Re: [PATCH] Justify/align image previews in org-mode

[Karthik Chikmagalur <karthikchikmagalur@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 4077 bytes --]

>> I've incorporated the following suggestions:
>>
>> - Order of precedence:
>>   + #+attr_org overrides #+attr_html and #+attr_latex
>>   + `:center t' overrides `:align ...'
>
> Why only html and latex? I think that it will be more consistent to
> follow what we do in `org-display-inline-image--width' - any #+attr_*
> attribute. And apart from html/latex, we have
> beamer/hugo/koma-letter/what not is implemented or will be implemented
> deriving from html/latex backend or with support of :center attribute.

Changed implementation to support any #+attr_.* keyword.

>> - Add a checker for `:align nil' to org-lint.  `:align nil' is not
>>   supported.
>
> I meant :align <anything> being not supported in #+attr_org. Not just nil.

org-lint now complains if anything other than `:align left|center|right'
or `:center t' are specified in #+attr_org.

>> +  #+vindex: org-image-align
>> +  Org mode can left-align, center or right-align the display of inline
>> +  images.  This setting is controlled (globally) by ~org-image-align~.
>> +  Only standalone links, /i.e/ links with no surrounding text in their
>
> Maybe "standalone images"?
> Also, please avoid i.e - this is a general Emacs documentation guideline
> to avoid specialized language like i.e., e.g., and iff.

Changed text, removed specialized language.

>> +  paragraphs (except whitespace) are affected.  Its value can be the
>> +  following:
>> +  - (default) nil, insert the image where the link appears in the
>> +    buffer.
>
> Why not simply setting the default to 'left and not having nil at all?

The original idea was that `left' and `nil' do the same thing, so it
should be fine to leave it at `nil'.  I changed the user option to
default to `left', and `nil' has been removed as an available option.
(It is still not an error to set it to `nil'.)

>> +  - The symbol ~left~, which is the same as nil.
>> +  - The symbol ~center~, which will preview standalone links centered
>> +    in the Emacs window.
>> +  - The symbol ~right~, which will preview standalone links
>> +    right-aligned in the Emacs window.
>
> "standalone" links is redundant here - you already mentioned that  

Fixed.

>> +  Inline image alignment can be specified for each link using the
>> +  =#+ATTR.*= keyword if it matches an alignment specification like:
>> +  #+begin_example
>> +  ,#+ATTR_HTML: :align center
>> +  #+end_example
>> +  Supported values for =:align= are =left=, =center= and =right=.
>
> I think that we do not need to specify the supported values here - they
> are the same as for `org-image-align' just above.

Removed.

>> +  Inline image display can also be centered using =:center=, as in
>
> I'd explain that inline image adjustment is also taken from :center
> attribute supported by some export backends (like HTML, LaTeX, and
> Beamer), when #+attr_org is not set.

Tweaked the description of :center.

>> +  #+begin_example
>> +  ,#+ATTR_HTML: :center t
>> +  #+end_example
>> +  Org will use the alignment specification from any =#+ATTR.*=
>> +  keyword, such as =#+ATTR_HTML= or =#+ATTR_LATEX=, but =#+ATTR_ORG=
>> +  (if present) will override the others.  For instance, this link
>> +  #+begin_example
>> +  ,#+ATTR_HTML: :align right
>> +  ,#+ATTR_ORG: :align center
>> +  [[/path/to/image/file.png]]
>> +  #+end_example
>> +  will be displayed centered.
>
> ... "but exported right-aligned to HTML"

Added.

>> +(defun org-lint-invalid-image-alignment (ast)
>> +  (org-element-map ast 'paragraph
>> +    (lambda (p)
>> +      (let ((bad-align-re ":align[[:space:]]+nil")
>> +            (keyword-string (mapconcat
>> +                             (lambda (attr)
>> +                               (or (car-safe (org-element-property attr p)) ""))
>> +                             '(:attr_org :attr_latex :attr_html) " ")))
>
> :align nil is perfectly valid for HTML.
> I thought to warn only about using anything but :align left/right/center
> in #+attr_org. And about :center <anything> in #+attr_org.

Yes, only the value of #+attr_org is checked now.

Patch v2 attached.

Karthik

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-org-Add-image-alignment-v2.patch --]
[-- Type: text/x-patch, Size: 10738 bytes --]

From 7176f43282749c06daf2756360633cc47d79b63c Mon Sep 17 00:00:00 2001
From: Karthik Chikmagalur <karthikchikmagalur@gmail.com>
Date: Mon, 18 Dec 2023 12:56:33 -0800
Subject: [PATCH] org: Add image alignment

* lisp/org.el (org-image--align, org-image-align,
org-toggle-inline-images): Add the ability to left-align, center
or right-align inline image previews in the Emacs window. This is
controlled globally using the new user option `org-image-align'.
Alignment can be specified per image using the `#+ATTR.*'
affiliated keywords.  The function `org-image--align' determines
the kind of alignment for its argument link.

