Add examples/sdlevents.tcl

Add example of integrating SDL event loop and the Tcl event loop

Signed-off-by: Steve Bennett <steveb@workware.net.au>

1 files changed, 76 insertions, 0 deletions

diff --git a/examples/sdlevents.tcl b/examples/sdlevents.tcl
new file mode 100644
index 0000000..e9f37d8
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+++ b/examples/sdlevents.tcl
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+package require sdl
+package require oo
+
+set xres 640
+set yres 384
+set s [sdl.screen $xres $yres "Jim Tcl - SDL, Eventloop integration"]
+
+set col(cyan) {0 255 255}
+set col(yellow) {255 255 0}
+set col(red) {255 0 0}
+set col(green) {0 255 0}
+set col(white) {255 255 255}
+set col(blue) {0 0 255}
+set ncols [dict size $col]
+
+set grey {50 50 50}
+
+class ball {
+	name -
+	pos {x 256 y 256}
+	color {255 255 255}
+	res {x 512 y 512}
+	delta {x 3 y 3}
+	radius 40
+}
+
+ball method draw {s} {
+	$s fcircle $pos(x) $pos(y) $radius {*}$color
+	foreach xy {x y} {
+		incr pos($xy) $delta($xy)
+		if {$pos($xy) <= $radius + $delta($xy) || $pos($xy) >= $res($xy) - $radius - $delta($xy) || [rand 50] == 1} {
+			set delta($xy) $(-1 * $delta($xy))
+			incr pos($xy) $(2 * $delta($xy))
+		}
+	}
+}
+
+foreach c [dict keys $col] {
+	set b [ball]
+	$b eval [list set name $c]
+	$b eval [list set res(x) $xres]
+	$b eval [list set res(y) $yres]
+	$b eval [list set pos(x) $($xres/2)]
+	$b eval [list set pos(y) $($yres/2)]
+	$b eval [list set color [list {*}$col($c) 150]]
+	lappend balls $b
+}
+
+proc draw {balls} {s} {
+	global x y dx dy xres yres
+	$s clear {*}$::grey
+	foreach ball $balls {
+		$ball draw $s
+	}
+	$s flip
+}
+
+# Example of integrating the Tcl event loop with SDL
+# We need to always be polling SDL, and also run the Tcl event loop
+
+# The Tcl event loop runs from within the SDL poll loop via
+# a (non-blocking) call to update
+proc heartbeat {} {
+	puts $([clock millis] % 1000000)
+	after 250 heartbeat
+}
+
+draw $balls
+heartbeat
+$s poll {
+	# 16ms = 60 frames/second
+	# Could take into account the drawing time
+	after 16
+	draw $balls
+	update
+}