Merge pull request 'fix(edit): curate the CalDAV colour picker (#22)' (!70) from fix/caldav-color-picker-v2 into release/v2.14.1

Reviewed-on: #70

CHANGELOG.md

@@ -5,6 +5,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+- A tidy colour picker on CalDAV calendars. For calendars synced by a CalDAV
+  app (such as DAVx5), the event colour picker showed every colour the account
+  publishes — nearly 150 swatches in alphabetical order, many of them
+  duplicates or near-identical shades. The picker now shows only visually
+  distinct colours, arranged as a rainbow; near-duplicate shades and the
+  washed-out neutrals are folded away so no two swatches look alike. Picked
+  colours still sync exactly as before, and calendars with hand-picked
+  palettes (like Google's) are unaffected. Thanks to @ptab for the report
+  ([#22]).
+
 ## [2.14.0] — 2026-07-06
 
 ### Added
@@ -865,6 +878,7 @@ automatically, with zero telemetry and no internet permission.
 [#18]: https://codeberg.org/jlmakiola/calendula/issues/18
 [#19]: https://codeberg.org/jlmakiola/calendula/issues/19
 [#20]: https://codeberg.org/jlmakiola/calendula/issues/20
+[#22]: https://codeberg.org/jlmakiola/calendula/issues/22
 [#24]: https://codeberg.org/jlmakiola/calendula/issues/24
 [#25]: https://codeberg.org/jlmakiola/calendula/issues/25
 [#27]: https://codeberg.org/jlmakiola/calendula/issues/27

app/src/main/AndroidManifest.xml

@@ -123,6 +123,22 @@
                 <data android:mimeType="vnd.android.cursor.dir/event" />
             </intent-filter>
 
+            <!-- Open an existing event another app/widget points at (e.g. tapping
+                 an event in the Todo Agenda widget): ACTION_VIEW on
+                 content://com.android.calendar/events/<id>, the way AOSP fires it.
+                 Matched by the provider's item MIME type, not the path — a
+                 content: VIEW intent carries the resolved type
+                 (vnd.android.cursor.item/event) and a path-only filter wouldn't
+                 match it. The occurrence's times ride as EXTRA_EVENT_BEGIN_TIME /
+                 EXTRA_EVENT_END_TIME when the launcher supplies them
+                 (MainActivity.viewEventKeyOrNull, issue #48). -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:mimeType="vnd.android.cursor.item/event" />
+            </intent-filter>
+
             <!-- Launcher long-press shortcuts (e.g. "New event"). -->
             <meta-data
                 android:name="android.app.shortcuts"

app/src/main/java/de/jeanlucmakiola/calendula/MainActivity.kt

@@ -32,6 +32,7 @@ import de.jeanlucmakiola.calendula.ui.common.LocalShowHourLines
 import de.jeanlucmakiola.calendula.ui.common.LocalUse24HourFormat
 import de.jeanlucmakiola.calendula.ui.WidgetNavRequest
 import de.jeanlucmakiola.calendula.ui.common.CalendarView
+import de.jeanlucmakiola.calendula.ui.detail.EventDetailViewModel.Companion.NO_OCCURRENCE_TIME
 import de.jeanlucmakiola.floret.components.DebugRibbon
 import de.jeanlucmakiola.calendula.ui.crash.CrashReportActivity
 import de.jeanlucmakiola.calendula.domain.FontRole
@@ -90,7 +91,7 @@ class MainActivity : AppCompatActivity() {
         }
 
         enableEdgeToEdge()
-        requestedDetailKey = intent.detailKeyOrNull()
+        requestedDetailKey = intent.detailKeyOrNull() ?: intent.viewEventKeyOrNull()
         requestedNav = intent.navRequestOrNull()
         requestedImportUri = intent.importUriOrNull()
         requestedInsertForm = intent.insertFormOrNull()
@@ -178,7 +179,7 @@ class MainActivity : AppCompatActivity() {
 
     override fun onNewIntent(intent: Intent) {
         super.onNewIntent(intent)
-        intent.detailKeyOrNull()?.let { requestedDetailKey = it }
+        (intent.detailKeyOrNull() ?: intent.viewEventKeyOrNull())?.let { requestedDetailKey = it }
         intent.navRequestOrNull()?.let { requestedNav = it }
         intent.importUriOrNull()?.let { requestedImportUri = it }
         intent.insertFormOrNull()?.let { requestedInsertForm = it }
@@ -293,6 +294,30 @@ class MainActivity : AppCompatActivity() {
         )
     }
 
