Cheat to go fast, but be careful in debug mode.

Turns out recording actual text metrics is currently really slow.
If we want to compete with the (cheating) status quo, gotta cheat too.

BUG=skia:
R=reed@google.com, robertphillips@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/494483002

diff --git a/src/core/SkRecordDraw.cpp b/src/core/SkRecordDraw.cpp
index e792d37..613c2c0 100644 (file)
--- a/src/core/SkRecordDraw.cpp
+++ b/src/core/SkRecordDraw.cpp
@@ -312,15 +312,23 @@ private:
     }
 
     static void AdjustTextForFontMetrics(SkRect* rect, const SkPaint& paint) {
-        // FIXME: These bounds should be tight (and correct), but reading SkFontMetrics is likely
-        // a performance bottleneck.  It's safe to overapproximate these metrics for speed.  E.g.
-        // fTop <= 1.5 * paint.getTextSize(), fXMax <= 8 * fTop, etc.
+#if SK_DEBUG
+        SkRect correct = *rect;
+#endif
+        const SkScalar yPad = 1.5f * paint.getTextSize(),  // In practice, this seems to be enough.
+                       xPad = 4.0f * yPad;                 // Hack for very wide Github logo font.
+        rect->outset(xPad, yPad);
+#if SK_DEBUG
         SkPaint::FontMetrics metrics;
         paint.getFontMetrics(&metrics);
-        rect->fLeft   += metrics.fXMin;
-        rect->fTop    += metrics.fTop;
-        rect->fRight  += metrics.fXMax;
-        rect->fBottom += metrics.fBottom;
+        correct.fLeft   += metrics.fXMin;
+        correct.fTop    += metrics.fTop;
+        correct.fRight  += metrics.fXMax;
+        correct.fBottom += metrics.fBottom;
+        SkASSERTF(rect->contains(correct), "%f %f %f %f vs. %f %f %f %f\n",
+                  -xPad, -yPad, +xPad, +yPad,
+                  metrics.fXMin, metrics.fTop, metrics.fXMax, metrics.fBottom);
+#endif
     }
 
     // Returns true if rect was meaningfully adjusted for the effects of paint,