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-rw-r--r--library/demos/pendulum.tcl33
1 files changed, 18 insertions, 15 deletions
diff --git a/library/demos/pendulum.tcl b/library/demos/pendulum.tcl
index 8512d24..e920c5d 100644
--- a/library/demos/pendulum.tcl
+++ b/library/demos/pendulum.tcl
@@ -3,7 +3,7 @@
# This demonstration illustrates how Tcl/Tk can be used to construct
# simulations of physical systems.
#
-# RCS: @(#) $Id: pendulum.tcl,v 1.4 2009/04/02 08:27:51 patthoyts Exp $
+# RCS: @(#) $Id: pendulum.tcl,v 1.5 2009/08/08 08:23:40 dkf Exp $
if {![info exists widgetDemo]} {
error "This script should be run from the \"widget\" demo."
@@ -35,10 +35,10 @@ $w.p add [labelframe $w.p.l2 -text "Phase Space"]
canvas $w.c -width 320 -height 200 -background white -bd 2 -relief sunken
$w.c create text 5 5 -anchor nw -text "Click to Adjust Bob Start Position"
# Coordinates of these items don't matter; they will be set properly below
-$w.c create line 0 25 320 25 -width 2 -fill grey50 -tags plate
-$w.c create line 1 1 1 1 -tags pendulumRod -width 3 -fill black
-$w.c create oval 1 1 2 2 -tags pendulumBob -fill yellow -outline black
-$w.c create oval 155 20 165 30 -fill grey50 -outline {}
+$w.c create line 0 25 320 25 -tags plate -fill grey50 -width 2
+$w.c create oval 155 20 165 30 -tags pivot -fill grey50 -outline {}
+$w.c create line 1 1 1 1 -tags rod -fill black -width 3
+$w.c create oval 1 1 2 2 -tags bob -fill yellow -outline black
pack $w.c -in $w.p.l1 -fill both -expand true
# Create the canvas containing the phase space graph; this consists of
@@ -62,6 +62,7 @@ set Theta 45.0
set dTheta 0.0
set pi 3.1415926535897933
set length 150
+set home 160
# This procedure makes the pendulum appear at the correct place on the
# canvas. If the additional arguments "at $x $y" are passed (the 'at'
@@ -70,20 +71,20 @@ set length 150
# length and angle are computed in reverse from the given location
# (which is taken to be the centre of the pendulum bob.)
proc showPendulum {canvas {at {}} {x {}} {y {}}} {
- global Theta dTheta pi length
- if {$at eq "at" && ($x!=160 || $y!=25)} {
+ global Theta dTheta pi length home
+ if {$at eq "at" && ($x!=$home || $y!=25)} {
set dTheta 0.0
- set x2 [expr {$x-160}]
- set y2 [expr {$y-25}]
- set length [expr {hypot($x2,$y2)}]
- set Theta [expr {atan2($x2,$y2)*180/$pi}]
+ set x2 [expr {$x - $home}]
+ set y2 [expr {$y - 25}]
+ set length [expr {hypot($x2, $y2)}]
+ set Theta [expr {atan2($x2, $y2) * 180/$pi}]
} else {
set angle [expr {$Theta * $pi/180}]
- set x [expr {160+$length*sin($angle)}]
- set y [expr {25+$length*cos($angle)}]
+ set x [expr {$home + $length*sin($angle)}]
+ set y [expr {25 + $length*cos($angle)}]
}
- $canvas coords pendulumRod 160 25 $x $y
- $canvas coords pendulumBob \
+ $canvas coords rod $home 25 $x $y
+ $canvas coords bob \
[expr {$x-15}] [expr {$y-15}] [expr {$x+15}] [expr {$y+15}]
}
showPendulum $w.c
@@ -127,6 +128,8 @@ bind $w.c <ButtonRelease-1> {
}
bind $w.c <Configure> {
%W coords plate 0 25 %w 25
+ set home [expr %w/2]
+ %W coords pivot [expr $home-5] 20 [expr $home+5] 30
}
bind $w.k <Configure> {
set psh [expr %h/2]