+    /**
+     * The detail key for an external "open this event" — ACTION_VIEW on
+     * `content://com.android.calendar/events/<id>`, the way AOSP fires it (e.g.
+     * tapping an existing event in the Todo Agenda widget, issue #48). Reuses the
+     * same occurrence-key channel as reminder taps. The launcher passes the
+     * occurrence's times as `EXTRA_EVENT_BEGIN_TIME` / `EXTRA_EVENT_END_TIME` when
+     * it has them; a bare URI omits them, so we carry [NO_OCCURRENCE_TIME] and
+     * [EventDetailViewModel] falls back to the event row's own DTSTART/DTEND
+     * rather than rendering at the epoch.
+     */
+    private fun Intent.viewEventKeyOrNull(): LongArray? {
+        if (action != Intent.ACTION_VIEW) return null
+        val uri = data ?: return null
+        if (uri.host != CALENDAR_PROVIDER_HOST) return null
+        val segments = uri.pathSegments
+        if (segments.firstOrNull() != "events") return null
+        val eventId = segments.getOrNull(1)?.toLongOrNull() ?: return null
+        return longArrayOf(
+            eventId,
+            longExtraOrNull(CalendarContract.EXTRA_EVENT_BEGIN_TIME) ?: NO_OCCURRENCE_TIME,
+            longExtraOrNull(CalendarContract.EXTRA_EVENT_END_TIME) ?: NO_OCCURRENCE_TIME,
+        )
+    }
+
     companion object {
         // The calendar provider's authority/host. A date tap arrives as
         // ACTION_VIEW on content://com.android.calendar/time/<epochMillis>.

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt

@@ -22,6 +22,7 @@ import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventAttendee
 import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
+import de.jeanlucmakiola.calendula.domain.curatedForPicker
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.EventStatus
@@ -63,10 +64,12 @@ interface CalendarDataSource {
 
     /**
      * The event-colour palette the calendar's account publishes
-     * (`CalendarContract.Colors`, `TYPE_EVENT`), sorted by key. Empty when the
-     * account exposes no palette (most local calendars, some CalDAV) — the
-     * signal that a custom colour can only be written as a raw `EVENT_COLOR`,
-     * which a synced calendar may drop on its next sync.
+     * (`CalendarContract.Colors`, `TYPE_EVENT`), curated for display — deduped,
+     * thinned to visually distinct swatches when oversized (CalDAV adapters
+     * publish all ~147 CSS3 names, #22) and hue-sorted; see [curatedForPicker].
+     * Empty when the account exposes no palette (most local calendars, some
+     * CalDAV) — the signal that a custom colour can only be written as a raw
+     * `EVENT_COLOR`, which a synced calendar may drop on its next sync.
      */
     fun eventColorPalette(calendarId: Long): List<EventColorOption>
 
@@ -492,7 +495,13 @@ class AndroidCalendarDataSource @Inject constructor(
         return resolver.query(
             uri,
             InstanceProjection.COLUMNS,
-            null, null,
+            // Hide cancelled occurrences: "delete only this event" writes a
+            // cancelled exception for the one instance (#47). A NULL status is a
+            // normal, un-cancelled event, so it must survive the filter — a bare
+            // `!= CANCELED` would drop it (NULL != 2 is NULL, not true).
+            "${CalendarContract.Instances.STATUS} IS NULL OR " +
+                "${CalendarContract.Instances.STATUS} != ${CalendarContract.Events.STATUS_CANCELED}",
+            null,
             CalendarContract.Instances.BEGIN + " ASC",
         )?.use { c -> c.mapAllNotNull { CursorColumnReader(c).toEventInstance() } } ?: emptyList()
     }
@@ -611,7 +620,7 @@ class AndroidCalendarDataSource @Inject constructor(
             c.mapAll { EventColorOption(key = it.getString(0).orEmpty(), argb = it.getInt(1)) }
         }
             ?.filter { it.key.isNotEmpty() }
-            ?.sortedBy { it.key }
+            ?.curatedForPicker()
             ?: emptyList()
     }
 
@@ -1183,15 +1192,25 @@ class AndroidCalendarDataSource @Inject constructor(
 
     override fun deleteOccurrence(eventId: Long, beginMillis: Long) {
         // A cancelled exception row hides exactly this occurrence; the sync
-        // adapter turns it into an EXDATE/cancelled VEVENT upstream.
-        val values = ContentValues().apply {
-            put(CalendarContract.Events.ORIGINAL_INSTANCE_TIME, beginMillis)
-            put(CalendarContract.Events.STATUS, CalendarContract.Events.STATUS_CANCELED)
-        }
+        // adapter turns it into an EXDATE/cancelled VEVENT upstream. It has to
+        // carry the full time set (DTSTART + DURATION + zone), not just STATUS:
+        // the provider only demotes the cloned exception to a single instance —
+        // clearing the inherited RRULE — when it can derive that instance from
+        // those columns. A STATUS-only cancel left the RRULE standing and
+        // cancelled the whole series, wiping every other occurrence (#47), the
+        // same trap the edit path documents (Codeberg #16).
+        val row = querySeriesRow(eventId)
+        val values = buildOccurrenceCancelValues(
+            originalInstanceMillis = beginMillis,
+            dtStartMillis = beginMillis,
+            duration = row.duration,
+            timezone = row.timezone,
+            allDay = row.allDay,
+        )
         val uri = ContentUris.withAppendedId(
             CalendarContract.Events.CONTENT_EXCEPTION_URI, eventId,
         )
-        resolver.insert(uri, values)
+        resolver.insert(uri, values.toContentValues())
             ?: throw WriteFailedException("cancel occurrence event id=$eventId begin=$beginMillis")
     }
 

