Change default style of Org block (no backgrounds)

As I explained in Emacs bug#52587,[1] Org has code that overrides themes
which prefer not to extend the block delimiter faces to the edge of the
window.  This practically means that we cannot have backgrounds for
those lines and keep them limited to the stretch of area covered by
their text.

As such, the default for Org block delimiter lines now is a gray
foreground with no distinct background colour.  The user option
'modus-themes-org-blocks' provides "blocky" alternatives that use
background colours---those extend to the edge of the window.

[1] <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=52587#46>

doc/modus-themes.info

@@ -1516,21 +1516,28 @@ Brief: Set the overall style of Org code blocks, quotes, and the like.
   3. ‘tinted-background’ (value ‘rainbow’ exists for backward
      compatibility)
 
-   The default means that the block has no distinct background of its
-own and uses the one that applies to the rest of the buffer.
+   Nil (the default) means that the block has no background of its own:
+it uses the one that applies to the rest of the buffer.  In this case,
+the delimiter lines have a gray color for their text, making them look
+exactly like all other Org properties.
 
    Option ‘gray-background’ applies a subtle gray background to the
-block’s contents.  It also affects the begin and end lines of the block:
-their background extends to the edge of the window for Emacs version >=
-27 where the ‘:extend’ keyword is recognized by ‘set-face-attribute’
-(this is contingent on the variable
-‘org-fontify-whole-block-delimiter-line’).
+block’s contents.  It also affects the begin and end lines of the block
+as they get another shade of gray as their background, which
+differentiates them from the contents of the block.  All background
+colors extend to the edge of the window, giving the area a rectangular,
+“blocky” presentation.
 
    Option ‘tinted-background’ uses a slightly colored background for the
 contents of the block.  The exact color will depend on the programming
 language and is controlled by the variable ‘org-src-block-faces’ (refer
 to the theme’s source code for the current association list).  For this
-to take effect, Org must be restarted with ‘M-x org-mode-restart’.
+to take effect, the Org buffer needs to be restarted with
+‘org-mode-restart’.  In this scenario, it may be better to inhibit the
+extension of the delimiter lines’ background to the edge of the window
+because Org does not provide a mechanism to update their colors
+depending on the contents of the block.  Disable the extension of such
+backgrounds by setting ‘org-fontify-whole-block-delimiter-line’ to nil.
 
