Always select the next higher density bucket when picking resources

Test: ran and updated Config_test.cpp
Fix: 183136881
Change-Id: Ife1575caedb2cf3fbc2d3659c34a52e1207575c6

2 files changed, 15 insertions, 17 deletions

diff --git a/libs/androidfw/ResourceTypes.cpp b/libs/androidfw/ResourceTypes.cpp
index cae2d0bc16b3..50117ce9e69b 100644
--- a/libs/androidfw/ResourceTypes.cpp
+++ b/libs/androidfw/ResourceTypes.cpp
@@ -2677,30 +2677,21 @@ bool ResTable_config::isBetterThan(const ResTable_config& o,
                 // DENSITY_ANY is now dealt with. We should look to
                 // pick a density bucket and potentially scale it.
                 // Any density is potentially useful
-                // because the system will scale it.  Scaling down
-                // is generally better than scaling up.
+                // because the system will scale it.  Always prefer
+                // scaling down.
                 int h = thisDensity;
                 int l = otherDensity;
                 bool bImBigger = true;
                 if (l > h) {
-                    int t = h;
-                    h = l;
-                    l = t;
+                    std::swap(l, h);
                     bImBigger = false;
                 }
 
-                if (requestedDensity >= h) {
-                    // requested value higher than both l and h, give h
-                    return bImBigger;
-                }
                 if (l >= requestedDensity) {
                     // requested value lower than both l and h, give l
                     return !bImBigger;
-                }
-                // saying that scaling down is 2x better than up
-                if (((2 * l) - requestedDensity) * h > requestedDensity * requestedDensity) {
-                    return !bImBigger;
                 } else {
+                    // otherwise give h
                     return bImBigger;
                 }
             }
diff --git a/libs/androidfw/tests/Config_test.cpp b/libs/androidfw/tests/Config_test.cpp
index b54915f03c29..f5fd0f20d580 100644
--- a/libs/androidfw/tests/Config_test.cpp
+++ b/libs/androidfw/tests/Config_test.cpp
@@ -27,15 +27,19 @@ namespace android {
 
 static ResTable_config selectBest(const ResTable_config& target,
                                   const Vector<ResTable_config>& configs) {
-  ResTable_config bestConfig;
-  memset(&bestConfig, 0, sizeof(bestConfig));
+  Vector<ResTable_config> matchedConfigs;
   const size_t configCount = configs.size();
   for (size_t i = 0; i < configCount; i++) {
     const ResTable_config& thisConfig = configs[i];
-    if (!thisConfig.match(target)) {
-      continue;
+    if (thisConfig.match(target)) {
+      matchedConfigs.add(thisConfig);
     }
+  }
 
+  ResTable_config bestConfig = matchedConfigs[0];
+  const size_t matchingConfigCount = matchedConfigs.size();
+  for (size_t i = 1; i < matchingConfigCount; i++) {
+    const ResTable_config& thisConfig = configs[i];
     if (thisConfig.isBetterThan(bestConfig, &target)) {
       bestConfig = thisConfig;
     }
@@ -75,6 +79,9 @@ TEST(ConfigTest, shouldSelectBestDensity) {
   configs.add(buildDensityConfig(int(ResTable_config::DENSITY_HIGH) + 20));
   ASSERT_EQ(expectedBest, selectBest(deviceConfig, configs));
 
+  configs.add(buildDensityConfig(int(ResTable_config::DENSITY_XHIGH) - 1));
+  ASSERT_EQ(expectedBest, selectBest(deviceConfig, configs));
+
   expectedBest = buildDensityConfig(ResTable_config::DENSITY_XHIGH);
   configs.add(expectedBest);
   ASSERT_EQ(expectedBest, selectBest(deviceConfig, configs));