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/EventWriteMapper.kt

@@ -182,6 +182,33 @@ internal fun buildOccurrenceExceptionValues(
     putAll(eventColorColumns(form.colorKey, form.color))
 }
 
+/**
+ * Column values for a *cancelled*-occurrence exception row ("delete only this
+ * event"): inserting them at `Events.CONTENT_EXCEPTION_URI/<id>` makes the
+ * provider clone the series row and cancel exactly this one instance.
+ *
+ * As with [buildOccurrenceExceptionValues], the occurrence must be anchored with
+ * DTSTART + DURATION so the provider derives a single instance and clears the
+ * inherited RRULE. A STATUS-only cancel skips that: the clone keeps the RRULE, so
+ * the *whole series* is cancelled and every other occurrence disappears
+ * (Codeberg #47). The occurrence's length/zone come straight from the series row
+ * — cancelling never changes them.
+ */
+internal fun buildOccurrenceCancelValues(
+    originalInstanceMillis: Long,
+    dtStartMillis: Long,
+    duration: String?,
+    timezone: String?,
+    allDay: Int,
+): Map<String, Any?> = buildMap {
+    put(CalendarContract.Events.ORIGINAL_INSTANCE_TIME, originalInstanceMillis)
+    put(CalendarContract.Events.DTSTART, dtStartMillis)
+    put(CalendarContract.Events.DURATION, duration)
+    put(CalendarContract.Events.EVENT_TIMEZONE, timezone)
+    put(CalendarContract.Events.ALL_DAY, allDay)
+    put(CalendarContract.Events.STATUS, CalendarContract.Events.STATUS_CANCELED)
+}
+
 /**
  * The `EVENT_COLOR` / `EVENT_COLOR_KEY` columns for a colour selection. A
  * [colorKey] writes the key alone (the provider derives `EVENT_COLOR` from the

