7 files changed, 472 insertions, 185 deletions

diff --git a/Android.mk b/Android.mk
index c8a21e084..b28929604 100644
--- a/Android.mk
+++ b/Android.mk
@@ -53,36 +53,21 @@ LOCAL_STATIC_LIBRARIES := \
 
 include $(BUILD_STATIC_LIBRARY)
 
-# recovery (static executable)
+# librecovery_ui (static library)
 # ===============================
 include $(CLEAR_VARS)
-
 LOCAL_SRC_FILES := \
-    adb_install.cpp \
-    device.cpp \
-    fuse_sdcard_provider.cpp \
-    recovery.cpp \
-    roots.cpp \
-    rotate_logs.cpp \
     screen_ui.cpp \
     ui.cpp \
     vr_ui.cpp \
-    wear_ui.cpp \
-
-LOCAL_MODULE := recovery
-
-LOCAL_FORCE_STATIC_EXECUTABLE := true
-
-LOCAL_REQUIRED_MODULES := e2fsdroid_static mke2fs_static mke2fs.conf
+    wear_ui.cpp
 
-ifeq ($(TARGET_USERIMAGES_USE_F2FS),true)
-ifeq ($(HOST_OS),linux)
-LOCAL_REQUIRED_MODULES += sload.f2fs mkfs.f2fs
-endif
-endif
+LOCAL_CFLAGS := -Wall -Werror
 
-LOCAL_CFLAGS += -DRECOVERY_API_VERSION=$(RECOVERY_API_VERSION)
-LOCAL_CFLAGS += -Wall -Werror
+LOCAL_MODULE := librecovery_ui
+LOCAL_STATIC_LIBRARIES := \
+    libminui \
+    libbase
 
 ifneq ($(TARGET_RECOVERY_UI_MARGIN_HEIGHT),)
 LOCAL_CFLAGS += -DRECOVERY_UI_MARGIN_HEIGHT=$(TARGET_RECOVERY_UI_MARGIN_HEIGHT)
@@ -132,11 +117,50 @@ else
 LOCAL_CFLAGS += -DRECOVERY_UI_VR_STEREO_OFFSET=0
 endif
 
+include $(BUILD_STATIC_LIBRARY)
+
+# recovery (static executable)
+# ===============================
+include $(CLEAR_VARS)
+
+LOCAL_SRC_FILES := \
+    adb_install.cpp \
+    device.cpp \
+    fuse_sdcard_provider.cpp \
+    recovery.cpp \
+    roots.cpp \
+    rotate_logs.cpp \
+
+
+LOCAL_MODULE := recovery
+
+LOCAL_FORCE_STATIC_EXECUTABLE := true
+
+LOCAL_REQUIRED_MODULES := e2fsdroid_static mke2fs_static mke2fs.conf
+
+ifeq ($(TARGET_USERIMAGES_USE_F2FS),true)
+ifeq ($(HOST_OS),linux)
+LOCAL_REQUIRED_MODULES += sload.f2fs mkfs.f2fs
+endif
+endif
+
+LOCAL_CFLAGS += -DRECOVERY_API_VERSION=$(RECOVERY_API_VERSION)
+LOCAL_CFLAGS += -Wall -Werror
+
 LOCAL_C_INCLUDES += \
     system/vold \
 
-LOCAL_STATIC_LIBRARIES := \
-    librecovery \
+LOCAL_STATIC_LIBRARIES := librecovery
+
+# If $(TARGET_RECOVERY_UI_LIB) is defined, the recovery calls make_device() from the
+# $(TARGET_RECOVERY_UI_LIB), which depends on the librecovery_ui.
+ifeq ($(TARGET_RECOVERY_UI_LIB),)
+  LOCAL_SRC_FILES += default_device.cpp
+else
+  LOCAL_STATIC_LIBRARIES += $(TARGET_RECOVERY_UI_LIB)
+endif
+
+LOCAL_STATIC_LIBRARIES += \
     libverifier \
     libbatterymonitor \
     libbootloader_message \
@@ -149,6 +173,7 @@ LOCAL_STATIC_LIBRARIES := \
     libminadbd \
     libasyncio \
     libfusesideload \
+    librecovery_ui \
     libminui \
     libpng \
     libcrypto_utils \
@@ -172,12 +197,6 @@ endif
 
