SkTypeface: fix non-determinism on AdvacedMetrics

Calculate fStemV and fCapHeight using SkPaint in SkPDFFont if needed.

Change-Id: Iaf762e6c44178fac659dfe9fa312d0caed9138ae
Reviewed-on: https://skia-review.googlesource.com/21535
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/pdf/SkPDFFont.cpp b/src/pdf/SkPDFFont.cpp
index f94dba7080..8fd833e716 100644
--- a/src/pdf/SkPDFFont.cpp
+++ b/src/pdf/SkPDFFont.cpp
@@ -156,6 +156,34 @@ const SkAdvancedTypefaceMetrics* SkPDFFont::GetMetrics(SkTypeface* typeface,
     if (!metrics) {
         metrics = skstd::make_unique<SkAdvancedTypefaceMetrics>();
     }
+
+    if (0 == metrics->fStemV || 0 == metrics->fCapHeight) {
+        SkPaint tmpPaint;
+        tmpPaint.setHinting(SkPaint::kNo_Hinting);
+        tmpPaint.setTypeface(sk_ref_sp(typeface));
+        tmpPaint.setTextSize(1000);  // glyph coordinate system
+        if (0 == metrics->fStemV) {
+            // Figure out a good guess for StemV - Min width of i, I, !, 1.
+            // This probably isn't very good with an italic font.
+            int16_t stemV = SHRT_MAX;
+            for (char c : {'i', 'I', '!', '1'}) {
+                SkRect bounds;
+                tmpPaint.measureText(&c, 1, &bounds);
+                stemV = SkTMin(stemV, SkToS16(SkScalarRoundToInt(bounds.width())));
+            }
+            metrics->fStemV = stemV;
+        }
+        if (0 == metrics->fCapHeight) {
+            // Figure out a good guess for CapHeight: average the height of M and X.
+            SkScalar capHeight = 0;
+            for (char c : {'M', 'X'}) {
+                SkRect bounds;
+                tmpPaint.measureText(&c, 1, &bounds);
+                capHeight += bounds.height();
+            }
+            metrics->fCapHeight = SkToS16(SkScalarRoundToInt(capHeight / 2));
+        }
+    }
     return canon->fTypefaceMetrics.set(id, std::move(metrics))->get();
 }