feat: allow letting pauses become new slides when exporting (#557)

This introduces the config property `export.pauses` which when defaults
to `ignore` but when set to `new_slide` causes the PDF export to contain
a new slide every time a pause is found.

Closes #555

config-file-schema.json

@@ -133,6 +133,14 @@
               "type": "null"
             }
           ]
+        },
+        "pauses": {
+          "description": "Whether pauses should create new slides.",
+          "allOf": [
+            {
+              "$ref": "#/definitions/PauseExportPolicy"
+            }
+          ]
         }
       },
       "additionalProperties": false
@@ -495,6 +503,25 @@
       },
       "additionalProperties": false
     },
+    "PauseExportPolicy": {
+      "description": "The policy for pauses when exporting.",
+      "oneOf": [
+        {
+          "description": "Whether to ignore pauses.",
+          "type": "string",
+          "enum": [
+            "ignore"
+          ]
+        },
+        {
+          "description": "Create a new slide when a pause is found.",
+          "type": "string",
+          "enum": [
+            "new_slide"
+          ]
+        }
+      ]
+    },
     "SlideTransitionConfig": {
       "type": "object",
       "required": [

src/config.rs

@@ -497,6 +497,22 @@ impl Default for SpeakerNotesConfig {
 pub struct ExportConfig {
     /// The dimensions to use for presentation exports.
     pub dimensions: Option<ExportDimensionsConfig>,
+
+    /// Whether pauses should create new slides.
+    #[serde(default)]
+    pub pauses: PauseExportPolicy,
+}
+
+/// The policy for pauses when exporting.
+#[derive(Clone, Debug, Default, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields, rename_all = "snake_case")]
+pub enum PauseExportPolicy {
+    /// Whether to ignore pauses.
+    #[default]
+    Ignore,
+
+    /// Create a new slide when a pause is found.
+    NewSlide,
 }
 
 /// The dimensions to use for presentation exports.

src/export/exporter.rs

@@ -1,7 +1,7 @@
 use crate::{
     MarkdownParser, Resources,
     code::execute::SnippetExecutor,
-    config::KeyBindingsConfig,
+    config::{KeyBindingsConfig, PauseExportPolicy},
     export::pdf::PdfRender,
     markdown::{parse::ParseError, text_style::Color},
     presentation::{
@@ -81,10 +81,15 @@ impl<'a> Exporter<'a> {
         themes: Themes,
         mut options: PresentationBuilderOptions,
         mut dimensions: WindowSize,
+        pause_policy: PauseExportPolicy,
     ) -> Self {
         // We don't want dynamically highlighted code blocks.
         options.allow_mutations = false;
         options.theme_options.font_size_supported = true;
+        options.pause_create_new_slide = match pause_policy {
+            PauseExportPolicy::Ignore => false,
+            PauseExportPolicy::NewSlide => true,
+        };
 
         // Make sure we have a 1:2 aspect ratio.
         let width = (0.5 * dimensions.columns as f64) / (dimensions.rows as f64 / dimensions.height as f64);
@@ -130,6 +135,7 @@ impl<'a> Exporter<'a> {
         let mut render = PdfRender::new(self.dimensions, output_directory);
         Self::log("waiting for images to be generated and code to be executed, if any...")?;
         Self::render_async_images(&mut presentation);
+
         for (index, slide) in presentation.into_slides().into_iter().enumerate() {
             let index = index + 1;
             Self::log(&format!("processing slide {index}..."))?;

src/main.rs

@@ -282,6 +282,7 @@ impl CoreComponents {
             theme_options: ThemeOptions { font_size_supported: TerminalEmulator::capabilities().font_size },
             pause_before_incremental_lists: config.defaults.incremental_lists.pause_before.unwrap_or(true),
             pause_after_incremental_lists: config.defaults.incremental_lists.pause_after.unwrap_or(true),
+            pause_create_new_slide: false,
         }
     }
 
@@ -415,6 +416,7 @@ fn run(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
             themes,
             builder_options,
             dimensions,
+            config.export.pauses,
         );
         let output_directory = match cli.export_temporary_path {
             Some(path) => OutputDirectory::external(path),

src/presentation/builder/mod.rs

@@ -71,6 +71,7 @@ pub struct PresentationBuilderOptions {
     pub theme_options: ThemeOptions,
     pub pause_before_incremental_lists: bool,
     pub pause_after_incremental_lists: bool,
+    pub pause_create_new_slide: bool,
 }
 
 impl PresentationBuilderOptions {
@@ -111,6 +112,7 @@ impl Default for PresentationBuilderOptions {
             theme_options: ThemeOptions { font_size_supported: false },
             pause_before_incremental_lists: true,
             pause_after_incremental_lists: true,
+            pause_create_new_slide: false,
         }
     }
 }
@@ -608,6 +610,12 @@ impl<'a> PresentationBuilder<'a> {
     }
 
     fn push_pause(&mut self) {
+        if self.options.pause_create_new_slide {
+            let operations = self.chunk_operations.clone();
+            self.terminate_slide();
+            self.chunk_operations = operations;
+            return;
+        }
         self.slide_state.last_chunk_ended_in_list = matches!(self.slide_state.last_element, LastElement::List { .. });
 
         let chunk_operations = mem::take(&mut self.chunk_operations);
@@ -1736,6 +1744,18 @@ theme:
         assert_eq!(slides[0].iter_chunks().count(), 1);
     }
 
+    #[test]
+    fn pause_new_slide() {
+        let elements = vec![
+            MarkdownElement::Paragraph(vec![Line::from("hi")]),
+            MarkdownElement::Comment { comment: "pause".into(), source_position: Default::default() },
+            MarkdownElement::Paragraph(vec![Line::from("bye")]),
+        ];
+        let options = PresentationBuilderOptions { pause_create_new_slide: true, ..Default::default() };
+        let slides = build_presentation_with_options(elements, options).into_slides();
+        assert_eq!(slides.len(), 2);
+    }
+
     #[test]
     fn skip_slide() {
         let elements = vec![

src/presentation/mod.rs

@@ -298,7 +298,7 @@ impl Slide {
         self.current_chunk().reset_mutations();
     }
 
-    fn show_all_chunks(&mut self) {
+    pub(crate) fn show_all_chunks(&mut self) {
         self.visible_chunks = self.chunks.len();
         for chunk in &self.chunks {
             chunk.apply_all_mutations();