 LOCAL_MODULE_PATH := $(TARGET_RECOVERY_ROOT_OUT)/sbin
 
-ifeq ($(TARGET_RECOVERY_UI_LIB),)
-  LOCAL_SRC_FILES += default_device.cpp
-else
-  LOCAL_STATIC_LIBRARIES += $(TARGET_RECOVERY_UI_LIB)
-endif
-
 ifeq ($(BOARD_CACHEIMAGE_PARTITION_SIZE),)
 LOCAL_REQUIRED_MODULES += recovery-persist recovery-refresh
 endif
diff --git a/screen_ui.cpp b/screen_ui.cpp
index c8fb5aa75..317e5529c 100644
--- a/screen_ui.cpp
+++ b/screen_ui.cpp
@@ -53,7 +53,98 @@ static double now() {
   return tv.tv_sec + tv.tv_usec / 1000000.0;
 }
 
-ScreenRecoveryUI::ScreenRecoveryUI()
+Menu::Menu(bool scrollable, size_t max_items, size_t max_length)
+    : scrollable_(scrollable),
+      max_display_items_(max_items),
+      max_item_length_(max_length),
+      text_headers_(nullptr),
+      menu_start_(0),
+      selection_(0) {
+  CHECK_LE(max_items, static_cast<size_t>(std::numeric_limits<int>::max()));
+}
+
+const char* const* Menu::text_headers() const {
+  return text_headers_;
+}
+
+std::string Menu::TextItem(size_t index) const {
+  CHECK_LT(index, text_items_.size());
+
+  return text_items_[index];
+}
+
+size_t Menu::MenuStart() const {
+  return menu_start_;
+}
+
+size_t Menu::MenuEnd() const {
+  return std::min(ItemsCount(), menu_start_ + max_display_items_);
+}
+
+size_t Menu::ItemsCount() const {
+  return text_items_.size();
+}
+
+bool Menu::ItemsOverflow(std::string* cur_selection_str) const {
+  if (!scrollable_ || static_cast<size_t>(ItemsCount()) <= max_display_items_) {
+    return false;
+  }
+
+  *cur_selection_str =
+      android::base::StringPrintf("Current item: %d/%zu", selection_ + 1, ItemsCount());
+  return true;
+}
+
+void Menu::Start(const char* const* headers, const char* const* items, int initial_selection) {
+  text_headers_ = headers;
+
+  // It's fine to have more entries than text_rows_ if scrollable menu is supported.
+  size_t max_items_count = scrollable_ ? std::numeric_limits<int>::max() : max_display_items_;
+  for (size_t i = 0; i < max_items_count && items[i] != nullptr; ++i) {
+    text_items_.emplace_back(items[i], strnlen(items[i], max_item_length_));
+  }
+
+  CHECK(!text_items_.empty());
+  selection_ = initial_selection;
+}
+
+// TODO(xunchang) modify the function parameters to button up & down.
+int Menu::Select(int sel) {
+  CHECK_LE(ItemsCount(), static_cast<size_t>(std::numeric_limits<int>::max()));
+  int count = ItemsCount();
+
+  // Wraps the selection at boundary if the menu is not scrollable.
+  if (!scrollable_) {
+    if (sel < 0) {
+      selection_ = count - 1;
+    } else if (sel >= count) {
+      selection_ = 0;
+    } else {
+      selection_ = sel;
+    }
+
+    return selection_;
+  }
+
+  if (sel < 0) {
+    selection_ = 0;
+  } else if (sel >= count) {
+    selection_ = count - 1;
+  } else {
+    if (static_cast<size_t>(sel) < menu_start_) {
+      menu_start_--;
+    } else if (static_cast<size_t>(sel) >= MenuEnd()) {
+      menu_start_++;
+    }
+    selection_ = sel;
+  }
+
+  return selection_;
+}
+
+ScreenRecoveryUI::ScreenRecoveryUI() : ScreenRecoveryUI(false) {}
+
+ScreenRecoveryUI::ScreenRecoveryUI(bool scrollable_menu)
     : kMarginWidth(RECOVERY_UI_MARGIN_WIDTH),
       kMarginHeight(RECOVERY_UI_MARGIN_HEIGHT),
       kAnimationFps(RECOVERY_UI_ANIMATION_FPS),
@@ -71,10 +162,7 @@ ScreenRecoveryUI::ScreenRecoveryUI()
       text_row_(0),
       show_text(false),
       show_text_ever(false),
-      menu_headers_(nullptr),
-      show_menu(false),
-      menu_items(0),
-      menu_sel(0),
+      scrollable_menu_(scrollable_menu),
       file_viewer_text_(nullptr),
       intro_frames(0),
       loop_frames(0),
@@ -407,13 +495,13 @@ int ScreenRecoveryUI::DrawWrappedTextLines(int x, int y, const char* const* line
 
 static const char* REGULAR_HELP[] = {
   "Use volume up/down and power.",
-  NULL
+  nullptr,
 };
 
 static const char* LONG_PRESS_HELP[] = {
   "Any button cycles highlight.",
   "Long-press activates.",
-  NULL
+  nullptr,
 };
 
