Hello monks and nuns!

before the end of the Tk questions months I have another tk question.

My goal is to have a canvas filling the mainwindow and I want to drow squares into this canvas to have evenly divided as a chessboard.

The first question about mainwindow geometry was already answered by the wise kcott in the CB, but I also put it here for completeness and for future readers:

• A mainwindow with geometry 100x100 goes from 0,0 to 100,100 ie it has 101 pixels! I found this very misleading.. but anyway it'snot the only problem i have.

Infact, even using a mainwindow with geometry 99x99 I have undesired pixels here and there: in the program below I try to create 4 squares to fulfill the main canvas (but they do not arrive at the east and south borders: run it to see). Also the pixel used to outline the square are problematic..

• canvas objects support the outline properties: is this added to the object area? I mean a square 50x50 with outline enabled (and is by default) ,means actually 51x51 one? It seems so: run my program and notice that north and west outlines are not shown as if they are outside of the visible area ( so -1,-1 as starting point).

Notice that -outline => undef means transparent (you'll see the red of the main big canvas underlying), but specifying no outline assumes black as default .

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
# uncomment if module is installed
# use Tk::WidgetDump;

my ($dx,$dy);
my $mw  = Tk::MainWindow->new();
# kcot gently confirmed that 100x100 in geometry means 
# from 0,0 to 100,100 aka 101 pixels!!
$mw->geometry("99x99");

# main underlying canvas is filled with RED
my $can = $mw->Canvas(
                -height => 100,
                -width  => 100,
                -bg => 'red',
)->pack( );

# used to dump coordinates
my %board;

# alternate colors for tales
my @alt_col = qw(gold2 green);

# squares for tales starting at 0,0
my ($sq_x,$sq_y) = (0,0);

foreach my $letter (('A'..'B')){
    unshift @alt_col, pop @alt_col;
    foreach my $num (1..2){
        # cycle colors
        unshift @alt_col, pop @alt_col;
        $can->createRectangle($sq_x, $sq_y, $sq_x+49,$sq_y+49,
            -fill => $alt_col[0],
            # outline undef means ransparent outline
        # if not specified defaults to black outline
        -outline => undef ,
            -tags=> ['first']
        );
        $board{$letter.$num} = {tx=>$sq_x,ty=>$sq_y,bx=>$sq_x+49,by=>$
+sq_y+49};
    # add 50
    $sq_x += 50;          
    }
    # reset x to 0 for new row
    $sq_x = 0;
    # add 50 to y
    $sq_y += 50;
    print "\n";
}

# legenda
print "ty = top Y    tx = top X    by = bottom Y    bx = bottom X\n";

# dump board coordinates
foreach my $key (sort keys %board){
    print     "$key -> ",
            ( map{"$_ $board{$key}{$_} "} 
                reverse sort keys %{$board{$key}}
            ),"\n";
}

$can->bind('first', '<1>', sub {&show_click();});
# uncomment if module is installed
# $mw->WidgetDump;
MainLoop;

sub show_click{
    my $ev = $can->XEvent;
    ($dx, $dy) = ($ev->x, $ev->y);
    print "CLICKED  $dx  $dy\n";
    my $cur_id = ($can->find('withtag','current'))[0];
    print "current canvas $cur_id\n\n";    
}
[download]

What the program outputs seems what I want; ie squares of 50 pixels sides:

ty = top Y      tx = top X      by = bottom Y   bx = bottom X
A1 -> ty 0 tx 0 by 49 bx 49
A2 -> ty 0 tx 50 by 49 bx 99
B1 -> ty 50 tx 0 by 99 bx 49
B2 -> ty 50 tx 50 by 99 bx 99
[download]

But what is shown on the screen seems misplaced toward north-west by one or more pixels. Also: when I dump the canvas I get:

# main canvas
width:    104
height:    99
reqwidth:    104
reqheight:    104

# squares coordinates dumped (from top left to bottom right) are:
0,0,49,49
50,0,99,49
0,50,49,99
50,50,99,99
# that reflect what I want
[download]

Thanks for the patience and happy Tk month!

L*

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