endSessionDialog: default to not installing updates on low battery

If the user's battery power is low, we should not check the checkbox to
install updates by default. Rationale: if the user's battery is not low,
it's very unlikely to run out during a normal system upgrade. Low
battery is defined as any level below 30%, matching our battery status
indicator.

We'll also change the battery warning to only display when battery is
actually low. However, we will still always warn on battery for full
system upgrades, since these are expected to take a long time.

Future improvement: it would be nice to make the checkbox insensitive
when on low power. However, I don't think we currently have a proper
style for insensitive checkboxes. I was unable to make it look good.

Lastly, note that I did not test this on a laptop. I tested this by
mocking the return values of _isDischargingBattery() and
_isBatteryLow().

Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2717

js/ui/endSessionDialog.js

@@ -18,7 +18,7 @@
  */
 
 const { AccountsService, Clutter, Gio,
-        GLib, GObject, Pango, Polkit, Shell, St }  = imports.gi;
+        GLib, GObject, Pango, Polkit, Shell, St, UPowerGlib: UPower }  = imports.gi;
 
 const CheckBox = imports.ui.checkBox;
 const Dialog = imports.ui.dialog;
@@ -31,6 +31,8 @@ const { loadInterfaceXML } = imports.misc.fileUtils;
 
 const _ITEM_ICON_SIZE = 64;
 
+const LOW_BATTERY_THRESHOLD = 30;
+
 const EndSessionDialogIface = loadInterfaceXML('org.gnome.SessionManager.EndSessionDialog');
 
 const logoutDialogContent = {
@@ -157,7 +159,7 @@ const LogindSession = Gio.DBusProxy.makeProxyWrapper(LogindSessionIface);
 const PkOfflineIface = loadInterfaceXML('org.freedesktop.PackageKit.Offline');
 const PkOfflineProxy = Gio.DBusProxy.makeProxyWrapper(PkOfflineIface);
 
-const UPowerIface = loadInterfaceXML('org.freedesktop.UPower');
+const UPowerIface = loadInterfaceXML('org.freedesktop.UPower.Device');
 const UPowerProxy = Gio.DBusProxy.makeProxyWrapper(UPowerIface);
 
 function findAppFromInhibitor(inhibitor) {
@@ -244,7 +246,7 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
 
         this._powerProxy = new UPowerProxy(Gio.DBus.system,
                                            'org.freedesktop.UPower',
-                                           '/org/freedesktop/UPower',
+                                           '/org/freedesktop/UPower/devices/DisplayDevice',
                                            (proxy, error) => {
                                                if (error) {
                                                    log(error.message);
@@ -279,7 +281,7 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
 
         this._batteryWarning = new St.Label({
             style_class: 'end-session-dialog-battery-warning',
-            text: _('Running on battery power: Please plug in before installing updates.'),
+            text: _('Low battery power: please plug in before installing updates.'),
         });
         this._batteryWarning.clutter_text.ellipsize = Pango.EllipsizeMode.NONE;
         this._batteryWarning.clutter_text.line_wrap = true;
@@ -329,6 +331,32 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
         this._user.disconnect(this._userChangedId);
     }
 
+    _isDischargingBattery() {
+        return this._powerProxy.IsPresent &&
+            this._powerProxy.State !== UPower.DeviceState.CHARGING &&
+            this._powerProxy.State !== UPower.DeviceState.FULLY_CHARGED;
+    }
+
+    _isBatteryLow() {
+        return this._isDischargingBattery() && this._powerProxy.Percentage < LOW_BATTERY_THRESHOLD;
+    }
+
+    _shouldShowLowBatteryWarning(dialogContent) {
+        if (!dialogContent.showBatteryWarning)
+            return false;
+
+        if (!this._isBatteryLow())
+            return false;
+
+        if (this._checkBox.checked)
+            return true;
+
+        // Show the warning if updates have already been triggered, but
+        // the user doesn't have enough permissions to cancel them.
+        let updatesAllowed = this._updatesPermission && this._updatesPermission.allowed;
+        return this._updateInfo.UpdatePrepared && this._updateInfo.UpdateTriggered && !updatesAllowed;
+    }
+
     _sync() {
         let open = this.state == ModalDialog.State.OPENING || this.state == ModalDialog.State.OPENED;
         if (!open)
@@ -342,10 +370,7 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
         if (dialogContent.subjectWithUpdates && this._checkBox.checked)
             subject = dialogContent.subjectWithUpdates;
 
-        if (dialogContent.showBatteryWarning) {
+        this._batteryWarning.visible = this._shouldShowLowBatteryWarning(dialogContent);
-            this._batteryWarning.visible =
-                this._powerProxy.OnBattery && this._checkBox.checked;
-        }
 
         let description;
         let displayTime = _roundSecondsToInterval(this._totalSecondsToStayOpen,
@@ -748,19 +773,17 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
         if (dialogContent.showOtherSessions)
             this._loadSessions();
 
-        let updateTriggered = this._updateInfo.UpdateTriggered;
-        let updatePrepared = this._updateInfo.UpdatePrepared;
         let updatesAllowed = this._updatesPermission && this._updatesPermission.allowed;
 
         _setCheckBoxLabel(this._checkBox, dialogContent.checkBoxText || '');
-        this._checkBox.visible = dialogContent.checkBoxText && updatePrepared && updatesAllowed;
+        this._checkBox.visible = dialogContent.checkBoxText && this._updateInfo.UpdatePrepared && updatesAllowed;
-        this._checkBox.checked = this._checkBox.visible;
 
-        // We show the warning either together with the checkbox, or when
+        if (this._type === DialogType.UPGRADE_RESTART)
-        // updates have already been triggered, but the user doesn't have
+            this._checkBox.checked = this._checkBox.visible && this._updateInfo.UpdateTriggered && !this._isDischargingBattery();
-        // enough permissions to cancel them.
+        else
-        this._batteryWarning.visible = dialogContent.showBatteryWarning &&
+            this._checkBox.checked = this._checkBox.visible && !this._isBatteryLow();
-                                        (this._checkBox.visible || updatePrepared && updateTriggered && !updatesAllowed);
+
+        this._batteryWarning.visible = this._shouldShowLowBatteryWarning(dialogContent);
 
         this._updateButtons();