On 8/13/08, zentara <zentara1@xxxxxxxxxxxxx> wrote:
On Tue, 12 Aug 2008 22:27:28 +0800
"Lazy Fox" <lazy.fox.wu@xxxxxxxxx> 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 = "<span font_family ='Arial '
foreground = '#000000'
size = '12000'
weight = 'ultralight'> Keys: 'Z' zoom in, 'z' zoom out, 's' save a PDF </span>";
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 = "<span font_family ='Arial '
foreground = '#000000'
size = '18000'
weight = 'bold'> X axis Label </span>";
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 = "<span font_family ='Arial '
foreground = '#0000ff'
size = '10000'
weight = 'light'> $x </span>";
$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 = "<span font_family ='Arial '
foreground = '#ff0000'
size = '8000'
weight = 'ultralight'> $x </span>";
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 = "<span font_family ='Arial '
foreground = '#000000'
size = '18000'
weight = 'bold'> Y axis Label </span>";
$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 = "<span font_family ='Arial '
foreground = '#0000ff'
size = '10000'
weight = 'light'> $y </span>";
$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 = "<span font_family ='Arial '
foreground = '#ff0000'
size = '8000'
weight = 'ultralight'> $y </span>";
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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