settings: one Brightness dimming section, one blank timeout

The page asked the same question twice because two daemons answer it, and
split the blank budget by held-vs-resting — which makes the user arbitrate a
guess the accelerometer is making. Held-ness belongs in the confidence
arithmetic as an adjustment to one budget, not as a second budget here.

surfaces/quickshell/modules/settings/IdleConfig.qml

@@ -58,23 +58,38 @@ ContentPage {
         { displayName: Translation.tr("5 min"),  icon: "timer", value: 300 },
         { displayName: Translation.tr("10 min"), icon: "timer", value: 600 }
     ]
-    // How long before the lock the dim starts. Wider range than the
+    // ONE dim setting, for both authorities.
-    // lock-screen grace below: this one has a whole idle-to-lock budget to sit
+    //
-    // inside, and 300 with a 10-minute lock is Casey's "the 15s dim starts at
+    // This used to be two: a session dim (15s–5min, before the lock) and a
-    // 9:45" shape at a larger scale.
+    // separate lock-screen dim grace (5–20s, before the blank). They are two
-    readonly property var dimGracePresets: [
+    // daemons, but they are not two questions — the user is answering "how
-        { displayName: Translation.tr("15s"),   icon: "brightness_medium", value: 15 },
+    // much warning do I get before the screen goes away", once. Splitting it
+    // made the page describe our architecture instead of their screen.
+    //
+    // Written to both: the shell's dimBeforeLockSeconds and sessiond's
+    // dim_grace_secs. The lock-screen side is clamped below, because a dim
+    // longer than the blank budget is a dim that never shows.
+    readonly property var dimPresets: [
+        { displayName: Translation.tr("5s"),    icon: "brightness_medium", value: 5 },
+        { displayName: Translation.tr("10s"),   icon: "brightness_medium", value: 10 },
         { displayName: Translation.tr("30s"),   icon: "brightness_medium", value: 30 },
         { displayName: Translation.tr("1 min"), icon: "brightness_medium", value: 60 },
-        { displayName: Translation.tr("3 min"), icon: "brightness_medium", value: 180 },
+        { displayName: Translation.tr("3 min"), icon: "brightness_medium", value: 180 }
-        { displayName: Translation.tr("5 min"), icon: "brightness_medium", value: 300 }
-    ]
-    readonly property var gracePresets: [
-        { displayName: Translation.tr("5s"),  icon: "brightness_medium", value: 5 },
-        { displayName: Translation.tr("10s"), icon: "brightness_medium", value: 10 },
-        { displayName: Translation.tr("20s"), icon: "brightness_medium", value: 20 }
     ]
 
+    // The lock screen cannot warn for longer than it waits. Clamp rather than
+    // refuse: the user picked a warning length, and the honest reading of
+    // "30s warning, 15s blank" is "warn as early as this screen allows".
+    function applyDim(v) {
+        Config.options.lock.idle.dimBeforeLockSeconds = v;
+        if (!SessiondPolicy.available)
+            return;
+        const blank = SessiondPolicy.lockBlankAfterSecs;
+        SessiondPolicy.apply({
+            dim_grace_secs: blank > 0 ? Math.max(1, Math.min(v, blank - 1)) : v
+        });
+    }
+
     // "2 min" reads better than "120 s" in a sentence about when things happen.
     function clockText(secs) {
         if (secs >= 60 && secs % 60 === 0)
@@ -171,22 +186,48 @@ ContentPage {
             options: page.idlePresets
         }
 
-        // Relative, not absolute. The two used to be independent seconds
+        StyledText {
-        // values and nothing stopped a dim set past the lock, which produced
+            Layout.fillWidth: true
-        // a dim that silently never fired. Choosing "how long before" makes
+            visible: !Config.options.lock.idle.nativeCoordinatorEnabled
-        // the relationship the thing the user sets, so moving the lock moves
+            wrapMode: Text.WordWrap
-        // the dim with it.
+            color: Appearance.colors.colError
+            font.pixelSize: Appearance.font.pixelSize.smaller
+            text: Translation.tr("The native coordinator is off, so these do not run.")
+        }
+    }
+
+    // --- Brightness dimming, one question ---------------------------------
+    // Deliberately not split by authority. Two daemons own the actuation, and
+    // the page used to say so by giving each its own dim control — which made
+    // the user answer the same question twice and left them to work out that
+    // the two interact. One control, written to both. See applyDim().
+    ContentSection {
+        icon: "brightness_medium"
+        title: Translation.tr("Brightness dimming")
+
+        ConfigSwitch {
+            buttonIcon: "brightness_low"
+            text: Translation.tr("Dim before the screen goes away")
+            checked: SessiondPolicy.dimWarning
+            enabled: SessiondPolicy.available
+            onCheckedChanged: {
+                if (SessiondPolicy.available && checked !== SessiondPolicy.dimWarning)
+                    SessiondPolicy.apply({ dim_warning: checked });
+            }
+        }
+
         ContentSubsectionLabel {
-            text: Translation.tr("Start dimming this long before locking")
+            text: Translation.tr("Start dimming this long before")
         }
         ConfigSelectionArray {
             currentValue: Config.options.lock.idle.dimBeforeLockSeconds
-            onSelected: v => Config.options.lock.idle.dimBeforeLockSeconds = v
+            onSelected: v => page.applyDim(v)
-            options: page.dimGracePresets
+            options: page.dimPresets
         }
 