* lisp/org-lint.el (org-lint-invalid-image-alignment): Add an
org-lint checker to catch invalid ":align" and ":center"
attributes in `#+attr_org' keywords.

* doc/org-manual.org: Document the new feature under the Images
section.
---
 doc/org-manual.org | 33 ++++++++++++++++
 lisp/org-lint.el   | 35 +++++++++++++++++
 lisp/org.el        | 94 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 158 insertions(+), 4 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index 5217e647d..186f08c51 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -11501,6 +11501,39 @@ command:
     and fall back on the original width if none is found.
 
 
+  #+vindex: org-image-align
+  Org mode can left-align, center or right-align the display of inline
+  images.  This setting is controlled (globally) by ~org-image-align~.
+  Only standalone images are affected, corresponding to links with no
+  surrounding text in their paragraph except for whitespace.  Its
+  value can be the following:
+  - (default) The symbol ~left~, which inserts the image where the
+    link appears in the buffer.
+  - The symbol ~center~, which will preview links centered in the
+    Emacs window.
+  - The symbol ~right~, which will preview links right-aligned in the
+    Emacs window.
+
+  Inline image alignment can be specified for each link using the
+  =#+ATTR.*= keyword if it matches an alignment specification like:
+  #+begin_example
+  ,#+ATTR_HTML: :align center
+  #+end_example
+  Org will use the alignment specification from any =#+ATTR.*=
+  keyword, such as =#+ATTR_HTML= or =#+ATTR_LATEX=, but =#+ATTR_ORG=
+  (if present) will override the others.  For instance, this link
+  #+begin_example
+  ,#+ATTR_HTML: :align right
+  ,#+ATTR_ORG: :align center
+  [[/path/to/image/file.png]]
+  #+end_example
+  will be displayed centered in Emacs but exported right-aligned to
+  HTML.
+
+  When =#+ATTR_ORG= is not set, inline image alignment is also read
+  from the =:center= attribute supported by some export backends (like
+  HTML, LaTeX and Beamer.)
+
 #+vindex: org-cycle-inline-images-display
 Inline images can also be displayed when cycling the folding state.
 When custom option ~org-cycle-inline-images-display~ is set, the
diff --git a/lisp/org-lint.el b/lisp/org-lint.el
index 0e2967b6c..3442d3571 100644
--- a/lisp/org-lint.el
+++ b/lisp/org-lint.el
@@ -964,6 +964,36 @@ Use \"export %s\" instead"
 		reports))))
     reports))
 
+(defun org-lint-invalid-image-alignment (ast)
+  (apply
+   #'nconc
+   (org-element-map ast 'paragraph
+     (lambda (p)
+       (let ((center-re ":center[[:space:]]+\\(\\S-+\\)")
+             (align-re ":align[[:space:]]+\\(\\S-+\\)")
+             (keyword-string
+              (car-safe (org-element-property :attr_org p)))
+             reports)
+         (when keyword-string
+           (when (and (string-match align-re keyword-string)
+                      (not (member (match-string 1 keyword-string)
+                                   '("left" "center" "right"))))
+             (push
+              (list (org-element-begin p)
+                    (format
+                     "\"%s\" not a supported value for #+ATTR_ORG keyword attribute \":align\"."
+                     (match-string 1 keyword-string)))
+              reports))
+           (when (and (string-match center-re keyword-string)
+                      (not (equal (match-string 1 keyword-string) "t")))
+             (push
+              (list (org-element-begin p)
+                    (format
+                     "\"%s\" not a supported value for #+ATTR_ORG keyword attribute \":center\"."
+                     (match-string 1 keyword-string)))
+              reports)))
+         reports)))))
+
 (defun org-lint-extraneous-element-in-footnote-section (ast)
   (org-element-map ast 'headline
     (lambda (h)
@@ -1390,6 +1420,11 @@ Use \"export %s\" instead"
   #'org-lint-invalid-keyword-syntax
   :trust 'low)
 
+(org-lint-add-checker 'invalid-image-alignment
+  "Report unsupported align attribute for keyword"
+  #'org-lint-invalid-image-alignment
+  :trust 'low)
+
 (org-lint-add-checker 'invalid-block
   "Report invalid blocks"
   #'org-lint-invalid-block
diff --git a/lisp/org.el b/lisp/org.el
index 59fe3d2d3..24e80970f 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -16175,6 +16175,25 @@ cache       Display remote images, and open them in separate buffers
 	  (const :tag "Display and silently update remote images" cache))
   :safe #'symbolp)
 
