Rework parameters and tweak a bit more

ob-svgbob.el

@@ -42,6 +42,9 @@
 
 (require 'ob)
 
+(eval-when-compile
+  (require 'cl-lib))
+
 (defcustom org-svgbob-executable "svgbob"
   "The path to the SVGBob binary.
 This can be installed from source using `cargo install svgbob_cli'"
@@ -53,26 +56,41 @@ This can be installed from source using `cargo install svgbob_cli'"
   :group 'org-babel
   :type 'string)
 
-(defcustom org-babel-svgbob-options
-  '((background . "transparent"))
-  "Options passed to the SVGBob executable."
-  :group 'org-babel
-  :type '(alist :value-type (symbol string)))
+(defconst org-babel-svgbob--parameters
+  '(:background :fill-color :font-family :font-size :scale :stroke-width)
+  "Recognised SVGBob parameter keys.")
 
 ;; So `org-edit-special' works.
-;; Since SVGBob is based on simple ASCII diagrams without a definite, this mode
-;; is derived from `artist-mode'.
 (unless (fboundp 'svgbob-mode)
-  (define-derived-mode svgbob-mode artist-mode "svgbob"))
+  (add-to-list 'org-src-lang-modes (cons "svgbob" 'fundamental)))
 
-(defun ob-svgbob-string-to-svg (str)
-  "Convert STR to SVG text and return a string of that."
-  (org-babel-eval
-   (concat svgbob-executable " "
-           (mapconcat (lambda (opt) (format "--%s %s " (symbol-name (car opt)) (cdr opt)))
-                      org-babel-svgbob-options
-                      " "))
-   str))
+(defun ob-svgbob-string-to-svg (str &optional parameters)
+  "Convert STR to SVG text and return a string of that.
+PARAMETERS should be a plist of svgbob parameters, and only keys
+that are members of `org-babel-svgbob--parameters' will be used."
+  (with-temp-buffer
+    (insert
+     (org-babel-eval
+      (concat org-svgbob-executable
+              (cl-loop for (key . val)
+                       in parameters
+                       when (memq key org-babel-svgbob--parameters)
+                       concat (format " --%s %S"
+                                      (substring (symbol-name key) 1)
+                                      val)))
+      str))
+    (when-let ((stroke-color (alist-get :stroke-color parameters)))
+      (goto-char (point-min))
+      (re-search-forward "^[ \t]*stroke: \\(black\\);\n")
+      (replace-match stroke-color t t nil 1))
+    (when-let ((text-color (alist-get :text-color parameters)))
+      (goto-char (point-min))
+      (search-forward "text {")
+      (re-search-forward "^[ \t]*fill: \\(black\\);\n")
+      (replace-match text-color t t nil 1))
+    (when-let ((file (alist-get :file parameters)))
+      (write-region nil nil file))
+    (buffer-string)))
 
 (defun ob-svgbob-region-to-svg (start end)
   "Convert a region to SVG text in a new buffer.
@@ -95,14 +113,16 @@ See `svgbob-region-to-svg' for more"
   (ob-svgbob-region-to-svg (point-min) (point-max)))
 
 (defvar org-babel-default-header-args:svgbob
-  '((:results . "file graphics") (:exports . "results"))
+  '((:results . "file graphics")
+    (:exports . "results")
+    (:background . "transparent"))
   "Default arguments to use when evaluating a dot source block.")
 
 (defun org-babel-execute:svgbob (body params)
   "Execute a block of svgbob with org-babel.
 Specifically, svgbob is called on BODY with PARAMS."
   (if (alist-get :file params)
-      (ob-svgbob-string-to-svg body)
+      (ob-svgbob-string-to-svg body params)
     (user-error "You need to specify a :file parameter")))
 
 (defun org-babel-prep-session:svgbob (_session _params)