+(autoload 'shr-color-visible "shr-color")
+(autoload 'shr-color->hexadecimal "shr-color")
+
+(defun shr-color-check (fg bg)
+ "Check that FG is visible on BG.
+Returns (fg bg) with corrected values.
+Returns nil if the colors that would be used are the default
+ones, in case fg and bg are nil."
+ (when (or fg bg)
+ (let ((fixed (cond ((null fg) 'fg)
+ ((null bg) 'bg))))
+ ;; Convert colors to hexadecimal, or set them to default.
+ (let ((fg (or (shr-color->hexadecimal fg)
+ (frame-parameter nil 'foreground-color)))
+ (bg (or (shr-color->hexadecimal bg)
+ (frame-parameter nil 'background-color))))
+ (cond ((eq fixed 'bg)
+ ;; Only return the new fg
+ (list nil (cadr (shr-color-visible bg fg t))))
+ ((eq fixed 'fg)
+ ;; Invert args and results and return only the new bg
+ (list (cadr (shr-color-visible fg bg t)) nil))
+ (t
+ (shr-color-visible bg fg)))))))
+
+(defun shr-colorize-region (start end fg &optional bg)
+ "Colorize region from START to END.
+Use foreground color FG and background color BG.
+Apply color check via `shr-color-check'."
+ (when (or fg bg)
+ (let ((new-colors (shr-color-check fg bg)))
+ (when new-colors
+ (shr-put-color start end :foreground (cadr new-colors))
+ (when bg
+ (shr-put-color start end :background (car new-colors)))))))
+
+;; Put a color in the region, but avoid putting colors on on blank
+;; text at the start of the line, and the newline at the end, to avoid
+;; ugliness. Also, don't overwrite any existing color information,
+;; since this can be called recursively, and we want the "inner" color
+;; to win.
+(defun shr-put-color (start end type color)
+ (save-excursion
+ (goto-char start)
+ (while (< (point) end)
+ (when (bolp)
+ (skip-chars-forward " "))
+ (when (> (line-end-position) (point))
+ (shr-put-color-1 (point) (min (line-end-position) end) type color))
+ (if (< (line-end-position) end)
+ (forward-line 1)
+ (goto-char end)))))
+
+(defun shr-put-color-1 (start end type color)
+ (let* ((old-props (get-text-property start 'face))
+ (do-put (not (memq type old-props)))
+ change)
+ (while (< start end)
+ (setq change (next-single-property-change start 'face nil end))
+ (when do-put
+ (put-text-property start change 'face
+ (nconc (list type color) old-props)))
+ (setq old-props (get-text-property change 'face))
+ (setq do-put (not (memq type old-props)))
+ (setq start change))
+ (when (and do-put
+ (> end start))
+ (put-text-property start end 'face
+ (nconc (list type color old-props))))))
+