Add functions for measuring cursor positioning
New functions for computing the correspondence between cursor
position and advance, respecting grapheme boundaries.
Change-Id: I620378d5f64cd74300cd43db522adeb555825dff
diff --git a/include/minikin/Layout.h b/include/minikin/Layout.h
index 543f553..930407a 100644
--- a/include/minikin/Layout.h
+++ b/include/minikin/Layout.h
@@ -106,9 +106,13 @@
float getAdvance() const;
// Get advances, copying into caller-provided buffer. The size of this
- // buffer must match the length of the string (nchars arg to doLayout).
+ // buffer must match the length of the string (count arg to doLayout).
void getAdvances(float* advances);
+ // The i parameter is an offset within the buf relative to start, it is < count, where
+ // start and count are the parameters to doLayout
+ float getCharAdvance(size_t i) const { return mAdvances[i]; }
+
void getBounds(MinikinRect* rect);
// Purge all caches, useful in low memory conditions
diff --git a/include/minikin/Measurement.h b/include/minikin/Measurement.h
new file mode 100644
index 0000000..fc47fa3
--- /dev/null
+++ b/include/minikin/Measurement.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MINIKIN_MEASUREMENT_H
+#define MINIKIN_MEASUREMENT_H
+
+#include <minikin/Layout.h>
+
+namespace android {
+
+float getRunAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count, size_t offset);
+
+size_t getOffsetForAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
+ float advance);
+
+}
+
+#endif // MINIKIN_MEASUREMENT_H
diff --git a/libs/minikin/Android.mk b/libs/minikin/Android.mk
index 34b535c..873f279 100644
--- a/libs/minikin/Android.mk
+++ b/libs/minikin/Android.mk
@@ -25,6 +25,7 @@
Hyphenator.cpp \
Layout.cpp \
LineBreaker.cpp \
+ Measurement.cpp \
MinikinInternal.cpp \
MinikinRefCounted.cpp \
MinikinFontFreeType.cpp \
diff --git a/libs/minikin/GraphemeBreak.cpp b/libs/minikin/GraphemeBreak.cpp
index 5d8978d..f8f386c 100644
--- a/libs/minikin/GraphemeBreak.cpp
+++ b/libs/minikin/GraphemeBreak.cpp
@@ -41,7 +41,7 @@
uint32_t c2 = 0;
size_t offset_back = offset;
U16_PREV(buf, start, offset_back, c1);
- U16_NEXT(buf, offset, count, c2);
+ U16_NEXT(buf, offset, start + count, c2);
int32_t p1 = u_getIntPropertyValue(c1, UCHAR_GRAPHEME_CLUSTER_BREAK);
int32_t p2 = u_getIntPropertyValue(c2, UCHAR_GRAPHEME_CLUSTER_BREAK);
// Rule GB3, CR x LF
@@ -54,7 +54,7 @@
}
// Rule GB5, / (Control | CR | LF)
if (p2 == U_GCB_CONTROL || p2 == U_GCB_CR || p2 == U_GCB_LF) {
- // exclude zero-width control characters from breaking (tailoring of TR29)
+ // exclude zero-width control characters from breaking (tailoring of UAX #29)
if (c2 == 0x00ad
|| (c2 >= 0x200b && c2 <= 0x200f)
|| (c2 >= 0x2028 && c2 <= 0x202e)
@@ -83,12 +83,12 @@
if (p2 == U_GCB_EXTEND || p2 == U_GCB_SPACING_MARK) {
if (c2 == 0xe33) {
// most other implementations break THAI CHARACTER SARA AM
- // (tailoring of TR29)
+ // (tailoring of UAX #29)
return true;
}
return false;
}
- // Cluster indic syllables togeter (tailoring of TR29)
+ // Cluster indic syllables together (tailoring of UAX #29)
if (u_getIntPropertyValue(c1, UCHAR_CANONICAL_COMBINING_CLASS) == 9 // virama
&& u_getIntPropertyValue(c2, UCHAR_GENERAL_CATEGORY) == U_OTHER_LETTER) {
return false;
diff --git a/libs/minikin/Measurement.cpp b/libs/minikin/Measurement.cpp
new file mode 100644
index 0000000..21df5d8
--- /dev/null
+++ b/libs/minikin/Measurement.cpp
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "Minikin"
+#include <cutils/log.h>
+
+#include <cmath>
+#include <unicode/uchar.h>
+
+#include <minikin/GraphemeBreak.h>
+#include <minikin/Measurement.h>
+
+namespace android {
+
+// These could be considered helper methods of layout, but need only be loosely coupled, so
+// are separate.
+
+float getRunAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
+ size_t offset) {
+ float advance = 0.0f;
+ size_t lastCluster = start;
+ float clusterWidth = 0.0f;
+ for (size_t i = start; i < offset; i++) {
+ float charAdvance = layout.getCharAdvance(i - start);
+ if (charAdvance != 0.0f) {
+ advance += charAdvance;
+ lastCluster = i;
+ clusterWidth = charAdvance;
+ }
+ }
+ if (offset < start + count && layout.getCharAdvance(offset) == 0.0f) {
+ // In the middle of a cluster, distribute width of cluster so that each grapheme cluster
+ // gets an equal share.
+ // TODO: get caret information out of font when that's available
+ size_t nextCluster;
+ for (nextCluster = offset + 1; nextCluster < start + count; nextCluster++) {
+ if (layout.getCharAdvance(nextCluster - start) != 0.0f) break;
+ }
+ int numGraphemeClusters = 0;
+ int numGraphemeClustersAfter = 0;
+ for (size_t i = lastCluster; i < nextCluster; i++) {
+ bool isAfter = i >= offset;
+ if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
+ numGraphemeClusters++;
+ if (isAfter) {
+ numGraphemeClustersAfter++;
+ }
+ }
+ }
+ if (numGraphemeClusters > 0) {
+ advance -= clusterWidth * numGraphemeClustersAfter / numGraphemeClusters;
+ }
+ }
+ return advance;
+}
+
+/**
+ * Essentially the inverse of getRunAdvance. Compute the value of offset for which the
+ * measured caret comes closest to the provided advance param, and which is on a grapheme
+ * cluster boundary.
+ *
+ * The actual implementation fast-forwards through clusters to get "close", then does a finer-grain
+ * search within the cluster and grapheme breaks.
+ */
+size_t getOffsetForAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
+ float advance) {
+ float x = 0.0f, xLastClusterStart = 0.0f, xSearchStart = 0.0f;
+ size_t lastClusterStart = start, searchStart = start;
+ for (size_t i = start; i < start + count; i++) {
+ if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
+ searchStart = lastClusterStart;
+ xSearchStart = xLastClusterStart;
+ }
+ float width = layout.getCharAdvance(i - start);
+ if (width != 0.0f) {
+ lastClusterStart = i;
+ xLastClusterStart = x;
+ x += width;
+ if (x > advance) {
+ break;
+ }
+ }
+ }
+ size_t best = searchStart;
+ float bestDist = FLT_MAX;
+ for (size_t i = searchStart; i <= start + count; i++) {
+ if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
+ // "getRunAdvance(layout, buf, start, count, bufSize, i) - advance" but more efficient
+ float delta = getRunAdvance(layout, buf, searchStart, count, i) + xSearchStart
+ - advance;
+ if (std::abs(delta) < bestDist) {
+ bestDist = std::abs(delta);
+ best = i;
+ }
+ if (delta >= 0.0f) {
+ break;
+ }
+ }
+ }
+ return best;
+}
+
+}