    Code blocks use their major mode’s colors only when the variable
 ‘org-src-fontify-natively’ is non-nil.  While quote/verse blocks require
@@ -5413,70 +5420,70 @@ Node: Matching parentheses52251
 Node: Active region53636
 Node: Diffs55049
 Node: Org mode blocks56655
-Node: Org agenda58582
-Node: Heading styles67084
-Node: UI typeface71509
-Node: Advanced customization72408
-Node: Per-theme customization settings73774
-Node: Case-by-case face specs using the themes' palette75079
-Node: Face specs at scale using the themes' palette79445
-Node: Remap face with local value84112
-Node: Cycle through arbitrary colors86537
-Node: Override colors92965
-Node: Override color saturation97774
-Node: Override colors through blending103453
-Node: Font configurations for Org and others106308
-Ref: Font configurations for Org and others-Footnote-1109133
-Node: Configure bold and italic faces109320
-Node: Custom Org user faces113447
-Node: Update Org block delimiter fontification117072
-Node: Measure color contrast118985
-Node: Load theme depending on time of day121708
-Node: Backdrop for pdf-tools122701
-Node: Decrease mode line height125396
-Node: A theme-agnostic hook for theme loading129521
-Node: Diffs with only the foreground131912
-Node: Face coverage134986
-Node: Supported packages135438
-Node: Indirectly covered packages141803
-Node: Notes on individual packages142791
-Node: Note on avy hints143831
-Node: Note on calendarel weekday and weekend colors144999
-Node: Note on underlines in compilation buffers146182
-Node: Note on inline Latex in Org buffers146994
-Node: Note on dimmerel147604
-Node: Note on display-fill-column-indicator-mode149089
-Node: Note on highlight-parenthesesel150652
-Node: Note on mmm-modeel background colors156641
-Node: Note for prism158956
-Node: Note for god-mode162110
-Node: Note on company-mode overlay pop-up163714
-Ref: Note on company-mode overlay pop-up-Footnote-1164404
-Ref: Note on company-mode overlay pop-up-Footnote-2164471
-Node: Note on ERC escaped color sequences164526
-Ref: Note on ERC escaped color sequences-Footnote-1165954
-Node: Note on powerline or spaceline166064
-Node: Note on SHR colors166478
-Node: Note on EWW and Elfeed fonts166901
-Node: Note on Helm grep167566
-Node: Note on vc-annotate-background-mode169041
-Node: Note on pdf-tools link hints169926
-Node: Frequently Asked Questions172358
-Node: Is the contrast ratio about adjacent colors?172914
-Node: What does it mean to avoid exaggerations?174421
-Node: Why are colors mostly variants of blue magenta cyan?176250
-Node: What is the best setup for legibility?180563
-Node: Contributing183175
-Node: Sources of the themes183572
-Node: Issues you can help with184208
-Node: Patches require copyright assignment to the FSF185408
-Node: Acknowledgements187703
-Node: Meta190537
-Node: GNU Free Documentation License192701
-Node: Indices218053
-Node: Function index218232
-Node: Variable index219439
-Node: Concept index221580
+Node: Org agenda59045
+Node: Heading styles67547
+Node: UI typeface71972
+Node: Advanced customization72871
+Node: Per-theme customization settings74237
+Node: Case-by-case face specs using the themes' palette75542
+Node: Face specs at scale using the themes' palette79908
+Node: Remap face with local value84575
+Node: Cycle through arbitrary colors87000
+Node: Override colors93428
+Node: Override color saturation98237
+Node: Override colors through blending103916
+Node: Font configurations for Org and others106771
+Ref: Font configurations for Org and others-Footnote-1109596
+Node: Configure bold and italic faces109783
+Node: Custom Org user faces113910
+Node: Update Org block delimiter fontification117535
+Node: Measure color contrast119448
+Node: Load theme depending on time of day122171
+Node: Backdrop for pdf-tools123164
+Node: Decrease mode line height125859
+Node: A theme-agnostic hook for theme loading129984
+Node: Diffs with only the foreground132375
+Node: Face coverage135449
+Node: Supported packages135901
+Node: Indirectly covered packages142266
+Node: Notes on individual packages143254
+Node: Note on avy hints144294
+Node: Note on calendarel weekday and weekend colors145462
+Node: Note on underlines in compilation buffers146645
+Node: Note on inline Latex in Org buffers147457
+Node: Note on dimmerel148067
+Node: Note on display-fill-column-indicator-mode149552
+Node: Note on highlight-parenthesesel151115
+Node: Note on mmm-modeel background colors157104
+Node: Note for prism159419
+Node: Note for god-mode162573
+Node: Note on company-mode overlay pop-up164177
+Ref: Note on company-mode overlay pop-up-Footnote-1164867
+Ref: Note on company-mode overlay pop-up-Footnote-2164934
+Node: Note on ERC escaped color sequences164989
+Ref: Note on ERC escaped color sequences-Footnote-1166417
+Node: Note on powerline or spaceline166527
+Node: Note on SHR colors166941
+Node: Note on EWW and Elfeed fonts167364
+Node: Note on Helm grep168029
+Node: Note on vc-annotate-background-mode169504
+Node: Note on pdf-tools link hints170389
+Node: Frequently Asked Questions172821
+Node: Is the contrast ratio about adjacent colors?173377
+Node: What does it mean to avoid exaggerations?174884
+Node: Why are colors mostly variants of blue magenta cyan?176713
+Node: What is the best setup for legibility?181026
+Node: Contributing183638
+Node: Sources of the themes184035
+Node: Issues you can help with184671
+Node: Patches require copyright assignment to the FSF185871
+Node: Acknowledgements188166
+Node: Meta191000
+Node: GNU Free Documentation License193164
+Node: Indices218516
+Node: Function index218695
+Node: Variable index219902
+Node: Concept index222043
 
 End Tag Table
 

doc/modus-themes.org

@@ -1405,20 +1405,28 @@ Possible values:
 2. ~gray-background~ (value ~grayscale~ exists for backward compatibility)
 3. ~tinted-background~ (value ~rainbow~ exists for backward compatibility)
 
-The default means that the block has no distinct background of its own
-and uses the one that applies to the rest of the buffer.
+Nil (the default) means that the block has no background of its own: it
+uses the one that applies to the rest of the buffer.  In this case, the
+delimiter lines have a gray color for their text, making them look
+exactly like all other Org properties.
 
 Option ~gray-background~ applies a subtle gray background to the block's
-contents.  It also affects the begin and end lines of the block: their
-background extends to the edge of the window for Emacs version >= 27
-where the ~:extend~ keyword is recognized by ~set-face-attribute~ (this is
-contingent on the variable ~org-fontify-whole-block-delimiter-line~).
+contents.  It also affects the begin and end lines of the block as they
+get another shade of gray as their background, which differentiates them
+from the contents of the block.  All background colors extend to the
+edge of the window, giving the area a rectangular, "blocky"
+presentation.
 
