Hide unavailable display scale options

shell/plugins/panels/monitor/Model.js

@@ -33,6 +33,55 @@ function cleanScale(scale, width, height) {
   return normalizeScale(scaleUnits / 120)
 }
 
+function matchingScaleIndex(scales, currentScale, width, height) {
+  var current = Number(currentScale)
+  if (!Array.isArray(scales) || !isFinite(current)) return -1
+
+  var bestIndex = -1
+  var bestDistance = Infinity
+  var normalizedCurrent = normalizeScale(current)
+  for (var i = 0; i < scales.length; i++) {
+    if (cleanScale(scales[i], width, height) !== normalizedCurrent) continue
+
+    var distance = Math.abs(Number(scales[i]) - current)
+    if (distance < bestDistance) {
+      bestIndex = i
+      bestDistance = distance
+    }
+  }
+  return bestIndex
+}
+
+function availableScales(scales, width, height) {
+  if (!Array.isArray(scales) || Number(width) <= 0 || Number(height) <= 0) return scales || []
+
+  var byEffectiveScale = {}
+  for (var i = 0; i < scales.length; i++) {
+    var requested = Number(scales[i])
+    var effective = Number(cleanScale(requested, width, height))
+
+    // Clean scales round upward. If the mode cannot reach the requested
+    // scale, cleanScale caps at its largest valid value and this preset is
+    // not actually available.
+    if (!isFinite(requested) || !isFinite(effective) || effective < requested) continue
+
+    var key = normalizeScale(effective)
+    var existing = byEffectiveScale[key]
+    if (!existing || Math.abs(requested - effective) < existing.distance) {
+      byEffectiveScale[key] = {
+        value: String(scales[i]),
+        index: i,
+        distance: Math.abs(requested - effective)
+      }
+    }
+  }
+
+  return Object.keys(byEffectiveScale)
+    .map(function(key) { return byEffectiveScale[key] })
+    .sort(function(a, b) { return a.index - b.index })
+    .map(function(candidate) { return candidate.value })
+}
+
 function brightnessName(percent) {
   var p = Math.round(percent)
   if (p >= 95) return "Sun blast"
@@ -70,6 +119,8 @@ if (typeof module !== "undefined") {
     clampBrightness: clampBrightness,
     normalizeScale: normalizeScale,
     cleanScale: cleanScale,
+    matchingScaleIndex: matchingScaleIndex,
+    availableScales: availableScales,
     brightnessName: brightnessName,
     parseDisplays: parseDisplays
   }

shell/plugins/panels/monitor/Panel.qml

@@ -38,7 +38,15 @@ Panel {
   //                  j/k walks each row.
   // Mouse hover on a target updates root state via the components' `hovered`
   // signal so keyboard cursor and pointer share one highlight.
-  readonly property var scaleValues: ["1", "1.25", "1.6", "2", "3", "4"]
+  readonly property var scalePresets: ["1", "1.25", "1.6", "2", "3", "4"]
+  readonly property var scaleValues: {
+    for (var i = 0; i < displays.length; i++) {
+      var display = displays[i]
+      if (display && display.focused)
+        return Model.availableScales(scalePresets, display.width, display.height)
+    }
+    return scalePresets
+  }
   property string focusSection: "scale"
   property int selectedIndex: 0
   property bool cursorActive: false
@@ -246,13 +254,13 @@ Panel {
     return Model.normalizeScale(scale)
   }
 
-  function effectiveScale(scale) {
+  function activeScaleIndex() {
     for (var i = 0; i < displays.length; i++) {
       var display = displays[i]
       if (display && display.focused)
-        return Model.cleanScale(scale, display.width, display.height)
+        return Model.matchingScaleIndex(scaleValues, monitorScale, display.width, display.height)
     }
-    return normalizeScale(scale)
+    return -1
   }
 
   // Playful mood-name for a given brightness percent. Bands intentionally
@@ -342,6 +350,7 @@ Panel {
 
   onBrightnessAvailableChanged: clampCursor()
   onDisplaysChanged: clampCursor()
+  onScaleValuesChanged: clampCursor()
   onVisibleSectionsChanged: clampCursor()
 
   // Only poll while the panel is open; the bar glyph tracks monitor count via
@@ -780,7 +789,7 @@ Panel {
     verticalPadding: Style.spacing.controlPaddingY
     bordered: true
 
-    active: root.normalizeScale(root.monitorScale) === root.effectiveScale(scaleValue)
+    active: root.activeScaleIndex() === scaleIndex
     hasCursor: root.cursorActive && root.focusSection === "scale" && root.selectedIndex === scaleIndex
 
     onClicked: root.setScale(scaleValue)

test/shell.d/monitor-test.sh

@@ -18,6 +18,31 @@ assertEqual(monitor.cleanScale(3, 1280, 800), '3.2', 'monitor matches clean VM s
 assertEqual(monitor.cleanScale(1.25, 1280, 800), '1.25', 'monitor preserves an already clean scale')
 assertEqual(monitor.cleanScale(1.25, 6016, 3384), '1.33', 'monitor matches clean physical display scale')
 assertEqual(monitor.cleanScale(1.6, 0, 800), '', 'monitor rejects a missing display mode')
+assertEqual(
+  monitor.matchingScaleIndex(['1', '1.25', '1.6', '2', '3', '4'], 3.2, 1280, 800),
+  4,
+  'monitor selects requested 3x for effective VM scale'
+)
+assertEqual(
+  monitor.matchingScaleIndex(['1', '1.25', '1.6', '2', '3', '4'], 4, 4, 4),
+  5,
+  'monitor selects only the closest preset when clean scales collide'
+)
+assertDeepEqual(
+  monitor.availableScales(['1', '1.25', '1.6', '2', '3', '4'], 1280, 800),
+  ['1', '1.25', '1.6', '2', '3', '4'],
+  'monitor keeps presets that produce unique reachable VM scales'
+)
+assertDeepEqual(
+  monitor.availableScales(['1', '1.25', '1.6', '2', '3', '4'], 5968, 3230),
+  ['1', '2'],
+  'monitor hides presets the current mode cannot reach'
+)
+assertDeepEqual(
+  monitor.availableScales(['1', '1.25', '1.6', '2', '3', '4'], 0, 0),
+  ['1', '1.25', '1.6', '2', '3', '4'],
+  'monitor keeps presets until display dimensions are known'
+)
 
 assertEqual(monitor.brightnessName(96), 'Sun blast', 'monitor names very bright displays')
 assertEqual(monitor.brightnessName(12), 'Candlelit', 'monitor names dim displays')