-        // Say what the pair actually does. A relationship the user has to
+        // Say what it actually does, on both surfaces, in one sentence each.
-        // compute in their head is one they will get wrong.
+        // A relationship the user has to compute in their head is one they
+        // will get wrong.
         StyledText {
             Layout.fillWidth: true
             wrapMode: Text.WordWrap
@@ -196,7 +237,7 @@ ContentPage {
                 const lock = Config.options.lock.idle.lockAfterSeconds;
                 const grace = Config.options.lock.idle.dimBeforeLockSeconds;
                 const dimAt = Math.max(1, Math.min(lock - 1, lock - grace));
-                return Translation.tr("Dims at %1, locks at %2.")
+                return Translation.tr("In use: dims at %1, locks at %2.")
                     .arg(page.clockText(dimAt))
                     .arg(page.clockText(lock));
             }
@@ -204,11 +245,19 @@ ContentPage {
 
         StyledText {
             Layout.fillWidth: true
-            visible: !Config.options.lock.idle.nativeCoordinatorEnabled
+            visible: SessiondPolicy.available
             wrapMode: Text.WordWrap
-            color: Appearance.colors.colError
+            color: Appearance.colors.colSubtext
             font.pixelSize: Appearance.font.pixelSize.smaller
-            text: Translation.tr("The native coordinator is off, so these do not run.")
+            text: {
+                const blank = SessiondPolicy.lockBlankAfterSecs;
+                if (blank === 0)
+                    return Translation.tr("On the lock screen: never blanks, so nothing dims.");
+                const g = SessiondPolicy.dimGraceSecs;
+                return Translation.tr("On the lock screen: dims %1 before blanking at %2.")
+                    .arg(page.clockText(g))
+                    .arg(page.clockText(blank));
+            }
         }
     }
 
@@ -245,51 +294,32 @@ ContentPage {
         // desk-clock case" — and nobody reasons about a lock screen in
         // 5-second increments. Values are still seconds on the wire; the
         // daemon's vocabulary does not change because the UI got legible.
+        // One blank timeout, not two.
+        //
+        // The daemon still has a separate held-vs-resting budget, and it is
+        // still the right idea — a phone in your hand should not blank on the
+        // same schedule as one face-up on a desk. It is not a *setting*
+        // though. Asking the user to pick two numbers made them responsible
+        // for arbitrating a guess the accelerometer was making on their
+        // behalf, and the machine already has a better vocabulary for that:
+        // §4's confidence arithmetic. Held-ness belongs there, as an
+        // adjustment to one budget, not as a second budget on this page.
+        //
+        // Until that lands, both fields get the same value, so the behaviour
+        // is uniform and predictable rather than silently forking on a sensor
+        // reading nothing surfaces.
         ContentSubsectionLabel {
-            text: Translation.tr("Blank after — on a table")
+            text: Translation.tr("Blank after")
         }
         ConfigSelectionArray {
             currentValue: SessiondPolicy.lockBlankAfterSecs
-            onSelected: v => SessiondPolicy.apply({ lock_blank_after_secs: v })
+            onSelected: v => SessiondPolicy.apply({
+                lock_blank_after_secs: v,
+                lock_blank_after_held_secs: v
+            })
             options: page.blankPresets
         }
 
-        ContentSubsectionLabel {
-            text: Translation.tr("Blank after — in your hand")
-        }
-        StyledText {
-            Layout.fillWidth: true
-            wrapMode: Text.WordWrap
-            color: Appearance.colors.colSubtext
-            font.pixelSize: Appearance.font.pixelSize.smaller
-            text: Translation.tr("Used when the accelerometer says the device is being held rather than resting.")
-        }
-        ConfigSelectionArray {
-            currentValue: SessiondPolicy.lockBlankAfterHeldSecs
-            onSelected: v => SessiondPolicy.apply({ lock_blank_after_held_secs: v })
-            options: page.blankPresets
-        }
-
-        ContentSubsectionLabel {
-            text: Translation.tr("Dim warning before blanking")
-        }
-        ConfigSelectionArray {
-            currentValue: SessiondPolicy.dimGraceSecs
-            onSelected: v => SessiondPolicy.apply({ dim_grace_secs: v })
-            options: page.gracePresets
-        }
-
-        ConfigSwitch {
-            buttonIcon: "brightness_low"
-            text: Translation.tr("Show the dim warning")
-            checked: SessiondPolicy.dimWarning
-            enabled: SessiondPolicy.available
-            onCheckedChanged: {
-                if (SessiondPolicy.available && checked !== SessiondPolicy.dimWarning)
-                    SessiondPolicy.apply({ dim_warning: checked });
-            }
-        }
-
         // Only claim the ordering guarantee when the daemon actually reports
         // the field. An older sessiond has no lock_ack_budget_secs, and
         // rendering that absence as "waits 0s" would be the page inventing a