Improve horizontal baseline detection.

The goal is to hint the baseline when hinting is possible, which is
to say when the glyphs are be aligned with the pixel grid. The
current code has three shortcomings.

1. correctly snaps when the horizontal baseline is on the x-axis but
not when on the y-axis. Instead it is snapping the horizontal
baseline when there is y-skew.

2. tests against the full device matrix instead of the relaxed
matrix used by the scaler context.

3. has range issues when relaxing the matrix.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1740163002

Review URL: https://codereview.chromium.org/1740163002

1 files changed, 13 insertions, 16 deletions

diff --git a/src/core/SkScalerContext.h b/src/core/SkScalerContext.h
index 302698ee4e..9249bfb2a9 100644
--- a/src/core/SkScalerContext.h
+++ b/src/core/SkScalerContext.h
@@ -20,6 +20,12 @@ class SkMaskFilter;
 class SkPathEffect;
 class SkRasterizer;
 
+enum SkAxisAlignment {
+    kNone_SkAxisAlignment,
+    kX_SkAxisAlignment,
+    kY_SkAxisAlignment
+};
+
 /*
  *  To allow this to be forward-declared, it must be its own typename, rather
  *  than a nested struct inside SkScalerContext (where it started).
@@ -245,6 +251,13 @@ public:
 
     const Rec& getRec() const { return fRec; }
 
+    /**
+    *  Return the axis (if any) that the baseline for horizontal text should land on.
+    *  As an example, the identity matrix will return kX_SkAxisAlignment
+    */
+    SkAxisAlignment computeAxisAlignmentForHText();
+
+
 protected:
     Rec         fRec;
 
@@ -340,22 +353,6 @@ private:
 
 ///////////////////////////////////////////////////////////////////////////////
 
-enum SkAxisAlignment {
-    kNone_SkAxisAlignment,
-    kX_SkAxisAlignment,
-    kY_SkAxisAlignment
-};
-
-/**
- *  Return the axis (if any) that the baseline for horizontal text will land on
- *  after running through the specified matrix.
- *
- *  As an example, the identity matrix will return kX_SkAxisAlignment
- */
-SkAxisAlignment SkComputeAxisAlignmentForHText(const SkMatrix& matrix);
-
-///////////////////////////////////////////////////////////////////////////////
-
 SkPaint::Hinting SkScalerContextRec::getHinting() const {
     unsigned hint = (fFlags & SkScalerContext::kHinting_Mask) >>
                                             SkScalerContext::kHinting_Shift;