Fix inconsistent Vegas scroll transition gaps caused by plugin-baked padding

src/vegas_mode/plugin_adapter.py

@@ -279,6 +279,19 @@ def _get_scroll_helper_content(
             # Copy the image to prevent modification
             img = cached_image.copy()
 
+            # Plugins that build their own ticker image via this shared
+            # ScrollHelper's create_scrolling_image() get a solid-black
+            # leading margin exactly `display_width` columns wide baked in
+            # (scroll_helper.py's "initial gap before first item"). Vegas mode
+            # adds its own leading gap/separator around every item already,
+            # so leaving this in stacks a second, uncontrolled blank margin on
+            # top of vegas_scroll.separator_width — making this plugin's
+            # transitions look inconsistent with plugins that provide content
+            # via get_vegas_content() (which carries no such margin). Strip it
+            # here so every plugin contributes only its real content and the
+            # gap between items is governed solely by separator_width.
+            img = self._strip_scroll_padding(img, scroll_helper, plugin_id)
+
             # Ensure correct height
             if img.height != self.display_height:
                 logger.info(
@@ -306,6 +319,69 @@ def _get_scroll_helper_content(
             logger.exception("[%s] Error getting scroll_helper content", plugin_id)
             return None
 
+    def _strip_scroll_padding(
+        self, img: Image.Image, scroll_helper: Any, plugin_id: str
+    ) -> Image.Image:
+        """
+        Crop off a plugin's own leading/trailing blank margins, if present.
+
+        create_scrolling_image() always pads the *start* of its cached image
+        with exactly `scroll_helper.display_width` columns of solid black
+        (0, 0, 0) ("initial gap before first item"). Some ticker-style plugins
+        also pad the *end* of their own cached image (e.g. so their standalone
+        display exits cleanly before looping). Vegas mode already adds its own
+        gap/separator around every item, so either margin left in place stacks
+        an extra, uncontrolled blank stretch on top of `separator_width` —
+        only when running inside Vegas mode does this matter, since the
+        plugin's own standalone display still wants that margin. Detect solid
+        black margins up to `scroll_helper.display_width` wide on each edge and
+        crop them here. Images built via set_scrolling_image() (no such
+        margins) are left untouched.
+
+        Args:
+            img: Captured scroll_helper.cached_image (already copied)
+            scroll_helper: The plugin's ScrollHelper instance
+            plugin_id: Plugin identifier for logging
+
+        Returns:
+            img, cropped on whichever edge(s) had a matching blank margin
+        """
+        pad_width = getattr(scroll_helper, 'display_width', None)
+        if not isinstance(pad_width, int) or pad_width <= 0 or pad_width >= img.width:
+            return img
+
+        def is_solid_black(strip: Image.Image) -> bool:
+            return strip.convert('RGB').getextrema() == ((0, 0), (0, 0), (0, 0))
+
+        left = pad_width if is_solid_black(img.crop((0, 0, pad_width, img.height))) else 0
+        right = (
+            pad_width
+            if is_solid_black(img.crop((img.width - pad_width, 0, img.width, img.height)))
+            else 0
+        )
+
+        if not left and not right:
+            return img
+
+        # Degenerate case (e.g. an all-black cached image): don't crop past
+        # zero width, just leave the image as-is.
+        if left + right >= img.width:
+            return img
+
+        cropped = img.crop((left, 0, img.width - right, img.height))
+
+        # Both edges matching at once is a much stronger signal of genuine
+        # baked-in padding than a single edge (which has a small chance of
+        # coinciding with real all-black content, e.g. a dark logo touching
+        # one boundary). Log that case at warning level so an unexpected
+        # double-edge crop is easy to spot in the field.
+        log = logger.warning if (left and right) else logger.info
+        log(
+            "[%s] Stripping scroll_helper padding (left=%dpx, right=%dpx): %dpx -> %dpx",
+            plugin_id, left, right, img.width, cropped.width
+        )
+        return cropped
+
     def _trigger_scroll_content_generation(
         self, plugin: 'BasePlugin', plugin_id: str, scroll_helper: Any
     ) -> Optional[Image.Image]:

