Support for different display numbers as envars

Change-type: minor
Signed-off-by: Alex Bucknall <[email protected]>

readme.md

@@ -61,6 +61,7 @@ The following environment variables allow configuration of the `browser` block:
 | Environment variable | Options | Default | Description |
 | --- | --- | --- | --- |
 |`LAUNCH_URL`|`http` or `https` URL|N\A|Web page to display|
+|`DISPLAY_NUM`|`n`|0|Display number to use|
 |`LOCAL_HTTP_DELAY`|Number (seconds)|0|Number of seconds to wait for a local HTTP service to start before trying to detect it|
 |`KIOSK`|`0`, `1`|`0`|Run in kiosk mode with no menus or status bars. <br/> `0` = off, `1` = on|
 |`SHOW_CURSOR`|`0`, `1`|`0`|Enables/disables the cursor when in kiosk mode<br/> `0` = off, `1` = on|

src/start.sh

@@ -18,7 +18,13 @@ echo "balenaBlocks browser version: $(<VERSION)"
 echo "Setting CPU Scaling Governor to 'performance'"
 echo 'performance' > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor 
 
- #Set whether to show a cursor or not
+# check if display number envar was set
+if [[ -z "$DISPLAY_NUM" ]]
+  then
+    export DISPLAY_NUM=0
+fi
+
+# set whether to show a cursor or not
 if [[ ! -z $SHOW_CURSOR ]] && [[ "$SHOW_CURSOR" -eq "1" ]]
   then
     export CURSOR=''
@@ -51,4 +57,4 @@ environment=$(env | grep -v -w '_' | awk -F= '{ st = index($0,"=");print substr(
 environment="${environment::-1}"
 
 # launch Chromium and whitelist the enVars so that they pass through to the su session
-su -w $environment -c "export DISPLAY=:0 && startx /usr/src/app/startx.sh $CURSOR" - chromium
+su -w $environment -c "export DISPLAY=:$DISPLAY_NUM && startx /usr/src/app/startx.sh $CURSOR" - chromium