Extract colors from wallpaper and dynamically update login screen overlay

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 168c632f511766e5a7433c295925a78d8a9b1ad1..30e6aa0cd04e7e60cb90961b39517383977db98a 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -11,6 +11,7 @@
 
 #include "ash/public/interfaces/constants.mojom.h"
 #include "ash/public/interfaces/tray_action.mojom.h"
+#include "ash/shelf/shelf_constants.h"
 #include "ash/shell.h"
 #include "ash/system/devicetype_utils.h"
 #include "ash/wm/lock_state_controller.h"
@@ -51,7 +52,6 @@
 #include "chrome/browser/chromeos/login/ui/login_feedback.h"
 #include "chrome/browser/chromeos/login/ui/webui_login_display.h"
 #include "chrome/browser/chromeos/login/users/multi_profile_user_controller.h"
-#include "chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 #include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
 #include "chrome/browser/chromeos/policy/device_local_account.h"
@@ -101,6 +101,7 @@
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/base/ime/chromeos/input_method_util.h"
 #include "ui/base/webui/web_ui_util.h"
+#include "ui/gfx/color_utils.h"
 
 namespace {
 
@@ -126,6 +127,11 @@ const char kNoLockScreenApps[] = "LOCK_SCREEN_APPS_STATE.NONE";
 const char kBackgroundLockScreenApps[] = "LOCK_SCREEN_APPS_STATE.BACKGROUND";
 const char kForegroundLockScreenApps[] = "LOCK_SCREEN_APPS_STATE.FOREGROUND";
 
+// The alpha value for the signin screen background.
+// TODO(crbug.com/732566): Move all constants related to views-based signin
+// screen to a separate file.
+constexpr int kLoginTranslucentAlpha = 76;
+
 static bool Contains(const std::vector<std::string>& container,
                      const std::string& value) {
   return std::find(container.begin(), container.end(), value) !=
@@ -352,6 +358,7 @@ SigninScreenHandler::SigninScreenHandler(
       lock_screen_apps::StateController::IsEnabled()) {
     lock_screen_apps_observer_.Add(lock_screen_apps::StateController::Get());
   }
+  WallpaperManager::Get()->AddObserver(this);
 }
 
 SigninScreenHandler::~SigninScreenHandler() {
@@ -371,6 +378,7 @@ SigninScreenHandler::~SigninScreenHandler() {
   network_state_informer_->RemoveObserver(this);
   proximity_auth::ScreenlockBridge::Get()->SetLockHandler(nullptr);
   proximity_auth::ScreenlockBridge::Get()->SetFocusedUser(EmptyAccountId());
+  WallpaperManager::Get()->RemoveObserver(this);
 }
 
 // static
@@ -977,6 +985,22 @@ void SigninScreenHandler::ReloadGaia(bool force_reload) {
   gaia_screen_handler_->ReloadGaia(force_reload);
 }
 
+void SigninScreenHandler::SetSigninScreenColors(SkColor dark_muted_color) {
+  // The dark muted color should have 100% opacity.
+  dark_muted_color = SkColorSetA(dark_muted_color, 0xFF);
+  SkColor base_color = color_utils::GetResultingPaintColor(
+      SkColorSetA(ash::kShelfDefaultBaseColor,
+                  ash::kShelfTranslucentColorDarkenAlpha),
+      dark_muted_color);
+  SkColor background_color =
+      SkColorSetA(base_color, ash::kShelfTranslucentAlpha);
+  SkColor scroll_color = SkColorSetA(base_color, kLoginTranslucentAlpha);
+  CallJS("login.AccountPickerScreen.setOverlayColors",
+         color_utils::SkColorToRgbaString(dark_muted_color),
+         color_utils::SkColorToRgbaString(scroll_color),
+         color_utils::SkColorToRgbaString(background_color));
+}
+
 void SigninScreenHandler::Initialize() {
   // Preload PIN keyboard if any of the users can authenticate via PIN.
   if (user_manager::UserManager::IsInitialized()) {
@@ -1017,6 +1041,17 @@ void SigninScreenHandler::OnCurrentScreenChanged(OobeScreen current_screen,
   }
 }
 
+void SigninScreenHandler::OnWallpaperColorsChanged() {
+  base::Optional<SkColor> color = WallpaperManager::Get()->prominent_color();
+  // If color extraction fails, use transparent as default.
+  if (!color.has_value())
+    color = SK_ColorTRANSPARENT;
+  SetSigninScreenColors(color.value());
+}
+
+void SigninScreenHandler::OnWallpaperAnimationFinished(
+    const AccountId& account_id) {}
+
 void SigninScreenHandler::ClearAndEnablePassword() {
   core_oobe_view_->ResetSignInUI(false);
 }