Here's a little bit of (heavily) commented code that simply sets up
the screen and draws a line. This should be more than enough to get
you started (it's almost how I started).
/* necessary headers */
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <cursor.h>
/* main routine */
void main(int argc, char *argv[])
{
int c;
void draw_line(void);
/* int initdraw(err_func, default_font, program_name)
If err_func is 0, use default
If default_font is 0, use default */
if (initdraw(0, 0, "program name") < 0)
sysfatal("could not initialize graphics");
draw_line();
for (;;) /* not the best way to wait for a key hit
I don't want to go into events here */
if (read(0, &c, 1) == 1)
break;
exits(0); /* graphics is automatically terminated */
}
So here's how you draw a line:
void draw_line(void)
{
/* this is how to create a color - see allocimage(2) for a complete
list */
Image *black_color = allocimage(display, Rect(0, 0, 1, 1),
RGB24, 1, DBlack);
Point a = Pt(3, 2), b = Pt(400, 900);
/* line(destination, from, to, from_end_type, to_end_type,
thickness,
source_color, point_to_use);
To get the thickness of the line, use the
equation
1 + (2 * thickness)
In this case, the thickness is 1.
Other choices for end types are Enddisc and
Endarrow.
Plan 9 is more powerful than this, however. You
can take any
color from any image or create more elaborate
arrows with
ARROW() as the type parameter. You can even mix
and match
types. But this is more advanced. Refer to
draw(2).
*/
line(screen, a, Endsquare, Endsquare, 0,
black_color, Pt(0, 0));
}
Just stick that in the code section.
On Nov 2, 2007, at 3:12 PM, Anant Narayanan wrote:
Pietro Gagliardi wrote:
cover in a clear way, so I think a tutorial should be put in. I
already
started writing one, and I think it would benefit from being in
- graphics and controls
While I am mostly able understand the other concepts you mention from
existing documentation, I find graphics (libdraw) to be somewhat
cryptic. I've always felt the need for a tutorial-style
introduction on
how to do graphics in Plan 9.
The current solution seems to be mostly be: "Read the code". Which
isn't
really as good.