 Option ~tinted-background~ uses a slightly colored background for the
 contents of the block.  The exact color will depend on the programming
 language and is controlled by the variable ~org-src-block-faces~ (refer to
 the theme's source code for the current association list).  For this to
-take effect, Org must be restarted with {{{kbd(M-x org-mode-restart)}}}.
+take effect, the Org buffer needs to be restarted with ~org-mode-restart~.
+In this scenario, it may be better to inhibit the extension of the
+delimiter lines' background to the edge of the window because Org does
+not provide a mechanism to update their colors depending on the contents
+of the block.  Disable the extension of such backgrounds by setting
+~org-fontify-whole-block-delimiter-line~ to nil.
 
 Code blocks use their major mode's colors only when the variable
 ~org-src-fontify-natively~ is non-nil.  While quote/verse blocks require

modus-themes.el

@@ -5,7 +5,7 @@
 ;; Author: Protesilaos Stavrou <info@protesilaos.com>
 ;; URL: https://gitlab.com/protesilaos/modus-themes
 ;; Version: 2.0.0
-;; Last-Modified: <2021-12-31 04:37:27 +0200>
+;; Last-Modified: <2021-12-31 05:55:23 +0200>
 ;; Package-Requires: ((emacs "27.1"))
 ;; Keywords: faces, theme, accessibility
 
@@ -2323,25 +2323,32 @@ variables `flymake-fringe-indicator-position' and
   :link '(info-link "(modus-themes) Language checkers"))
 
 (defcustom modus-themes-org-blocks nil
-  "Use a subtle gray or color-coded background for Org blocks.
+  "Set the overall style of Org code blocks, quotes, and the like.
 
-Nil (the default) means that the block has no distinct background
-of its own and uses the one that applies to the rest of the
-buffer.
+Nil (the default) means that the block has no background of its
+own: it uses the one that applies to the rest of the buffer.  In
+this case, the delimiter lines have a gray color for their text,
+making them look exactly like all other Org properties.
 
 Option `gray-background' applies a subtle gray background to the
 block's contents.  It also affects the begin and end lines of the
-block: their background extends to the edge of the window for
-Emacs version >= 27 where the ':extend' keyword is recognized by
-`set-face-attribute' (this is contingent on the variable
-`org-fontify-whole-block-delimiter-line').
+block as they get another shade of gray as their background,
+which differentiates them from the contents of the block.  All
+background colors extend to the edge of the window, giving the
+area a rectangular, \"blocky\" presentation.
 
 Option `tinted-background' uses a slightly colored background for
 the contents of the block.  The exact color will depend on the
 programming language and is controlled by the variable
 `org-src-block-faces' (refer to the theme's source code for the
 current association list).  For this to take effect, the Org
-buffer needs to be restarted with `org-mode-restart'.
+buffer needs to be restarted with `org-mode-restart'.  In this
+scenario, it may be better to inhibit the extension of the
+delimiter lines' background to the edge of the window because Org
+does not provide a mechanism to update their colors depending on
+the contents of the block.  Disable the extension of such
+backgrounds by setting `org-fontify-whole-block-delimiter-line'
+to nil.
 
 Code blocks use their major mode's colors only when the variable
 `org-src-fontify-natively' is non-nil.  While quote/verse blocks
@@ -2353,7 +2360,7 @@ Older versions of the themes provided options `grayscale' (or
 are aliases for `gray-background' and `tinted-background',
 respectively."
   :group 'modus-themes
-  :package-version '(modus-themes . "1.4.0")
+  :package-version '(modus-themes . "2.1.0")
   :version "28.1"
   :type '(choice
           (const :format "[%v] %t\n" :tag "No Org block background (default)" nil)
@@ -3526,8 +3533,9 @@ set to `rainbow'."
     ('gray-background (list :background bg :foreground fg :extend t))
     ('grayscale (list :background bg :foreground fg :extend t))
     ('greyscale (list :background bg :foreground fg :extend t))
+    ('tinted-background (list :background bgaccent :foreground fgaccent :extend nil))
     ('rainbow (list :background bgaccent :foreground fgaccent :extend nil))
-    (_ (list :background bg :foreground fg :extend nil))))
+    (_ (list :foreground fg :extend nil))))
 
 (defun modus-themes--mode-line-attrs
     (fg bg fg-alt bg-alt fg-accent bg-accent border border-3d &optional alt-style fg-distant)