Introduction

The Cosmos Graphic Subsystem (abbr. CGS) is based on the abstraction of Canvas that is an empty space in which the user of CGS can draw its content. CGS is not a widget toolkit like Winforms or Gnome / GTK, but is thought to be more lower level and is the basic foundation in which widget toolkits will be implemented. CGS hides the graphics driver (so far VGA, VBE and SVGAII) used and it is thought to be the universal way to draw on the screen in Cosmos.

FullScreenCanvas

The FullScreenCanvas provides two methods to get a canvas instance for the screen. It automatically chooses the best available driver to use.

public static Canvas GetFullScreenCanvas(Mode mode): gets the instance of Canvas representing the complete screen in the specified mode. Some modes that are currently available are as follows: (depends on the backend used)

320x240, 32
640x480, 32
800x600, 32
1024x768, 32
1280x720, 32
1280x768, 32
1280x1024, 32
1366x768, 32
1680x1050, 32
1920x1080, 32
1920x1200, 32

public static Canvas GetFullScreenCanvas(): gets the instance of Canvas representing the complete screen in the best driver available on your platform.

Canvas

List of Properties of the Canvas class

Mode: get / set the mode of the video card to mode. It throws if the selected mode is not supported by the video card.
DefaultGraphicMode: default graphic mode this will change based on the underlying hardware
AvailableModes: list of the available modes supported this will change based on the underlying hardware

List of Methods of the Canvas class

Clear(Color color) clear the entire Canvas using the specified color as background

void DrawPoint(Color color, int x, int y) draws a point at the coordinates specified by x and y with the specified pen

void DrawLine(Color color, int x_start, int y_start, int x_end, int y_end) draws a line at the coordinates specified by x_start, y_start and x_end, y_end with the specified pen

void DrawRectangle(Color color, int x_start, int y_start,int width, int height) draws a rectangle specified by a coordinate pair, a width, and a height with the specified pen

void DrawImage(Image image, int x, int y) draws an image at the x and y specified

void DrawString(String string, Font font, Brush brush, int x, int y) draws a string with the specified font and brush at the specified x and y coordinates

void Display() is only required when using a double buffered driver, swaps the 2 buffers which causes all changes to be displayed

Really simple right?

A working example (DevKit only!)

using System;
using Sys = Cosmos.System;
using Cosmos.System.Graphics;

namespace GraphicTest
{
    public class Kernel : Sys.Kernel
    {
        Canvas canvas;

        private readonly Bitmap bitmap = new Bitmap(10, 10,
                new byte[] { 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0,
                    255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255,
                    0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255,
                    0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 23, 59, 88, 255,
                    23, 59, 88, 255, 0, 255, 243, 255, 0, 255, 243, 255, 23, 59, 88, 255, 23, 59, 88, 255, 0, 255, 243, 255, 0,
                    255, 243, 255, 0, 255, 243, 255, 23, 59, 88, 255, 153, 57, 12, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255,
                    243, 255, 0, 255, 243, 255, 153, 57, 12, 255, 23, 59, 88, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243,
                    255, 0, 255, 243, 255, 0, 255, 243, 255, 72, 72, 72, 255, 72, 72, 72, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0,
                    255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 72, 72,
                    72, 255, 72, 72, 72, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255,
                    10, 66, 148, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255,
                    243, 255, 10, 66, 148, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 10, 66, 148, 255, 10, 66, 148, 255,
                    10, 66, 148, 255, 10, 66, 148, 255, 10, 66, 148, 255, 10, 66, 148, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255,
                    243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 10, 66, 148, 255, 10, 66, 148, 255, 10, 66, 148, 255, 10, 66, 148,
                    255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255,
                    0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, 0, 255, 243, 255, }, ColorDepth.ColorDepth32);
        
        protected override void BeforeRun()
        {
            // If all works correctly you should not really see this :-)
            Console.WriteLine("Cosmos booted successfully. Let's go in Graphical Mode");

            /*
            You don't have to specify the Mode, but here we do to show that you can.
            To not specify the Mode and pick the best one, use:
            canvas = FullScreenCanvas.GetFullScreenCanvas();
            */
            canvas = FullScreenCanvas.GetFullScreenCanvas(new Mode(640, 480, ColorDepth.ColorDepth32));

            // This will clear the canvas with the specified color.
            canvas.Clear(Color.Blue);
        }

        protected override void Run()
        {
            try
            {
                // A red Point
                canvas.DrawPoint(Color.Red, 69, 69);

                // A GreenYellow horizontal line
                canvas.DrawLine(Color.GreenYellow, 250, 100, 400, 100);

                // An IndianRed vertical line
                canvas.DrawLine(Color.IndianRed, 350, 150, 350, 250);

                // A MintCream diagonal line
                canvas.DrawLine(Color.MintCream, 250, 150, 400, 250);

                // A PaleVioletRed rectangle
                canvas.DrawRectangle(Color.PaleVioletRed, 350, 350, 80, 60);

                // A LimeGreen rectangle
                canvas.DrawRectangle(Color.LimeGreen, 450, 450, 80, 60);

                // A bitmap
                canvas.DrawImage(bitmap, 100, 150);
                
                canvas.Display(); // Required for something to be displayed when using a double buffered driver
                
                Console.ReadKey();
                Sys.Power.Shutdown();
            }
            catch (Exception e)
            {
                Debugger.Send("Exception occurred: " + e.Message);
                Sys.Power.Shutdown();
            }
        }
    }
}

Limitations of the current implementation

1. Only 32-bit color depth is actually supported. The API provides methods to set a resolution with 24, 16, 8 and 4 bit but the low level Bochs driver has not yet implemented them. If you use SVGAIICanvas, you can use 24 bit Color depth, and if you use VGACanvas there are 3 modes: 320x200x8, 640x480x4 and 720x480x4.

2. In addition, some other nice things could be implemented:

   • Plugging System.Drawing functions for easier manipulation of colors.
   • Plugging of System.Drawing functions for easier implementation of image conversion.

3. CGS interacts badly with uncaught exceptions and the Kernel.Stop method: the screen will freeze without displaying any error message whatsoever. You must use the Sys.Power.Shutdown() function to properly shut down your computer.

Old examples

On the internet, there have been a lot of tutorials explaining how to use graphics in Cosmos, but most of them are outdated. Just remember that the new Mouse class is Sys.MouseManager and Pen has been replaced with Color.

Last updated on 28 July 2023.