Expand the separator-line style to work on TTY and graphics as needed (Emacs bug#81754)

Thanks to Dmitry Gutov for suggesting this in Emacs bug#81754:
<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=81754>

doc/modus-themes.info

@@ -6626,19 +6626,19 @@ Ideas and user feedback
      Rellermeyer, Burgess Chang, Charlotte Van Petegem, Christian
      Tietze, Christopher Dimech, Christopher League, Damien Cassou,
      Daniel Mendler, Dario Gjorgjevski, David Edmondson, Davor Rotim,
-     Divan Santana, Dominik Schrempf, Eliraz Kedmi, Emanuele Michele
-     Alberto Monterosso, Eshel Yaron, Farasha Euker, Feng Shu, Filippo
-     Argiolas, Gaston Cabotin, Gautier Ponsinet, Gerry Agbobada,
-     Gianluca Recchia, Gonçalo Marrafa, Guilherme Semente, Gustavo
-     Barros, Hörmetjan Yiltiz, Ilja Kocken, Imran Khan, Iris Garcia,
-     Ivan Popovych, Jabir Ali Ouassou, James Ferguson, JD Smith, Jeremy
-     Friesen, Jerry Zhang, Johannes Grødem, John Haman, John Sullivan,
-     John Wick, Jonas Collberg, Jorge Morais, Joshua O'Connor, Julio C.
-     Villasante, Kenta Usami, Kevin Fleming, Kévin Le Gouguec, Kevin
-     Kainan Li, Kostadin Ninev, Laith Bahodi, Lasse Lindner, Len Trigg,
-     Lennart C. Karssen, Lucas Jimenez, Luis Miguel Castañeda, Magne
-     Hov, Manuel Giraud, Manuel Uberti, Mark Bestley, Mark Burton, Mark
-     Simpson, Marko Kocic, Markus Beppler, Matt Armstrong, Matthias
+     Divan Santana, Dmitry Gutov, Dominik Schrempf, Eliraz Kedmi,
+     Emanuele Michele Alberto Monterosso, Eshel Yaron, Farasha Euker,
+     Feng Shu, Filippo Argiolas, Gaston Cabotin, Gautier Ponsinet, Gerry
+     Agbobada, Gianluca Recchia, Gonçalo Marrafa, Guilherme Semente,
+     Gustavo Barros, Hörmetjan Yiltiz, Ilja Kocken, Imran Khan, Iris
+     Garcia, Ivan Popovych, Jabir Ali Ouassou, James Ferguson, JD Smith,
+     Jeremy Friesen, Jerry Zhang, Johannes Grødem, John Haman, John
+     Sullivan, John Wick, Jonas Collberg, Jorge Morais, Joshua O'Connor,
+     Julio C.  Villasante, Kenta Usami, Kevin Fleming, Kévin Le Gouguec,
+     Kevin Kainan Li, Kostadin Ninev, Laith Bahodi, Lasse Lindner, Len
+     Trigg, Lennart C. Karssen, Lucas Jimenez, Luis Miguel Castañeda,
+     Magne Hov, Manuel Giraud, Manuel Uberti, Mark Bestley, Mark Burton,
+     Mark Simpson, Marko Kocic, Markus Beppler, Matt Armstrong, Matthias
      Fuchs, Mattias Engdegård, Mauro Aranda, Maxime Tréca, Michael
      Goldenberg, Mike Crowe, Morgan Smith, Morgan Willcock, Morten
      Kjeldgaard, Murilo Pereira, Nicky van Foreest, Nicolas De Jaeghere,
@@ -7506,11 +7506,11 @@ Node: Sources of the themes280883
 Node: Issues you can help with281624
 Node: Patches require copyright assignment to the FSF282946
 Node: Acknowledgements285160
-Node: GNU Free Documentation License290090
-Node: Indices315253
-Node: Function index315432
-Node: Variable index320041
-Node: Concept index324618
+Node: GNU Free Documentation License290105
+Node: Indices315268
+Node: Function index315447
+Node: Variable index320056
+Node: Concept index324633
 
