1 files changed, 104 insertions, 0 deletions
diff --git a/library/demos/aniwave.tcl b/library/demos/aniwave.tcl
new file mode 100644
index 0000000..6122132
--- /dev/null
+++ b/library/demos/aniwave.tcl
@@ -0,0 +1,104 @@
+# aniwave.tcl --
+#
+# This demonstration script illustrates how to adjust canvas item
+# coordinates in a way that does something fairly similar to waveform
+# display.
+
+if {![info exists widgetDemo]} {
+    error "This script should be run from the \"widget\" demo."
+}
+
+package require Tk
+
+set w .aniwave
+catch {destroy $w}
+toplevel $w
+wm title $w "Animated Wave Demonstration"
+wm iconname $w "aniwave"
+positionWindow $w
+
+label $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." 
+pack $w.msg -side top
+
+## See Code / Dismiss buttons
+set btns [addSeeDismiss $w.buttons $w]
+pack $btns -side bottom -fill x
+
+# Create a canvas large enough to hold the wave. In fact, the wave
+# sticks off both sides of the canvas to prevent visual glitches.
+pack [canvas $w.c -width 300 -height 200 -background black] -padx 10 -pady 10 -expand yes
+
+# Ensure that this this is an array
+array set animationCallbacks {}
+
+# Creates a coordinates list of a wave. This code does a very sketchy
+# job and relies on Tk's line smoothing to make things look better.
+set waveCoords {}
+for {set x -10} {$x<=300} {incr x 5} {
+    lappend waveCoords $x 100
+}
+lappend waveCoords $x 0 [incr x 5] 200
+
+# Create a smoothed line and arrange for its coordinates to be the
+# contents of the variable waveCoords.
+$w.c create line $waveCoords -tags wave -width 1 -fill green -smooth 1
+proc waveCoordsTracer {w args} {
+    global waveCoords
+    # Actual visual update will wait until we have finished
+    # processing; Tk does that for us automatically.
+    $w.c coords wave $waveCoords
+}
+trace add variable waveCoords write [list waveCoordsTracer $w]
+
+# Basic motion handler. Given what direction the wave is travelling
+# in, it advances the y coordinates in the coordinate-list one step in
+# that direction.
+proc basicMotion {} {
+    global waveCoords direction
+    set oc $waveCoords
+    for {set i 1} {$i<[llength $oc]} {incr i 2} {
+	if {$direction eq "left"} {
+	    lset waveCoords $i [lindex $oc \
+		    [expr {$i+2>[llength $oc] ? 1 : $i+2}]]
+	} else {
+	    lset waveCoords $i \
+		    [lindex $oc [expr {$i-2<0 ? "end" : $i-2}]]
+	}
+    }
+}
+
+# Oscillation handler. This detects whether to reverse the direction
+# of the wave by checking to see if the peak of the wave has moved off
+# the screen (whose size we know already.)
+proc reverser {} {
+    global waveCoords direction
+    if {[lindex $waveCoords 1] < 10} {
+	set direction "right"
+    } elseif {[lindex $waveCoords end] < 10} {
+	set direction "left"
+    }
+}
+
+# Main animation "loop". This calls the two procedures that handle the
+# movement repeatedly by scheduling asynchronous calls back to itself
+# using the [after] command. This procedure is the fundamental basis
+# for all animated effect handling in Tk.
+proc move {} {
+    basicMotion
+    reverser
+
+    # Theoretically 100 frames-per-second (==10ms between frames)
+    global animationCallbacks
+    set animationCallbacks(simpleWave) [after 10 move]
+}
+
+# Initialise our remaining animation variables
+set direction "left"
+set animateAfterCallback {}
+# Arrange for the animation loop to stop when the canvas is deleted
+bind $w.c <Destroy> {
+    after cancel $animationCallbacks(simpleWave)
+    unset animationCallbacks(simpleWave)
+}
+# Start the animation processing
+move