Cosmos Graphic Subsystem
The Cosmos Graphic Subsystem (CGS from now on) 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 as Winforms or Gnome / GTK but is thought to be more lower level and it will be the basic in which widget toolkits will be implemented. CGS hides the graphics driver (so far VGA, VBE and SVGA II) 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
public static Canvas GetFullScreenCanvas(): gets the instance of Canvas representing the complete screen in the best driver available on your platform
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(Pen pen, int x, int y) draws a point at the coordinates specified by x and y with the specified pen
void DrawLine(Pen pen, 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(Pen pen, 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?
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.
canvas = FullScreenCanvas.GetFullScreenCanvas(new Mode(640, 480, ColorDepth.ColorDepth32));
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)
{
mDebugger.Send("Exception occurred: " + e.Message);
Sys.Power.Shutdown();
}
}
}
} Limitations of the current implementation 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.
In addition, some other nice things could be implemented:
Plugging System.Drawing functions for easier manipulation of colors CGS interacts badly with the uncaught exceptions and 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.