Add single-output-sway helper script

This doesn't implement HEADLESS mode yet - there are still add corner
cases to fix there.

Signed-off-by: Jim Ramsay <[email protected]>

examples/README.md

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+# Example Scripts
+
+The scripts here are examples of how you can automate interesting things with the wayvncctl IPC events.
+
+## event-watcher
+
+This is a pretty simple example that just demonstrates how to tie the
+`wayvncctl event-receive` event loop into a bash script. It logs when clients
+connect and disconnect.
+
+## single-output-sway
+
+This is more purposeful, and implements an idea for multi-output wayland
+servers, collapsing all outputs down to one when the first client connects, and
+restoring the configuration when the last client exits.
+
+The mechanism used to collapse the outputs depends on the version of sway installed:
+
+- For sway-1.7 and earlier, the script just temporarily disables all outputs
+  except the one being captured. This moves all workspaces to the single
+  remaining output.
+
+- For sway-1.8 and later, the script creates a temporary virtual output called
+  `HEADLESS-1' and then disables all physical outputs, which moves all
+  workspaces to the virtual output. On disconnect, all original physical
+  outputs are re-enabled, and the virtual output is destroyed.

examples/single-output-sway

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+#!/bin/bash
+
+WAYVNCCTL=${WAYVNCCTL:-wayvncctl}
+SWAYMSG=${SWAYMSG:-swaymsg}
+
+OUTPUTS_TO_RECONNECT=()
+restore_outputs() {
+    [[ ${#OUTPUTS_TO_RECONNECT[@]} -ge 1 ]] || return
+    echo "Restoring original output state"
+    for output in "${OUTPUTS_TO_RECONNECT[@]}"; do
+        echo "Re-enabling output $output"
+        $SWAYMSG output "$output" enable
+    done
+    OUTPUTS_TO_RECONNECT=()
+}
+trap restore_outputs EXIT
+
+collapse_outputs() {
+    for output in $($WAYVNCCTL -j get-outputs | jq -r '.[] | select(.captured==false).name'); do
+        echo "Disabling extra output $output"
+        $SWAYMSG output "$output" disable
+        OUTPUTS_TO_RECONNECT+=("$output")
+    done
+}
+
+connection_count_now() {
+    local count=$1
+    if [[ $count == 1 ]]; then
+        collapse_outputs
+    elif [[ $count == 0 ]]; then
+        restore_outputs
+    fi
+}
+
+while IFS= read -r EVT; do
+    case "$(jq -r '.method' <<<"$EVT")" in
+        client-*onnected)
+            count=$(jq -r '.params.connection_count' <<<"$EVT")
+            connection_count_now "$count"
+            ;;
+        wayvnc-shutdown)
+            echo "wayvncctl is no longer running"
+            connection_count_now 0
+            ;;
+        wayvnc-startup)
+            echo "Ready to receive wayvnc events"
+            ;;
+    esac
+done < <("$WAYVNCCTL" --wait --reconnect --json event-receive)
+