Add native lib for the android display backend

It's not used by crosvm yet. And there are many TODOs left.

* Rename to libandroid_display_backend.so
* Use binderRPC over UDS
* Don't copy frames (b/331900473)
* Write in Rust

Bug: 325929966
Test: m
Change-Id: Ib4e5589d6200c5758a06e95fb5103e70b837bdae
diff --git a/libs/android_display_backend/Android.bp b/libs/android_display_backend/Android.bp
new file mode 100644
index 0000000..f818951
--- /dev/null
+++ b/libs/android_display_backend/Android.bp
@@ -0,0 +1,54 @@
+aidl_interface {
+    name: "libcrosvm_android_display_service",
+    srcs: [
+        "aidl/android/crosvm/ICrosvmAndroidDisplayService.aidl",
+    ],
+    include_dirs: [
+        "frameworks/native/aidl/gui",
+    ],
+    local_include_dir: "aidl",
+    unstable: true,
+    backend: {
+        java: {
+            enabled: true,
+        },
+        cpp: {
+            enabled: false,
+        },
+        rust: {
+            enabled: false,
+        },
+        ndk: {
+            enabled: true,
+            // To use Surface
+            additional_shared_libraries: [
+                "libnativewindow",
+            ],
+            apex_available: [
+                "//apex_available:platform",
+                "com.android.virt",
+            ],
+        },
+    },
+}
+
+cc_library_static {
+    name: "libcrosvm_android_display_client",
+    srcs: [
+        "crosvm_android_display_client.cpp",
+    ],
+    stl: "libc++_static",
+    whole_static_libs: [
+        "libcrosvm_android_display_service-ndk",
+        "libyuv",
+        "libc++_static",
+    ],
+    shared_libs: [
+        "libbinder_ndk",
+        "libnativewindow",
+    ],
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.virt",
+    ],
+}
diff --git a/libs/android_display_backend/aidl/android/crosvm/ICrosvmAndroidDisplayService.aidl b/libs/android_display_backend/aidl/android/crosvm/ICrosvmAndroidDisplayService.aidl
new file mode 100644
index 0000000..c7bfc80
--- /dev/null
+++ b/libs/android_display_backend/aidl/android/crosvm/ICrosvmAndroidDisplayService.aidl
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2024 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.
+ */
+
+package android.crosvm;
+
+import android.view.Surface;
+
+/**
+ * Service to provide Crosvm with an Android Surface for showing a guest's
+ * display.
+ */
+interface ICrosvmAndroidDisplayService {
+    void setSurface(inout Surface surface);
+
+    void removeSurface();
+}
diff --git a/libs/android_display_backend/crosvm_android_display_client.cpp b/libs/android_display_backend/crosvm_android_display_client.cpp
new file mode 100644
index 0000000..91412af
--- /dev/null
+++ b/libs/android_display_backend/crosvm_android_display_client.cpp
@@ -0,0 +1,266 @@
+/*
+ * Copyright 2024 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.
+ */
+
+#include <aidl/android/crosvm/BnCrosvmAndroidDisplayService.h>
+#include <android/binder_manager.h>
+#include <android/binder_process.h>
+#include <android/native_window.h>
+#include <android/native_window_aidl.h>
+#include <libyuv.h>
+#include <stdint.h>
+#include <utils/Errors.h>
+
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+#include <vector>
+
+#define LIBEXPORT __attribute__((visibility("default"))) extern "C"
+
+typedef void (*android_display_log_callback_type)(const char* message);
+
+static void android_display_log_callback_stub(const char* message) {
+    (void)message;
+}
+
+namespace {
+
+class DisplayService : public aidl::android::crosvm::BnCrosvmAndroidDisplayService {
+public:
+    DisplayService() = default;
+    virtual ~DisplayService() = default;
+
+    ndk::ScopedAStatus setSurface(aidl::android::view::Surface* surface) override {
+        {
+            std::lock_guard lk(mSurfaceReadyMutex);
+            mSurface = std::make_unique<aidl::android::view::Surface>(surface->release());
+        }
+        mSurfaceReady.notify_one();
+        return ::ndk::ScopedAStatus::ok();
+    }
+
+    ndk::ScopedAStatus removeSurface() override {
+        {
+            std::lock_guard lk(mSurfaceReadyMutex);
+            mSurface = nullptr;
+        }
+        mSurfaceReady.notify_one();
+        return ::ndk::ScopedAStatus::ok();
+    }
+
+    aidl::android::view::Surface* getSurface() {