app/src/main/java/de/jeanlucmakiola/calendula/domain/EventColorPalette.kt

@@ -0,0 +1,185 @@
+package de.jeanlucmakiola.calendula.domain
+
+import kotlin.math.abs
+import kotlin.math.atan2
+import kotlin.math.cbrt
+import kotlin.math.hypot
+import kotlin.math.pow
+import kotlin.math.roundToInt
+import kotlin.math.sqrt
+
+/**
+ * Curates an account's published event palette for the colour picker.
+ *
+ * Sync adapters differ wildly in what they publish: Google exposes a
+ * hand-picked two-dozen set, while CalDAV adapters (DAVx5) dump all ~147 CSS3
+ * named colours — including exact-value aliases (aqua/cyan, the gray/grey
+ * spelling pairs) and dozens of visually indistinguishable whites and grays
+ * (#22).
+ *
+ * Crucially, curation runs against the colour the picker actually *paints*, not
+ * the raw provider value. The picker softens every swatch through [pastelArgb]:
+ * it pins lightness to a constant and caps saturation, so the raw palette's
+ * lightness axis is invisible on screen. Two raw colours that look different —
+ * a navy and a mid blue — paint as one swatch, and every neutral (black, the
+ * grays, white) paints as the same pale tint. Judging distinctness in raw
+ * space, as before, left near-identical painted swatches and stranded the
+ * neutrals as a run of look-alike "pinks" at the end of the grid.
+ *
+ * Three steps, all in painted space:
+ *  1. Collapse swatches that paint identically to one (alphabetically-first key
+ *     wins, deterministically) — this folds aliases, dark/light shades of a
+ *     hue, and all the neutrals together.
+ *  2. Oversized palettes (> [CURATION_TRIGGER_SIZE]) drop the washed-out
+ *     neutral-origin tints (painted chroma < [PASTEL_CHROMA_FLOOR]) and are
+ *     then thinned to visually distinct colours: most vivid first, a colour is
+ *     kept only when at least [MIN_DELTA_E] (CIE76, painted Lab) from every
+ *     colour already kept. Small palettes are already curated by their adapter
+ *     and pass through whole.
+ *  3. The survivors are ordered like a rainbow — continuously by painted hue —
+ *     with the wheel cut at its single widest empty gap so the one unavoidable
+ *     seam lands in dead space and no hue family is torn across both ends.
+ *
+ * Every surviving option keeps its provider [EventColorOption.key], so a pick
+ * still round-trips through sync.
+ */
+fun List<EventColorOption>.curatedForPicker(): List<EventColorOption> {
+    val painted = sortedBy { it.key }
+        .distinctBy { pastelArgb(it.argb) }
+        .map { it to Lab.of(pastelArgb(it.argb)) }
+    val kept = if (painted.size <= CURATION_TRIGGER_SIZE) {
+        painted
+    } else {
+        thin(painted.filter { (_, lab) -> lab.chroma >= PASTEL_CHROMA_FLOOR })
+    }
+    return orderAroundWheel(kept).map { (option, _) -> option }
+}
+
+/**
+ * Orders swatches continuously around the (painted) hue wheel, then cuts the
+ * circle at its widest angular gap so the single seam lands in empty space
+ * instead of mid-family. Saturation breaks ties, vivid first.
+ */
+private fun orderAroundWheel(
+    swatches: List<Pair<EventColorOption, Lab>>,
+): List<Pair<EventColorOption, Lab>> {
+    if (swatches.size < 2) return swatches
+    val byHue = swatches.sortedWith(
+        compareBy({ (_, lab) -> lab.hue }, { (_, lab) -> -lab.chroma }),
+    )
+    // Split the wheel after the largest empty arc between neighbouring hues;
+    // the default is the wrap gap (last hue back round to the first), i.e. the
+    // familiar 0→360 order, and we only rotate away from it for a wider void.
+    var cutAfter = byHue.lastIndex
+    var widestGap = 360.0 - byHue.last().second.hue + byHue.first().second.hue
+    for (i in 0 until byHue.lastIndex) {
+        val gap = byHue[i + 1].second.hue - byHue[i].second.hue
+        if (gap > widestGap) {
+            widestGap = gap
+            cutAfter = i
+        }
+    }
+    return byHue.subList(cutAfter + 1, byHue.size) + byHue.subList(0, cutAfter + 1)
+}
+
+/** Greedy max-distance filter: vivid colours stake out clusters first. */
+private fun thin(
+    swatches: List<Pair<EventColorOption, Lab>>,
+): List<Pair<EventColorOption, Lab>> {
+    val byVividness = swatches
+        .sortedWith(compareByDescending<Pair<EventColorOption, Lab>> { it.second.chroma }.thenBy { it.first.key })
+    val kept = mutableListOf<Pair<EventColorOption, Lab>>()
+    for (candidate in byVividness) {
+        if (kept.none { it.second.deltaE(candidate.second) < MIN_DELTA_E }) kept += candidate
+    }
+    return kept
+}
+
+/**
+ * The softening the colour picker paints over every swatch: keep the hue, scale
+ * and clamp saturation into a gentle band, and pin value to a constant so
+ * nothing screams and everything reads on the surface. Value is fixed here so
+ * curation is theme-independent — only hue and saturation distinguish painted
+ * swatches.
+ *
+ * This is a self-contained mirror of floret-kit's `pastelize` hue/saturation
+ * shaping (`de.jeanlucmakiola.floret.components.pastelize`), with value pinned
+ * rather than theme-picked. Curation must reason about the colour the picker
+ * paints, so the two shapings have to agree: if floret's saturation band or
+ * curve changes, update this in step.
+ */
+fun pastelArgb(rawArgb: Int): Int {
+    val r = ((rawArgb shr 16) and 0xFF) / 255f
+    val g = ((rawArgb shr 8) and 0xFF) / 255f
+    val b = (rawArgb and 0xFF) / 255f
+    val max = maxOf(r, g, b)
+    val min = minOf(r, g, b)
+    val delta = max - min
+    val hue = when {
+        delta == 0f -> 0f
+        max == r -> 60f * (((g - b) / delta) % 6f)
+        max == g -> 60f * (((b - r) / delta) + 2f)
+        else -> 60f * (((r - g) / delta) + 4f)
+    }.let { if (it < 0f) it + 360f else it }
+    val sat = (if (max == 0f) 0f else delta / max) * 0.6f
+    val s = sat.coerceIn(0.25f, 0.65f)
+    val v = PASTEL_VALUE
+    val c = v * s
+    val x = c * (1f - abs((hue / 60f) % 2f - 1f))
+    val m = v - c
+    val (rr, gg, bb) = when {
+        hue < 60f -> Triple(c, x, 0f)
+        hue < 120f -> Triple(x, c, 0f)
+        hue < 180f -> Triple(0f, c, x)
+        hue < 240f -> Triple(0f, x, c)
+        hue < 300f -> Triple(x, 0f, c)
+        else -> Triple(c, 0f, x)
+    }
+    fun channel(value: Float) = ((value + m) * 255f).roundToInt().coerceIn(0, 255)
+    return (0xFF shl 24) or (channel(rr) shl 16) or (channel(gg) shl 8) or channel(bb)
+}
+
+/** Reference lightness for curation; the picker paints at this on dark surfaces. */
+private const val PASTEL_VALUE = 0.82f
+
+/** Palettes at most this big skip the thinning (Google's ~26 pass through). */
+private const val CURATION_TRIGGER_SIZE = 36
+
+/** Minimum CIE76 ΔE between surviving painted swatches. */
+private const val MIN_DELTA_E = 13.0
+
+/**
+ * Painted-chroma floor for oversized palettes: below this a swatch is a washed-
+ * out tint — the neutrals and near-whites the saturation clamp muddies — so it
+ * is dropped rather than shown as pale filler.
+ */
+private const val PASTEL_CHROMA_FLOOR = 22.0
+
+/** CIE Lab (D65) — the space where Euclidean distance ≈ perceived difference. */
+private class Lab(val l: Double, val a: Double, val b: Double) {
+    val chroma: Double get() = hypot(a, b)
+
+    /** Hue angle in degrees, 0–360, around the Lab a-b plane. */
+    val hue: Double get() = (Math.toDegrees(atan2(b, a)) + 360.0) % 360.0
+
+    fun deltaE(other: Lab): Double =
+        sqrt((l - other.l).pow(2) + (a - other.a).pow(2) + (b - other.b).pow(2))
+
+    companion object {
+        fun of(argb: Int): Lab {
+            fun linear(shift: Int): Double {
+                val c = ((argb shr shift) and 0xFF) / 255.0
+                return if (c <= 0.04045) c / 12.92 else ((c + 0.055) / 1.055).pow(2.4)
+            }
+            val r = linear(16)
+            val g = linear(8)
+            val b = linear(0)
+            val x = (0.4124 * r + 0.3576 * g + 0.1805 * b) / 0.95047
+            val y = 0.2126 * r + 0.7152 * g + 0.0722 * b
+            val z = (0.0193 * r + 0.1192 * g + 0.9505 * b) / 1.08883
+            fun f(t: Double) = if (t > 0.008856) cbrt(t) else 7.787 * t + 16.0 / 116.0
+            val fy = f(y)
+            return Lab(116 * fy - 16, 500 * (f(x) - fy), 200 * (fy - f(z)))
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailViewModel.kt

