feat(html): pause HTML slides with SPACE key (#539)

* feat(html): pause HTML slides with `SPACE` key

Pressing <kbd>SPACE</kbd> key now pauses the slides, instead of skipping it.

* chore(fmt): auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -17,6 +17,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   view is always available. Previously, it was only included if the slides
   had notes.
   [#538](https://github.com/jeertmans/manim-slides/pull/538)
+- Pressing <kbd>SPACE</kbd> key now pauses the slides, instead of skipping it.
+  Previously, it was not possible to pause HTML slides, which can be very annoying
+  when trying to explain something.
+  [#539](https://github.com/jeertmans/manim-slides/pull/539)
   
 (v5.5.0)=
 ## [v5.5.0](https://github.com/jeertmans/manim-slides/compare/v5.4.2...v5.5.0)

manim_slides/templates/revealjs.html

@@ -262,6 +262,23 @@
         // Time before the cursor is hidden (in ms)
         hideCursorTime: {{ hide_cursor_time }}
       });
+      // Override SPACE to play / pause the video
+      Reveal.addKeyBinding(
+        {
+          keyCode: 32,
+          key: 'SPACE',
+          description: 'Play / pause video'
+        },
+        () => {
+          var currentVideos = Reveal.getCurrentSlide().slideBackgroundContentElement.getElementsByTagName("video");
+          if (currentVideos.length > 0) {
+            if (currentVideos[0].paused == true) currentVideos[0].play();
+            else currentVideos[0].pause();
+          } else {
+            Reveal.next();
+          }
+        }
+      );
       {% if one_file %}
       // Fix found by @t-fritsch and @Rapsssito on GitHub
       // see: https://github.com/hakimel/reveal.js/discussions/3362#discussioncomment-11733074.