 End Tag Table
 

doc/modus-themes.org

@@ -6404,39 +6404,40 @@ The Modus themes are a collective effort.  Every bit of work matters.
   L.{{{space()}}} Contovounesios, Bernd Rellermeyer, Burgess Chang,
   Charlotte Van Petegem, Christian Tietze, Christopher Dimech,
   Christopher League, Damien Cassou, Daniel Mendler, Dario
-  Gjorgjevski, David Edmondson, Davor Rotim, Divan Santana, Dominik
-  Schrempf, Eliraz Kedmi, Emanuele Michele Alberto Monterosso, Eshel
-  Yaron, Farasha Euker, Feng Shu, Filippo Argiolas, Gaston Cabotin,
-  Gautier Ponsinet, Gerry Agbobada, Gianluca Recchia, Gonçalo Marrafa,
-  Guilherme Semente, Gustavo Barros, Hörmetjan Yiltiz, Ilja Kocken,
-  Imran Khan, Iris Garcia, Ivan Popovych, Jabir Ali Ouassou, James
-  Ferguson, JD Smith, Jeremy Friesen, Jerry Zhang, Johannes Grødem,
-  John Haman, John Sullivan, John Wick, Jonas Collberg, Jorge Morais,
-  Joshua O'Connor, Julio C. Villasante, Kenta Usami, Kevin Fleming,
-  Kévin Le Gouguec, Kevin Kainan Li, Kostadin Ninev, Laith Bahodi,
-  Lasse Lindner, Len Trigg, Lennart C.{{{space()}}} Karssen, Lucas
-  Jimenez, Luis Miguel Castañeda, Magne Hov, Manuel Giraud, Manuel
-  Uberti, Mark Bestley, Mark Burton, Mark Simpson, Marko Kocic, Markus
-  Beppler, Matt Armstrong, Matthias Fuchs, Mattias Engdegård, Mauro
-  Aranda, Maxime Tréca, Michael Goldenberg, Mike Crowe, Morgan Smith,
-  Morgan Willcock, Morten Kjeldgaard, Murilo Pereira, Nicky van
-  Foreest, Nicolas De Jaeghere, Nicolas Semrau, Olaf Meeuwissen,
-  Oliver Epper, Pablo Stafforini, Paul Poloskov, Pengji Zhang, Pete
-  Kazmier, Peter Wu, Philip Kaludercic, Pierre Téchoueyres, Pranshu
-  Sharma, Przemysław Kryger, Robert Hepple, Roman Rudakov, Roshan
-  Shariff, Russell Sim, Ryan Phillips, Rytis Paškauskas, Rudolf
-  Adamkovič, Sam Kleinman, Samuel Culpepper, Saša Janiška, Shreyas
-  Ragavan, Simon Pugnet, Stéphane Marks, Steve Downey, Tassilo Horn,
-  Thanos Apollo, Thibaut Verron, Thomas Heartman, Togan Muftuoglu,
-  Tony Zorman, Trey Merkley, Tomasz Hołubowicz, Toon Claes, Troy
-  Brown, Uri Sharf, Utkarsh Singh, Vincent Foley, Yuta Yamamoto,
-  Zoltan Kiraly. As well as users: Ben, CsBigDataHub1, Emacs Contrib,
-  Eugene, Fourchaux, Fredrik, Moesasji, Nick, Summer Emacs, TheBlob42,
-  TitusMu, Trey, aikrahguzar, amano-kenji, baconabo, bangedorrunt,
-  bepolymathe, bit9tream, case-lambda, chainedghost, derek-upham,
-  doolio, fleimgruber, gitrj95, iSeeU, jixiuf, ltmsyvag, okamsn,
-  pedro-nonfree, pRot0ta1p, realazy, shimeike, shipmints, soaringbird,
-  tumashu, vpxyz, wakamenod.
+  Gjorgjevski, David Edmondson, Davor Rotim, Divan Santana, Dmitry
+  Gutov, Dominik Schrempf, Eliraz Kedmi, Emanuele Michele Alberto
+  Monterosso, Eshel Yaron, Farasha Euker, Feng Shu, Filippo Argiolas,
+  Gaston Cabotin, Gautier Ponsinet, Gerry Agbobada, Gianluca Recchia,
