Calculate line breaks using Minikin

This patch moves the calculation of line breaks for StaticLayout into
the new LineBreaker class provided by Minikin. This specific patch
should preserve existing functionality, but perhaps performance is
better, and the movement opens the door to much more sophisticated
line-breaking.

Change-Id: Iafccb9da4e3559bbeaeb2c7c85f86ddfd8ae2fa1

2 files changed, 34 insertions, 26 deletions

diff --git a/core/java/android/text/Layout.java b/core/java/android/text/Layout.java
index fcf1828..928bf16 100644
--- a/core/java/android/text/Layout.java
+++ b/core/java/android/text/Layout.java
@@ -1153,7 +1153,10 @@ public abstract class Layout {
                 return end - 1;
             }
 
-            if (ch != ' ' && ch != '\t') {
+            // Note: keep this in sync with Minikin LineBreaker::isLineEndSpace()
+            if (!(ch == ' ' || ch == '\t' || ch == 0x1680 ||
+                    (0x2000 <= ch && ch <= 0x200A && ch != 0x2007) ||
+                    ch == 0x205F || ch == 0x3000)) {
                 break;
             }
 
diff --git a/core/java/android/text/StaticLayout.java b/core/java/android/text/StaticLayout.java
index ee39e27..b47418f 100644
--- a/core/java/android/text/StaticLayout.java
+++ b/core/java/android/text/StaticLayout.java
@@ -170,8 +170,9 @@ public class StaticLayout extends Layout {
          * Measurement and break iteration is done in native code. The protocol for using
          * the native code is as follows.
          *
-         * For each paragraph, do a nSetText of the paragraph text. Then, for each run within the
-         * paragraph:
+         * For each paragraph, do a nSetText of the paragraph text. Also do nSetLineWidth.
+         *
+         * Then, for each run within the paragraph:
          *  - setLocale (this must be done at least for the first run, optional afterwards)
          *  - one of the following, depending on the type of run:
          *    + addStyleRun (a text run, to be measured in native code)
@@ -459,7 +460,26 @@ public class StaticLayout extends Layout {
             byte[] chdirs = measured.mLevels;
             int dir = measured.mDir;
             boolean easy = measured.mEasy;
-            nSetText(b.mNativePtr, chs, paraEnd - paraStart);
+
+            // tab stop locations
+            int[] variableTabStops = null;
+            if (spanned != null) {
+                TabStopSpan[] spans = getParagraphSpans(spanned, paraStart,
+                        paraEnd, TabStopSpan.class);
+                if (spans.length > 0) {
+                    int[] stops = new int[spans.length];
+                    for (int i = 0; i < spans.length; i++) {
+                        stops[i] = spans[i].getTabStop();
+                    }
+                    Arrays.sort(stops, 0, stops.length);
+                    variableTabStops = stops;
+                }
+            }
+
+            int breakStrategy = 0;  // 0 = kBreakStrategy_Greedy
+            nSetupParagraph(b.mNativePtr, chs, paraEnd - paraStart,
+                    firstWidth, firstWidthLineCount, restWidth,
+                    variableTabStops, TAB_INCREMENT, breakStrategy);
 
             // measurement has to be done before performing line breaking
             // but we don't want to recompute fontmetrics or span ranges the
@@ -505,25 +525,9 @@ public class StaticLayout extends Layout {
                 spanEndCacheCount++;
             }
 
-            // tab stop locations
-            int[] variableTabStops = null;
-            if (spanned != null) {
-                TabStopSpan[] spans = getParagraphSpans(spanned, paraStart,
-                        paraEnd, TabStopSpan.class);
-                if (spans.length > 0) {
-                    int[] stops = new int[spans.length];
-                    for (int i = 0; i < spans.length; i++) {
-                        stops[i] = spans[i].getTabStop();
-                    }
-                    Arrays.sort(stops, 0, stops.length);
-                    variableTabStops = stops;
-                }
-            }
-
             nGetWidths(b.mNativePtr, widths);
-            int breakCount = nComputeLineBreaks(b.mNativePtr, paraEnd - paraStart, firstWidth,
-                    firstWidthLineCount, restWidth, variableTabStops, TAB_INCREMENT, false, lineBreaks,
-                    lineBreaks.breaks, lineBreaks.widths, lineBreaks.flags, lineBreaks.breaks.length);
+            int breakCount = nComputeLineBreaks(b.mNativePtr, lineBreaks, lineBreaks.breaks,
+                    lineBreaks.widths, lineBreaks.flags, lineBreaks.breaks.length);
 
             int[] breaks = lineBreaks.breaks;
             float[] lineWidths = lineBreaks.widths;
@@ -966,7 +970,10 @@ public class StaticLayout extends Layout {
     private static native void nFinishBuilder(long nativePtr);
     private static native void nSetLocale(long nativePtr, String locale);
 
-    private static native void nSetText(long nativePtr, char[] text, int length);
+    // Set up paragraph text and settings; done as one big method to minimize jni crossings
+    private static native void nSetupParagraph(long nativePtr, char[] text, int length,
+            float firstWidth, int firstWidthLineCount, float restWidth,
+            int[] variableTabStops, int defaultTabStop, int breakStrategy);
 
     private static native float nAddStyleRun(long nativePtr, long nativePaint,
             long nativeTypeface, int start, int end, boolean isRtl);
@@ -983,9 +990,7 @@ public class StaticLayout extends Layout {
     // the arrays inside the LineBreaks objects are passed in as well
     // to reduce the number of JNI calls in the common case where the
     // arrays do not have to be resized
-    private static native int nComputeLineBreaks(long nativePtr,
-            int length, float firstWidth, int firstWidthLineCount, float restWidth,
-            int[] variableTabStops, int defaultTabStop, boolean optimize, LineBreaks recycle,
+    private static native int nComputeLineBreaks(long nativePtr, LineBreaks recycle,
             int[] recycleBreaks, float[] recycleWidths, boolean[] recycleFlags, int recycleLength);
 
     private int mLineCount;