Don't let UnderlineSpans affect text width

Previously, text that was partially annotated with an UnderlineSpan
could have a different width than text without it, since underlined
text was separated into a separate piece of text and was measured
separately, causing kerning at the span boundaries to disappear.

Change-Id: I118de8524c500fb6a4b05b1bf65fe93dc67f204c
Bug: 32907446
Test: cts-tradefed run cts-dev --module CtsTextTestCases
Test: manual

1 files changed, 65 insertions, 28 deletions

diff --git a/core/java/android/text/TextLine.java b/core/java/android/text/TextLine.java
index 756e9a0e2f2a..e287bf7741f6 100644
--- a/core/java/android/text/TextLine.java
+++ b/core/java/android/text/TextLine.java
@@ -24,6 +24,8 @@ import android.text.Layout.TabStops;
 import android.text.style.CharacterStyle;
 import android.text.style.MetricAffectingSpan;
 import android.text.style.ReplacementSpan;
+import android.text.style.UnderlineSpan;
+import android.util.IntArray;
 import android.util.Log;
 
 import com.android.internal.util.ArrayUtils;
@@ -66,6 +68,8 @@ class TextLine {
     private final SpanSet<ReplacementSpan> mReplacementSpanSpanSet =
             new SpanSet<ReplacementSpan>(ReplacementSpan.class);
 
+    private final IntArray mUnderlines = new IntArray();
+
     private static final TextLine[] sCached = new TextLine[3];
 
     /**
@@ -695,6 +699,37 @@ class TextLine {
         fmi.leading = Math.max(fmi.leading, previousLeading);
     }
 
+    private static void drawUnderline(TextPaint wp, Canvas c, int color, float thickness,
+            float xstart, float xend, int baseline) {
+        // kStdUnderline_Offset = 1/9, defined in SkTextFormatParams.h
+        final float underlineTop = baseline + wp.baselineShift + (1.0f / 9.0f) * wp.getTextSize();
+
+        final int previousColor = wp.getColor();
+        final Paint.Style previousStyle = wp.getStyle();
+        final boolean previousAntiAlias = wp.isAntiAlias();
+
+        wp.setStyle(Paint.Style.FILL);
+        wp.setAntiAlias(true);
+
+        wp.setColor(color);
+        c.drawRect(xstart, underlineTop, xend, underlineTop + thickness, wp);
+
+        wp.setStyle(previousStyle);
+        wp.setColor(previousColor);
+        wp.setAntiAlias(previousAntiAlias);
+    }
+
+    private float getRunAdvance(TextPaint wp, int start, int end, int contextStart, int contextEnd,
+            boolean runIsRtl, int offset) {
+        if (mCharsValid) {
+            return wp.getRunAdvance(mChars, start, end, contextStart, contextEnd, runIsRtl, offset);
+        } else {
+            final int delta = mStart;
+            return wp.getRunAdvance(mText, delta + start, delta + end,
+                    delta + contextStart, delta + contextEnd, runIsRtl, delta + offset);
+        }
+    }
+
     /**
      * Utility function for measuring and rendering text.  The text must
      * not include a tab.
@@ -734,14 +769,7 @@ class TextLine {
         float ret = 0;
 
         if (needWidth || (c != null && (wp.bgColor != 0 || wp.underlineColor != 0 || runIsRtl))) {
-            if (mCharsValid) {
-                ret = wp.getRunAdvance(mChars, start, end, contextStart, contextEnd,
-                        runIsRtl, offset);
-            } else {
-                int delta = mStart;
-                ret = wp.getRunAdvance(mText, delta + start, delta + end,
-                        delta + contextStart, delta + contextEnd, runIsRtl, delta + offset);
-            }
+            ret = getRunAdvance(wp, start, end, contextStart, contextEnd, runIsRtl, offset);
         }
 
         if (c != null) {
@@ -762,22 +790,23 @@ class TextLine {
             }
 
             if (wp.underlineColor != 0) {
-                // kStdUnderline_Offset = 1/9, defined in SkTextFormatParams.h
-                float underlineTop = y + wp.baselineShift + (1.0f / 9.0f) * wp.getTextSize();
-
-                int previousColor = wp.getColor();
-                Paint.Style previousStyle = wp.getStyle();
-                boolean previousAntiAlias = wp.isAntiAlias();
-
-                wp.setStyle(Paint.Style.FILL);
-                wp.setAntiAlias(true);
-
-                wp.setColor(wp.underlineColor);
-                c.drawRect(x, underlineTop, x + ret, underlineTop + wp.underlineThickness, wp);
+                drawUnderline(wp, c, wp.underlineColor, wp.underlineThickness, x, x + ret, y);
+            }
 
-                wp.setStyle(previousStyle);
-                wp.setColor(previousColor);
-                wp.setAntiAlias(previousAntiAlias);
+            final int numUnderlines = mUnderlines.size();
+            if (numUnderlines != 0) {
+                // kStdUnderline_Thickness = 1/18, defined in SkTextFormatParams.h
+                final float thickness = (1.0f / 18.0f) * wp.getTextSize();
+                for (int i = 0; i < numUnderlines; i += 2) {
+                    final int underlineStart = Math.max(mUnderlines.get(i), start);
+                    final int underlineEnd = Math.min(mUnderlines.get(i + 1), offset);
+                    final float underlineXStart = getRunAdvance(
+                            wp, start, end, contextStart, contextEnd, runIsRtl, underlineStart);
+                    final float underlineXEnd = getRunAdvance(
+                            wp, start, end, contextStart, contextEnd, runIsRtl, underlineEnd);
+                    drawUnderline(wp, c, wp.getColor(), thickness,
+                            underlineXStart, underlineXEnd, y);
+                }
             }
 
             drawTextRun(c, wp, start, end, contextStart, contextEnd, runIsRtl,
@@ -950,19 +979,27 @@ class TextLine {
                 continue;
             }
 
+            mUnderlines.clear();
             for (int j = i, jnext; j < mlimit; j = jnext) {
-                jnext = mCharacterStyleSpanSet.getNextTransition(mStart + j, mStart + inext) -
-                        mStart;
+                jnext = mCharacterStyleSpanSet.getNextTransitionSkipping(
+                            UnderlineSpan.class, mStart + j, mStart + inext
+                        ) - mStart;
                 int offset = Math.min(jnext, mlimit);
 
                 wp.set(mPaint);
                 for (int k = 0; k < mCharacterStyleSpanSet.numberOfSpans; k++) {
+                    final int spanStart = mCharacterStyleSpanSet.spanStarts[k];
+                    final int spanEnd = mCharacterStyleSpanSet.spanEnds[k];
                     // Intentionally using >= and <= as explained above
-                    if ((mCharacterStyleSpanSet.spanStarts[k] >= mStart + offset) ||
-                            (mCharacterStyleSpanSet.spanEnds[k] <= mStart + j)) continue;
+                    if ((spanStart >= mStart + offset) || (spanEnd <= mStart + j)) continue;
 
                     CharacterStyle span = mCharacterStyleSpanSet.spans[k];
-                    span.updateDrawState(wp);
+                    if (span.getClass() == UnderlineSpan.class) {
+                        mUnderlines.add(spanStart);
+                        mUnderlines.add(spanEnd);
+                    } else {
+                        span.updateDrawState(wp);
+                    }
                 }
 
                 wp.setHyphenEdit(adjustHyphenEdit(j, jnext, wp.getHyphenEdit()));