feat: report all caption render errors instead of stopping on first error

pycaption/exceptions.py

@@ -48,3 +48,9 @@ class CaptionRendererError(Exception):
     Error raised when caption content cannot be rendered correctly,
     e.g. text runs off screen or required glyphs are missing from the font.
     """
+
+
+class CaptionRendererErrorGroup(ExceptionGroup):
+    """
+    Exception group which contains multiple :class:`CaptionRenderError` instances.
+    """

pycaption/subtitler_image_based.py

@@ -10,7 +10,7 @@
 from langcodes import Language, tag_distance
 
 from pycaption.base import BaseWriter, CaptionSet, Caption, CaptionNode, CaptionList
-from pycaption.exceptions import CaptionRendererError
+from pycaption.exceptions import CaptionRendererError, CaptionRendererErrorGroup
 from pycaption.geometry import UnitEnum, Size
 
 
@@ -211,17 +211,26 @@ def write_images(
         fnt = ImageFont.truetype(fnt, font_size)
         index = 1
 
+        # Try to render all images and collect all exceptions
+        image_exceptions = []
         for i, cap_list in enumerate(caps_final):
             # Create RGBA image with transparent background
             img = Image.new('RGBA', (self.video_width, self.video_height), (0, 0, 0, 0))
             draw = ImageDraw.Draw(img)
-            self.printLine(draw, cap_list, fnt, position, align)
+            try:
+                self.printLine(draw, cap_list, fnt, position, align)
+            except CaptionRendererError as e:
+                image_exceptions.append(e)
+                continue
 
             # Pass RGBA image to subclass - each subclass converts as needed
             self.save_image(tmpDir, index, img)
 
             index = index + 1
 
+        if len(image_exceptions) > 0:
+            raise CaptionRendererErrorGroup("Errors while rendering captions", image_exceptions)
+
         return caps_final, overlapping
 
     def printLine(self, draw: ImageDraw, caption_list: Caption, fnt: ImageFont, position: str = 'bottom',
@@ -298,7 +307,7 @@ def printLine(self, draw: ImageDraw, caption_list: Caption, fnt: ImageFont, posi
             if text_left < 0 or text_top < 0 or text_right > self.video_width or (
                     position != 'bottom' and text_bottom > self.video_height):
                 raise CaptionRendererError(
-                    f'Text runs off screen: text="{text}"'
+                    f'Text at {caption.format_start()} runs off screen: text="{text}"'
                 )
 
             border = (*self.borderColor, 255)  # Add alpha for RGBA

tests/test_subtitler_image_based.py

@@ -6,8 +6,8 @@
 from PIL import Image, ImageDraw, ImageFont
 
 from pycaption import SRTReader
-from pycaption.base import Caption, CaptionNode
-from pycaption.exceptions import CaptionRendererError
+from pycaption.base import Caption, CaptionList, CaptionNode
+from pycaption.exceptions import CaptionRendererError, CaptionRendererErrorGroup
 from pycaption.filtergraph import FiltergraphWriter
 from pycaption.geometry import Layout, Point, Size, UnitEnum
 from pycaption.subtitler_image_based import SubtitleImageBasedWriter
@@ -19,9 +19,9 @@
 )
 
 
-def make_caption(text, layout_info=None):
+def make_caption(text, layout_info=None, start=0):
     nodes = [CaptionNode.create_text(text)]
-    return Caption(0, 1000000, nodes, layout_info=layout_info)
+    return Caption(start, start+1000000, nodes, layout_info=layout_info)
 
 
 def make_source_layout(x_pct, y_pct):
@@ -47,7 +47,7 @@ def test_long_text_runs_off(self):
         writer, draw = make_writer_and_draw(200, 100)
         fnt = ImageFont.truetype(FONT_PATH, 20)
         caption = make_caption("This text is way too long to fit on a tiny screen")
-        with pytest.raises(CaptionRendererError, match="Text runs off screen"):
+        with pytest.raises(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"):
             writer.printLine(draw, [caption], fnt, position='bottom', align='center')
 
 
@@ -62,7 +62,7 @@ def test_long_text_runs_off(self):
         writer, draw = make_writer_and_draw(200, 100)
         fnt = ImageFont.truetype(FONT_PATH, 20)
         caption = make_caption("This text is way too long to fit on a tiny screen")
-        with pytest.raises(CaptionRendererError, match="Text runs off screen"):
+        with pytest.raises(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"):
             writer.printLine(draw, [caption], fnt, position='bottom', align='left')
 
 
@@ -77,7 +77,7 @@ def test_long_text_runs_off(self):
         writer, draw = make_writer_and_draw(200, 100)
         fnt = ImageFont.truetype(FONT_PATH, 20)
         caption = make_caption("This text is way too long to fit on a tiny screen")
-        with pytest.raises(CaptionRendererError, match="Text runs off screen"):
+        with pytest.raises(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"):
             writer.printLine(draw, [caption], fnt, position='bottom', align='right')
 
 
@@ -95,7 +95,7 @@ def test_right_sticks_out(self):
         fnt = ImageFont.truetype(FONT_PATH, 20)
         layout = make_source_layout(x_pct=80, y_pct=50)
         caption = make_caption("This text sticks out on the right", layout_info=layout)
-        with pytest.raises(CaptionRendererError, match="Text runs off screen"):
+        with pytest.raises(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"):
             writer.printLine(draw, [caption], fnt, position='source', align='left')
 
     def test_left_sticks_out(self):
@@ -105,9 +105,30 @@ def test_left_sticks_out(self):
         fnt = ImageFont.truetype(FONT_PATH, 20)
         layout = make_source_layout(x_pct=10, y_pct=50)
         caption = make_caption("This text sticks out on the left", layout_info=layout)
-        with pytest.raises(CaptionRendererError, match="Text runs off screen"):
+        with pytest.raises(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"):
             writer.printLine(draw, [caption], fnt, position='source', align='left')
 
+    def test_exception_group(self, tmp_path):
+        """
+        The main ``write_images`` interface collects all exceptions and reports them in a ``CaptionRendererErrorGroup``.
+        """
+        # 200px wide screen, text at x=80% (x=160), text wider than remaining space
+        writer, draw = make_writer_and_draw(200, 200)
+        layout = make_source_layout(x_pct=80, y_pct=50)
+        cap_list = CaptionList(
+            [
+                make_caption("This text sticks out on the right 1", layout_info=layout),
+                make_caption("This text sticks out on the right 2", layout_info=layout, start=2000000)
+            ],
+            layout
+        )
+        with pytest.RaisesGroup(
+            pytest.RaisesExc(CaptionRendererError, match="Text at 00:00:00.000 runs off screen"),
+            pytest.RaisesExc(CaptionRendererError, match="Text at 00:00:02.000 runs off screen"),
+        ) as rg:
+            writer.write_images(cap_list, "en", str(tmp_path), position='source', align='left')
+        assert isinstance(rg.value, CaptionRendererErrorGroup), "Should be wrapped in a CaptionRendererErrorGroup"
+
 
 class TestBaselineAlignment:
     """Render subtitle images with/without descenders to visually verify