Part highlighting is available again.

Blizzy’s toolbar support.
Hiding UI when F2 is pressed.

GameData/CriticalTemperatureGauge/Plugins/CriticalTemperatureGauge.version

@@ -13,7 +13,7 @@
     "MAJOR": 1,
     "MINOR": 1,
     "PATCH": 3,
-    "BUILD": 3
+    "BUILD": 4
   },
   "KSP_VERSION":
   {

src/CriticalTemperatureGauge/AppLauncher.cs

@@ -0,0 +1,131 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using KSP.UI.Screens;
+using UnityEngine;
+
+namespace CriticalTemperatureGauge
+{
+	/// <summary>
+	/// Class that adds the AppLauncher button.
+	/// </summary>
+	[KSPAddon(KSPAddon.Startup.Flight, false)]
+	public class AppLauncher : MonoBehaviour
+	{
+		// Resources
+		static readonly Texture2D AppLauncherButtonTexture =
+			GameDatabase.Instance.GetTexture(Static.TexturePath + "AppLauncherButton", false);
+
+		ApplicationLauncherButton _appLauncherButton;
+		readonly SettingsWindow _settingsWindow = new SettingsWindow();
+
+		public void Update()
+		{
+			if(_appLauncherButton != null)
+				_appLauncherButton.VisibleInScenes = Static.Settings.ShowAppLauncherButton
+					? ApplicationLauncher.AppScenes.FLIGHT | ApplicationLauncher.AppScenes.MAPVIEW
+					: ApplicationLauncher.AppScenes.NEVER;
+		}
+
+		public bool ButtonState
+		{
+			get
+			{
+				return _settingsWindow.IsLogicallyVisible;
+			}
+			set
+			{
+				if(value)
+					_appLauncherButton?.SetTrue();
+				else
+					_appLauncherButton?.SetFalse();
+			}
+		}
+
+		// KSP events:
+
+		public void Start()
+		{
+			OnGUIApplicationLauncherReady();
+			Static.AppLauncher = this;
+		}
+
+		public void Awake()
+		{
+			GameEvents.onGUIApplicationLauncherReady.Add(OnGUIApplicationLauncherReady);
+			GameEvents.onGameSceneLoadRequested.Add(OnSceneChangeRequest);
+			GameEvents.onShowUI.Add(OnShowUI);
+			GameEvents.onHideUI.Add(OnHideUI);
+		}
+
+		internal void OnDestroy()
+		{
+			GameEvents.onGUIApplicationLauncherReady.Remove(OnGUIApplicationLauncherReady);
+			GameEvents.onGameSceneLoadRequested.Remove(OnSceneChangeRequest);
+			GameEvents.onShowUI.Remove(OnShowUI);
+			GameEvents.onHideUI.Remove(OnHideUI);
+			RemoveAppLauncherButton();
+			Static.AppLauncher = null;
+		}
+
+		public void OnGUI()
+		{
+			_settingsWindow.DrawGUI();
+		}
+
+		void OnGUIApplicationLauncherReady()
+		{
+			AddAppLauncherButton();
+		}
+
+		void OnSceneChangeRequest(GameScenes scene)
+		{
+			RemoveAppLauncherButton();
+		}
+
+		void OnShowUI()
+		{
+			_settingsWindow.CanShow = true;
+		}
+
+		void OnHideUI()
+		{
+			_settingsWindow.CanShow = false;
+		}
+
+		/// <summary>Shows the settings window when the button is pressed.</summary>
+		void OnButtonOn()
+		{
+			_settingsWindow.Show();
+		}
+
+		/// <summary>Hides the settings window when the button is pressed again.</summary>
+		void OnButtonOff()
+		{
+			_settingsWindow.Hide();
+		}
+
+		/// <summary>Adds the button to the appLauncher.</summary>
+		void AddAppLauncherButton()
+		{
+			if(_appLauncherButton == null)
+				_appLauncherButton = ApplicationLauncher.Instance.AddModApplication(
+					onTrue: OnButtonOn,
+					onFalse: OnButtonOff,
+					onHover: null,
+					onHoverOut: null,
+					onEnable: null,
+					onDisable: null,
+					visibleInScenes: ApplicationLauncher.AppScenes.NEVER,
+					texture: AppLauncherButtonTexture);
+			Update();
+		}
+
+		/// <summary>Removes the button from the appLauncher.</summary>
+		void RemoveAppLauncherButton()
+		{
+			if(_appLauncherButton != null)
+				ApplicationLauncher.Instance.RemoveModApplication(_appLauncherButton);
+		}
+	}
+}

src/CriticalTemperatureGauge/BlizzysToolbar.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CriticalTemperatureGauge
+{
+	public class BlizzysToolbar
+	{
+		const string ButtonId = "Settings";
+		const string ButtonTexturePath = Static.TexturePath + "BizzysToolbarButton";
+
+		IButton _toolbarButton;
+
+		public void Start()
+		{
+			if(ToolbarManager.ToolbarAvailable)
+			{
+				_toolbarButton = ToolbarManager.Instance.add(nameof(CriticalTemperatureGauge), nameof(CriticalTemperatureGauge) + ButtonId);
+				_toolbarButton.TexturePath = ButtonTexturePath;
+				_toolbarButton.ToolTip = Static.PluginTitle;
+				_toolbarButton.OnClick += e =>
+				{
+					if(Static.AppLauncher != null && e.MouseButton == 0 /* Left mouse button */)
+						Static.AppLauncher.ButtonState = !Static.AppLauncher.ButtonState;
+				};
+			}
+		}
+
+		public void Destroy()
+		{
+			_toolbarButton?.Destroy();
+		}
+	}
+}