@@ -141,13 +141,20 @@ class EventDetailViewModel @Inject constructor(
     private suspend fun loadDetail(target: Target): EventDetailUiState = try {
         val detail = repository.eventDetail(target.eventId)
         // The Events row holds the series start; replace it with this
-        // occurrence's time so recurring events render correctly.
-        val corrected = detail.copy(
-            instance = detail.instance.copy(
-                start = Instant.fromEpochMilliseconds(target.beginMillis),
-                end = Instant.fromEpochMilliseconds(target.endMillis),
-            ),
-        )
+        // occurrence's time so recurring events render correctly. An external
+        // "open event" that names no occurrence ([NO_OCCURRENCE_TIME] — e.g. a
+        // bare content://.../events/<id> VIEW intent, issue #48) keeps the row's
+        // own DTSTART/DTEND instead of overriding it to the epoch.
+        val corrected = if (target.beginMillis == NO_OCCURRENCE_TIME) {
+            detail
+        } else {
+            detail.copy(
+                instance = detail.instance.copy(
+                    start = Instant.fromEpochMilliseconds(target.beginMillis),
+                    end = Instant.fromEpochMilliseconds(target.endMillis),
+                ),
+            )
+        }
         val calendar = repository.calendars().first()
             .firstOrNull { it.id == corrected.instance.calendarId }
         EventDetailUiState.Success(
@@ -168,6 +175,16 @@ class EventDetailViewModel @Inject constructor(
 
     /** A tapped occurrence: the series [eventId] plus this occurrence's own times. */
     private data class Target(val eventId: Long, val beginMillis: Long, val endMillis: Long)
+
+    companion object {
+        /**
+         * Sentinel begin/end for an "open this event" that names no occurrence —
+         * a bare `content://com.android.calendar/events/<id>` VIEW intent with no
+         * `EXTRA_EVENT_BEGIN_TIME` (issue #48). [loadDetail] then keeps the event
+         * row's own DTSTART/DTEND instead of overriding it to the epoch.
+         */
+        const val NO_OCCURRENCE_TIME: Long = Long.MIN_VALUE
+    }
 }
 
