Userspace: Implement basic task bar

This bar only shows current time but its something to work on later!

userspace/programs/CMakeLists.txt

@@ -30,6 +30,7 @@ set(USERSPACE_PROGRAMS
 	sudo
 	sync
 	tee
+	TaskBar
 	Terminal
 	touch
 	u8sum

userspace/programs/TaskBar/CMakeLists.txt

@@ -0,0 +1,12 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(TaskBar ${SOURCES})
+banan_link_library(TaskBar ban)
+banan_link_library(TaskBar libc)
+banan_link_library(TaskBar libfont)
+banan_link_library(TaskBar libgui)
+banan_include_headers(TaskBar libinput)
+
+install(TARGETS TaskBar OPTIONAL)

userspace/programs/TaskBar/main.cpp

@@ -0,0 +1,71 @@
+#include <LibFont/Font.h>
+#include <LibGUI/Window.h>
+
+#include <time.h>
+
+int main()
+{
+	constexpr uint32_t padding = 3;
+	constexpr uint32_t bg_color = 0xFF202020;
+	constexpr uint32_t fg_color = 0xFFFFFFFF;
+
+	auto font = MUST(LibFont::Font::load("/usr/share/fonts/lat0-16.psfu"_sv));
+
+	auto window = MUST(LibGUI::Window::create(0, font.height() + 2 * padding, "TaskBar"));
+
+	auto attributes = window->get_attributes();
+	attributes.title_bar = false;
+	attributes.movable = false;
+	attributes.alpha_channel = false;
+	attributes.rounded_corners = false;
+	window->set_attributes(attributes);
+
+	window->set_position(0, 0);
+
+	window->fill(bg_color);
+	window->invalidate();
+
+	time_t last_update;
+	const auto update_time_string =
+		[&]()
+		{
+			last_update = time(nullptr);
+			BAN::StringView time_sv = ctime(&last_update);
+			time_sv = time_sv.substring(0, time_sv.size() - 1); // new line
+
+			const uint32_t text_w = time_sv.size() * font.width();
+			const uint32_t text_h = font.height();
+			const uint32_t text_x = window->width() - text_w - padding;
+			const uint32_t text_y = padding;
+
+			window->fill_rect(text_x, text_y, text_w, text_h, bg_color);
+			window->draw_text(time_sv, font, text_x, text_y, fg_color);
+			window->invalidate(text_x, text_y, text_w, text_h);
+		};
+
+	for (;;)
+	{
+		update_time_string();
+
+		constexpr uint64_t ns_per_s = 1'000'000'000;
+
+		timespec current_ts;
+		clock_gettime(CLOCK_REALTIME, &current_ts);
+
+		uint64_t current_ns = 0;
+		current_ns += current_ts.tv_sec * ns_per_s;
+		current_ns += current_ts.tv_nsec;
+
+		uint64_t target_ns = current_ns;
+		if (auto rem = target_ns % ns_per_s)
+			target_ns += ns_per_s - rem;
+
+		uint64_t sleep_ns = target_ns - current_ns;
+
+		timespec sleep_ts;
+		sleep_ts.tv_sec  = sleep_ns / ns_per_s;
+		sleep_ts.tv_nsec = sleep_ns % ns_per_s;
+
+		nanosleep(&sleep_ts, nullptr);
+	}
+}