feat: allow exporting to html (#566)

the main modifications are
- makes every page exist in a separate container
- allows switching pages via left and right arrows
- merges the css from an outside file to directly within the html
- zooms the content to fit the browser width

src/export/exporter.rs

@@ -2,7 +2,7 @@ use crate::{
     MarkdownParser, Resources,
     code::execute::SnippetExecutor,
     config::{KeyBindingsConfig, PauseExportPolicy},
-    export::pdf::PdfRender,
+    export::output::{ExportRenderer, OutputFormat},
     markdown::{parse::ParseError, text_style::Color},
     presentation::{
         Presentation,
@@ -98,24 +98,12 @@ impl<'a> Exporter<'a> {
         Self { parser, default_theme, resources, third_party, code_executor, themes, options, dimensions }
     }
 
-    /// Export the given presentation into PDF.
-    ///
-    /// This uses a separate `presenterm-export` tool.
-    pub fn export_pdf(
-        mut self,
+    fn build_renderer(
+        &mut self,
         presentation_path: &Path,
         output_directory: OutputDirectory,
-        output_path: Option<&Path>,
-    ) -> Result<(), ExportError> {
-        println!(
-            "exporting using rows={}, columns={}, width={}, height={}",
-            self.dimensions.rows, self.dimensions.columns, self.dimensions.width, self.dimensions.height
-        );
-
-        println!("checking for weasyprint...");
-        Self::validate_weasyprint_exists()?;
-        Self::log("weasyprint installation found")?;
-
+        renderer: OutputFormat,
+    ) -> Result<ExportRenderer, ExportError> {
         let content = fs::read_to_string(presentation_path).map_err(ExportError::ReadPresentation)?;
         let elements = self.parser.parse(&content)?;
 
@@ -132,7 +120,7 @@ impl<'a> Exporter<'a> {
         .build(elements)?;
         Self::validate_theme_colors(&presentation)?;
 
-        let mut render = PdfRender::new(self.dimensions, output_directory);
+        let mut render = ExportRenderer::new(self.dimensions.clone(), output_directory, renderer);
         Self::log("waiting for images to be generated and code to be executed, if any...")?;
         Self::render_async_images(&mut presentation);
 
@@ -143,10 +131,32 @@ impl<'a> Exporter<'a> {
         }
         Self::log("invoking weasyprint...")?;
 
+        Ok(render)
+    }
+
+    /// Export the given presentation into PDF.
+    pub fn export_pdf(
+        mut self,
+        presentation_path: &Path,
+        output_directory: OutputDirectory,
+        output_path: Option<&Path>,
+    ) -> Result<(), ExportError> {
+        println!(
+            "exporting using rows={}, columns={}, width={}, height={}",
+            self.dimensions.rows, self.dimensions.columns, self.dimensions.width, self.dimensions.height
+        );
+
+        println!("checking for weasyprint...");
+        Self::validate_weasyprint_exists()?;
+        Self::log("weasyprint installation found")?;
+
+        let render = self.build_renderer(presentation_path, output_directory, OutputFormat::Pdf)?;
+
         let pdf_path = match output_path {
             Some(path) => path.to_path_buf(),
             None => presentation_path.with_extension("pdf"),
         };
+
         render.generate(&pdf_path)?;
 
         execute!(
@@ -158,6 +168,36 @@ impl<'a> Exporter<'a> {
         Ok(())
     }
 
+    /// Export the given presentation into HTML.
+    pub fn export_html(
+        mut self,
+        presentation_path: &Path,
+        output_directory: OutputDirectory,
+        output_path: Option<&Path>,
+    ) -> Result<(), ExportError> {
+        println!(
+            "exporting using rows={}, columns={}, width={}, height={}",
+            self.dimensions.rows, self.dimensions.columns, self.dimensions.width, self.dimensions.height
+        );
+
+        let render = self.build_renderer(presentation_path, output_directory, OutputFormat::Html)?;
+
+        let output_path = match output_path {
+            Some(path) => path.to_path_buf(),
+            None => presentation_path.with_extension("html"),
+        };
+
+        render.generate(&output_path)?;
+
+        execute!(
+            io::stdout(),
+            PrintStyledContent(
+                format!("output file is at {}\n", output_path.display()).stylize().with(Color::Green.into())
+            )
+        )?;
+        Ok(())
+    }
+
     fn render_async_images(presentation: &mut Presentation) {
         let poller = Poller::launch();
         let mut pollables = Vec::new();

