Fix that TextLine overwrites wordSpcing on paint

TextLine is using wordSpcing for justification. And previously,
TextLine will overwrite wordSpcing even justification is not on.
This CL make sure that TextLine only changes wordSpcing when
justification is on.

Bug: 122471618
Test: atest TextLineTest
Change-Id: I6f1e2f6c17b65f92d7a5bb064fdafbf5df9ef8f7

core/java/android/text/StaticLayout.java

@@ -376,9 +376,13 @@ public class StaticLayout extends Layout {
          * Set paragraph justification mode. The default value is
          * {@link Layout#JUSTIFICATION_MODE_NONE}. If the last line is too short for justification,
          * the last line will be displayed with the alignment set by {@link #setAlignment}.
+         * When Justification mode is JUSTIFICATION_MODE_INTER_WORD, wordSpacing on the given
+         * {@link Paint} will be ignored. This behavior also affects Spans which change the
+         * wordSpacing.
          *
          * @param justificationMode justification mode for the paragraph.
          * @return this builder, useful for chaining.
+         * @see Paint#setWordSpacing(float)
          */
         @NonNull
         public Builder setJustificationMode(@JustificationMode int justificationMode) {

core/java/android/text/TextLine.java

@@ -75,8 +75,9 @@ public class TextLine {
     private int mEllipsisEnd;
 
     // Additional width of whitespace for justification. This value is per whitespace, thus
-    // the line width will increase by mAddedWidth x (number of stretchable whitespaces).
-    private float mAddedWidth;
+    // the line width will increase by mAddedWidthForJustify x (number of stretchable whitespaces).
+    private float mAddedWidthForJustify;
+    private boolean mIsJustifying;
 
     private final TextPaint mWorkPaint = new TextPaint();
     private final TextPaint mActivePaint = new TextPaint();
@@ -229,7 +230,8 @@ public class TextLine {
             }
         }
         mTabs = tabStops;
-        mAddedWidth = 0;
+        mAddedWidthForJustify = 0;
+        mIsJustifying = false;
 
         mEllipsisStart = ellipsisStart != ellipsisEnd ? ellipsisStart : 0;
         mEllipsisEnd = ellipsisStart != ellipsisEnd ? ellipsisEnd : 0;
@@ -255,7 +257,8 @@ public class TextLine {
             return;
         }
         final float width = Math.abs(measure(end, false, null));
-        mAddedWidth = (justifyWidth - width) / spaces;
+        mAddedWidthForJustify = (justifyWidth - width) / spaces;
+        mIsJustifying = true;
     }
 
     /**
@@ -713,7 +716,9 @@ public class TextLine {
 
         TextPaint wp = mWorkPaint;
         wp.set(mPaint);
-        wp.setWordSpacing(mAddedWidth);
+        if (mIsJustifying) {
+            wp.setWordSpacing(mAddedWidthForJustify);
+        }
 
         int spanStart = runStart;
         int spanLimit;
@@ -849,7 +854,9 @@ public class TextLine {
             FontMetricsInt fmi, boolean needWidth, int offset,
             @Nullable ArrayList<DecorationInfo> decorations) {
 
-        wp.setWordSpacing(mAddedWidth);
+        if (mIsJustifying) {
+            wp.setWordSpacing(mAddedWidthForJustify);
+        }
         // Get metrics first (even for empty strings or "0" width runs)
         if (fmi != null) {
             expandMetricsFromPaint(fmi, wp);

core/tests/coretests/src/android/text/TextLineTest.java

@@ -253,6 +253,18 @@ public class TextLineTest {
                 new float[]{0.0f, -10.0f, -10.0f, -100.0f, -110.0f, -110.0f});
     }
 
+    @Test
+    public void testMeasure_wordSpacing() {
+        final TextPaint paint = new TextPaint();
+        paint.setTypeface(TYPEFACE);
+        paint.setTextSize(10.0f);  // make 1em = 10px
+        paint.setWordSpacing(10.0f);
+
+        TextLine tl = getTextLine("I I", paint);
+        assertMeasurements(tl, 3, false,
+                new float[]{0.0f, 10.0f, 120.0f, 130.0f});
+    }
+
     @Test
     public void testHandleRun_ellipsizedReplacementSpan_isSkipped() {
         final Spannable text = new SpannableStringBuilder("This is a... text");