SCC: caption management refactoring (#395)

Author: valnoel

src/main/python/ttconv/scc/content.py renamed to src/main/python/ttconv/scc/caption_line.py

@@ -23,31 +23,33 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-"""SCC caption content"""
+"""SCC caption line"""
 
 from __future__ import annotations
 
-import copy
 import logging
-from typing import Optional, List, Union
+from typing import List, Union
 
-from ttconv.time_code import SmpteTimeCode
+from ttconv.scc.caption_text import SccCaptionText
 
 LOGGER = logging.getLogger(__name__)
 
-ROLL_UP_BASE_ROW = 15
-
 
 class SccCaptionLine:
   """Caption paragraph line"""
 
+  @staticmethod
+  def default():
+    """Initializes a default caption paragraph line"""
+    return SccCaptionLine(0, 0)
+
   def __init__(self, row: int, indent: int):
-    self._texts: List[SccCaptionText] = []
     self._row: int = row  # Row in the active area
     self._indent: int = indent  # Indentation in the active area
 
     self._cursor: int = 0  # Position of the cursor on the line
-    self._current_text: Optional[SccCaptionText] = None  # Text content where the cursor is
+    self._current_text: SccCaptionText = SccCaptionText()  # Text content where the cursor is
+    self._texts: List[SccCaptionText] = [self._current_text]
 
   def add_text(self, text: Union[SccCaptionText, str]):
     """Add text to line"""
@@ -58,42 +60,40 @@ def add_text(self, text: Union[SccCaptionText, str]):
       self._cursor = self.get_length()
 
     elif isinstance(text, str):
+      remaining_text = text
 
-      if self._current_text is None:
-        # Initialize a new text element if necessary
-        self._texts.append(SccCaptionText(text))
-        self._current_text = self._texts[-1]
-        self._cursor = self._current_text.get_length()
-
-      else:
-        remaining_text = text
-
-        # While the cursor is not on the last text element, and some text remains
-        while self._current_text is not self._texts[-1] and len(remaining_text) > 0:
-          available = self._current_text.get_length() - self.get_current_text().get_cursor()
-          text_to_write = remaining_text[:available]
+      # While the cursor is not on the last text element, and some text remains
+      while self._current_text is not self._texts[-1] and len(remaining_text) > 0:
+        available = self._current_text.get_length() - self._current_text.get_cursor()
+        text_to_write = remaining_text[:available]
 
-          # Replace current text element content
-          self._current_text.append(text_to_write)
-          self.set_cursor(self._cursor + len(text_to_write))
-          remaining_text = remaining_text[available:]
+        # Replace current text element content
+        self._append_text(text_to_write)
+        remaining_text = remaining_text[available:]
 
-        # If some text remains on the last text element
-        if len(remaining_text) > 0:
-          assert self._current_text is self._texts[-1]
+      # If some text remains on the last text element
+      if len(remaining_text) > 0:
+        assert self._current_text is self._texts[-1]
 
-          # Replace and append to current text element content
-          self._current_text.append(remaining_text)
-          self.set_cursor(self._cursor + len(remaining_text))
+        # Replace and append to current text element content
+        self._append_text(remaining_text)
 
     else:
       raise ValueError("Unsupported text type for SCC caption line")
 
+  def _append_text(self, text: str):
+    """Appends text and update cursor position"""
+    self._current_text.append(text)
+    if self._cursor < 0:
+      self._cursor = 0
+
+    self.set_cursor(self._cursor + len(text))
+
   def indent(self, indent: int):
     """Indent current line"""
     self._indent += indent
 
-  def get_current_text(self) -> Optional[SccCaptionText]:
+  def get_current_text(self) -> SccCaptionText:
     """Returns current text content"""
     return self._current_text
 
@@ -142,24 +142,26 @@ def get_indent(self) -> int:
   def clear(self):
     """Clears the line text contents"""
     self._texts.clear()
-    self._current_text = None
+    self._current_text = SccCaptionText()
+    self._texts = [self._current_text]
     self.set_cursor(0)
 
   def is_empty(self) -> bool:
     """Returns whether the line text is empty or not"""
-    # no caption texts or an empty text
-    return len(self._texts) == 0 or (len(self._texts) == 1 and self._texts[-1].get_text() == "")
+    return self.get_length() == 0
 
   def get_leading_spaces(self) -> int:
     """Returns the number of leading space characters of the line"""
     index = 0
     leading_spaces = 0
-    first_text = self.get_texts()[index].get_text()
 
-    while first_text.isspace() and index < len(self.get_texts()):
-      leading_spaces += len(first_text)
-      index += 1
+    while index < len(self.get_texts()):
       first_text = self.get_texts()[index].get_text()
+      if first_text.isspace():
+        leading_spaces += len(first_text)
+        index += 1
+      else:
+        break
 
     return leading_spaces + len(first_text) - len(first_text.lstrip())
 
