Initial pass at accelerating processing of large documents

Author: palemieux

src/main/python/ttconv/isd.py

@@ -199,12 +199,17 @@ def _region_always_has_background(region: typing.Type[model.Region]) -> bool:
       return False
 
     bg_color: styles.ColorType = region.get_style(styles.StyleProperties.BackgroundColor)
+    if bg_color is None:
+      bg_color = region.get_doc().get_initial_value(styles.StyleProperties.BackgroundColor);
     if bg_color is not None:
       if bg_color.ident is not styles.ColorType.Colorimetry.RGBA8:
         raise RuntimeError(f"Unsupported colorimetry system: {bg_color.ident}")
 
       if bg_color.components[3] == 0:
         return False
+    else:
+      # no background color specified, so transparent
+      return False
 
     return True
 

src/test/python/test_isd_cache.py

@@ -27,6 +27,7 @@
 
 # pylint: disable=R0201,C0115,C0116
 
+from fractions import Fraction
 import unittest
 from ttconv.isd import ISD
 import ttconv.model as model
@@ -37,6 +38,34 @@
 
 class ISDCacheTests(unittest.TestCase):
 
+  def test_large_number_of_regions(self):
+    doc = model.ContentDocument()
+    body = model.Body(doc)
+    doc.set_body(body)
+
+    for i in range(1000):
+      r_id = "r" + str(i)
+      r = model.Region(r_id, doc)
+      doc.put_region(r)
+
+      div = model.Div(doc)
+      div.set_region(r)
+      body.push_child(div)
+
+      p = model.P(doc)
+      p.set_begin(Fraction(2*i))
+      p.set_end(Fraction(2*i + 1))
+      div.push_child(p)
+
+      span = model.Span(doc)
+      span.push_child(model.Text(doc, f"div {i} content"))
+      p.push_child(span)
+
+    sig_times = ISD.significant_times(doc)
+
+    for t in sig_times:
+      ISD.from_model(doc, t, sig_times)
+
   def test_show_background(self):
     ttml_doc = """<tt xml:lang="en"
     xmlns="http://www.w3.org/ns/ttml"