perf(common): rasterize outlined text once instead of nine times (#718)

New draw_text_outlined(draw, xy, text, font, fill, outline_color=(0, 0, 0), offsets=OUTLINE_SQUARE) in src/common/text_helper.py, with OUTLINE_SQUARE and OUTLINE_CROSS. It rasterizes the string once and stamps the mask at each outline offset instead of one draw.text per offset: the same pixels as the nine-draw loop (an equivalence sweep across the bundled fonts, image and font modes, colours and positions pins it, on Windows and Linux), about 8x faster per outlined string. Fractional coordinates, multiline text, fonts other than a plain FreeTypeFont, other image modes and a replaced draw.text take the old loop. SportsCoreSharedMixin._draw_text_with_outline and TextHelper.draw_text_with_outline draw through it; the scoreboards' own game_renderer loops adopt it in a ledmatrix-plugins change after a core release.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/common/README.md

@@ -380,6 +380,19 @@ Created by `DisplayController`; works with any plugin.
 `get_text_dimensions()`, `center_text()`, `wrap_text()`,
 `draw_multiline_text()`, `create_text_image()`.
 
+`draw_text_outlined(draw, xy, text, font, fill, outline_color=(0, 0, 0),
+offsets=OUTLINE_SQUARE)` (Unreleased) draws the text in `outline_color` at
+each offset, then in `fill` on top: the same pixels as one `draw.text` per
+offset, but the string is rasterized once. `OUTLINE_SQUARE` is the
+eight-sided one-pixel outline the scoreboards draw, `OUTLINE_CROSS` the
+four-sided one. Fractional coordinates (a whole-pixel float such as `52.0`
+is fine), multiline text, fonts other than a plain `FreeTypeFont`, image modes
+other than RGB, RGBA and L, and a subclassed or replaced `draw.text` take
+the `draw.text` loop unchanged. `TextHelper.draw_text_with_outline()` and
+the scoreboards' `SportsCoreSharedMixin._draw_text_with_outline()` use it.
+A plugin that also runs on older cores should guard the import and keep its
+own loop as the fallback.
+
 ## Logging
 
 Modules here create their logger with `logging.getLogger(__name__)`, which is