@@ -178,81 +180,3 @@ def get_trailing_spaces(self) -> int:
 
   def __repr__(self):
     return "<" + self.__class__.__name__ + " " + str(self.__dict__) + ">"
-
-
-class SccCaptionText:
-  """Caption text content with specific positional, temporal and styling attributes"""
-
-  def __init__(self, text: Optional[str] = ""):
-    self._begin: Optional[SmpteTimeCode] = None
-    self._end: Optional[SmpteTimeCode] = None
-    self._style_properties = {}
-    self._text: str = ""
-    self._cursor = 0  # Cursor in the text
-
-    if text is not None and text != "":
-      self.append(text)
-
-  def set_begin(self, time_code: SmpteTimeCode):
-    """Sets begin time code"""
-    self._begin = copy.copy(time_code)
-
-  def get_begin(self) -> SmpteTimeCode:
-    """Returns the begin time code"""
-    return self._begin
-
-  def set_end(self, time_code: SmpteTimeCode):
-    """Sets end time code"""
-    self._end = copy.copy(time_code)
-
-  def get_end(self) -> SmpteTimeCode:
-    """Returns the end time code"""
-    return self._end
-
-  def get_text(self) -> str:
-    """Returns the text"""
-    return self._text
-
-  def get_length(self) -> int:
-    """Returns text length"""
-    return len(self._text)
-
-  def is_empty(self) -> bool:
-    """Returns whether the text is empty or not"""
-    return self.get_length() == 0
-
-  def append(self, text: str):
-    """Add or replace text content at cursor position"""
-    # print("Append text: ", text, "to", self._text, "at", self._cursor)
-    self._text = self._text[:self._cursor] + text + self._text[(self._cursor + len(text)):]
-    self._cursor += len(text)
-    # print("\t=>", self._text, ", cursor:", self._cursor)
-
-  def set_cursor_at(self, position: int):
-    """Set text cursor position"""
-    self._cursor = position
-
-  def get_cursor(self) -> int:
-    """Returns the cursor position"""
-    return self._cursor
-
-  def backspace(self):
-    """Remove last character"""
-    self._text = self._text[:-1]
-
-  def get_style_properties(self) -> dict:
-    """Sets the style properties map"""
-    return self._style_properties
-
-  def add_style_property(self, style_property, value):
-    """Adds a style property"""
-    if value is None:
-      return
-    self._style_properties[style_property] = value
-
-  def has_same_style_properties(self, other):
-    """Returns whether the current text has the same style properties as the other text"""
-    return self._style_properties == other.get_style_properties()
-
-  def __repr__(self):
-    return "<" + self.__class__.__name__ + " " + str(self.__dict__) + ">"

src/main/python/ttconv/scc/paragraph.py renamed to src/main/python/ttconv/scc/caption_paragraph.py

@@ -32,8 +32,9 @@
 from typing import Optional, List, Dict, Union
 
 from ttconv.model import Region, ContentDocument, P, Br, Span, Text
-from ttconv.scc.content import SccCaptionText, SccCaptionLine
-from ttconv.scc.style import SccCaptionStyle
+from ttconv.scc.caption_line import SccCaptionLine
+from ttconv.scc.caption_style import SccCaptionStyle
+from ttconv.scc.caption_text import SccCaptionText
 from ttconv.scc.utils import get_position_from_offsets, get_extent_from_dimensions, convert_cells_to_percentages
 from ttconv.style_properties import CoordinateType, ExtentType, StyleProperties, LengthType, DisplayAlignType, ShowBackgroundType, \
   TextAlignType, NamedColors
@@ -51,6 +52,11 @@
 class SccCaptionParagraph:
   """Caption paragraph"""
 
+  @staticmethod
+  def default(caption_style: SccCaptionStyle = SccCaptionStyle.Unknown):
+    """Initializes a default caption paragraph"""
+    return SccCaptionParagraph(caption_style=caption_style)
+
   def __init__(self, safe_area_x_offset: int = 0, safe_area_y_offset: int = 0,
                caption_style: SccCaptionStyle = SccCaptionStyle.Unknown):
     self._caption_id: str = ""
@@ -69,6 +75,8 @@ def __init__(self, safe_area_x_offset: int = 0, safe_area_y_offset: int = 0,
     self._current_line: Optional[SccCaptionLine] = None
     # Lines per row in the active area (will be separated by line-breaks)
     self._caption_lines: Dict[int, SccCaptionLine] = {}
+    # Initialize first default line
+    self.new_caption_line()
 
     self._caption_style: SccCaptionStyle = caption_style
     self._style_properties = {}
@@ -85,15 +93,15 @@ def set_begin(self, time_code):
     """Sets caption begin time code"""
     self._begin = copy.copy(time_code)
 
-  def get_begin(self) -> SmpteTimeCode:
+  def get_begin(self) -> Optional[SmpteTimeCode]:
     """Returns the caption begin time code"""
     return self._begin
 
   def set_end(self, time_code):
     """Sets caption end time code"""
     self._end = copy.copy(time_code)
 
-  def get_end(self) -> SmpteTimeCode:
+  def get_end(self) -> Optional[SmpteTimeCode]:
     """Returns the caption end time code"""
     return self._end
 
