Restrict third-party shell plugin capabilities

Reported-by: Roger Piñol <rogerpicar@gmail.com>

shell/services/PluginShellApi.qml

@@ -0,0 +1,75 @@
+import QtQuick
+
+// Capability-scoped shell surface for installed third-party plugins.
+//
+// The callbacks are closed over one plugin id by shell.qml. A plugin can call
+// them directly, but it cannot widen their scope: ordinary plugins are limited
+// to their own id, and full-bar callbacks independently enforce their explicit
+// non-authentication UI scope. Keeping the host shell out of this object's
+// properties also prevents ordinary QML object traversal from turning the
+// facade back into the root ShellRoot.
+QtObject {
+  id: api
+
+  required property string pluginId
+
+  property var appLibrary: null
+  property var bar: null
+  property var barConfig: ({})
+
+  property var _serviceLookup: null
+  property var _firstPartyServiceLookup: null
+  property var _pluginShellLookup: null
+  property var _barEntryShellLookup: null
+  property var _summon: null
+  property var _hide: null
+  property var _toggle: null
+  property var _isOpen: null
+  property var _updateSettings: null
+  property var _mutateBarConfig: null
+
+  function serviceFor(id) {
+    return _serviceLookup ? _serviceLookup(String(id || "")) : null
+  }
+
+  // Only full-bar facades receive narrow proxies for the specific
+  // non-authentication services used by the built-in bar widgets.
+  function firstPartyServiceFor(id) {
+    return _firstPartyServiceLookup
+      ? _firstPartyServiceLookup(String(id || "")) : null
+  }
+
+  function pluginShellForId(id) {
+    return _pluginShellLookup ? _pluginShellLookup(String(id || "")) : null
+  }
+
+  function pluginShellForBarEntry(ownerId, moduleName) {
+    return _barEntryShellLookup
+      ? _barEntryShellLookup(String(ownerId || ""), String(moduleName || "")) : null
+  }
+
+  function summon(id, payloadJson) {
+    return _summon ? _summon(String(id || ""), String(payloadJson || "")) : false
+  }
+
+  function hide(id) {
+    return _hide ? _hide(String(id || "")) : false
+  }
+
+  function toggle(id, payloadJson) {
+    return _toggle ? _toggle(String(id || ""), String(payloadJson || "")) : false
+  }
+
+  function isPluginOpen(id) {
+    return _isOpen ? _isOpen(String(id || "")) : false
+  }
+
+  function updateEntryInline(id, settings) {
+    return _updateSettings ? _updateSettings(String(id || ""), settings) : false
+  }
+
+  function mutateShellConfig(mutator) {
+    return _mutateBarConfig && typeof mutator === "function"
+      ? _mutateBarConfig(mutator) : false
+  }
+}