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..4f2f5a8eb135caf7650c00831d39300915c1f4d1 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 {
 
@@ -352,6 +353,7 @@ 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 +373,7 @@ 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 +980,28 @@ void SigninScreenHandler::ReloadGaia(bool force_reload) {
   gaia_screen_handler_->ReloadGaia(force_reload);
 }
 
+void SigninScreenHandler::SetSigninScreenColors(const SkColor& dm_color) {

[jdufault, 2017/06/12 21:37:28]

Just pass a SkColor dm_color parameter and mutate it. FYI, SkColor is an int so
no performance penalty.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:35]

Done. Originally I wanted to prevent mistakenly changing this value but it seems
not necessary.

+  // The dark muted color should have 100% opacity.
+  SkColor dm_sk_color = dm_color;

[jdufault, 2017/06/12 21:37:29]

avoid non-obvious acronyms (dm). It makes the code harder to quickly parse/read.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+  dm_sk_color = SkColorSetA(dm_sk_color, 0xFF);

[jdufault, 2017/06/12 21:37:29]

FYI: naming here is confusing; what is the difference between dm_sk_color and
dm_color? This should get cleaned up by mutating param directly.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:35]

Done.

+  SkColor base_sk_color = color_utils::GetResultingPaintColor(
+      SkColorSetA(ash::kShelfDefaultBaseColor,
+                  ash::kShelfTranslucentColorDarkenAlpha),
+      dm_sk_color);
+  SkColor background_sk_color =

[jdufault, 2017/06/12 21:37:29]

background_sk_color -> background_color

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+      SkColorSetA(base_sk_color, ash::kShelfTranslucentAlpha);
+  // The alpha value for the signin screen background. This constant will be
+  // moved to a separate file when views-based signin screen is being

[jdufault, 2017/06/12 21:37:29]

Add TODO and file a bug.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+  // developed.
+  constexpr int kLoginTranslucentAlpha = 76;

[jdufault, 2017/06/12 21:37:29]

move to anonymous namespace

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+  SkColor scroll_sk_color = SkColorSetA(base_sk_color, kLoginTranslucentAlpha);

[jdufault, 2017/06/12 21:37:29]

scroll_sk_color -> scroll_color

[Wenzhao (Colin) Zang, 2017/06/12 23:40:35]

Done.

+  // Transform SkColor values to rgba strings.

[jdufault, 2017/06/12 21:37:28]

Remove comment, it is immediately obvious.

[Wenzhao (Colin) Zang, 2017/06/12 23:40:34]

Done.

+  CallJS("login.AccountPickerScreen.setOverlayColors",
+         color_utils::SkColorToRgbaString(dm_sk_color),
+         color_utils::SkColorToRgbaString(scroll_sk_color),
+         color_utils::SkColorToRgbaString(background_sk_color));
+}
+
 void SigninScreenHandler::Initialize() {
   // Preload PIN keyboard if any of the users can authenticate via PIN.
   if (user_manager::UserManager::IsInitialized()) {
@@ -1017,6 +1042,14 @@ void SigninScreenHandler::OnCurrentScreenChanged(OobeScreen current_screen,
   }
 }
 
+void SigninScreenHandler::OnColorCalculationComplete() {
+  SkColor dm_color = WallpaperManager::Get()->prominent_color();
+  SetSigninScreenColors(dm_color);
+}
+
+void SigninScreenHandler::OnWallpaperAnimationFinished(
+    const AccountId& account_id) {}
+
 void SigninScreenHandler::ClearAndEnablePassword() {
   core_oobe_view_->ResetSignInUI(false);
 }