+(defcustom org-image-align 'left
+  "How to align images previewed using `org-display-inline-images'.
+
+Only stand-alone image links are affected by this setting.  These
+are links without surrounding text.
+
+Possible values of this option are:
+
+left     Insert image at specified position.
+center   Center image previews.
+right    Right-align image previews."
+  :group 'org-appearance
+  :package-version '(Org . "9.7")
+  :type '(choice
+          (const :tag "Left align (or don\\='t align) image previews" left)
+	  (const :tag "Center image previews" center)
+	  (const :tag "Right align image previews" right))
+  :safe #'symbolp)
+
 (defun org--create-inline-image (file width)
   "Create image located at FILE, or return nil.
 WIDTH is the width of the image.  The image may not be created
@@ -16293,8 +16312,9 @@ buffer boundaries with possible narrowing."
                               (expand-file-name path))))
 		  (when (and file (file-exists-p file))
 		    (let ((width (org-display-inline-image--width link))
-			  (old (get-char-property-and-overlay
-				(org-element-property :begin link)
+			  (align (org-image--align link))
+                          (old (get-char-property-and-overlay
+				(org-element-begin link)
 				'org-image-overlay)))
 		      (if (and (car-safe old) refresh)
                           (image-flush (overlay-get (cdr old) 'display))
@@ -16304,8 +16324,8 @@ buffer boundaries with possible narrowing."
 				       (org-element-property :begin link)
 				       (progn
 					 (goto-char
-					  (org-element-property :end link))
-					 (skip-chars-backward " \t")
+					  (org-element-end link))
+					 (unless (eolp) (skip-chars-backward " \t"))
 					 (point)))))
                               ;; FIXME: See bug#59902.  We cannot rely
                               ;; on Emacs to update image if the file
@@ -16319,6 +16339,15 @@ buffer boundaries with possible narrowing."
 			       (list 'org-display-inline-remove-overlay))
 			      (when (boundp 'image-map)
 				(overlay-put ov 'keymap image-map))
+                              (when align
+                                (overlay-put
+                                 ov 'before-string
+                                 (propertize
+                                  " " 'face 'default
+                                  'display
+                                  (pcase align
+                                    ("center" `(space :align-to (- center (0.5 . ,image))))
+                                    ("right"  `(space :align-to (- right ,image)))))))
 			      (push ov org-inline-image-overlays))))))))))))))))
 
 (defvar visual-fill-column-width) ; Silence compiler warning
@@ -16380,6 +16409,63 @@ buffer boundaries with possible narrowing."
       org-image-actual-width)
      (t nil))))
 
+(defun org-image--align (link)
+  "Determine the alignment of the image link.
+
+In decreasing order of priority, this is controlled:
+- Per image by the value of `:center' or ``:align' in the
+affiliated keyword `#+attr_org'.
+- By the `#+attr_html' or `#+attr_latex` keywords with valid
+  `:center' or `:align' values.
+- Globally by the user option `org-image-align'.
+
+The result is either nil or one of the strings \"left\",
+\"center\" or \"right\".
+
+\"center\" will cause the image preview to be centered, \"right\"
+will cause it to be right-aligned.  A value of \"left\" or nil
+implies no special alignment."
+  (let ((par (org-element-lineage link 'paragraph)))
+    ;; Only align when image is not surrounded by paragraph text:
+    (when (and (= (org-element-begin link)
+                  (save-excursion
+                    (goto-char (org-element-contents-begin par))
+                    (skip-chars-forward "\t ")
+                    (point)))           ;account for leading space
+                                        ;before link
+               (<= (- (org-element-contents-end par)
+                      (org-element-end link))
+                   1))                  ;account for trailing newline
+                                        ;at end of paragraph
+      (save-match-data
+        ;; Look for a valid ":center t" or ":align left|center|right"
+        ;; attribute.
+        ;;
+        ;; An attr_org keyword has the highest priority, with
+        ;; any attr.* next.  Choosing between these is
+        ;; unspecified.
+        (let ((center-re ":\\(center\\)[[:space:]]+t\\b")
+              (align-re ":align[[:space:]]+\\(left\\|center\\|right\\)\\b")
+              attr-align)
+          (catch 'exit
+            (org-element-properties-mapc
+             (lambda (propname propval)
+               (when (and propval
+                          (string-match-p ":attr.*" (symbol-name propname)))
+                 (setq propval (car-safe propval))
+                 (when (or (string-match center-re propval)
+                           (string-match align-re propval))
+                   (setq attr-align (match-string 1 propval))
+                   (when (eq propname :attr_org)
+                     (throw 'exit t)))))
+             par))
+          (if attr-align
+              (when (member attr-align '("center" "right")) attr-align)
+            ;; No image-specific keyword, check global alignment property
+            (when (memq org-image-align '(center right))
+              (symbol-name org-image-align))))))))
+
+
 (defun org-display-inline-remove-overlay (ov after _beg _end &optional _len)
   "Remove inline-display overlay if a corresponding region is modified."
   (when (and ov after)
-- 
2.40.1