1# aniwave.tcl -- 2# 3# This demonstration script illustrates how to adjust canvas item 4# coordinates in a way that does something fairly similar to waveform 5# display. 6 7if {![info exists widgetDemo]} { 8 error "This script should be run from the \"widget\" demo." 9} 10 11package require Tk 12 13set w .aniwave 14catch {destroy $w} 15toplevel $w 16wm title $w "Animated Wave Demonstration" 17wm iconname $w "aniwave" 18positionWindow $w 19 20label $w.msg -font $font -wraplength 4i -justify left -text "This demonstration contains a canvas widget with a line item inside it. The animation routines work by adjusting the coordinates list of the line; a trace on a variable is used so updates to the variable result in a change of position of the line." 21pack $w.msg -side top 22 23## See Code / Dismiss buttons 24set btns [addSeeDismiss $w.buttons $w] 25pack $btns -side bottom -fill x 26 27# Create a canvas large enough to hold the wave. In fact, the wave 28# sticks off both sides of the canvas to prevent visual glitches. 29pack [canvas $w.c -width 300 -height 200 -background black] -padx 10 -pady 10 -expand yes 30 31# Ensure that this this is an array 32array set animationCallbacks {} 33 34# Creates a coordinates list of a wave. This code does a very sketchy 35# job and relies on Tk's line smoothing to make things look better. 36set waveCoords {} 37for {set x -10} {$x<=300} {incr x 5} { 38 lappend waveCoords $x 100 39} 40lappend waveCoords $x 0 [incr x 5] 200 41 42# Create a smoothed line and arrange for its coordinates to be the 43# contents of the variable waveCoords. 44$w.c create line $waveCoords -tags wave -width 1 -fill green -smooth 1 45proc waveCoordsTracer {w args} { 46 global waveCoords 47 # Actual visual update will wait until we have finished 48 # processing; Tk does that for us automatically. 49 $w.c coords wave $waveCoords 50} 51trace add variable waveCoords write [list waveCoordsTracer $w] 52 53# Basic motion handler. Given what direction the wave is travelling 54# in, it advances the y coordinates in the coordinate-list one step in 55# that direction. 56proc basicMotion {} { 57 global waveCoords direction 58 set oc $waveCoords 59 for {set i 1} {$i<[llength $oc]} {incr i 2} { 60 if {$direction eq "left"} { 61 lset waveCoords $i [lindex $oc \ 62 [expr {$i+2>[llength $oc] ? 1 : $i+2}]] 63 } else { 64 lset waveCoords $i \ 65 [lindex $oc [expr {$i-2<0 ? "end" : $i-2}]] 66 } 67 } 68} 69 70# Oscillation handler. This detects whether to reverse the direction 71# of the wave by checking to see if the peak of the wave has moved off 72# the screen (whose size we know already.) 73proc reverser {} { 74 global waveCoords direction 75 if {[lindex $waveCoords 1] < 10} { 76 set direction "right" 77 } elseif {[lindex $waveCoords end] < 10} { 78 set direction "left" 79 } 80} 81 82# Main animation "loop". This calls the two procedures that handle the 83# movement repeatedly by scheduling asynchronous calls back to itself 84# using the [after] command. This procedure is the fundamental basis 85# for all animated effect handling in Tk. 86proc move {} { 87 basicMotion 88 reverser 89 90 # Theoretically 100 frames-per-second (==10ms between frames) 91 global animationCallbacks 92 set animationCallbacks(simpleWave) [after 10 move] 93} 94 95# Initialise our remaining animation variables 96set direction "left" 97set animateAfterCallback {} 98# Arrange for the animation loop to stop when the canvas is deleted 99bind $w.c <Destroy> { 100 after cancel $animationCallbacks(simpleWave) 101 unset animationCallbacks(simpleWave) 102} 103# Start the animation processing 104move 105