[RFC] Limit inline image width by default (was: feature request: easy embedding of images)

[Ihor Radchenko]

Alexis Gallagher <alexisgallagher@gmail.com> writes:

>       •       the image is automatically resized to maintain aspect ratio and 
> fit horizontally with a civilized margin, so that I can resize my emacs 
> window without the image disappearing or swamping the other content. 

We cannot automatically resize images in Elisp. At least, I know no good
way to do it reliably.

But we can try to improve the defaults for wide images.

See the tentative patch.

>From 180e322c2c79ea88d87f908299a5c0e69c47a7b2 Mon Sep 17 00:00:00 2001
Message-Id: 
<180e322c2c79ea88d87f908299a5c0e69c47a7b2.1679581960.git.yantar92@posteo.net>
From: Ihor Radchenko <yantar92@posteo.net>
Date: Thu, 23 Mar 2023 15:31:33 +0100
Subject: [PATCH] lisp/org.el: Allow limiting inline image width

* lisp/org.el (org-image-max-width): New custom variable controlling
max inline image width.
(org--create-inline-image): Use the new variable.
* doc/org-manual.org (Images):
* etc/ORG-NEWS (New customization ~org-image-max-width~ limiting the
displayed inline image width): Document the new variable.
---
 doc/org-manual.org | 20 +++++++++++++++++---
 etc/ORG-NEWS       | 15 +++++++++++++++
 lisp/org.el        | 29 ++++++++++++++++++++++++++++-
 3 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index 37fd3df14..3d729bdf6 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -11495,14 +11495,19 @@ ** Images
 
 
   #+vindex: org-image-actual-width
+  #+vindex: org-image-max-width
   #+cindex: @samp{ORG-IMAGE-ACTUAL-WIDTH}, property
   By default, Org mode displays inline images according to their
-  actual width.  You can customize the displayed image width using
+  actual width, but no wider than ~fill-column~ characters.
+
+  You can customize the displayed image width using
   ~org-image-actual-width~ variable (globally) or
   =ORG-IMAGE-ACTUAL-WIDTH= property (subtree-level)[fn:: The width can
   be customized in Emacs >= 24.1, built with imagemagick support.].
   Their value can be the following:
   - (default) Non-nil, use the actual width of images when inlining them.
+    It the actual width is too wide, limit it according to
+    ~org-image-max-width~.
   - When set to a number, use imagemagick (when available) to set the
     image's width to this value.
   - When set to a number in a list, try to get the width from any
@@ -11512,8 +11517,17 @@ ** Images
     #+end_example
     and fall back on that number if none is found.
   - When set to nil, try to get the width from an =#+ATTR.*= keyword
-    and fall back on the original width if none is found.
-
+    and fall back on the original width or ~org-image-max-width~ if
+    none is found.
+
+  ~org-image-max-width~ limits the maximum displayed image width, but
+  only when the image width is not set explicitly.  Possible maximum
+  width can be set to:
+  - (default) ~fill-column~, limit width to ~fill-column~ number of
+    characters.
+  - ~window~, limit width to current window width.
+  - integer number, limit width that specified number of pixels.
+  - nil, do not limit the width.
 
 #+vindex: org-cycle-inline-images-display
 Inline images can also be displayed when cycling the folding state.
diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index 4d45e6507..2611cc570 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -24,6 +24,21 @@ consider 
[[https://gitlab.com/jackkamm/ob-python-mode-mode][ob-python-mode-mode]
 has been ported to.
 
 ** New and changed options
+*** New customization ~org-image-max-width~ limiting the displayed inline 
image width
+
+New custom variable ~org-image-max-width~ limits the maximum inline
+image width, but only when the inline image width is not explicitly
+set via ~org-image-actual-width~, =ORG-IMAGE-ACTUAL-WIDTH= property,
+or =#+ATTR*= keyword.
+
+By default, when ~org-image-actual-width~ is set to t,
+~org-image-max-width~ takes effect.  Its default value is set to
+~fill-column~, limiting the image previews to ~fill-column~ number of
+characters.
+
+To fall back to previous defaults, where the inline image width is not
+constrained, set ~org-image-max-width~ to nil.
+
 *** New ~org-cite-natbib-export-bibliography~ option defining fallback 
bibliography style
 
 ~natbib~ citation export processor now uses
diff --git a/lisp/org.el b/lisp/org.el
index 20e6ea6d9..43d659536 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -15096,6 +15096,24 @@ (defcustom org-image-actual-width t
          (list :tag "Use #+ATTR* or a number of pixels" (integer))
          (const :tag "Use #+ATTR* or don't resize" nil)))
 
+(defcustom org-image-max-width 'fill-column
+  "When non-nil, limit the displayed image width.
+This setting only takes effect when `org-image-actual-width' is set to
+t or when #+ATTR* is set to t.
+
+Possible values:
+- `fill-column' :: limit width to `fill-column'
+- `window'      :: limit width to window width
+- number        :: limit width to number in pixels
+- nil             :: do not limit image width"
+  :group 'org-appearance
+  :package-version '(Org . "9.7")
+  :type '(choice
+          (const :tag "Do not limit image width" nil)
+          (const :tag "Limit to `fill-column'" fill-column)
+          (const :tag "Limit to window width" window)
+          (integer :tag "Limit to a number of pixels")))
+
 (defcustom org-agenda-inhibit-startup nil
   "Inhibit startup when preparing agenda buffers.
 When this variable is t, the initialization of the Org agenda
@@ -16229,7 +16247,16 @@ (defun org--create-inline-image (file width)
                         width
                         'imagemagick)
                    remote?
-                   :width width :scale 1))))
+                   :width width
+                    :max-width
+                    (pcase org-image-max-width
+                      (`fill-column (pixel-fill-width fill-column))
+                      (`window (window-width nil t))
+                      ((pred integerp) org-image-max-width)
+                      (`nil nil)
+                      (_ (error "Unsupported value of `org-image-max-width': 
%S"
+                                org-image-max-width)))
+                    :scale 1))))
 
 (defun org-display-inline-images (&optional include-linked refresh beg end)
   "Display inline images.
-- 
2.39.1

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>