test: Add a convenience script to disable the screensaver when testing

If the screensaver activates, it can cause failures when attempting to
render into an xlib window, so inhibit if we know how.

test/Makefile.am

@@ -126,7 +126,7 @@ cairo_test_trace_DEPENDENCIES = \
 endif
 
 BUILT_SOURCES += cairo-test-constructors.c
-EXTRA_DIST += $(BUILT_SOURCES) $(noinst_SCRIPTS) COPYING make-cairo-test-constructors.sh
+EXTRA_DIST += $(BUILT_SOURCES) $(noinst_SCRIPTS) COPYING make-cairo-test-constructors.sh run-cairo-test-suite.sh
 CLEANFILES += $(BUILT_SOURCES)
 
 # All tests which have a reference image go here.

test/run-cairo-test-suite.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -m
+
+if `which gnome-screensaver-command`; then
+	gnome-screensaver-command -i -n "cairo-test-suite" -r "Cairo needs to read back from the screen in order to test rendering to xlib" &
+	pid=$!
+
+	restore_screensaver() { kill $pid; }
+else
+	restore_screensaver() { :; }
+fi
+
+trap cleanup SIGINT SIGTERM
+
+./cairo-test-suite "$*"
+
+restore_screensaver