TextLayoutCache - fix diacritics composition

- normalize (with ICU) each BiDi run before shaping them

We are normalizing by "chuncks" and starting from the end of the string. Each "chunck"
is composed of the main code point and its associated diacritics.

Fix bug #5738435 TextLayoutCache should be able to take care about diacritics during shaping

Change-Id: I7288027a7fa8eafb8b9f38d449625be60214548a

1 files changed, 76 insertions, 8 deletions

diff --git a/core/jni/android/graphics/TextLayoutCache.cpp b/core/jni/android/graphics/TextLayoutCache.cpp
index 81bf4d5..fac3679 100644
--- a/core/jni/android/graphics/TextLayoutCache.cpp
+++ b/core/jni/android/graphics/TextLayoutCache.cpp
@@ -19,6 +19,8 @@
 #include "TextLayoutCache.h"
 #include "TextLayout.h"
 #include "SkFontHost.h"
+#include <unicode/unistr.h>
+#include <unicode/normlzr.h>
 
 extern "C" {
   #include "harfbuzz-unicode.h"
@@ -503,7 +505,8 @@ void TextLayoutEngine::computeValues(SkPaint* paint, const UChar* chars,
 static void logGlyphs(HB_ShaperItem shaperItem) {
     LOGD("         -- glyphs count=%d", shaperItem.num_glyphs);
     for (size_t i = 0; i < shaperItem.num_glyphs; i++) {
-        LOGD("         -- glyph[%d] = %d, offset.x = %f, offset.y = %f", i, shaperItem.glyphs[i],
+        LOGD("         -- glyph[%d] = %d, offset.x = %0.2f, offset.y = %0.2f", i,
+                shaperItem.glyphs[i],
                 HBFixedToFloat(shaperItem.offsets[i].x),
                 HBFixedToFloat(shaperItem.offsets[i].y));
     }
@@ -519,8 +522,73 @@ void TextLayoutEngine::computeRunValues(SkPaint* paint, const UChar* chars,
         return;
     }
 
+    UErrorCode error = U_ZERO_ERROR;
+    bool useNormalizedString = false;
+    for (ssize_t i = count - 1; i >= 0; --i) {
+        UChar ch1 = chars[i];
+        if (::ublock_getCode(ch1) == UBLOCK_COMBINING_DIACRITICAL_MARKS) {
+            // So we have found a diacritic, let's get now the main code point which is paired
+            // with it. As we can have several diacritics in a row, we need to iterate back again
+#if DEBUG_GLYPHS
+            LOGD("The BiDi run '%s' is containing a Diacritic at position %d",
+                    String8(chars, count).string(), int(i));
+#endif
+            ssize_t j = i - 1;
+            for (; j >= 0;  --j) {
+                UChar ch2 = chars[j];
+                if (::ublock_getCode(ch2) != UBLOCK_COMBINING_DIACRITICAL_MARKS) {
+                    break;
+                }
+            }
+
+            // We could not found the main code point, so we will just use the initial chars
+            if (j < 0) {
+                break;
+            }
+
+#if DEBUG_GLYPHS
+            LOGD("Found main code point at index %d", int(j));
+#endif
+            // We found the main code point, so we can normalize the "chunck" and fill
+            // the remaining with ZWSP so that the Paint.getTextWidth() APIs will still be able
+            // to get one advance per char
+            mBuffer.remove();
+            Normalizer::normalize(UnicodeString(chars + j, i - j + 1),
+                    UNORM_NFC, 0 /* no options */, mBuffer, error);
+            if (U_SUCCESS(error)) {
+                if (!useNormalizedString) {
+                    useNormalizedString = true;
+                    mNormalizedString.setTo(false /* not terminated*/, chars, count);
+                }
+                // Set the normalized chars
+                for (ssize_t k = j; k < j + mBuffer.length(); ++k) {
+                    mNormalizedString.setCharAt(k, mBuffer.charAt(k - j));
+                }
+                // Fill the remain part with ZWSP (ZWNJ and ZWJ would lead to weird results
+                // because some fonts are missing those glyphs)
+                for (ssize_t k = j + mBuffer.length(); k <= i; ++k) {
+                    mNormalizedString.setCharAt(k, UNICODE_ZWSP);
+                }
+            }
+            i = j - 1;
+        }
+    }
+
+#if DEBUG_GLYPHS
+    if (useNormalizedString) {
+        LOGD("Will use normalized string '%s', length = %d",
+                    String8(mNormalizedString.getTerminatedBuffer(),
+                            mNormalizedString.length()).string(),
+                    mNormalizedString.length());
+    } else {
+        LOGD("Normalization cannot be done, using initial string");
+    }
+#endif
+
+    assert(mNormalizedString.length() == count);
+
     // Set the string properties
-    mShaperItem.string = chars;
+    mShaperItem.string = useNormalizedString ? mNormalizedString.getTerminatedBuffer() : chars;
     mShaperItem.stringLength = count;
 
     // Define shaping paint properties
@@ -532,14 +600,14 @@ void TextLayoutEngine::computeRunValues(SkPaint* paint, const UChar* chars,
 
     // Split the BiDi run into Script runs. Harfbuzz will populate the pos, length and script
     // into the shaperItem
-    ssize_t indexFontRun = isRTL ? count - 1 : 0;
+    ssize_t indexFontRun = isRTL ? mShaperItem.stringLength - 1 : 0;
     unsigned numCodePoints = 0;
     jfloat totalAdvance = 0;
     while ((isRTL) ?
-            hb_utf16_script_run_prev(&numCodePoints, &mShaperItem.item, chars,
-                    count, &indexFontRun):
-            hb_utf16_script_run_next(&numCodePoints, &mShaperItem.item, chars,
-                    count, &indexFontRun)) {
+            hb_utf16_script_run_prev(&numCodePoints, &mShaperItem.item, mShaperItem.string,
+                    mShaperItem.stringLength, &indexFontRun):
+            hb_utf16_script_run_next(&numCodePoints, &mShaperItem.item, mShaperItem.string,
+                    mShaperItem.stringLength, &indexFontRun)) {
 
         ssize_t startScriptRun = mShaperItem.item.pos;
         size_t countScriptRun = mShaperItem.item.length;
@@ -611,7 +679,7 @@ void TextLayoutEngine::computeRunValues(SkPaint* paint, const UChar* chars,
 #if DEBUG_ADVANCES
         LOGD("Returned advances");
         for (size_t i = 0; i < countScriptRun; i++) {
-            LOGD("         -- hb-adv[%d] = %f, log_clusters = %d, total = %f", i,
+            LOGD("         -- hb-adv[%d] = %0.2f, log_clusters = %d, total = %0.2f", i,
                     (*outAdvances)[i], mShaperItem.log_clusters[i], totalFontRunAdvance);
         }
 #endif