 /** A filesystem-safe `.ics` file name from an event title (or a fallback). */

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditScreen.kt

@@ -1747,12 +1747,21 @@ private fun ColorPickerDialog(
             modifier = Modifier.padding(horizontal = 24.dp, vertical = 8.dp),
         ) {
             if (palette.isNotEmpty()) {
+                // The event's current colour may not be in the curated palette
+                // (a thinned near-duplicate, or a raw colour set elsewhere) —
+                // append it so the selection ring has a home.
+                val swatches = palette.map { it.argb }.let {
+                    if (selected != null && selected !in it) it + selected else it
+                }
                 ColorSwatchRow(
-                    colors = palette.map { it.argb },
+                    colors = swatches,
                     selected = selected,
                     onSelect = { argb ->
-                        palette.firstOrNull { it.argb == argb }
-                            ?.let { onPickKey(it.key, it.argb) }
+                        val option = palette.firstOrNull { it.argb == argb }
+                        // The appended current colour has no provider key to
+                        // write — it is already the event's colour, so just
+                        // close.
+                        if (option != null) onPickKey(option.key, option.argb) else onDismiss()
                     },
                     dark = dark,
                 )

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/EventWriteMapperTest.kt

@@ -220,6 +220,46 @@ class EventWriteMapperTest {
         assertThat(values).containsEntry(CalendarContract.Events.DESCRIPTION, null)
     }
 
+    // --- buildOccurrenceCancelValues ("delete only this event") ---
+
+    @Test
+    fun `occurrence cancel anchors a single instance and cancels only it`() {
+        val values = buildOccurrenceCancelValues(
+            originalInstanceMillis = 1_700_000_000_000L,
+            dtStartMillis = 1_700_000_000_000L,
+            duration = "P3600S",
+            timezone = "Europe/Berlin",
+            allDay = 0,
+        )
+        assertThat(values[CalendarContract.Events.ORIGINAL_INSTANCE_TIME])
+            .isEqualTo(1_700_000_000_000L)
+        // DTSTART + DURATION make the provider derive a single instance and drop
+        // the inherited RRULE, so only this occurrence is cancelled — not the
+        // whole series (#47). DTEND is never sent (the provider rejects it).
+        assertThat(values[CalendarContract.Events.DTSTART]).isEqualTo(1_700_000_000_000L)
+        assertThat(values[CalendarContract.Events.DURATION]).isEqualTo("P3600S")
+        assertThat(values[CalendarContract.Events.EVENT_TIMEZONE]).isEqualTo("Europe/Berlin")
+        assertThat(values[CalendarContract.Events.STATUS])
+            .isEqualTo(CalendarContract.Events.STATUS_CANCELED)
+        assertThat(values).doesNotContainKey(CalendarContract.Events.DTEND)
+        assertThat(values).doesNotContainKey(CalendarContract.Events.RRULE)
+    }
+
+    @Test
+    fun `all-day occurrence cancel keeps the all-day flag and utc zone`() {
+        val values = buildOccurrenceCancelValues(
+            originalInstanceMillis = 1_700_000_000_000L,
+            dtStartMillis = 1_700_000_000_000L,
+            duration = "P1D",
+            timezone = "UTC",
+            allDay = 1,
+        )
+        assertThat(values[CalendarContract.Events.ALL_DAY]).isEqualTo(1)
+        assertThat(values[CalendarContract.Events.EVENT_TIMEZONE]).isEqualTo("UTC")
+        assertThat(values[CalendarContract.Events.STATUS])
+            .isEqualTo(CalendarContract.Events.STATUS_CANCELED)
+    }
+
     // --- per-event colour ---
 
