library: Add Memory Monitor entry (#508)

* library: Add Memory Monitor entry

* Update main.json

* Update main.blp

* Memory Monitor: Suggestions

Author: AkshayWarrier

src/Library/demos/Memory Monitor/main.blp

@@ -0,0 +1,12 @@
+using Gtk 4.0;
+using Adw 1;
+
+Adw.StatusPage {
+  title: _("Memory Monitor");
+  description: _("Monitor system memory");
+
+  LinkButton {
+    label: "API Reference";
+    uri: "https://docs.gtk.org/gio/iface.MemoryMonitor.html";
+  }
+}

src/Library/demos/Memory Monitor/main.js

@@ -0,0 +1,27 @@
+import Gio from "gi://Gio";
+
+const memory_monitor = Gio.MemoryMonitor.dup_default();
+
+const cache = new Map();
+cache.set("a", 1);
+cache.set("b", 2);
+cache.set("c", 3);
+
+memory_monitor.connect("low-memory-warning", (monitor, level) => {
+  // Use inequalities for checking as new levels may be added in the future
+  if (level >= Gio.MemoryMonitorWarningLevel.LOW) {
+    // Processes should free up unneeded resources
+    console.log("Warning Level: Low");
+    drop_caches();
+  } else if (level >= Gio.MemoryMonitorWarningLevel.MEDIUM) {
+    // Processes should try harder to free up unneeded resources
+    console.log("Warning Level: Medium");
+  } else if (level >= Gio.MemoryMonitorWarningLevel.CRITICAL) {
+    // system will start terminating processes to reclaim memory
+    console.log("Warning Level: Critical");
+  }
+});
+
+function drop_caches() {
+  cache.clear();
+}

src/Library/demos/Memory Monitor/main.json

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+{
+  "category": "platform",
+  "description": "Monitor system memory",
+  "panels": ["code", "preview"],
+  "autorun": true
+}