 // Redraws everything on the screen. Does not flip pages. Should only be called with updateMutex
@@ -428,8 +516,13 @@ void ScreenRecoveryUI::draw_screen_locked() {
   gr_color(0, 0, 0, 255);
   gr_clear();
 
+  draw_menu_and_text_buffer_locked(HasThreeButtons() ? REGULAR_HELP : LONG_PRESS_HELP);
+}
+
+// Draws the menu and text buffer on the screen. Should only be called with updateMutex locked.
+void ScreenRecoveryUI::draw_menu_and_text_buffer_locked(const char* const* help_message) {
   int y = kMarginHeight;
-  if (show_menu) {
+  if (menu_) {
     static constexpr int kMenuIndent = 4;
     int x = kMarginWidth + kMenuIndent;
 
@@ -440,26 +533,46 @@ void ScreenRecoveryUI::draw_screen_locked() {
     for (const auto& chunk : android::base::Split(recovery_fingerprint, ":")) {
       y += DrawTextLine(x, y, chunk.c_str(), false);
     }
-    y += DrawTextLines(x, y, HasThreeButtons() ? REGULAR_HELP : LONG_PRESS_HELP);
 
+    y += DrawTextLines(x, y, help_message);
+
+    // Draw menu header.
     SetColor(HEADER);
-    // Ignore kMenuIndent, which is not taken into account by text_cols_.
-    y += DrawWrappedTextLines(kMarginWidth, y, menu_headers_);
+    if (!menu_->scrollable()) {
+      y += DrawWrappedTextLines(x, y, menu_->text_headers());
+    } else {
+      y += DrawTextLines(x, y, menu_->text_headers());
+      // Show the current menu item number in relation to total number if items don't fit on the
+      // screen.
+      std::string cur_selection_str;
+      if (menu_->ItemsOverflow(&cur_selection_str)) {
+        y += DrawTextLine(x, y, cur_selection_str.c_str(), true);
+      }
+    }
 
+    // Draw menu items.
     SetColor(MENU);
-    y += DrawHorizontalRule(y) + 4;
-    for (int i = 0; i < menu_items; ++i) {
-      if (i == menu_sel) {
+    // Do not draw the horizontal rule for wear devices.
+    if (!menu_->scrollable()) {
+      y += DrawHorizontalRule(y) + 4;
+    }
+    for (size_t i = menu_->MenuStart(); i < menu_->MenuEnd(); ++i) {
+      bool bold = false;
+      if (i == static_cast<size_t>(menu_->selection())) {
         // Draw the highlight bar.
         SetColor(IsLongPress() ? MENU_SEL_BG_ACTIVE : MENU_SEL_BG);
-        DrawHighlightBar(0, y - 2, ScreenWidth(), char_height_ + 4);
+
+        int bar_height = char_height_ + 4;
+        DrawHighlightBar(0, y - 2, ScreenWidth(), bar_height);
+
         // Bold white text for the selected item.
         SetColor(MENU_SEL_FG);
-        y += DrawTextLine(x, y, menu_[i].c_str(), true);
-        SetColor(MENU);
-      } else {
-        y += DrawTextLine(x, y, menu_[i].c_str(), false);
+        bold = true;
       }
+
+      y += DrawTextLine(x, y, menu_->TextItem(i).c_str(), bold);
+
+      SetColor(MENU);
     }
     y += DrawHorizontalRule(y);
   }
@@ -864,15 +977,10 @@ void ScreenRecoveryUI::ShowFile(const char* filename) {
 void ScreenRecoveryUI::StartMenu(const char* const* headers, const char* const* items,
                                  int initial_selection) {
   pthread_mutex_lock(&updateMutex);
-  if (text_rows_ > 0 && text_cols_ > 0) {
-    menu_headers_ = headers;
-    menu_.clear();
-    for (size_t i = 0; i < text_rows_ && items[i] != nullptr; ++i) {
-      menu_.emplace_back(std::string(items[i], strnlen(items[i], text_cols_ - 1)));
-    }
-    menu_items = static_cast<int>(menu_.size());
-    show_menu = true;
-    menu_sel = initial_selection;
+  if (text_rows_ > 0 && text_cols_ > 1) {
+    menu_ = std::make_unique<Menu>(scrollable_menu_, text_rows_, text_cols_ - 1);
+    menu_->Start(headers, items, initial_selection);
+
     update_screen_locked();
   }
   pthread_mutex_unlock(&updateMutex);
@@ -880,16 +988,13 @@ void ScreenRecoveryUI::StartMenu(const char* const* headers, const char* const*
 