     @Test

app/src/test/java/de/jeanlucmakiola/calendula/domain/EventColorPaletteTest.kt

@@ -0,0 +1,214 @@
+package de.jeanlucmakiola.calendula.domain
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class EventColorPaletteTest {
+
+    @Test
+    fun `empty palette stays empty`() {
+        assertThat(emptyList<EventColorOption>().curatedForPicker()).isEmpty()
+    }
+
+    @Test
+    fun `exact duplicate values collapse to the alphabetically first key`() {
+        val curated = listOf(
+            EventColorOption("cyan", 0xFF00FFFF.toInt()),
+            EventColorOption("aqua", 0xFF00FFFF.toInt()),
+            EventColorOption("red", 0xFFFF0000.toInt()),
+        ).curatedForPicker()
+
+        assertThat(curated.map { it.key }).containsExactly("aqua", "red")
+    }
+
+    @Test
+    fun `small palettes pass through whole, so Google's curated set is untouched`() {
+        // A Google-like palette: two dozen distinct hand-picked colours.
+        val palette = (0 until 24).map {
+            val hue = it * 15
+            EventColorOption("$it", hsvArgb(hue.toFloat()))
+        }
+
+        val curated = palette.curatedForPicker()
+
+        assertThat(curated).containsExactlyElementsIn(palette)
+    }
+
+    @Test
+    fun `oversized CSS3 palette thins to a pickable number of distinct swatches`() {
+        val curated = css3Palette().curatedForPicker()
+
+        // The whole point of #22: ~147 published colours become a single
+        // manageable grid instead of a full screen.
+        assertThat(curated.size).isAtLeast(30)
+        assertThat(curated.size).isAtMost(60)
+    }
+
+    @Test
+    fun `curation never invents colours or drops keys`() {
+        val source = css3Palette()
+        val curated = source.curatedForPicker()
+
+        assertThat(source).containsAtLeastElementsIn(curated)
+        assertThat(curated.map { it.argb }).containsNoDuplicates()
+    }
+
+    @Test
+    fun `spelling-alias pairs never both survive`() {
+        val keys = css3Palette().curatedForPicker().map { it.key }.toSet()
+
+        val aliasPairs = listOf(
+            "aqua" to "cyan",
+            "fuchsia" to "magenta",
+            "gray" to "grey",
+            "darkgray" to "darkgrey",
+            "dimgray" to "dimgrey",
+            "lightgray" to "lightgrey",
+            "slategray" to "slategrey",
+            "lightslategray" to "lightslategrey",
+            "darkslategray" to "darkslategrey",
+        )
+        aliasPairs.forEach { (a, b) ->
+            assertThat(keys.contains(a) && keys.contains(b)).isFalse()
+        }
+    }
+
+    @Test
+    fun `neutrals collapse to one painted tint instead of a run of look-alikes`() {
+        // Black and every gray paint as the same pale swatch (the picker pins
+        // lightness and floors saturation), so only one survives — no stranded
+        // run of look-alike "pinks" at the end of the grid (#22).
+        val curated = listOf(
+            EventColorOption("black", 0xFF000000.toInt()),
+            EventColorOption("gray", 0xFF808080.toInt()),
+            EventColorOption("darkgray", 0xFFA9A9A9.toInt()),
+            EventColorOption("blue", 0xFF0000FF.toInt()),
+            EventColorOption("red", 0xFFFF0000.toInt()),
+        ).curatedForPicker().map { it.key }
+
+        assertThat(curated).containsNoneOf("gray", "darkgray") // folded into black
+        assertThat(curated).containsAtLeast("black", "red", "blue")
+    }
+
+    @Test
+    fun `a dark and a light shade of one hue collapse to a single swatch`() {
+        // The picker paints every swatch at one fixed lightness, so navy and a
+        // mid blue are indistinguishable once painted — keep just one.
+        val curated = listOf(
+            EventColorOption("navy", 0xFF000080.toInt()),
+            EventColorOption("blue", 0xFF0000FF.toInt()),
+        ).curatedForPicker()
+
+        assertThat(curated).hasSize(1)
+    }
+
+    @Test
+    fun `the wheel is cut once, keeping each hue family contiguous`() {
+        // Twelve pure hues, deliberately shuffled; a small palette passes the
+        // thinning stage untouched so only the ordering is under test.
+        val shuffledHues = listOf(0, 300, 60, 180, 120, 240, 30, 330, 90, 210, 150, 270)
+        val curated = shuffledHues
+            .map { EventColorOption("$it", hsvArgb(it.toFloat())) }
+            .curatedForPicker()
+            .map { it.key.toInt() }
+
+        // A proper single-seam sweep around the wheel descends exactly once
