Use the "scaled" font when computing baselines for SVG text

Fredrik Söderquist · chromium-wpt-export-bot · commit 9a5320a17363 · 2019-10-15T16:06:38.000-04:00
The font code (FontMetrics::AscentDescentWithHacks specifically) will (may) mangle (round) the ascent and descent, meaning that for small font-sizes all precision is lost. Using our (potentially) "rescaled" Font for computing the baseline for text gives us a chance to recover some of the precision lost in the rounding process. Bug: 1013859 Change-Id: Ieaadaf558315b8a082331ac76deeb52bcf3b11c9 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1859961 Reviewed-by: Stephen Chenney <schenney@chromium.org> Commit-Queue: Fredrik Söderquist <fs@opera.com> Cr-Commit-Position: refs/heads/master@{#706091}
diff --git a/svg/text/reftests/dominant-baseline-hanging-small-font-size.svg b/svg/text/reftests/dominant-baseline-hanging-small-font-size.svg
@@ -0,0 +1,13 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:h="http://www.w3.org/1999/xhtml">
+  <metadata>
+    <title>'dominant-baseline: hanging' on &#x3c;text&#x3e; with small font-size</title>
+    <h:link rel="help" href="https://svgwg.org/svg2-draft/text.html#TextAnchoringProperties"/>
+    <h:link rel="match" href="../../embedded/reference/green-rect-100x100.svg"/>
+    <h:link rel="stylesheet" type="text/css" href="/fonts/ahem.css"/>
+  </metadata>
+  <rect width="100" height="100" fill="red"/>
+  <svg viewBox="0 0 0.4 0.4" width="100" height="100">
+    <text dominant-baseline="hanging" fill="green"
+          font-size="0.5" font-family="Ahem">X</text>
+  </svg>
+</svg>
