Support configureable width and height of reveal presentations (#2104)

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

nbconvert/exporters/slides.py

@@ -168,6 +168,24 @@ def _reveal_url_prefix_default(self):
         """,
     ).tag(config=True)
 
+    reveal_width = Unicode(
+        "",
+        help="""
+        width used to determine the aspect ratio of your presentation.
+        Use the horizontal pixels available on your inteded presentation
+        equpment.
+        """,
+    ).tag(config=True)
+
+    reveal_height = Unicode(
+        "",
+        help="""
+        height used to determine the aspect ratio of your presentation.
+        Use the horizontal pixels available on your inteded presentation
+        equpment.
+        """,
+    ).tag(config=True)
+
     font_awesome_url = Unicode(
         "https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.css",
         help="""
@@ -186,4 +204,6 @@ def _init_resources(self, resources):
         resources["reveal"]["transition"] = self.reveal_transition
         resources["reveal"]["scroll"] = self.reveal_scroll
         resources["reveal"]["number"] = self.reveal_number
+        resources["reveal"]["height"] = self.reveal_height
+        resources["reveal"]["width"] = self.reveal_width
         return resources

share/templates/reveal/index.html.j2

@@ -6,6 +6,8 @@
 {% set reveal_theme = resources.reveal.theme | default('white', true) %}
 {% set reveal_transition = resources.reveal.transition | default('slide', true) %}
 {% set reveal_number = resources.reveal.number | default('', true) %}
+{% set reveal_width = resources.reveal.width | default('960', true) %}
+{% set reveal_height = resources.reveal.height | default('700', true) %}
 {% set reveal_scroll = resources.reveal.scroll | default(false, true) | json_dumps %}
 
 {%- block header -%}
@@ -154,7 +156,10 @@ require(
             history: true,
             transition: "{{reveal_transition}}",
             slideNumber: "{{reveal_number}}",
-            plugins: [RevealNotes]
+            plugins: [RevealNotes],
+            width: {{reveal_width}},
+			      height: {{reveal_height}},
+
         });
 
         var update = function(event){