= draw: example: simple program illustrating image primitives This  manual  page  presents  a self-contained simple programthat illustrates most  of  the  feature  of  the  basic  drawlibrary.   It  must  be  run  at  the top-level Inferno shellprompt, not within a window system, as it establishes its ownconnection to the display and writes directly on the display,not in a private window. The program exercises the drawing primitives, taking particu‐lar  care  to maintain a consistent coordinate system for thecombinations of images on the display.  Comments in the  codeintroduce each step.     implement Test;     include "sys.m";        include "draw.m";        Test: module    {         init:     fn(ctxt: ref Draw->Context, argv: list of string);    };        init(nil: ref Draw->Context, nil: list of string)    {         sys := load Sys Sys->PATH;         draw := load Draw Draw->PATH;         Display, Font, Rect, Point, Image, Screen: import draw;             #         # Set up connection to display and initialize colours.         #         display := draw->Display.allocate(nil);         disp := display.image;         red := display.color(Draw->Red);         blue := display.color(Draw->Blue);         white := display.color(Draw->White);         yellow := display.color(Draw->Yellow);             #         # Paint the screen red.         #         disp.draw(disp.r, red, nil, disp.r.min);         sys->sleep(5000);             #         # Texture a region with rectangular tiles.         #         texture := display.newimage(((0,0),(2,3)),              disp.chans, 1, Draw->Black);         texture.clipr = ((-10000,-10000),(10000,10000));         # put something in the texture         texture.draw(((0,0),(1,3)), white, nil, (0,0));         texture.draw(((0,0),(2, 1)), white, nil, (0,0));         # use texture as both source and mask to let         # destination colour show through         disp.draw(((100,100),(200,300)), texture,              texture, (0,0));         sys->sleep(5000);             #         # White-out a quarter of the pixels in a region,         # to make the region appear shaded.         #         stipple := display.newimage(((0,0),(2,2)),                        disp.chans, 1, Draw->Transparent);         stipple.draw(((0,0),(1,1)), display.opaque,                        nil, (0,0));         disp.draw(((100,100),(300,250)), white,                        stipple, (0,0));         sys->sleep(5000);             #         # Draw textured characters.         #         font := Font.open(display, "*default*");         disp.text((100,310), texture, (0,0), font,                   "Hello world");         sys->sleep(5000);             #         # Draw picture in elliptical frame.         #         delight := display.open("/icons/delight.bit");         piccenter := delight.r.min.add(delight.r.max).div(2);         disp.fillellipse((250,250), 150, 50,              delight, piccenter);         disp.ellipse((250,250), 150, 50, 3, yellow, (0,0));         sys->sleep(5000);             #         # Draw a parabolic brush stroke using an elliptical brush         # to reveal more of the picture, consistent with what's         # already visible.         #         dx : con 15;         dy : con 3;         brush := display.newimage(((0,0),(2*dx+1,2*dy+1)), disp.chans,                                   0, Draw->Black);         brush.fillellipse((dx,dy), dx, dy, display.white,                        (0,0));         for(x:=delight.r.min.x; x<delight.r.max.x; x++){              y := (x-piccenter.x)*(x-piccenter.x)/80;              y += 2*dy+1;   # so whole brush is visible at top              xx := x+(250-piccenter.x)-dx;              yy := y+(250-piccenter.y)-dy;              disp.gendraw(((xx,yy),(xx+2*dx+1,yy+2*dy+1)),                           delight, (x-dx, y-dy), brush,                   (0,0));         }    }