Re: Please give me some suggestion about my application

From: "Lazy Fox" <lazy fox wu gmail com>
To: gtk-list gnome org
Subject: Re: Please give me some suggestion about my application
Date: Wed, 13 Aug 2008 10:16:32 +0800

I'm sorry, what is "Goo::Canvas"? I can't find it in the "GTK+ Reference Manual"

On 8/13/08, zentara <zentara1 sbcglobal net> wrote:

On Tue, 12 Aug 2008 22:27:28 +0800
"Lazy Fox" <lazy fox wu gmail com> wrote:

> I want to draw a loopback-able dynamic curve, just like the following
>picture:
>http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/18030.jpg
>
>The curve is keeping going, from left to right. When reach the right border,
>it will loopback to the left border, and do this again and again.
>
>But, when the curve loopback to the left border, the existent drawing will
>not
>be erased immediately. Instead, the older drawing will be erased step by
>step,
>where the new curve is drawing.
>
>Considering the efficiency. In this case, which widget should I draw on?
>How can I erase the image step by step,
>not erase all of it? Which function should I use?

I apologize to the c experts for this Perl, :-), but it's so easy for
me to prototype in Perl. Here is an example of what you can do on
the Goo::Canvas.

I simulated the beat pulse with a weird sine wave, but it should show you
how nice it could work. The axis are a bit extra, but I already had this
example, to show how to invert the y axis direction to get a standard cartesian
plot, i.e. y increases going up.
I also took the liberty of making a recursive sub call for this demo, but it
should'nt be hard to feed in real data. Of course, c will be faster, but
it's up to you to port it, if you like it.

#!/usr/bin/perl -w
use strict;
use warnings;
use Goo::Canvas;
use Gtk2 '-init';
use Glib qw(TRUE FALSE);
use Gtk2::Gdk::Keysyms;

my $scale = 1;

my $window = Gtk2::Window->new('toplevel');
$window->signal_connect('delete_event' => sub { Gtk2->main_quit; });
$window->set_size_request(800, 600);

my $swin = Gtk2::ScrolledWindow->new;
$swin->set_shadow_type('in');
$window->add($swin);

my ($cwidth,$cheight)= (1200,1200);
my $canvas = Goo::Canvas->new();
$canvas->set_size_request(800, 650);
$canvas->set_bounds(0, 0, $cwidth, $cheight);
my $black = Gtk2::Gdk::Color->new (0x0000,0x0000,0x0000);
my $white = Gtk2::Gdk::Color->new (0xFFFF,0xFFFF,0xFFFF);
$canvas->modify_base('normal',$white );
$swin->add($canvas);

my $root = $canvas->get_root_item();

my ($margin_x,$margin_y) = (100,100);

my $g = Goo::Canvas::Group->new($root);
$g->scale(1,-1); #reverse direction of y axis, so graphing will be normal cartesian
$g->translate(0 + $margin_x, -1200 + $margin_y); #notice translations are reversed
$canvas->scroll_to(0,$cheight);

# add a background rect filling $g, so button press will be detected
# otherwise $g will be invisible to button-press-event
my $rect = Goo::Canvas::Rect->new(
 $g, 0, 0, $cwidth,$cheight,
 'line-width' => 1,
 'stroke-color' => 'white', #invisible on white bg
 'fill-color' => 'white', # must be filled for mouse event sensitivity
 );

# some key help
my $markup = " Keys: 'Z' zoom in, 'z' zoom out, 's' save a PDF ";

my $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 -80 , 80 , -1,
 'w',
 'use markup' => 1,
 );

 $text->scale(1,-1);

$g->signal_connect('button-press-event',
 \&on_g_button_press);

$canvas->signal_connect_after('key_press_event', \&on_key_press);
$canvas->can_focus(TRUE);
$canvas->grab_focus($root);

&set_axis();
&plot();

$window->show_all();

Gtk2->main;

sub set_axis{

# x axis
my $xline = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [0,0,900,0],
 'stroke-color' => 'black',
 'line-width' => 3,
 );

#label
 my $markup = " X axis Label ";

 my $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 450 , 80 , -1,
 'center',
 'use markup' => 1,
 );

 $text->scale(1,-1);

for my $x (0..900){

 if ($x % 100 == 0){
 my $xtick = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [$x,0,$x,-25],
 'stroke-color' => 'black',
 'line-width' => 3,
 );

 $markup = " $x ";