 int ScreenRecoveryUI::SelectMenu(int sel) {
   pthread_mutex_lock(&updateMutex);
-  if (show_menu) {
-    int old_sel = menu_sel;
-    menu_sel = sel;
-
-    // Wrap at top and bottom.
-    if (menu_sel < 0) menu_sel = menu_items - 1;
-    if (menu_sel >= menu_items) menu_sel = 0;
+  if (menu_) {
+    int old_sel = menu_->selection();
+    sel = menu_->Select(sel);
 
-    sel = menu_sel;
-    if (menu_sel != old_sel) update_screen_locked();
+    if (sel != old_sel) {
+      update_screen_locked();
+    }
   }
   pthread_mutex_unlock(&updateMutex);
   return sel;
@@ -897,8 +1002,8 @@ int ScreenRecoveryUI::SelectMenu(int sel) {
 
 void ScreenRecoveryUI::EndMenu() {
   pthread_mutex_lock(&updateMutex);
-  if (show_menu && text_rows_ > 0 && text_cols_ > 0) {
-    show_menu = false;
+  if (menu_) {
+    menu_.reset();
     update_screen_locked();
   }
   pthread_mutex_unlock(&updateMutex);
diff --git a/screen_ui.h b/screen_ui.h
index f05761c42..c1222a576 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -20,6 +20,7 @@
 #include <pthread.h>
 #include <stdio.h>
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -28,6 +29,70 @@
 // From minui/minui.h.
 struct GRSurface;
 
+// This class maintains the menu selection and display of the screen ui.
+class Menu {
+ public:
+  Menu(bool scrollable, size_t max_items, size_t max_length);
+
+  bool scrollable() const {
+    return scrollable_;
+  }
+
+  int selection() const {
+    return selection_;
+  }
+
+  // Returns count of menu items.
+  size_t ItemsCount() const;
+  // Returns the index of the first menu item.
+  size_t MenuStart() const;
+  // Returns the index of the last menu item + 1.
+  size_t MenuEnd() const;
+
+  // Menu example:
+  // info:                           Android Recovery
+  //                                 ....
+  // help messages:                  Swipe up/down to move
+  //                                 Swipe left/right to select
+  // empty line (horizontal rule):
+  // menu headers:                   Select file to view
+  // menu items:                     /cache/recovery/last_log
+  //                                 /cache/recovery/last_log.1
+  //                                 /cache/recovery/last_log.2
+  //                                 ...
+  const char* const* text_headers() const;
+  std::string TextItem(size_t index) const;
+
+  // Checks if the menu items fit vertically on the screen. Returns true and set the
+  // |cur_selection_str| if the items exceed the screen limit.
+  bool ItemsOverflow(std::string* cur_selection_str) const;
+
+  // Starts the menu with |headers| and |items| in text. Sets the default selection to
+  // |initial_selection|.
+  void Start(const char* const* headers, const char* const* items, int initial_selection);
+
+  // Sets the current selection to |sel|. Handle the overflow cases depending on if the menu is
+  // scrollable.
+  int Select(int sel);
+
+ private:
+  // The menu is scrollable to display more items. Used on wear devices who have smaller screens.
+  const bool scrollable_;
+  // The max number of menu items to fit vertically on a screen.
+  const size_t max_display_items_;
+  // The length of each item to fit horizontally on a screen.
+  const size_t max_item_length_;
+
+  // Internal storage for the menu headers and items in text.
+  const char* const* text_headers_;
+  std::vector<std::string> text_items_;
+
+  // The first item to display on the screen.
+  size_t menu_start_;
+  // Current menu selection.
+  int selection_;
+};
+
 // Implementation of RecoveryUI appropriate for devices with a screen
 // (shows an icon + a progress bar, text logging, menu, etc.)
 class ScreenRecoveryUI : public RecoveryUI {
@@ -44,6 +109,7 @@ class ScreenRecoveryUI : public RecoveryUI {
   };
 
