Add support for explicit tabs and newlines.

core/src/html/layout.rs

@@ -194,6 +194,14 @@ impl<'a, 'gc> LayoutContext<'a, 'gc> {
         }
     }
 
+    /// Adjust the text layout cursor down to the next line in response to an
+    /// explicit newline.
+    fn explicit_newline(&mut self, mc: MutationContext<'gc, '_>) {
+        self.newline(mc);
+
+        self.is_first_line = true;
+    }
+
     /// Adjust the text layout cursor down to the next line.
     ///
     /// This function will also adjust any layout boxes on the current line to
@@ -212,6 +220,30 @@ impl<'a, 'gc> LayoutContext<'a, 'gc> {
         self.has_line_break = true;
     }
 
+    /// Adjust the text layout cursor in response to a tab.
+    ///
+    /// Tabs can do two separate things in Flash, depending on whether or not
+    /// tab stops have been manually determined. If they have been, then the
+    /// text cursor goes to the next closest tab stop that has not yet been
+    /// passed, or if no such stop exists, tabs do nothing. If no tab stops
+    /// exist, then the cursor is advanced to some position modulo the natural
+    /// tab index.
+    fn tab(&mut self) {
+        if self.current_line_span.tab_stops.is_empty() {
+            let modulo_factor = Twips::from_pixels(self.current_line_span.size * 2.75);
+            let stop_modulo_tab =
+                ((self.cursor.x().get() / modulo_factor.get()) + 1) * modulo_factor.get();
+            self.cursor.set_x(Twips::new(stop_modulo_tab));
+        } else {
+            for stop in self.current_line_span.tab_stops.iter() {
+                let twips_stop = Twips::from_pixels(*stop);
+                if twips_stop > self.cursor.x() {
+                    self.cursor.set_x(twips_stop);
+                }
+            }
+        }
+    }
+
     /// Enter a new span.
     fn newspan(&mut self, first_span: &TextSpan) {
         if self.current_line.is_none() {
@@ -435,12 +467,31 @@ impl<'gc> LayoutBox<'gc> {
     ) -> (Option<GcCell<'gc, LayoutBox<'gc>>>, BoxBounds<Twips>) {
         let mut layout_context = LayoutContext::new(bounds, fs.text());
 
-        for (start, _end, text, span) in fs.iter_spans() {
+        for (span_start, _end, span_text, span) in fs.iter_spans() {
             if let Some(font) = layout_context.resolve_font(context, movie.clone(), &span) {
                 layout_context.newspan(span);
 
                 let font_size = Twips::from_pixels(span.size);
                 let letter_spacing = Twips::from_pixels(span.letter_spacing);
+
+                for text in span_text.split(&['\n', '\t'][..]) {
+                    let slice_start = text.as_ptr() as usize - span_text.as_ptr() as usize;
+                    let delimiter = if slice_start > 0 {
+                        span_text
+                            .get(slice_start - 1..)
+                            .and_then(|s| s.chars().next())
+                    } else {
+                        None
+                    };
+
+                    match delimiter {
+                        Some('\n') => layout_context.explicit_newline(context.gc_context),
+                        Some('\t') => layout_context.tab(),
+                        _ => {}
+                    }
+
+                    let start = span_start + slice_start;
+
                     let mut last_breakpoint = 0;
 
                     if is_word_wrap {
@@ -508,6 +559,7 @@ impl<'gc> LayoutBox<'gc> {
                     }
                 }
             }
+        }
 
         layout_context.end_layout(context.gc_context)
     }