SF: Introduce DisplaySnapshot
DisplaySnapshot stores the immutable state of a physical display,
captured on hotplug. The SurfaceFlinger class stores a map from
PhysicalDisplayId to PhysicalDisplay, a new class that augments
this state with the sp<DisplayToken>.
Later, DisplayDevice will be removed, and SF::mDisplays will map
wp<DisplayToken> to compositionengine::Display.
Bug: 241285876
Test: libsurfaceflinger_unittest
Test: dumpsys SurfaceFlinger --displays
Change-Id: I172df87c4a7a9cf64659ff9cfbd6df195ee4bc8d
diff --git a/services/surfaceflinger/Display/DisplayMap.h b/services/surfaceflinger/Display/DisplayMap.h
new file mode 100644
index 0000000..baf0da9
--- /dev/null
+++ b/services/surfaceflinger/Display/DisplayMap.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright 2022 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.
+ */
+
+#pragma once
+
+#include <ftl/small_map.h>
+
+namespace android::display {
+
+// The static capacities were chosen to exceed a typical number of physical and/or virtual displays.
+
+template <typename Key, typename Value>
+using DisplayMap = ftl::SmallMap<Key, Value, 5>;
+
+template <typename Key, typename Value>
+using PhysicalDisplayMap = ftl::SmallMap<Key, Value, 3>;
+
+} // namespace android::display