test/test_vegas_plugin_adapter.py

@@ -0,0 +1,138 @@
+"""
+Tests for src/vegas_mode/plugin_adapter.py
+
+Covers PluginAdapter._strip_scroll_padding(): the heuristic that crops a
+plugin's own baked-in leading/trailing blank margins before Vegas mode
+composites the content, so vegas_scroll.separator_width is the only gap
+applied between items.
+"""
+
+import logging
+
+import pytest
+from PIL import Image
+
+from src.common.scroll_helper import ScrollHelper
+from src.vegas_mode.plugin_adapter import PluginAdapter
+
+
+class FakeDisplayManager:
+    width = 64
+    height = 32
+
+
+class FakePlugin:
+    def __init__(self, scroll_helper):
+        self.scroll_helper = scroll_helper
+
+
+@pytest.fixture
+def adapter():
+    return PluginAdapter(FakeDisplayManager())
+
+
+def _solid(width: int, height: int, color: tuple) -> Image.Image:
+    """Create a solid-color RGB image of the given dimensions."""
+    return Image.new('RGB', (width, height), color)
+
+
+class TestStripScrollPadding:
+    def test_leading_pad_from_create_scrolling_image_is_stripped(self, adapter):
+        sh = ScrollHelper(64, 32)
+        item = _solid(40, 32, (200, 50, 50))
+        sh.create_scrolling_image([item], item_gap=10, element_gap=0)
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+        assert images[0].width == 40
+        assert images[0].getpixel((0, 0)) == (200, 50, 50)
+
+    def test_leading_and_trailing_pad_both_stripped(self, adapter):
+        sh = ScrollHelper(64, 32)
+        content_w = 80
+        full = _solid(64 + content_w + 64, 32, (0, 0, 0))
+        full.paste(_solid(content_w, 32, (10, 220, 30)), (64, 0))
+        sh.set_scrolling_image(full)
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+        assert images[0].width == content_w
+        assert images[0].getpixel((0, 0)) == (10, 220, 30)
+        assert images[0].getpixel((content_w - 1, 0)) == (10, 220, 30)
+
+    def test_leading_only_pad_stripped_trailing_content_kept(self, adapter):
+        sh = ScrollHelper(64, 32)
+        content_w = 80
+        full = _solid(64 + content_w, 32, (0, 0, 0))
+        full.paste(_solid(content_w, 32, (5, 5, 250)), (64, 0))
+        sh.set_scrolling_image(full)
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+        assert images[0].width == content_w
+        assert images[0].getpixel((0, 0)) == (5, 5, 250)
+
+    def test_trailing_only_pad_stripped_leading_content_kept(self, adapter):
+        sh = ScrollHelper(64, 32)
+        content_w = 80
+        full = _solid(content_w + 64, 32, (0, 0, 0))
+        full.paste(_solid(content_w, 32, (5, 5, 250)), (0, 0))
+        sh.set_scrolling_image(full)
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+        assert images[0].width == content_w
+        assert images[0].getpixel((0, 0)) == (5, 5, 250)
+
+    def test_no_margin_image_left_untouched(self, adapter):
+        sh = ScrollHelper(64, 32)
+        raw = _solid(150, 32, (5, 5, 5))
+        raw.paste(_solid(50, 32, (123, 45, 67)), (0, 0))
+        sh.set_scrolling_image(raw)
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "no_margin")
+        assert images[0].width == 150
+
+    def test_degenerate_all_black_image_left_untouched(self, adapter):
+        sh = ScrollHelper(64, 32)
+        sh.set_scrolling_image(_solid(50, 32, (0, 0, 0)))
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "all_black")
+        assert images[0].width == 50
+
+    def test_missing_display_width_attribute_left_untouched(self, adapter):
+        sh = ScrollHelper(64, 32)
+        item = _solid(40, 32, (200, 50, 50))
+        sh.create_scrolling_image([item], item_gap=10, element_gap=0)
+        original_width = sh.cached_image.width
+        del sh.display_width
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+        assert images[0].width == original_width
+
+    def test_pad_width_not_smaller_than_image_left_untouched(self, adapter):
+        sh = ScrollHelper(64, 32)
+        sh.set_scrolling_image(_solid(64, 32, (0, 0, 0)))
+
+        images = adapter._get_scroll_helper_content(FakePlugin(sh), "narrow")
+        assert images[0].width == 64
+
+    def test_both_edges_matching_logs_warning(self, adapter, caplog):
+        sh = ScrollHelper(64, 32)
+        content_w = 80
+        full = _solid(64 + content_w + 64, 32, (0, 0, 0))
+        full.paste(_solid(content_w, 32, (10, 220, 30)), (64, 0))
+        sh.set_scrolling_image(full)
+
+        with caplog.at_level(logging.WARNING, logger="src.vegas_mode.plugin_adapter"):
+            adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+
+        assert any("Stripping scroll_helper padding" in r.message for r in caplog.records)
+
+    def test_single_edge_match_logs_info_not_warning(self, adapter, caplog):
+        sh = ScrollHelper(64, 32)
+        item = _solid(40, 32, (200, 50, 50))
+        sh.create_scrolling_image([item], item_gap=10, element_gap=0)
+
+        with caplog.at_level(logging.INFO, logger="src.vegas_mode.plugin_adapter"):
+            adapter._get_scroll_helper_content(FakePlugin(sh), "ticker")
+
+        strip_records = [r for r in caplog.records if "Stripping scroll_helper padding" in r.message]
+        assert len(strip_records) == 1
+        assert strip_records[0].levelno == logging.INFO