@@ -105,18 +113,20 @@ def get_safe_area_y_offset(self):
     """Returns the safe area y offset"""
     return self._safe_area_y_offset
 
+  def set_caption_style(self, caption_style: SccCaptionStyle):
+    """Sets the caption style"""
+    self._caption_style = caption_style
+
   def get_caption_style(self) -> SccCaptionStyle:
     """Returns the caption style"""
     return self._caption_style
 
-  def get_current_line(self) -> Optional[SccCaptionLine]:
+  def get_current_line(self) -> SccCaptionLine:
     """Returns the current caption line"""
     return self._current_line
 
-  def get_current_text(self) -> Optional[SccCaptionText]:
+  def get_current_text(self) -> SccCaptionText:
     """Returns the current caption text"""
-    if self._current_line is None:
-      return None
     return self._current_line.get_current_text()
 
   def append_text(self, text: str):
@@ -150,9 +160,14 @@ def get_style_property(self, style_property) -> Optional:
   def set_cursor_at(self, row: int, indent: Optional[int] = None):
     """Set cursor position and initialize a new line if necessary"""
 
-    # Remove current line if empty (useless)
-    if self._current_line is not None and self._current_line.is_empty():
-      del self._caption_lines[self._current_line.get_row()]
+    if self._caption_lines.get(self._current_line.get_row()) is not None:
+      # Set current line if necessary
+      if self._caption_lines.get(self._current_line.get_row()) is not self._current_line:
+        self._current_line = self._caption_lines.get(self._current_line.get_row())
+
+      # Remove current line if empty (i.e. useless)
+      if self._current_line.is_empty():
+        del self._caption_lines[self._current_line.get_row()]
 
     self._cursor = (row, indent if indent is not None else 0)
 
@@ -162,7 +177,7 @@ def set_cursor_at(self, row: int, indent: Optional[int] = None):
     self._current_line = self._caption_lines.get(row)
 
     if indent is not None:
-      self._current_line.set_cursor(self._cursor[1] - self._current_line.get_indent())
+      self._update_current_line_cursor()
 
   def get_cursor(self) -> (int, int):
     """Returns cursor coordinates"""
@@ -176,12 +191,29 @@ def indent_cursor(self, indent: int):
       # If the current line is empty, set cursor indent as a line tabulation
       self._current_line.indent(indent)
     else:
-      self._current_line.set_cursor(self._cursor[1] - self._current_line.get_indent())
+      self._update_current_line_cursor()
+
+  def _update_current_line_cursor(self):
+    """Updates cursor position on current line"""
+    new_cursor_position = self._cursor[1] - self._current_line.get_indent()
+
+    if new_cursor_position < 0:
+      self._current_line.indent(new_cursor_position)
+
+    self._current_line.set_cursor(new_cursor_position)
 
   def get_lines(self) -> Dict[int, SccCaptionLine]:
     """Returns the paragraph lines per row"""
     return self._caption_lines
 
+  def is_empty(self) -> bool:
+    """Returns whether the paragraph has no content"""
+    return self._get_length() == 0
+
+  def _get_length(self) -> int:
+    """Returns the total length of contained text"""
+    return sum([line.get_length() for line in self._caption_lines.values()])
+
   def copy_lines(self) -> Dict[int, SccCaptionLine]:
     """Copy paragraph lines (without time attributes)"""
     lines_copy = {}
@@ -199,10 +231,6 @@ def copy_lines(self) -> Dict[int, SccCaptionLine]:
 
   def new_caption_text(self):
     """Appends a new caption text content, and keeps reference on it"""
-    if self._current_line is None:
-      LOGGER.warning("Add a new caption line to add new caption text")
-      self.new_caption_line()
-
     self._current_line.add_text(SccCaptionText())
 
   def new_caption_line(self):
@@ -227,7 +255,7 @@ def roll_up(self):
 
   def get_origin(self) -> CoordinateType:
     """Computes and returns the current paragraph origin, based on its content"""
-    if len(self._caption_lines) > 0:
+    if not self.is_empty():
       x_offsets = [text.get_indent() for text in self._caption_lines.values()]
       y_offsets = [text.get_row() - 1 for text in self._caption_lines.values()]
 
@@ -237,7 +265,7 @@ def get_origin(self) -> CoordinateType:
 
   def get_extent(self) -> ExtentType:
     """Computes and returns the current paragraph extent, based on its content"""
-    if len(self._caption_lines) == 0:
+    if self.is_empty():
       return get_extent_from_dimensions(0, 0)
 
     paragraph_rows = self._caption_lines.keys()
@@ -260,6 +288,9 @@ def guess_text_alignment(self) -> TextAlignType:
     def get_line_right_offset(line: SccCaptionLine) -> int:
       return SCC_ROOT_CELL_RESOLUTION_COLUMNS - (line.get_indent() + line.get_length())
 
+    if self.is_empty():
+      return TextAlignType.start
+
     # look for longest line
     longest_line = max(self._caption_lines.values(), key=lambda line: line.get_length())