   ScreenRecoveryUI();
+  explicit ScreenRecoveryUI(bool scrollable_menu);
 
   bool Init(const std::string& locale) override;
 
@@ -101,6 +167,7 @@ class ScreenRecoveryUI : public RecoveryUI {
   virtual void draw_background_locked();
   virtual void draw_foreground_locked();
   virtual void draw_screen_locked();
+  virtual void draw_menu_and_text_buffer_locked(const char* const* help_message);
   virtual void update_screen_locked();
   virtual void update_progress_locked();
 
@@ -184,10 +251,8 @@ class ScreenRecoveryUI : public RecoveryUI {
   bool show_text;
   bool show_text_ever;  // has show_text ever been true?
 
-  std::vector<std::string> menu_;
-  const char* const* menu_headers_;
-  bool show_menu;
-  int menu_items, menu_sel;
+  bool scrollable_menu_;
+  std::unique_ptr<Menu> menu_;
 
   // An alternate text screen, swapped with 'text_' when we're viewing a log file.
   char** file_viewer_text_;
diff --git a/tests/Android.mk b/tests/Android.mk
index b3584fe87..9a71371fa 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -23,6 +23,7 @@ LOCAL_MODULE := recovery_unit_test
 LOCAL_COMPATIBILITY_SUITE := device-tests
 LOCAL_STATIC_LIBRARIES := \
     libverifier \
+    librecovery_ui \
     libminui \
     libotautil \
     libupdater \
@@ -38,8 +39,9 @@ LOCAL_SRC_FILES := \
     unit/dirutil_test.cpp \
     unit/locale_test.cpp \
     unit/rangeset_test.cpp \
+    unit/screen_ui_test.cpp \
     unit/sysutil_test.cpp \
-    unit/zip_test.cpp \
+    unit/zip_test.cpp
 