+  Gonçalo Marrafa, Guilherme Semente, Gustavo Barros, Hörmetjan
+  Yiltiz, Ilja Kocken, Imran Khan, Iris Garcia, Ivan Popovych, Jabir
+  Ali Ouassou, James Ferguson, JD Smith, Jeremy Friesen, Jerry Zhang,
+  Johannes Grødem, John Haman, John Sullivan, John Wick, Jonas
+  Collberg, Jorge Morais, Joshua O'Connor, Julio C. Villasante, Kenta
+  Usami, Kevin Fleming, Kévin Le Gouguec, Kevin Kainan Li, Kostadin
+  Ninev, Laith Bahodi, Lasse Lindner, Len Trigg, Lennart
+  C.{{{space()}}} Karssen, Lucas Jimenez, Luis Miguel Castañeda, Magne
+  Hov, Manuel Giraud, Manuel Uberti, Mark Bestley, Mark Burton, Mark
+  Simpson, Marko Kocic, Markus Beppler, Matt Armstrong, Matthias
+  Fuchs, Mattias Engdegård, Mauro Aranda, Maxime Tréca, Michael
+  Goldenberg, Mike Crowe, Morgan Smith, Morgan Willcock, Morten
+  Kjeldgaard, Murilo Pereira, Nicky van Foreest, Nicolas De Jaeghere,
+  Nicolas Semrau, Olaf Meeuwissen, Oliver Epper, Pablo Stafforini,
+  Paul Poloskov, Pengji Zhang, Pete Kazmier, Peter Wu, Philip
+  Kaludercic, Pierre Téchoueyres, Pranshu Sharma, Przemysław Kryger,
+  Robert Hepple, Roman Rudakov, Roshan Shariff, Russell Sim, Ryan
+  Phillips, Rytis Paškauskas, Rudolf Adamkovič, Sam Kleinman, Samuel
+  Culpepper, Saša Janiška, Shreyas Ragavan, Simon Pugnet, Stéphane
+  Marks, Steve Downey, Tassilo Horn, Thanos Apollo, Thibaut Verron,
+  Thomas Heartman, Togan Muftuoglu, Tony Zorman, Trey Merkley, Tomasz
+  Hołubowicz, Toon Claes, Troy Brown, Uri Sharf, Utkarsh Singh,
+  Vincent Foley, Yuta Yamamoto, Zoltan Kiraly. As well as users: Ben,
+  CsBigDataHub1, Emacs Contrib, Eugene, Fourchaux, Fredrik, Moesasji,
+  Nick, Summer Emacs, TheBlob42, TitusMu, Trey, aikrahguzar,
+  amano-kenji, baconabo, bangedorrunt, bepolymathe, bit9tream,
+  case-lambda, chainedghost, derek-upham, doolio, fleimgruber,
+  gitrj95, iSeeU, jixiuf, ltmsyvag, okamsn, pedro-nonfree, pRot0ta1p,
+  realazy, shimeike, shipmints, soaringbird, tumashu, vpxyz,
+  wakamenod.
 
 + Packaging :: Basil L.{{{space()}}} Contovounesios, Eli Zaretskii,
   Glenn Morris, Mauro Aranda, Richard Stallman, Stefan Kangas (core

modus-themes.el

@@ -4614,7 +4614,12 @@ If COLOR is unspecified, then return :box unspecified."
     `(rectangle-preview ((,c :background ,bg-active :foreground ,fg-main)))
     `(region ((,c :background ,bg-region :foreground ,fg-region)))
     `(secondary-selection ((,c :background ,bg-hover-secondary :foreground ,fg-main)))
-    `(separator-line ((,c :underline ,bg-active)))
+    `(separator-line
+      ((default :extend t)
+       (((type tty))
+        :foreground ,border :strike-through t)
+       (t
+        :height 1 :background ,border :foreground ,border)))
     `(shadow ((,c :foreground ,fg-dim)))
     `(success ((,c :inherit modus-themes-bold :foreground ,info)))
     `(trailing-whitespace ((,c :background ,bg-space-err)))