From 5460351c834d619e7d03cd8f06b549059df24ed4 Mon Sep 17 00:00:00 2001
From: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
Date: Thu, 24 Mar 2016 23:20:45 +0100
Subject: impressive-display: Work around buggy impressive polling feature.

---
 impressive-display/bin/impressive-display | 74 ++++++++++++++++++++++++++-----
 1 file changed, 62 insertions(+), 12 deletions(-)

diff --git a/impressive-display/bin/impressive-display b/impressive-display/bin/impressive-display
index a9a0512..5bd2a28 100755
--- a/impressive-display/bin/impressive-display
+++ b/impressive-display/bin/impressive-display
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-set -x
+# set -x
 
 # Copyright (C) 2012-2016 by Debian Edu project, http://wiki.debian.org/DebianEdu
 #       Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
@@ -47,7 +47,6 @@ PDF_URL_SLAVES=""
 PDF_URL_MASTERS_CREDS=""
 PDF_URL_SLAVES_CREDS=""
 
-
 PDF_FILE_MASTERS=""
 PDF_FILE_SLAVES=""
 
@@ -147,12 +146,16 @@ if [ -n "$HTTP_PROXY_URL" ]; then
 	export ftp_proxy="$HTTP_PROXY_URL"
 fi
 
+IMPRESSIVE_PID=""
+
 WORKDIR="$HOME/.impressive-display-data"
 LOOPFILE="$WORKDIR/PDFFILE_DOWNLOAD_LOOP_ACTIVE"
 mkdir -p "$WORKDIR"
 
-function stop_pdfdownload_loop {
-    rm -f ~/PDFDOWNLOAD_LOOP
+function cleanup {
+	rm -f "$WORKDIR/PDFDOWNLOAD_LOOP"
+	rm -f "$WORKDIR/IMPRESSIVE_ACTIVE"
+	rm -f "$WORKDIR/IMPRESSIVE_EXIT"
 }
 
 function pdf_is_portrait {
@@ -184,16 +187,63 @@ function merge_portrait_documents {
 		cd $WORKDIR && 	pdfnup "$WORKDIR/impressive-pdffile.pdf" && cd - 1>/dev/null
 		mv "$WORKDIR/impressive-pdffile-nup.pdf" "$WORKDIR/impressive-pdffile-display.pdf"
 	else
-		mv "$WORKDIR/impressive-pdffile.pdf" "$WORKDIR/impressive-pdffile-display.pdf"
+		cp "$WORKDIR/impressive-pdffile.pdf" "$WORKDIR/impressive-pdffile-display.pdf"
 	fi
 }
 
 function download_pdffile {
+	if [ -r "$WORKDIR/impressive-pdffile.pdf" ]; then
+		cp "$WORKDIR/impressive-pdffile.pdf" "$WORKDIR/impressive-pdffile-previous.pdf"
+	fi
 	if [ -n "$PDF_URL_CREDS" ]; then
 		creds="-u $PDF_URL_CREDS"
 	fi
 	curl $creds "$PDF_URL" 1> "$WORKDIR/impressive-pdffile.pdf" 2>/dev/null
 	merge_portrait_documents
+
+	cmp -s  "$WORKDIR/impressive-pdffile.pdf" "$WORKDIR/impressive-pdffile-previous.pdf"> /dev/null
+	if [ $? -eq 1 ]; then
+		rm -f "$WORKDIR/IMPRESSIVE_ACTIVE"
+	fi
+}
+
+function reloadable_impressive {
+
+	# on GL systems add: --supersample -k 
+	if which impressive 1>/dev/null; then
+
+		fade_options="--transition None"
+
+		while [ ! -e "$WORKDIR/IMPRESSIVE_EXIT" ]; do
+			impressive ${fade_options} --fake-fullscreen --wrap -a ${SLIDE_DURATION} --nologo "${pdffile}" 1>/dev/null &
+			IMPRESSIVE_PID=$!
+
+			touch "$WORKDIR/IMPRESSIVE_ACTIVE"
+			while [ -e "$WORKDIR/IMPRESSIVE_ACTIVE" ]; do
+				sleep 1
+
+				if [ -e "$WORKDIR/IMPRESSIVE_EXIT" ]; then
+					break
+				fi
+
+			done
+			kill $IMPRESSIVE_PID
+			rm "$WORKDIR/IMPRESSIVE_ACTIVE"
+		done
+	fi
+}
+
+function close_other_impressive_display {
+
+	# if we see another active impressive-display instance, trigger its exit...
+	if [ -e "$WORKDIR/IMPRESSIVE_ACTIVE" ]; then
+		touch "$WORKDIR/IMPRESSIVE_EXIT"
+	fi
+
+	# wait for other impressive-display instance to disappear
+	while [ -e "$WORKDIR/IMPRESSIVE_ACTIVE" ]; do
+		sleep 1
+	done
 }
 
 # do an initial PDF retrieval..
@@ -201,13 +251,13 @@ if [ -n "$PDF_URL" ]; then
 
 	download_pdffile
 
-	trap "stop_pdfdownload_loop" SIGINT SIGTERM ERR
+	trap "cleanup" SIGINT SIGTERM ERR
 
 	if [ "x$DOWNLOAD_INTERVAL" != "x0" ]; then
 		touch $LOOPFILE
 		(
 			while true; do
-				if [ ! -e $LOOPFILE ]; then
+				if [ ! -e $LOOPFILE ] || [ -e $WORKDIR/IMPRESSIVE_EXIT ]; then
 					break
 				else
 					sleep $DOWNLOAD_INTERVAL
@@ -243,11 +293,11 @@ if [ -n "$pdffile" ]; then
 
 	fade_options="--transition None"
 
-	# on GL systems add: --supersample -k 
-	if which impressive 1>/dev/null; then
-		impressive ${fade_options} --fake-fullscreen --wrap --poll 30 -a ${SLIDE_DURATION} --nologo "${pdffile}" 1>/dev/null
-	fi
-	stop_pdfdownload_loop
+	close_other_impressive_display
+
+	reloadable_impressive
+
+	cleanup
 
 fi
 
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