Add bounds checking to nine patch scaling

bug:17114103

Better handle the case, when scaling the divs in a nine patch, where
divs fall outside of the bounds of the bitmap.

Change-Id: I244b9c45b938c2a15f29e4563a86825ee9439b5f

1 files changed, 30 insertions, 17 deletions

diff --git a/core/jni/android/graphics/BitmapFactory.cpp b/core/jni/android/graphics/BitmapFactory.cpp
index 2ce1b15..62ea351 100644
--- a/core/jni/android/graphics/BitmapFactory.cpp
+++ b/core/jni/android/graphics/BitmapFactory.cpp
@@ -18,6 +18,7 @@
 #include <android_runtime/AndroidRuntime.h>
 #include <androidfw/Asset.h>
 #include <androidfw/ResourceTypes.h>
+#include <cutils/compiler.h>
 #include <netinet/in.h>
 #include <stdio.h>
 #include <sys/mman.h>
@@ -87,29 +88,41 @@ static bool optionsJustBounds(JNIEnv* env, jobject options) {
     return options != NULL && env->GetBooleanField(options, gOptions_justBoundsFieldID);
 }
 
-static void scaleNinePatchChunk(android::Res_png_9patch* chunk, float scale) {
-    chunk->paddingLeft = int(chunk->paddingLeft * scale + 0.5f);
-    chunk->paddingTop = int(chunk->paddingTop * scale + 0.5f);
-    chunk->paddingRight = int(chunk->paddingRight * scale + 0.5f);
-    chunk->paddingBottom = int(chunk->paddingBottom * scale + 0.5f);
-
-    int32_t* xDivs = chunk->getXDivs();
-    for (int i = 0; i < chunk->numXDivs; i++) {
-        xDivs[i] = int32_t(xDivs[i] * scale + 0.5f);
-        if (i > 0 && xDivs[i] == xDivs[i - 1]) {
-            xDivs[i]++;
+static void scaleDivRange(int32_t* divs, int count, float scale, int maxValue) {
+    for (int i = 0; i < count; i++) {
+        divs[i] = int32_t(divs[i] * scale + 0.5f);
+        if (i > 0 && divs[i] == divs[i - 1]) {
+            divs[i]++; // avoid collisions
         }
     }
 
-    int32_t* yDivs = chunk->getYDivs();
-    for (int i = 0; i < chunk->numYDivs; i++) {
-        yDivs[i] = int32_t(yDivs[i] * scale + 0.5f);
-        if (i > 0 && yDivs[i] == yDivs[i - 1]) {
-            yDivs[i]++;
+    if (CC_UNLIKELY(divs[count - 1] > maxValue)) {
+        // if the collision avoidance above put some divs outside the bounds of the bitmap,
+        // slide outer stretchable divs inward to stay within bounds
+        int highestAvailable = maxValue;
+        for (int i = count - 1; i >= 0; i--) {
+            divs[i] = highestAvailable;
+            if (i > 0 && divs[i] <= divs[i-1]){
+                // keep shifting
+                highestAvailable = divs[i] - 1;
+            } else {
+                break;
+            }
         }
     }
 }
 
+static void scaleNinePatchChunk(android::Res_png_9patch* chunk, float scale,
+        int scaledWidth, int scaledHeight) {
+    chunk->paddingLeft = int(chunk->paddingLeft * scale + 0.5f);
+    chunk->paddingTop = int(chunk->paddingTop * scale + 0.5f);
+    chunk->paddingRight = int(chunk->paddingRight * scale + 0.5f);
+    chunk->paddingBottom = int(chunk->paddingBottom * scale + 0.5f);
+
+    scaleDivRange(chunk->getXDivs(), chunk->numXDivs, scale, scaledWidth);
+    scaleDivRange(chunk->getYDivs(), chunk->numYDivs, scale, scaledHeight);
+}
+
 static SkColorType colorTypeForScaledOutput(SkColorType colorType) {
     switch (colorType) {
         case kUnknown_SkColorType:
@@ -330,7 +343,7 @@ static jobject doDecode(JNIEnv* env, SkStreamRewindable* stream, jobject padding
     jbyteArray ninePatchChunk = NULL;
     if (peeker.mPatch != NULL) {
         if (willScale) {
-            scaleNinePatchChunk(peeker.mPatch, scale);
+            scaleNinePatchChunk(peeker.mPatch, scale, scaledWidth, scaledHeight);
         }
 
         size_t ninePatchArraySize = peeker.mPatch->serializedSize();