NAME

draw: example − simple program illustrating image primitives

DESCRIPTION

This manual page presents a self-contained simple program that illustrates most of the feature of the basic draw library.  It must be run at the top-level Inferno shell prompt, not within a window system, as it establishes its own connection to the display and writes directly on the display, not in a private window. 

The program exercises the drawing primitives, taking particular care to maintain a consistent coordinate system for the combinations of images on the display.  Comments in the code introduce 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)); } }