Userspace: Start work on GUI and WindowServer

Current implementation can create custom windows and each window has
its own framebuffer. When window wants to write its framebuffer to the
screen it will send a message to the WindowServer using unix sockets.

userspace/test-window/CMakeLists.txt

@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(test-window CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(test-window ${SOURCES})
+target_compile_options(test-window PUBLIC -O2 -g)
+target_link_libraries(test-window PUBLIC libc ban libgui)
+
+add_custom_target(test-window-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/test-window ${BANAN_BIN}/
+	DEPENDS test-window
+)

userspace/test-window/main.cpp

@@ -0,0 +1,61 @@
+#include <BAN/Debug.h>
+
+#include <LibGUI/Window.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+
+void randomize_color(BAN::UniqPtr<LibGUI::Window>& window)
+{
+	uint32_t color = ((rand() % 255) << 16) | ((rand() % 255) << 8) | ((rand() % 255) << 0);
+	for (uint32_t y = 0; y < window->height(); y++)
+		for (uint32_t x = 0; x < window->width(); x++)
+			window->set_pixel(x, y, color);
+	window->invalidate();
+}
+
+int main()
+{
+	timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	srand(ts.tv_nsec);
+
+	auto window_or_error = LibGUI::Window::create(300, 200);
+	if (window_or_error.is_error())
+	{
+		dprintln("{}", window_or_error.error());
+		return 1;
+	}
+
+	auto window = window_or_error.release_value();
+	window->set_mouse_button_event_callback(
+		[&](LibGUI::EventPacket::MouseButtonEvent event)
+		{
+			if (event.pressed && event.button == LibGUI::EventPacket::MouseButton::Left)
+				randomize_color(window);
+
+			const char* button;
+			switch (event.button)
+			{
+				case LibGUI::EventPacket::MouseButton::Left: button = "left"; break;
+				case LibGUI::EventPacket::MouseButton::Right: button = "right"; break;
+				case LibGUI::EventPacket::MouseButton::Middle: button = "middle"; break;
+				case LibGUI::EventPacket::MouseButton::Extra1: button = "extra1"; break;
+				case LibGUI::EventPacket::MouseButton::Extra2: button = "extra2"; break;
+			}
+			dprintln("mouse button '{}' {} at {}, {}", button, event.pressed ? "pressed" : "released", event.x, event.y);
+		}
+	);
+
+	randomize_color(window);
+
+	for (;;)
+	{
+		window->poll_events();
+
+		timespec duration;
+		duration.tv_sec = 0;
+		duration.tv_nsec = 16'666'666;
+		nanosleep(&duration, nullptr);
+	}
+}