 $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 $x-1 , 10 , 1,
 'north-east',
 'use markup' => 1,
 'wrap' => 'char');

 $text->scale(1,-1);

 }elsif ($x % 10 == 0){

 my $xtick = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [$x,0,$x,-15],
 'stroke-color' => 'red',
 'line-width' => 1,
 );

 my $markup = " $x ";

 my $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 $x-1 , 6 , 1,
 'north-east',
 'use markup' => 1,
 'wrap' => 'char');

 $text->scale(1,-1);

 }
}

# y axis
my $yline = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [0,0,0,900],
 'stroke-color' => 'black',
 'line-width' => 3,
 );

#label
 $markup = " Y axis Label ";

 $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 -70 ,-450 , -1,
 'center',
 'use markup' => 1,
 );

 $text->scale(1,-1);
 $text->rotate(-90,-70,-450);

for my $y (0..900){

 if ($y % 100 == 0){
 my $ytick = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [0,$y,-25,$y],
 'stroke-color' => 'black',
 'line-width' => 3,
 );

 $markup = " $y ";

 $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 -25 , -$y -8 , -1,
 'north-east',
 'use markup' => 1,
 );

 $text->scale(1,-1);

 }elsif ($y % 10 == 0){

 my $ytick = Goo::Canvas::Polyline->new(
 $g, TRUE,
 [0,$y,-15,$y],
 'stroke-color' => 'red',
 'line-width' => 1,
 );

 my $markup = " $y ";

 my $text = Goo::Canvas::Text->new(
 $g,
 $markup,
 -16 , -$y - 6 , -1,
 'north-east',
 'use markup' => 1,
 );

 $text->scale(1,-1);

 }
}

}

sub plot{

 my $points_ref = [0,300,0,300];

 my $points = Goo::Canvas::Points->new( $points_ref ); #need 2 points min

 my $poly = Goo::Canvas::Polyline->new(
 $g, FALSE,
 undef, # points need to be set after creation
 'stroke-color' => 'green',
 'line-width' => 2,
 );

 #setting after line creation, sets the 'points' property by name
 $poly->set(points => $points);

my $x = 0; my $y = 0;

 Glib::Timeout->add (100, sub {
 $x+= 10;
 $y = 300 + rand 100*sin( $x / 500);

 if( $x > 301 ){

 my $num = $g->find_child ($poly);
 $g->remove_child($num);
 &plot();
 return FALSE;
 }

 push @$points_ref, $x, $y;
 $points = Goo::Canvas::Points->new( $points_ref ); #need 2 points min
 $poly->set(points => $points);
 return TRUE;
 });

}

sub on_g_button_press {
 #print "@_\n";
 my ( $group, $widget, $event ) = @_;
 print $widget ,' ',$event->type, ' ','button',' ',$event->button,"\n";
 my ($x,$y) = ($event->x,$event->y);
 print "$x $y\n";
 return 0;
}

sub on_key_press {
 # print "@_\n";
 my ( $canvas, $event ) = @_;
 # print $event->type,"\n";

 if ( $event->keyval == $Gtk2::Gdk::Keysyms{Z} ) {
 $scale += .1;
 $canvas->set_scale($scale);
 $canvas->scroll_to(0,$cheight);
 }

 if ( $event->keyval == $Gtk2::Gdk::Keysyms{z} ) {
 $scale -= .1;
 $canvas->set_scale($scale);
 $canvas->set_scale($scale);
 $canvas->scroll_to(0,$cheight);
 }

 if ( $event->keyval == $Gtk2::Gdk::Keysyms{s} ) {
 write_pdf($canvas);
 }

# print "key was ", chr( $event->keyval ), "\n";

 return 0;
}

sub write_pdf {
 #print "@_\n";
 my $canvas = shift;
 print "Write PDF...\n";

 my $scale = $canvas->get_scale;
 print "scale->$scale\n";

 my $surface = Cairo::PdfSurface->create("$0-$scale.pdf",
 $scale*$cwidth, $scale*$cheight);

 my $cr = Cairo::Context->create($surface);

 # needed to save scaled version
 $cr->scale($scale, $scale);

 $canvas->render($cr, undef, 1);
 $cr->show_page;
 print "done\n";
 return TRUE;
}

__END__

zentara

--
I'm not really a human, but I play one on earth.
http://zentara.net/Remember_How_Lucky_You_Are.html

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References:
- Please give me some suggestion about my application
  - From: Lazy Fox
- Re: Please give me some suggestion about my application
  - From: zentara

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