a way to appropriately change the image position in spite of some hours of intense Internet search.
Here the only making to me sense elisp code I was able to find online and used to accomplish what you see in the above image.
;; default max-image-size defined in src/image.c -> 10 pixels (setq max-image-size 128) ;; very large icon size (defvar imgEmacsLogo16x16 (create-image "emacs_logo-round_icon_16x16.png" nil nil :scale 1.0 :transform-smoothing t ) " TYPE DATA-P -> nil nil Emacs logo 16x16 img " );defvar imgEmacsLogo16x16 (defvar re-imgEmacsLogo16x16 "ä") (setq beforStrChar "") (setq afterStrChar "") (setq case-fold-search nil) ;; case sensitive search ;;(setq case-fold-search t) ;; search ignoring case (defun nextOverlay-forEmacsLogoImg16x16 (&optional limit) (when (re-search-forward re-imgEmacsLogo16x16 limit t ) ;; ^-- start at point regex_string --^ BOUND NO-ERROR COUNT=1 (setq beg (match-beginning 0) ;; 0 -> which regex capt. group? end (match-end 0) str (match-string 0) );set the above values first then create an overlay (setq ov (make-overlay beg end)) (overlay-put ov 'display imgEmacsLogo16x16) (overlay-put ov 'face 'default) (overlay-put ov 'evaporate 1 ) (overlay-put ov 'before-string beforStrChar ) (overlay-put ov 'after-string afterStrChar ) (overlay-put ov 'slice '(17 19 16 16)) (message "nextOverlay for \"%s\" beg %s end %s " str beg end))) (font-lock-add-keywords nil ;; MODE nil -> curr. buffer ( lisp-mode emacs-lisp-mode python-mode ... ) ;; list with keywords: '((nextOverlay-forEmacsLogoImg16x16 (0 'font-lock-keyword-face t))) t)
slice seems to have no impact on the image position.
How can I change the relative position of the shown overlay image within the buffer text?
P.S. I am not really happy with the used code. It appears to me that it unnecessary creates one overlay after another at the same place but I am not sure if it is actually the case. In addition to it the code makes it necessary to move the cursor to the begin of the text and to do some editing there in order to get all the overlays displayed. I am wondering how it comes that I am failing to find a simple and well explained code example to see how it can be done ... Hmmm ...
UPDATE: as long as I don't know how to write code to define the anchor and the descent of an image the work around is to adjust the image to the size of the characters. This gives following result:
As you can see from the positioning of the logo image within the text flow here on stackexchange and in Emacs that the behavior is different. Emacs seems to place the bottom edge of the image far below the bottom line of the text.