Merge metadata from transaction instead of replace

This was replacing metadata when set in transactions rather
than merging. To fix this, merge has been augmented to also
report if a change occurred and to erase empty entries (as
a mechanism to "unset" metadata)

Bug: 122925737
Test: Added more unittests
Change-Id: Ia854cbcc1ddd334f18ffacea667cbb98778ec210

1 files changed, 15 insertions, 2 deletions

diff --git a/libs/gui/LayerMetadata.cpp b/libs/gui/LayerMetadata.cpp
index 745433a605..04d2871c77 100644
--- a/libs/gui/LayerMetadata.cpp
+++ b/libs/gui/LayerMetadata.cpp
@@ -31,10 +31,23 @@ LayerMetadata::LayerMetadata(const LayerMetadata& other) = default;
 
 LayerMetadata::LayerMetadata(LayerMetadata&& other) = default;
 
-void LayerMetadata::merge(const LayerMetadata& other) {
+bool LayerMetadata::merge(const LayerMetadata& other, bool eraseEmpty) {
+    bool changed = false;
     for (const auto& entry : other.mMap) {
-        mMap[entry.first] = entry.second;
+        auto it = mMap.find(entry.first);
+        if (it != mMap.cend() && it->second != entry.second) {
+            if (eraseEmpty && entry.second.empty()) {
+                mMap.erase(it);
+            } else {
+                it->second = entry.second;
+            }
+            changed = true;
+        } else if (it == mMap.cend() && !entry.second.empty()) {
+            mMap[entry.first] = entry.second;
+            changed = true;
+        }
     }
+    return changed;
 }
 
 status_t LayerMetadata::writeToParcel(Parcel* parcel) const {