src/export/mod.rs

@@ -1,3 +1,3 @@
 pub mod exporter;
 pub(crate) mod html;
-pub(crate) mod pdf;
+pub(crate) mod output;

src/export/output.rs

@@ -39,6 +39,7 @@ struct HtmlSlide {
 impl HtmlSlide {
     fn new(grid: TerminalGrid, content_manager: &mut ContentManager) -> Result<Self, ExportError> {
         let mut rows = Vec::new();
+        rows.push(String::from("<div class=\"container\">"));
         for (y, row) in grid.rows.into_iter().enumerate() {
             let mut finalized_row = "<div class=\"content-line\"><pre>".to_string();
             let mut current_style = row.first().map(|c| c.style).unwrap_or_default();
@@ -73,6 +74,7 @@ impl HtmlSlide {
             finalized_row.push_str("</pre></div>");
             rows.push(finalized_row);
         }
+        rows.push(String::from("</div>"));
 
         Ok(HtmlSlide { rows, background_color: grid.background_color.as_ref().map(color_to_html) })
     }
@@ -122,17 +124,29 @@ impl ContentManager {
     }
 }
 
-pub(crate) struct PdfRender {
+pub(crate) enum OutputFormat {
+    Pdf,
+    Html,
+}
+
+pub(crate) struct ExportRenderer {
     content_manager: ContentManager,
+    output_format: OutputFormat,
     dimensions: WindowSize,
     html_body: String,
     background_color: Option<String>,
 }
 
-impl PdfRender {
-    pub(crate) fn new(dimensions: WindowSize, output_directory: OutputDirectory) -> Self {
+impl ExportRenderer {
+    pub(crate) fn new(dimensions: WindowSize, output_directory: OutputDirectory, output_type: OutputFormat) -> Self {
         let image_manager = ContentManager::new(output_directory);
-        Self { content_manager: image_manager, dimensions, html_body: "".to_string(), background_color: None }
+        Self {
+            content_manager: image_manager,
+            dimensions,
+            html_body: "".to_string(),
+            background_color: None,
+            output_format: output_type,
+        }
     }
 
     pub(crate) fn process_slide(&mut self, slide: Slide) -> Result<(), ExportError> {
@@ -152,19 +166,24 @@ impl PdfRender {
         Ok(())
     }
 
-    pub(crate) fn generate(self, pdf_path: &Path) -> Result<(), ExportError> {
+    pub(crate) fn generate(self, output_path: &Path) -> Result<(), ExportError> {
         let html_body = &self.html_body;
-        let html = format!(
-            r#"<html>
-<head>
-</head>
-<body>
-{html_body}</body>
-</html>"#
-        );
+        let script = include_str!("script.js");
         let width = (self.dimensions.columns as f64 * FONT_SIZE as f64 * FONT_SIZE_WIDTH).ceil();
         let height = self.dimensions.rows * LINE_HEIGHT;
         let background_color = self.background_color.unwrap_or_else(|| "black".into());
+        let container = match self.output_format {
+            OutputFormat::Pdf => String::from("display: contents;"),
+            OutputFormat::Html => String::from(
+                "
+                    width: 100%;
+                    height: 100%;
+                    display: flex;
+                    flex-direction: column;
+                    align-items: center;
+                ",
+            ),
+        };
         let css = format!(
             r"
         pre {{
@@ -180,8 +199,14 @@ impl PdfRender {
             margin: 0;
             font-size: {FONT_SIZE}px;
             line-height: {LINE_HEIGHT}px;
-            background-color: {background_color};
             width: {width}px;
+            height: {height}px;
+            transform-origin: top left;
+            background-color: {background_color};
+        }}
+
+        .container {{
+            {container}
         }}
 
         .content-line {{
@@ -191,25 +216,73 @@ impl PdfRender {
             width: {width}px;
         }}
 
+        .hidden {{
+            display: none;
+        }}
+
         @page {{
             margin: 0;
             height: {height}px;
             width: {width}px;
         }}"
         );
+        let html_script = match self.output_format {
+            OutputFormat::Pdf => String::new(),
+            OutputFormat::Html => {
+                format!(
+                    "
+<script>
+let originalWidth = {width};
+let originalHeight = {height};
+{script}
+</script>"
+                )
+            }
+        };
+        let style = match self.output_format {
+            OutputFormat::Pdf => String::new(),
+            OutputFormat::Html => format!(
+                "
+<head>
+<style>
+{css}
+</style>
+</head>
+                "
+            ),
+        };
+        let html = format!(
+            r"
+<html>
+{style}
+<body>
+{html_body}
+{html_script}
+</body>
+</html>"
+        );
 
