Task: Draw a clock





Java: import java.awt.*;
import java.awt.event.*;
import static java.lang.Math.*;
import java.time.LocalTime;
import javax.swing.*;

class Clock extends JPanel {

    final float degrees06 = (float) (PI / 30);
    final float degrees30 = degrees06 * 5;
    final float degrees90 = degrees30 * 3;

    final int size = 590;
    final int spacing = 40;
    final int diameter = size - 2 * spacing;
    final int cx = diameter / 2 + spacing;
    final int cy = diameter / 2 + spacing;

    public Clock() {
        setPreferredSize(new Dimension(size, size));
        setBackground(Color.white);

        new Timer(1000, (ActionEvent e) -> {
            repaint();
        }).start();
    }

    @Override
    public void paintComponent(Graphics gg) {
        super.paintComponent(gg);
        Graphics2D g = (Graphics2D) gg;
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

        drawFace(g);

        final LocalTime time  = LocalTime.now();
        int hour = time.getHour();
        int minute = time.getMinute();
        int second = time.getSecond();

        float angle = degrees90 - (degrees06 * second);
        drawHand(g, angle, diameter / 2 - 30, Color.red);

        float minsecs = (minute + second / 60.0F);
        angle = degrees90 - (degrees06 * minsecs);
        drawHand(g, angle, diameter / 3 + 10, Color.black);

        float hourmins = (hour + minsecs / 60.0F);
        angle = degrees90 - (degrees30 * hourmins);
        drawHand(g, angle, diameter / 4 + 10, Color.black);
    }

    private void drawFace(Graphics2D g) {
        g.setStroke(new BasicStroke(2));
        g.setColor(Color.white);
        g.fillOval(spacing, spacing, diameter, diameter);
        g.setColor(Color.black);
        g.drawOval(spacing, spacing, diameter, diameter);
    }

    private void drawHand(Graphics2D g, float angle, int radius, Color color) {
        int x = cx + (int) (radius * cos(angle));
        int y = cy - (int) (radius * sin(angle));
        g.setColor(color);
        g.drawLine(cx, cy, x, y);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setTitle("Clock");
            f.setResizable(false);
            f.add(new Clock(), BorderLayout.CENTER);
            f.pack();
            f.setLocationRelativeTo(null);
            f.setVisible(true);
        });
    }
}







Ada: with Ada.Numerics.Elementary_Functions;
with Ada.Calendar.Formatting;
with Ada.Calendar.Time_Zones;

with SDL.Video.Windows.Makers;
with SDL.Video.Renderers.Makers;
with SDL.Events.Events;

procedure Draw_A_Clock is
   use Ada.Calendar;
   use Ada.Calendar.Formatting;
   Window   : SDL.Video.Windows.Window;
   Renderer : SDL.Video.Renderers.Renderer;
   Event    : SDL.Events.Events.Events;
   Offset   : Time_Zones.Time_Offset;

   procedure Draw_Clock (Stamp : Time)
   is
      use SDL.C;
      use Ada.Numerics.Elementary_Functions;
      Radi : constant array (0 .. 59) of int := (0 | 15 | 30 | 45 => 2,
                                                 5 | 10 | 20 | 25 | 35 | 40 | 50 | 55 => 1,
                                                 others => 0);
      Diam : constant array (0 .. 59) of int := (0 | 15 | 30 | 45 => 5,
                                                 5 | 10 | 20 | 25 | 35 | 40 | 50 | 55 => 3,
                                                 others => 1);
      Width  : constant int   := Window.Get_Surface.Size.Width;
      Height : constant int   := Window.Get_Surface.Size.Height;
      Radius : constant Float := Float (int'Min (Width, Height));
      R_1    : constant Float := 0.48 * Radius;
      R_2    : constant Float := 0.35 * Radius;
      R_3    : constant Float := 0.45 * Radius;
      R_4    : constant Float := 0.47 * Radius;
      Hour   : constant Hour_Number   := Formatting.Hour   (Stamp, Offset);
      Minute : constant Minute_Number := Formatting.Minute (Stamp, Offset);
      Second : constant Second_Number := Formatting.Second (Stamp);

      function To_X (A : Float; R : Float) return int is
         (Width / 2 + int (R * Sin (A, 60.0)));

      function To_Y (A : Float; R : Float) return int is
         (Height / 2 - int (R * Cos (A, 60.0)));

   begin
      SDL.Video.Renderers.Makers.Create (Renderer, Window.Get_Surface);
      Renderer.Set_Draw_Colour ((0, 0, 150, 255));
      Renderer.Fill (Rectangle => (0, 0, Width, Height));
      Renderer.Set_Draw_Colour ((200, 200, 200, 255));
      for A in 0 .. 59 loop
         Renderer.Fill (Rectangle => (To_X (Float (A), R_1) - Radi (A),
                                      To_Y (Float (A), R_1) - Radi (A), Diam (A), Diam (A)));
      end loop;
      Renderer.Set_Draw_Colour ((200, 200, 0, 255));
      Renderer.Draw (Line => ((Width / 2, Height / 2),
                              (To_X (5.0 * (Float (Hour) + Float (Minute) / 60.0), R_2),
                               To_Y (5.0 * (Float (Hour) + Float (Minute) / 60.0), R_2))));
      Renderer.Draw (Line => ((Width / 2, Height / 2),
                              (To_X (Float (Minute) + Float (Second) / 60.0, R_3),
                               To_Y (Float (Minute) + Float (Second) / 60.0, R_3))));
      Renderer.Set_Draw_Colour ((220, 0, 0, 255));
      Renderer.Draw (Line => ((Width / 2, Height / 2),
                              (To_X (Float (Second), R_4),
                               To_Y (Float (Second), R_4))));
      Renderer.Fill (Rectangle => (Width / 2 - 3, Height / 2 - 3, 7, 7));
   end Draw_Clock;

   function Poll_Quit return Boolean is
      use type SDL.Events.Event_Types;
   begin
      while SDL.Events.Events.Poll (Event) loop
         if Event.Common.Event_Type = SDL.Events.Quit then
            return True;
         end if;
      end loop;
      return False;
   end Poll_Quit;

begin
   Offset := Time_Zones.UTC_Time_Offset;

   if not SDL.Initialise (Flags => SDL.Enable_Screen) then
      return;
   end if;

   SDL.Video.Windows.Makers.Create (Win      => Window,
                                    Title    => "Draw a clock",
                                    Position => SDL.Natural_Coordinates'(X => 10, Y => 10),
                                    Size     => SDL.Positive_Sizes'(300, 300),
                                    Flags    => SDL.Video.Windows.Resizable);
   loop
      Draw_Clock (Clock);
      Window.Update_Surface;
      delay 0.200;
      exit when Poll_Quit;
   end loop;

   Window.Finalize;
   SDL.Finalise;
end Draw_A_Clock;