+        std::unique_lock lk(mSurfaceReadyMutex);
+        mSurfaceReady.wait(lk, [this] { return mSurface != nullptr; });
+        return mSurface.get();
+    }
+
+private:
+    std::condition_variable mSurfaceReady;
+    std::mutex mSurfaceReadyMutex;
+    std::unique_ptr<aidl::android::view::Surface> mSurface;
+};
+
+void ErrorF(android_display_log_callback_type error_callback, const char* format, ...) {
+    char buffer[1024];
+
+    va_list vararg;
+    va_start(vararg, format);
+    vsnprintf(buffer, sizeof(buffer), format, vararg);
+    va_end(vararg);
+
+    error_callback(buffer);
+}
+
+} // namespace
+
+struct android_display_context {
+    uint32_t width;
+    uint32_t height;
+    std::shared_ptr<DisplayService> displayService;
+};
+
+LIBEXPORT
+struct android_display_context* create_android_display_context(
+        const char* name, size_t name_len, android_display_log_callback_type error_callback) {
+    auto ctx = new android_display_context();
+
+    auto service = ::ndk::SharedRefBase::make<DisplayService>();
+
+    if (strlen(name) != name_len) {
+        ErrorF(error_callback, "Invalid service name length. Expected %u, actual %u", name_len,
+               strlen(name));
+        return nullptr;
+    }
+
+    auto status = AServiceManager_addService(service->asBinder().get(), name);
+    if (status != STATUS_OK) {
+        ErrorF(error_callback, "Failed to register %s",
+               aidl::android::crosvm::ICrosvmAndroidDisplayService::descriptor);
+        return nullptr;
+    }
+
+    ABinderProcess_startThreadPool();
+
+    auto surface = service->getSurface();
+    ctx->width = static_cast<uint32_t>(ANativeWindow_getWidth(surface->get()));
+    ctx->height = static_cast<uint32_t>(ANativeWindow_getHeight(surface->get()));
+    ctx->displayService = service;
+    return ctx;
+}
+
+LIBEXPORT
+void destroy_android_display_context(android_display_log_callback_type error_callback,
+                                     struct android_display_context* ctx) {
+    if (!ctx) {
+        ErrorF(error_callback, "Invalid context.");
+        return;
+    }
+
+    delete ctx;
+}
+
+LIBEXPORT
+uint32_t get_android_display_width(android_display_log_callback_type error_callback,
+                                   struct android_display_context* ctx) {
+    if (!ctx) {
+        ErrorF(error_callback, "Invalid context.");
+        return -1;
+    }
+    if (!ctx->displayService->getSurface()) {
+        ErrorF(error_callback, "Invalid context surface for ctx:%p.", ctx);
+        return -1;
+    }
+    return ctx->width;
+}
+
+LIBEXPORT
+uint32_t get_android_display_height(android_display_log_callback_type error_callback,
+                                    struct android_display_context* ctx) {
+    if (!ctx) {
+        ErrorF(error_callback, "Invalid context.");
+        return -1;
+    }
+    if (!ctx->displayService->getSurface()) {
+        ErrorF(error_callback, "Invalid context surface for ctx:%p.", ctx);
+        return -1;
+    }
+    return ctx->height;
+}
+
+uint16_t RGBA8888ToRGB565(uint8_t r, uint8_t g, uint8_t b, uint8_t a) {
+    (void)a;
+    return (static_cast<uint16_t>(r >> 3) << 11) | (static_cast<uint16_t>(g >> 2) << 5) |
+            (static_cast<uint16_t>(b >> 3) << 0);
+}
+
+LIBEXPORT
+void blit_android_display(android_display_log_callback_type error_callback,
+                          struct android_display_context* ctx, uint32_t width, uint32_t height,
+                          uint8_t* pixels, size_t pixels_num_bytes) {
+    if (!ctx) {
+        ErrorF(error_callback, "Invalid context.");
+        return;
+    }
+    if (!ctx->displayService->getSurface()) {
+        ErrorF(error_callback, "Invalid context surface.");
+        return;
+    }
+    if (pixels_num_bytes != width * height * 4) {
+        ErrorF(error_callback, "Invalid buffer size.");
+        return;
+    }
+    ANativeWindow* anw = ctx->displayService->getSurface()->get();
+    if (!anw) {
+        ErrorF(error_callback, "Invalid context surface.");
+        return;
+    }
+
+    ANativeWindow_Buffer anwBuffer = {};
+    if (ANativeWindow_lock(anw, &anwBuffer, nullptr) != android::OK) {
+        ErrorF(error_callback, "Failed to lock ANativeWindow.");
+        return;
+    }
+
+    // Source is always BGRA8888.
