1 files changed, 125 insertions, 0 deletions
diff --git a/js/ui/pointerWatcher.js b/js/ui/pointerWatcher.js
new file mode 100644
index 0000000..2af35b6
--- /dev/null
+++ b/js/ui/pointerWatcher.js
@@ -0,0 +1,125 @@
+// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
+/* exported getPointerWatcher */
+
+const { GLib } = imports.gi;
+
+// We stop polling if the user is idle for more than this amount of time
+var IDLE_TIME = 1000;
+
+// This file implements a reasonably efficient system for tracking the position
+// of the mouse pointer. We simply query the pointer from the X server in a loop,
+// but we turn off the polling when the user is idle.
+
+let _pointerWatcher = null;
+function getPointerWatcher() {
+    if (_pointerWatcher == null)
+        _pointerWatcher = new PointerWatcher();
+
+    return _pointerWatcher;
+}
+
+var PointerWatch = class {
+    constructor(watcher, interval, callback) {
+        this.watcher = watcher;
+        this.interval = interval;
+        this.callback = callback;
+    }
+
+    // remove:
+    // remove this watch. This function may safely be called
+    // while the callback is executing.
+    remove() {
+        this.watcher._removeWatch(this);
+    }
+};
+
+var PointerWatcher = class {
+    constructor() {
+        this._idleMonitor = global.backend.get_core_idle_monitor();
+        this._idleMonitor.add_idle_watch(IDLE_TIME, this._onIdleMonitorBecameIdle.bind(this));
+        this._idle = this._idleMonitor.get_idletime() > IDLE_TIME;
+        this._watches = [];
+        this.pointerX = null;
+        this.pointerY = null;
+    }
+
+    // addWatch:
+    // @interval: hint as to the time resolution needed. When the user is
+    //   not idle, the position of the pointer will be queried at least
+    //   once every this many milliseconds.
+    // @callback to call when the pointer position changes - takes
+    //   two arguments, X and Y.
+    //
+    // Set up a watch on the position of the mouse pointer. Returns a
+    // PointerWatch object which has a remove() method to remove the watch.
+    addWatch(interval, callback) {
+        // Avoid unreliably calling the watch for the current position
+        this._updatePointer();
+
+        let watch = new PointerWatch(this, interval, callback);
+        this._watches.push(watch);
+        this._updateTimeout();
+        return watch;
+    }
+
+    _removeWatch(watch) {
+        for (let i = 0; i < this._watches.length; i++) {
+            if (this._watches[i] == watch) {
+                this._watches.splice(i, 1);
+                this._updateTimeout();
+                return;
+            }
+        }
+    }
+
+    _onIdleMonitorBecameActive() {
+        this._idle = false;
+        this._updatePointer();
+        this._updateTimeout();
+    }
+
+    _onIdleMonitorBecameIdle() {
+        this._idle = true;
+        this._idleMonitor.add_user_active_watch(this._onIdleMonitorBecameActive.bind(this));
+        this._updateTimeout();
+    }
+
+    _updateTimeout() {
+        if (this._timeoutId) {
+            GLib.source_remove(this._timeoutId);
+            this._timeoutId = 0;
+        }
+
+        if (this._idle || this._watches.length == 0)
+            return;
+
+        let minInterval = this._watches[0].interval;
+        for (let i = 1; i < this._watches.length; i++)
+            minInterval = Math.min(this._watches[i].interval, minInterval);
+
+        this._timeoutId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, minInterval,
+            this._onTimeout.bind(this));
+        GLib.Source.set_name_by_id(this._timeoutId, '[gnome-shell] this._onTimeout');
+    }
+
+    _onTimeout() {
+        this._updatePointer();
+        return GLib.SOURCE_CONTINUE;
+    }
+
+    _updatePointer() {
+        let [x, y] = global.get_pointer();
+        if (this.pointerX == x && this.pointerY == y)
+            return;
+
+        this.pointerX = x;
+        this.pointerY = y;
+
+        for (let i = 0; i < this._watches.length;) {
+            let watch = this._watches[i];
+            watch.callback(x, y);
+            if (watch == this._watches[i]) // guard against self-removal
+                i++;
+        }
+    }
+};