 LOCAL_C_INCLUDES := bootable/recovery
 LOCAL_SHARED_LIBRARIES := liblog
diff --git a/tests/unit/screen_ui_test.cpp b/tests/unit/screen_ui_test.cpp
new file mode 100644
index 000000000..be6799f2e
--- /dev/null
+++ b/tests/unit/screen_ui_test.cpp
@@ -0,0 +1,198 @@
+/*
+ * Copyright (C) 2018 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 "screen_ui.h"
+
+#include <string>
+
+#include <gtest/gtest.h>
+
+constexpr const char* HEADER[] = { "header", nullptr };
+constexpr const char* ITEMS[] = { "items1", "items2", "items3", "items4", "1234567890", nullptr };
+
+TEST(ScreenUITest, StartPhoneMenuSmoke) {
+  Menu menu(false, 10, 20);
+  ASSERT_FALSE(menu.scrollable());
+
+  menu.Start(HEADER, ITEMS, 0);
+  ASSERT_EQ(HEADER[0], menu.text_headers()[0]);
+  ASSERT_EQ(5u, menu.ItemsCount());
+
+  std::string message;
+  ASSERT_FALSE(menu.ItemsOverflow(&message));
+  for (size_t i = 0; i < menu.ItemsCount(); i++) {
+    ASSERT_EQ(ITEMS[i], menu.TextItem(i));
+  }
+
+  ASSERT_EQ(0, menu.selection());
+}
+
+TEST(ScreenUITest, StartWearMenuSmoke) {
+  Menu menu(true, 10, 8);
+  ASSERT_TRUE(menu.scrollable());
+
+  menu.Start(HEADER, ITEMS, 1);
+  ASSERT_EQ(HEADER[0], menu.text_headers()[0]);
+  ASSERT_EQ(5u, menu.ItemsCount());
+
+  std::string message;
+  ASSERT_FALSE(menu.ItemsOverflow(&message));
+  for (size_t i = 0; i < menu.ItemsCount() - 1; i++) {
+    ASSERT_EQ(ITEMS[i], menu.TextItem(i));
+  }
+  // Test of the last item is truncated
+  ASSERT_EQ("12345678", menu.TextItem(4));
+  ASSERT_EQ(1, menu.selection());
+}
+
+TEST(ScreenUITest, StartPhoneMenuItemsOverflow) {
+  Menu menu(false, 1, 20);
+  ASSERT_FALSE(menu.scrollable());
+
+  menu.Start(HEADER, ITEMS, 0);
+  ASSERT_EQ(1u, menu.ItemsCount());
+
+  std::string message;
+  ASSERT_FALSE(menu.ItemsOverflow(&message));
+  for (size_t i = 0; i < menu.ItemsCount(); i++) {
+    ASSERT_EQ(ITEMS[i], menu.TextItem(i));
+  }
+
+  ASSERT_EQ(0u, menu.MenuStart());
+  ASSERT_EQ(1u, menu.MenuEnd());
+}
+
+TEST(ScreenUITest, StartWearMenuItemsOverflow) {
+  Menu menu(true, 1, 20);
+  ASSERT_TRUE(menu.scrollable());
+
+  menu.Start(HEADER, ITEMS, 0);
+  ASSERT_EQ(5u, menu.ItemsCount());
+
+  std::string message;
+  ASSERT_TRUE(menu.ItemsOverflow(&message));
+  ASSERT_EQ("Current item: 1/5", message);
+
+  for (size_t i = 0; i < menu.ItemsCount(); i++) {
+    ASSERT_EQ(ITEMS[i], menu.TextItem(i));
+  }
+
+  ASSERT_EQ(0u, menu.MenuStart());
+  ASSERT_EQ(1u, menu.MenuEnd());
+}
+
+TEST(ScreenUITest, PhoneMenuSelectSmoke) {
+  Menu menu(false, 10, 20);
+
+  int sel = 0;
+  menu.Start(HEADER, ITEMS, sel);
+  // Mimic down button 10 times (2 * items size)
+  for (int i = 0; i < 10; i++) {
+    sel = menu.Select(++sel);
+    ASSERT_EQ(sel, menu.selection());
+
+    // Wraps the selection for unscrollable menu when it reaches the boundary.
+    int expected = (i + 1) % 5;
+    ASSERT_EQ(expected, menu.selection());
+
+    ASSERT_EQ(0u, menu.MenuStart());
+    ASSERT_EQ(5u, menu.MenuEnd());
+  }
+
+  // Mimic up button 10 times
+  for (int i = 0; i < 10; i++) {
+    sel = menu.Select(--sel);
+    ASSERT_EQ(sel, menu.selection());
+
+    int expected = (9 - i) % 5;
+    ASSERT_EQ(expected, menu.selection());
+
+    ASSERT_EQ(0u, menu.MenuStart());
+    ASSERT_EQ(5u, menu.MenuEnd());
+  }
+}
+
+TEST(ScreenUITest, WearMenuSelectSmoke) {
+  Menu menu(true, 10, 20);
+
+  int sel = 0;
+  menu.Start(HEADER, ITEMS, sel);
+  // Mimic pressing down button 10 times (2 * items size)
+  for (int i = 0; i < 10; i++) {
+    sel = menu.Select(++sel);
+    ASSERT_EQ(sel, menu.selection());
+
+    // Stops the selection at the boundary if the menu is scrollable.
+    int expected = std::min(i + 1, 4);
+    ASSERT_EQ(expected, menu.selection());
+
+    ASSERT_EQ(0u, menu.MenuStart());
+    ASSERT_EQ(5u, menu.MenuEnd());
+  }
+
+  // Mimic pressing up button 10 times
+  for (int i = 0; i < 10; i++) {
+    sel = menu.Select(--sel);
+    ASSERT_EQ(sel, menu.selection());
+
+    int expected = std::max(3 - i, 0);
+    ASSERT_EQ(expected, menu.selection());
+
+    ASSERT_EQ(0u, menu.MenuStart());
+    ASSERT_EQ(5u, menu.MenuEnd());
+  }
+}
+
+TEST(ScreenUITest, WearMenuSelectItemsOverflow) {
+  Menu menu(true, 3, 20);
+
+  int sel = 1;
+  menu.Start(HEADER, ITEMS, sel);
+  ASSERT_EQ(5u, menu.ItemsCount());
+
+  // Scroll the menu to the end, and check the start & end of menu.
+  for (int i = 0; i < 3; i++) {
+    sel = menu.Select(++sel);
+    ASSERT_EQ(i + 2, sel);
+    ASSERT_EQ(static_cast<size_t>(i), menu.MenuStart());
+    ASSERT_EQ(static_cast<size_t>(i + 3), menu.MenuEnd());
+  }
+
+  // Press down button one more time won't change the MenuStart() and MenuEnd().
+  sel = menu.Select(++sel);
+  ASSERT_EQ(4, sel);
+  ASSERT_EQ(2u, menu.MenuStart());
+  ASSERT_EQ(5u, menu.MenuEnd());
+
+  // Scroll the menu to the top.
+  // The expected menu sel, start & ends are:
+  // sel 3, start 2, end 5
+  // sel 2, start 2, end 5
+  // sel 1, start 1, end 4
+  // sel 0, start 0, end 3
+  for (int i = 0; i < 4; i++) {
+    sel = menu.Select(--sel);
+    ASSERT_EQ(3 - i, sel);
+    ASSERT_EQ(static_cast<size_t>(std::min(3 - i, 2)), menu.MenuStart());
+    ASSERT_EQ(static_cast<size_t>(std::min(6 - i, 5)), menu.MenuEnd());
+  }
+
+  // Press up button one more time won't change the MenuStart() and MenuEnd().
+  sel = menu.Select(--sel);
+  ASSERT_EQ(0, sel);
+  ASSERT_EQ(0u, menu.MenuStart());
+  ASSERT_EQ(3u, menu.MenuEnd());
+}
diff --git a/wear_ui.cpp b/wear_ui.cpp
index ca6b1b102..118e43508 100644
--- a/wear_ui.cpp
+++ b/wear_ui.cpp
@@ -17,7 +17,6 @@
 #include "wear_ui.h"
 
