if 0 {July 15th 2004 - MG After a quick search of the Wiki, I couldn't find a page explaining how to do this, so thought I'd knock something up myself. On a canvas widget, if you have an item which you want to move, it's simple enough to do; $widget move $item $xAmount $yAmount. But, if you want the movement to be animated - so that the item moves a bit at a time - it's a little more difficult. This is something I wanted for my Spider Solitaire game, so that the cards could be dealt in a slightly more noticable fashion; once I finish this page and get around to adding it to the game, you can see it for a working implimentation. (Hence the example :)
The proc below works so that the item on the canvas moves an even amount (by both X and Y) every time. The variables passed to it are $c (the path to the canvas widget), $item (the ID of the item on the canvas, returned by canvas create), $tox and $toy (the x and y coords to move to, respectively), $time (how long to wait between each move), and $steps, which can be moved to speed it up more (see below).
$steps works like this: if you're moving from coords 0 0 to coords 100 50, by default it'll move one x coordinate and half a y coordinate at a time: to 1 .5, 2 1, 3 1.5, etc. $steps will be multiplied by the default amount; so, with $steps set to 4, it'll move to 4 2, 8 4, 12 6, and so on. (No, explaining things I code isn't my strong point;)
Anyway, here's the code. :)
}
# Mike Griffiths, July 15th 2004.
# Move an item on a canvas from one coordinate set to another, animated.
proc cMove {c item tox toy {time 25} {steps 1}} {
scan [$c coords $item] "%s %s" origx origy
set diffx [expr {abs($origx-$tox)}]
set diffy [expr {abs($origy-$toy)}]
if { $diffx > $diffy } {
set stepy [expr {$steps*1}] ; set stepx [expr {$steps*(double($diffx) / $diffy)}]
} else {
set stepx [expr {$steps*1}] ; set stepy [expr {$steps*(double($diffy) / $diffx)}]
}
set dirx ">" ; set diry ">"
if { $origx > $tox } {
set stepx [expr {$stepx*-1}] ; set dirx "<"
}
if { $origy > $toy } {
set stepy [expr {$stepy*-1}] ; set diry "<"
}
while {1} {
scan [$c coords $item] "%s %s" nowx nowy
if { [expr {round(($nowx-$tox)+($nowy-$toy))}] == 0 } {return;}
if { [expr {round($nowx-$tox)}] == 0 } {
set stepx 0
} elseif " [expr {$nowx+$stepx}] $dirx $tox " {
set stepx [expr {$tox-$nowx}]
}
if { [expr {round($nowy-$toy)}] == 0 } {
set stepy 0
} elseif " [expr {$nowy+$stepy}] $diry $toy " {
set stepy [expr {$toy-$nowy}]
}
$c move $item $stepx $stepy
update idletasks
after $time
}
};# moveif 0 {
And a small demo...
}
pack [canvas .c -height 500 -width 500 -bg "dark green"]
image create photo myimg -format gif -data {
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hVChLaun3b1kABADs=}
set item [.c create image 100 100 -image myimg -anchor center]
move .c $item 250 375 10if 0 {
[Category Animation] (kind of:) | [Canvas]]