monitors: settings module, try live then keep or revert

Apply evals each monitor's hl.monitor line, one call each because eval
wraps its argument in a return. Keep writes sections/monitors.lua whole;
Revert or 15s without an answer is hyprctl reload, which reapplies the
untouched file. A refusal also reloads, since an earlier monitor's eval
may have gone through.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

3 files changed, 182 insertions, 0 deletions

diff --git a/desktop/modules/monitors/MonitorsModule.qml b/desktop/modules/monitors/MonitorsModule.qml
new file mode 100644
index 0000000..3ed9b22
--- /dev/null
+++ b/desktop/modules/monitors/MonitorsModule.qml
@@ -0,0 +1,157 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+import Quickshell
+import Quickshell.Io
+import Quickshell.Hyprland
+import QtQuick
+import "../.."
+import "Mon.js" as M
+
+// The connected monitors, read from hyprctl monitors -j into a draft. Apply
+// runs each monitor's hl.monitor line through hyprctl eval, which applies it
+// at once or refuses it (exit 7) and changes nothing; then Keep writes
+// sections/monitors.lua, which this page owns whole, and Revert, or 15s with
+// no answer, is hyprctl reload, which reapplies the untouched file. A
+// setting that blanks a screen never reaches the file.
+Module {
+    id: mm
+    name: "monitors"
+    label: "Monitors"
+    // nf-fa-desktop, present in Inconsolata Nerd Font.
+    icon: ""
+    settings: true
+    group: "Hyprland"
+    dirty: mm.changed
+    keywords: ["monitor", "display", "screen", "resolution", "refresh", "hz", "scale", "rotation", "vrr", "position", "layout"]
+
+    readonly property string file: (Quickshell.env("XDG_CONFIG_HOME") || Quickshell.env("HOME") + "/.config")
+                                   + "/hypr/sections/monitors.lua"
+
+    // What hyprctl last reported, and the page's edit of it.
+    property var orig: []
+    property var draft: []
+    readonly property bool changed: JSON.stringify(mm.draft) !== JSON.stringify(mm.orig)
+    readonly property bool valid: mm.draft.every(d => /^\d+(\.\d+)?$/.test(d.scale) && +d.scale > 0)
+    // An Apply is live and waiting for Keep or Revert.
+    property bool pending: false
+    property int countdown: 0
+    property string error: ""
+    property string notice: ""
+    // The reload after a refusal must not replace the draft being fixed.
+    property bool skipRead: false
+
+    function refresh() { if (!mm.changed && !mm.pending) mm.read(); }
+
+    function read() {
+        mm.error = "";
+        readProc.running = false;
+        readProc.running = true;
+    }
+
+    property Process readProc: Process {
+        command: ["hyprctl", "monitors", "-j"]
+        stdout: StdioCollector {
+            onStreamFinished: {
+                let list;
+                try { list = JSON.parse(this.text); } catch (e) { return; }
+                mm.orig = list.map(M.draft);
+                mm.draft = list.map(M.draft);
+            }
+        }
+    }
+
+    // Keep's write, Revert's reload: both end in configreloaded.
+    property Connections reloads: Connections {
+        target: Hyprland
+        function onRawEvent(event) {
+            if (event.name !== "configreloaded" || mm.pending) return;
+            if (mm.skipRead) { mm.skipRead = false; return; }
+            mm.read();
+        }
+    }
+
+    // Changes one field of monitor i; a new array so bindings see it.
+    function set(i, key, value) {
+        const next = mm.draft.slice();
+        next[i] = Object.assign({}, next[i]);
+        next[i][key] = value;
+        mm.draft = next;
+        mm.notice = "";
+    }
+
+    function apply() {
+        mm.error = "";
+        mm.notice = "";
+        applyProc.command = ["sh", "-c", 'for l; do hyprctl eval "$l" || exit 7; done', "sh"]
+            .concat(mm.draft.map(M.lua));
+        applyProc.running = false;
+        applyProc.running = true;
+    }
+
+    property Process applyProc: Process {
+        stdout: StdioCollector { id: applyOut }
+        onExited: code => {
+            if (code !== 0) {
+                const line = applyOut.text.trim().split("\n").filter(l => l.startsWith("error:"))[0] || "";
+                mm.error = line.replace(/^error: .*?:1: /, "") || "Hyprland refused it.";
+                // An earlier monitor's eval may have gone through.
+                mm.skipRead = true;
+                Quickshell.execDetached(["hyprctl", "reload"]);
+                return;
+            }
+            mm.pending = true;
+            mm.countdown = 15;
+            tick.restart();
+        }
+    }
+
+    property Timer tick: Timer {
+        interval: 1000
+        repeat: true
+        onTriggered: if (--mm.countdown <= 0) mm.revert()
+    }
+
+    function keep() {
+        tick.stop();
+        mm.pending = false;
+        fv.setText(M.file(mm.draft));
+        mm.notice = "saved";
+    }
+
+    // Also what leaving the page while pending does.
+    function revert() {
+        tick.stop();
+        mm.pending = false;
+        Quickshell.execDetached(["hyprctl", "reload"]);
+    }
+
+    property FileView fv: FileView {
+        path: mm.file
+        atomicWrites: true
+        printErrors: false
+    }
+
+    Component.onCompleted: mm.read()
+
+    page: Component {
+        Page {
+            title: "Monitors"
+            actions: Component {
+                SaveBar { saveText: "Apply"; dirty: mm.changed && !mm.pending; valid: mm.valid
+                          note: mm.valid ? "" : "Scale must be a positive number."
+                          notice: mm.notice; error: mm.error; busy: mm.applyProc.running
+                          onSave: mm.apply(); onDiscard: mm.read() }
+            }
+            MonitorsPage { width: parent.width; mod: mm }
+        }
+    }
+}
diff --git a/desktop/modules/monitors/MonitorsPage.qml b/desktop/modules/monitors/MonitorsPage.qml
new file mode 100644
index 0000000..3df7b1c
--- /dev/null
+++ b/desktop/modules/monitors/MonitorsPage.qml
@@ -0,0 +1,23 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+import QtQuick
+import "../.."
+
+Column {
+    id: page
+    required property QtObject mod
+    Text {
+        text: page.mod.draft.map(d => d.name + " " + d.mode).join(", ")
+        font { family: Theme.fontFamily; pixelSize: Theme.fontSize - 2 }
+        color: Theme.text
+    }
+}
diff --git a/desktop/shell.qml b/desktop/shell.qml
index d1dc7dc..660c4a5 100644
--- a/desktop/shell.qml
+++ b/desktop/shell.qml
@@ -31,6 +31,7 @@ import "modules/git"
 import "modules/hyprland"
 import "modules/kdeconnect"
 import "modules/mail"
+import "modules/monitors"
 import "modules/network"
 import "modules/notes"
 import "modules/notifications"
@@ -97,6 +98,7 @@ ShellRoot {
             ShellsModule {},
             BindsModule {},
             OptionsModule {},
+            MonitorsModule {},
             ObsScenesModule {},
             AssistantModule { id: asstSettings },
             PresetsModule {},