 #include <pthread.h>
-#include <stdio.h>  // TODO: Remove after killing the call to sprintf().
 #include <string.h>
 
 #include <string>
@@ -27,7 +26,8 @@
 #include <minui/minui.h>
 
 WearRecoveryUI::WearRecoveryUI()
-    : kProgressBarBaseline(RECOVERY_UI_PROGRESS_BAR_BASELINE),
+    : ScreenRecoveryUI(true),
+      kProgressBarBaseline(RECOVERY_UI_PROGRESS_BAR_BASELINE),
       kMenuUnusableRows(RECOVERY_UI_MENU_UNUSABLE_ROWS) {
   // TODO: kMenuUnusableRows should be computed based on the lines in draw_screen_locked().
 
@@ -65,13 +65,10 @@ static const char* SWIPE_HELP[] = {
   "Swipe up/down to move.",
   "Swipe left/right to select.",
   "",
-  NULL
+  nullptr,
 };
 
-// TODO merge drawing routines with screen_ui
 void WearRecoveryUI::draw_screen_locked() {
-  char cur_selection_str[50];
-
   draw_background_locked();
   if (!show_text) {
     draw_foreground_locked();
@@ -79,68 +76,7 @@ void WearRecoveryUI::draw_screen_locked() {
     SetColor(TEXT_FILL);
     gr_fill(0, 0, gr_fb_width(), gr_fb_height());
 
-    int y = kMarginHeight;
-    int x = kMarginWidth;
-    if (show_menu) {
-      std::string recovery_fingerprint =
-          android::base::GetProperty("ro.bootimage.build.fingerprint", "");
-      SetColor(HEADER);
-      y += DrawTextLine(x + 4, y, "Android Recovery", true);
-      for (auto& chunk : android::base::Split(recovery_fingerprint, ":")) {
-        y += DrawTextLine(x + 4, y, chunk.c_str(), false);
-      }
-
-      // This is actually the help strings.
-      y += DrawTextLines(x + 4, y, SWIPE_HELP);
-      SetColor(HEADER);
-      y += DrawTextLines(x + 4, y, menu_headers_);
-
-      // Show the current menu item number in relation to total number if
-      // items don't fit on the screen.
-      if (menu_items > menu_end - menu_start) {
-        sprintf(cur_selection_str, "Current item: %d/%d", menu_sel + 1, menu_items);
-        gr_text(gr_sys_font(), x + 4, y, cur_selection_str, 1);
-        y += char_height_ + 4;
-      }
-
-      // Menu begins here
-      SetColor(MENU);
-
-      for (int i = menu_start; i < menu_end; ++i) {
-        if (i == menu_sel) {
-          // draw the highlight bar
-          SetColor(MENU_SEL_BG);
-          gr_fill(x, y - 2, gr_fb_width() - x, y + char_height_ + 2);
-          // white text of selected item
-          SetColor(MENU_SEL_FG);
-          if (menu_[i][0]) {
-            gr_text(gr_sys_font(), x + 4, y, menu_[i].c_str(), 1);
-          }
-          SetColor(MENU);
-        } else if (menu_[i][0]) {
-          gr_text(gr_sys_font(), x + 4, y, menu_[i].c_str(), 0);
-        }
-        y += char_height_ + 4;
-      }
-      SetColor(MENU);
-      y += 4;
-      gr_fill(0, y, gr_fb_width(), y + 2);
-      y += 4;
-    }
-
-    SetColor(LOG);
-
-    // display from the bottom up, until we hit the top of the
-    // screen, the bottom of the menu, or we've displayed the
-    // entire text buffer.
-    int row = text_row_;
-    size_t count = 0;
-    for (int ty = gr_fb_height() - char_height_ - kMarginHeight; ty > y + 2 && count < text_rows_;
-         ty -= char_height_, ++count) {
-      gr_text(gr_sys_font(), x + 4, ty, text_[row], 0);
-      --row;
-      if (row < 0) row = text_rows_ - 1;
-    }
+    draw_menu_and_text_buffer_locked(SWIPE_HELP);
   }
 }
 