         let html_path = self.content_manager.persist_file("index.html", html.as_bytes())?;
         let css_path = self.content_manager.persist_file("styles.css", css.as_bytes())?;
-        ThirdPartyTools::weasyprint(&[
-            "-s",
-            css_path.to_string_lossy().as_ref(),
-            "--presentational-hints",
-            "-e",
-            "utf8",
-            html_path.to_string_lossy().as_ref(),
-            pdf_path.to_string_lossy().as_ref(),
-        ])
-        .run()?;
+
+        match self.output_format {
+            OutputFormat::Pdf => {
+                ThirdPartyTools::weasyprint(&[
+                    "-s",
+                    css_path.to_string_lossy().as_ref(),
+                    "--presentational-hints",
+                    "-e",
+                    "utf8",
+                    html_path.to_string_lossy().as_ref(),
+                    output_path.to_string_lossy().as_ref(),
+                ])
+                .run()?;
+            }
+            OutputFormat::Html => {
+                fs::write(output_path, html.as_bytes())?;
+            }
+        }
+
         Ok(())
     }
 }

src/export/script.js

@@ -0,0 +1,45 @@
+document.addEventListener('DOMContentLoaded', function() {
+  const allLines = document.querySelectorAll('body > div');
+  const pageBreakMarkers = document.querySelectorAll('.container');
+  let currentPageIndex = 0;
+
+
+  function showCurrentPage() {
+    allLines.forEach((line) => {
+      line.classList.add('hidden');
+    });
+
+    allLines[currentPageIndex].classList.remove('hidden');
+  }
+
+
+  function scaler() {
+    var w = document.documentElement.clientWidth;
+    var h = document.documentElement.clientHeight;
+    let widthScaledAmount= w/originalWidth;
+    let heightScaledAmount= h/originalHeight;
+    let scaledAmount = Math.min(widthScaledAmount, heightScaledAmount);
+    document.querySelector("body").style.transform = `scale(${scaledAmount})`;
+  }
+
+  function handleKeyPress(event) {
+    if (event.key === 'ArrowLeft') {
+      if (currentPageIndex > 0) {
+        currentPageIndex--;
+        showCurrentPage();
+      }
+    } else if (event.key === 'ArrowRight') {
+      if (currentPageIndex < pageBreakMarkers.length - 1) {
+        currentPageIndex++;
+        showCurrentPage();
+      }
+    }
+  }
+
+  document.addEventListener('keydown', handleKeyPress);
+  window.addEventListener("resize", scaler);
+
+  scaler();
+  showCurrentPage();
+});
+

src/main.rs

@@ -68,15 +68,19 @@ struct Cli {
     path: Option<PathBuf>,
 
     /// Export the presentation as a PDF rather than displaying it.
-    #[clap(short, long)]
+    #[clap(short, long, group = "export")]
     export_pdf: bool,
 
+    /// Export the presentation as a HTML rather than displaying it.
+    #[clap(long, group = "export")]
+    export_html: bool,
+
     /// The path in which to store temporary files used when exporting.
-    #[clap(long, requires = "export_pdf")]
+    #[clap(long, requires = "export")]
     export_temporary_path: Option<PathBuf>,
 
     /// The output path for the exported PDF.
-    #[clap(short = 'o', long = "output", requires = "export_pdf")]
+    #[clap(short = 'o', long = "output", requires = "export")]
     export_output: Option<PathBuf>,
 
     /// Generate a JSON schema for the configuration file.
@@ -401,7 +405,7 @@ fn run(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
     let parser = MarkdownParser::new(&arena);
     let validate_overflows =
         overflow_validation_enabled(&present_mode, &config.defaults.validate_overflows) || cli.validate_overflows;
-    if cli.export_pdf {
+    if cli.export_pdf || cli.export_html {
         let dimensions = match config.export.dimensions {
             Some(dimensions) => WindowSize {
                 rows: dimensions.rows,
@@ -426,7 +430,11 @@ fn run(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
             Some(path) => OutputDirectory::external(path),
             None => OutputDirectory::temporary(),
         }?;
-        exporter.export_pdf(&path, output_directory, cli.export_output.as_deref())?;
+        if cli.export_pdf {
+            exporter.export_pdf(&path, output_directory, cli.export_output.as_deref())?;
+        } else {
+            exporter.export_html(&path, output_directory, cli.export_output.as_deref())?;
+        }
     } else {
         let SpeakerNotesComponents { events_listener, events_publisher } =
             SpeakerNotesComponents::new(&cli, &config, &path)?;