LibGUI: Add support for focusable windows and mouse capturing

These are essential parts of a window server! This allows making TaskBar
non-focusable.

userspace/libraries/LibGUI/include/LibGUI/Packet.h

@@ -162,6 +162,7 @@ namespace LibGUI
 		WindowInvalidate,
 		WindowSetPosition,
 		WindowSetAttributes,
+		WindowSetMouseCapture,
 
 		DestroyWindowEvent,
 		CloseWindowEvent,
@@ -174,35 +175,49 @@ namespace LibGUI
 	namespace WindowPacket
 	{
 
-		DEFINE_PACKET(WindowCreate,
+		DEFINE_PACKET(
+			WindowCreate,
 			uint32_t, width,
 			uint32_t, height,
 			BAN::String, title
 		);
 
-		DEFINE_PACKET(WindowCreateResponse,
+		DEFINE_PACKET(
+			WindowCreateResponse,
 			uint32_t, width,
 			uint32_t, height,
 			long, smo_key
 		);
 
-		DEFINE_PACKET(WindowInvalidate,
+		DEFINE_PACKET(
+			WindowInvalidate,
 			uint32_t, x,
 			uint32_t, y,
 			uint32_t, width,
 			uint32_t, height
 		);
 
-		DEFINE_PACKET(WindowSetPosition,
+		DEFINE_PACKET(
+			WindowSetPosition,
 			int32_t, x,
 			int32_t, y
 		);
 
-		DEFINE_PACKET(WindowSetAttributes,
-			bool, title_bar,
-			bool, rounded_corners,
-			bool, movable,
-			bool, alpha_channel
+		DEFINE_PACKET_EXTRA(
+			WindowSetAttributes,
+			struct Attributes {
+				bool title_bar;
+				bool movable;
+				bool focusable;
+				bool rounded_corners;
+				bool alpha_channel;
+			},
+			Attributes, attributes
+		);
+
+		DEFINE_PACKET(
+			WindowSetMouseCapture,
+			bool, captured
 		);
 
 	}

userspace/libraries/LibGUI/include/LibGUI/Window.h

@@ -14,12 +14,14 @@ namespace LibGUI
 	class Window
 	{
 	public:
-		struct Attributes
-		{
-			bool title_bar       { true };
-			bool movable         { true };
-			bool rounded_corners { true };
-			bool alpha_channel   { false };
+		using Attributes = WindowPacket::WindowSetAttributes::Attributes;
+
+		static constexpr Attributes default_attributes = {
+			.title_bar       = true,
+			.movable         = true,
+			.focusable       = true,
+			.rounded_corners = true,
+			.alpha_channel   = false,
 		};
 
 	public:
@@ -58,6 +60,8 @@ namespace LibGUI
 		bool invalidate(int32_t x, int32_t y, uint32_t width, uint32_t height);
 		bool invalidate() { return invalidate(0, 0, width(), height()); }
 
+		bool set_mouse_capture(bool captured);
+
 		bool set_position(int32_t x, int32_t y);
 
 		Attributes get_attributes() const { return m_attributes; }