Use LocalisableStrings where possible to leverage localisable text flow

osu.Game/Graphics/UserInterface/OsuCheckbox.cs

@@ -8,6 +8,7 @@ using osu.Framework.Graphics;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.UserInterface;
 using osu.Framework.Input.Events;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.Containers;
 
 namespace osu.Game.Graphics.UserInterface
@@ -19,7 +20,7 @@ namespace osu.Game.Graphics.UserInterface
         /// </summary>
         protected virtual bool PlaySoundsOnUserChange => true;
 
-        public string LabelText
+        public LocalisableString LabelText
         {
             set
             {

osu.Game/Graphics/UserInterfaceV2/LabelledDrawable.cs

@@ -8,6 +8,7 @@ using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.Containers;
 using osu.Game.Overlays;
 using osuTK;
@@ -156,18 +157,18 @@ namespace osu.Game.Graphics.UserInterfaceV2
             descriptionText.Colour = osuColour.Yellow;
         }
 
-        public string Label
+        public LocalisableString Label
         {
             set => labelText.Text = value;
         }
 
-        public string Description
+        public LocalisableString Description
         {
             set
             {
                 descriptionText.Text = value;
 
-                if (!string.IsNullOrEmpty(value))
+                if (value == default)
                     descriptionText.Show();
                 else
                     descriptionText.Hide();

osu.Game/Online/Placeholders/ClickablePlaceholder.cs

@@ -3,6 +3,7 @@
 
 using System;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
 
@@ -12,7 +13,7 @@ namespace osu.Game.Online.Placeholders
     {
         public Action Action;
 
-        public ClickablePlaceholder(string actionMessage, IconUsage icon)
+        public ClickablePlaceholder(LocalisableString actionMessage, IconUsage icon)
         {
             OsuTextFlowContainer textFlow;
 

osu.Game/Online/Placeholders/MessagePlaceholder.cs

@@ -3,14 +3,15 @@
 
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
 
 namespace osu.Game.Online.Placeholders
 {
     public class MessagePlaceholder : Placeholder
     {
-        private readonly string message;
+        private readonly LocalisableString message;
 
-        public MessagePlaceholder(string message)
+        public MessagePlaceholder(LocalisableString message)
         {
             AddIcon(FontAwesome.Solid.ExclamationCircle, cp =>
             {

osu.Game/Overlays/Dialog/PopupDialog.cs

@@ -10,6 +10,7 @@ using osu.Framework.Graphics.Effects;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Input.Events;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.Backgrounds;
 using osu.Game.Graphics.Containers;
 using osuTK;
@@ -42,9 +43,9 @@ namespace osu.Game.Overlays.Dialog
             set => icon.Icon = value;
         }
 
-        private string headerText;
+        private LocalisableString headerText;
 
-        public string HeaderText
+        public LocalisableString HeaderText
         {
             get => headerText;
             set
@@ -57,9 +58,9 @@ namespace osu.Game.Overlays.Dialog
             }
         }
 
-        private string bodyText;
+        private LocalisableString bodyText;
 
-        public string BodyText
+        public LocalisableString BodyText
         {
             get => bodyText;
             set

osu.Game/Overlays/Notifications/ProgressNotification.cs

@@ -10,6 +10,7 @@ using osu.Framework.Graphics.Colour;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
@@ -22,7 +23,7 @@ namespace osu.Game.Overlays.Notifications
     {
         private const float loading_spinner_size = 22;
 
-        public string Text
+        public LocalisableString Text
         {
             set => Schedule(() => textDrawable.Text = value);
         }

osu.Game/Overlays/Notifications/SimpleNotification.cs

@@ -7,6 +7,7 @@ using osu.Framework.Graphics.Colour;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
 using osuTK;
@@ -15,9 +16,9 @@ namespace osu.Game.Overlays.Notifications
 {
     public class SimpleNotification : Notification
     {
-        private string text = string.Empty;
+        private LocalisableString text;
 
-        public string Text
+        public LocalisableString Text
         {
             get => text;
             set

osu.Game/Screens/Edit/Timing/SliderWithTextBoxInput.cs

@@ -6,6 +6,7 @@ using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.UserInterface;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.UserInterfaceV2;
 using osu.Game.Overlays.Settings;
 
@@ -16,7 +17,7 @@ namespace osu.Game.Screens.Edit.Timing
     {
         private readonly SettingsSlider<T> slider;
 
-        public SliderWithTextBoxInput(string labelText)
+        public SliderWithTextBoxInput(LocalisableString labelText)
         {
             LabelledTextBox textbox;