+    auto* src = reinterpret_cast<uint32_t*>(pixels);
+    auto srcWidth = static_cast<uint32_t>(width);
+    auto srcHeight = static_cast<uint32_t>(height);
+    auto srcStrideBytes = srcWidth * 4;
+    auto srcStridePixels = srcWidth;
+
+    auto dstWidth = static_cast<uint32_t>(anwBuffer.width);
+    auto dstHeight = static_cast<uint32_t>(anwBuffer.height);
+
+    // Scale to fit if needed.
+    std::vector<uint32_t> scaledSrc;
+    if (srcWidth != dstWidth || srcHeight != dstHeight) {
+        const float ratioWidth = static_cast<float>(dstWidth) / static_cast<float>(srcWidth);
+        const float ratioHeight = static_cast<float>(dstHeight) / static_cast<float>(srcHeight);
+        const float ratioUsed = std::min(ratioWidth, ratioHeight);
+
+        uint32_t scaledSrcWidth = static_cast<uint32_t>(static_cast<float>(srcWidth) * ratioUsed);
+        uint32_t scaledSrcHeight = static_cast<uint32_t>(static_cast<float>(srcHeight) * ratioUsed);
+        uint32_t scaledSrcStrideBytes = scaledSrcWidth * 4;
+        uint32_t scaledSrcStridePixels = scaledSrcWidth;
+
+        scaledSrc.resize(scaledSrcHeight * scaledSrcStridePixels);
+
+        libyuv::ARGBScale(reinterpret_cast<uint8_t*>(src), srcStrideBytes, srcWidth, srcHeight,
+                          reinterpret_cast<uint8_t*>(scaledSrc.data()), scaledSrcStrideBytes,
+                          scaledSrcWidth, scaledSrcHeight, libyuv::kFilterBilinear);
+
+        src = scaledSrc.data();
+        srcWidth = scaledSrcWidth;
+        srcHeight = scaledSrcHeight;
+        srcStrideBytes = scaledSrcStrideBytes;
+        srcStridePixels = scaledSrcStridePixels;
+    }
+
+    if (anwBuffer.format == AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM) {
+        auto* dst = reinterpret_cast<uint32_t*>(anwBuffer.bits);
+        auto dstStridePixels = static_cast<uint32_t>(anwBuffer.stride);
+
+        for (uint32_t h = 0; h < std::min(srcHeight, dstHeight); h++) {
+            for (uint32_t w = 0; w < std::min(srcWidth, dstWidth); w++) {
+                dst[(h * dstStridePixels) + w] = src[(h * srcStridePixels) + w];
+            }
+        }
+    } else if (anwBuffer.format == AHARDWAREBUFFER_FORMAT_R5G6B5_UNORM) {
+        auto* dst = reinterpret_cast<uint16_t*>(anwBuffer.bits);
+        auto dstWidth = static_cast<uint32_t>(anwBuffer.width);
+        auto dstHeight = static_cast<uint32_t>(anwBuffer.height);
+        auto dstStridePixels = static_cast<uint32_t>(anwBuffer.stride);
+
+        for (uint32_t h = 0; h < std::min(srcHeight, dstHeight); h++) {
+            for (uint32_t w = 0; w < std::min(srcWidth, dstWidth); w++) {
+                uint32_t srcPixel = src[(h * srcStridePixels) + w];
+                uint8_t* srcPixelBytes = reinterpret_cast<uint8_t*>(&srcPixel);
+                uint8_t r = srcPixelBytes[2];
+                uint8_t g = srcPixelBytes[1];
+                uint8_t b = srcPixelBytes[0];
+                uint8_t a = srcPixelBytes[3];
+                dst[(h * dstStridePixels) + w] = RGBA8888ToRGB565(r, g, b, a);
+            }
+        }
+    } else {
+        ErrorF(error_callback, "Unhandled format: %d", anwBuffer.format);
+    }
+
+    if (ANativeWindow_unlockAndPost(anw) != android::OK) {
+        ErrorF(error_callback, "Failed to unlock and post ANativeWindow.");
+        return;
+    }
+}
diff --git a/libs/android_display_backend/crosvm_android_display_client.h b/libs/android_display_backend/crosvm_android_display_client.h
new file mode 100644
index 0000000..75b845b
--- /dev/null
+++ b/libs/android_display_backend/crosvm_android_display_client.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2024 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.
+ */
+
+extern "C" {
+
+typedef void (*android_display_log_callback_type)(const char* message);
+
+static void android_display_log_callback_stub(const char* message) {
+    (void)message;
+}
+
+struct android_display_context {
+    uint32_t test;
+};
+
+__attribute__((visibility("default"))) struct android_display_context*
+create_android_display_context(const char* name, size_t name_len,
+                               android_display_log_callback_type error_callback);
+
+__attribute__((visibility("default"))) void destroy_android_display_context(
+        android_display_log_callback_type error_callback, struct android_display_context* ctx);
+
+} // extern C