@@ -156,45 +92,11 @@ void WearRecoveryUI::StartMenu(const char* const* headers, const char* const* it
                                int initial_selection) {
   pthread_mutex_lock(&updateMutex);
   if (text_rows_ > 0 && text_cols_ > 0) {
-    menu_headers_ = headers;
-    menu_.clear();
-    // "i < text_rows_" is removed from the loop termination condition,
-    // which is different from the one in ScreenRecoveryUI::StartMenu().
-    // Because WearRecoveryUI supports scrollable menu, it's fine to have
-    // more entries than text_rows_. The menu may be truncated otherwise.
-    // Bug: 23752519
-    for (size_t i = 0; items[i] != nullptr; i++) {
-      menu_.emplace_back(std::string(items[i], strnlen(items[i], text_cols_ - 1)));
-    }
-    menu_items = static_cast<int>(menu_.size());
-    show_menu = true;
-    menu_sel = initial_selection;
-    menu_start = 0;
-    menu_end = text_rows_ - 1 - kMenuUnusableRows;
-    if (menu_items <= menu_end) menu_end = menu_items;
-    update_screen_locked();
-  }
-  pthread_mutex_unlock(&updateMutex);
-}
+    menu_ = std::make_unique<Menu>(scrollable_menu_, text_rows_ - kMenuUnusableRows - 1,
+                                   text_cols_ - 1);
+    menu_->Start(headers, items, initial_selection);
 
-int WearRecoveryUI::SelectMenu(int sel) {
-  int old_sel;
-  pthread_mutex_lock(&updateMutex);
-  if (show_menu) {
-    old_sel = menu_sel;
-    menu_sel = sel;
-    if (menu_sel < 0) menu_sel = 0;
-    if (menu_sel >= menu_items) menu_sel = menu_items - 1;
-    if (menu_sel < menu_start) {
-      menu_start--;
-      menu_end--;
-    } else if (menu_sel >= menu_end && menu_sel < menu_items) {
-      menu_end++;
-      menu_start++;
-    }
-    sel = menu_sel;
-    if (menu_sel != old_sel) update_screen_locked();
+    update_screen_locked();
   }
   pthread_mutex_unlock(&updateMutex);
-  return sel;
-}
+}
\ No newline at end of file
diff --git a/wear_ui.h b/wear_ui.h
index 739b4cb1d..8b24cb73e 100644
--- a/wear_ui.h
+++ b/wear_ui.h
@@ -25,10 +25,8 @@ class WearRecoveryUI : public ScreenRecoveryUI {
 
   void SetStage(int current, int max) override;
 
-  // menu display
   void StartMenu(const char* const* headers, const char* const* items,
                  int initial_selection) override;
-  int SelectMenu(int sel) override;
 
  protected:
   // progress bar vertical position, it's centered horizontally
@@ -45,8 +43,6 @@ class WearRecoveryUI : public ScreenRecoveryUI {
  private:
   void draw_background_locked() override;
   void draw_screen_locked() override;
-
-  int menu_start, menu_end;
 };
 
 #endif  // RECOVERY_WEAR_UI_H