+        // (at the seam). The old bucketed sort could scatter a family across
+        // both ends, producing extra descents.
+        val descents = curated.indices.count { i ->
+            curated[(i + 1) % curated.size] < curated[i]
+        }
+        assertThat(descents).isEqualTo(1)
+    }
+
+    @Test
+    fun `CSS3 survivors span the whole rainbow`() {
+        val keys = css3Palette().curatedForPicker().map { it.key }
+        fun has(vararg families: String) = keys.any { k -> families.any { k.contains(it) } }
+
+        // Which exact name represents a hue family depends on the vivid-first
+        // thinning, so assert each family survives, not a specific key.
+        assertThat(has("red", "crimson", "firebrick", "tomato", "maroon", "brown")).isTrue()
+        assertThat(has("orange", "gold", "goldenrod", "peru", "sienna", "salmon")).isTrue()
+        assertThat(has("green", "olive", "lime", "chartreuse", "forest", "sea")).isTrue()
+        assertThat(has("blue", "navy", "dodger", "steel", "royal", "sky", "aqua")).isTrue()
+        assertThat(has("violet", "purple", "magenta", "orchid", "fuchsia", "indigo", "plum")).isTrue()
+    }
+
+    private fun hsvArgb(hue: Float): Int {
+        val h = hue / 60f
+        val sector = h.toInt() % 6
+        val f = h - h.toInt()
+        val q = ((1 - f) * 255).toInt()
+        val t = (f * 255).toInt()
+        return when (sector) {
+            0 -> argb(255, t, 0)
+            1 -> argb(q, 255, 0)
+            2 -> argb(0, 255, t)
+            3 -> argb(0, q, 255)
+            4 -> argb(t, 0, 255)
+            else -> argb(255, 0, q)
+        }
+    }
+
+    private fun argb(r: Int, g: Int, b: Int): Int =
+        (0xFF shl 24) or (r shl 16) or (g shl 8) or b
+
+    /** The exact set ical4android/DAVx5 publishes: CSS3's 147 named colours. */
+    private fun css3Palette(): List<EventColorOption> = CSS3.map { (name, rgb) ->
+        EventColorOption(name, 0xFF000000.toInt() or rgb)
+    }
+
+    private val CSS3 = mapOf(
+        "aliceblue" to 0xF0F8FF, "antiquewhite" to 0xFAEBD7, "aqua" to 0x00FFFF,
+        "aquamarine" to 0x7FFFD4, "azure" to 0xF0FFFF, "beige" to 0xF5F5DC,
+        "bisque" to 0xFFE4C4, "black" to 0x000000, "blanchedalmond" to 0xFFEBCD,
+        "blue" to 0x0000FF, "blueviolet" to 0x8A2BE2, "brown" to 0xA52A2A,
+        "burlywood" to 0xDEB887, "cadetblue" to 0x5F9EA0, "chartreuse" to 0x7FFF00,
+        "chocolate" to 0xD2691E, "coral" to 0xFF7F50, "cornflowerblue" to 0x6495ED,
+        "cornsilk" to 0xFFF8DC, "crimson" to 0xDC143C, "cyan" to 0x00FFFF,
+        "darkblue" to 0x00008B, "darkcyan" to 0x008B8B, "darkgoldenrod" to 0xB8860B,
+        "darkgray" to 0xA9A9A9, "darkgreen" to 0x006400, "darkgrey" to 0xA9A9A9,
+        "darkkhaki" to 0xBDB76B, "darkmagenta" to 0x8B008B, "darkolivegreen" to 0x556B2F,
+        "darkorange" to 0xFF8C00, "darkorchid" to 0x9932CC, "darkred" to 0x8B0000,
+        "darksalmon" to 0xE9967A, "darkseagreen" to 0x8FBC8F, "darkslateblue" to 0x483D8B,
+        "darkslategray" to 0x2F4F4F, "darkslategrey" to 0x2F4F4F, "darkturquoise" to 0x00CED1,
+        "darkviolet" to 0x9400D3, "deeppink" to 0xFF1493, "deepskyblue" to 0x00BFFF,
+        "dimgray" to 0x696969, "dimgrey" to 0x696969, "dodgerblue" to 0x1E90FF,
+        "firebrick" to 0xB22222, "floralwhite" to 0xFFFAF0, "forestgreen" to 0x228B22,
+        "fuchsia" to 0xFF00FF, "gainsboro" to 0xDCDCDC, "ghostwhite" to 0xF8F8FF,
+        "gold" to 0xFFD700, "goldenrod" to 0xDAA520, "gray" to 0x808080,
+        "green" to 0x008000, "greenyellow" to 0xADFF2F, "grey" to 0x808080,
+        "honeydew" to 0xF0FFF0, "hotpink" to 0xFF69B4, "indianred" to 0xCD5C5C,
+        "indigo" to 0x4B0082, "ivory" to 0xFFFFF0, "khaki" to 0xF0E68C,
+        "lavender" to 0xE6E6FA, "lavenderblush" to 0xFFF0F5, "lawngreen" to 0x7CFC00,
+        "lemonchiffon" to 0xFFFACD, "lightblue" to 0xADD8E6, "lightcoral" to 0xF08080,
+        "lightcyan" to 0xE0FFFF, "lightgoldenrodyellow" to 0xFAFAD2, "lightgray" to 0xD3D3D3,
+        "lightgreen" to 0x90EE90, "lightgrey" to 0xD3D3D3, "lightpink" to 0xFFB6C1,
+        "lightsalmon" to 0xFFA07A, "lightseagreen" to 0x20B2AA, "lightskyblue" to 0x87CEFA,
+        "lightslategray" to 0x778899, "lightslategrey" to 0x778899, "lightsteelblue" to 0xB0C4DE,
+        "lightyellow" to 0xFFFFE0, "lime" to 0x00FF00, "limegreen" to 0x32CD32,
+        "linen" to 0xFAF0E6, "magenta" to 0xFF00FF, "maroon" to 0x800000,
+        "mediumaquamarine" to 0x66CDAA, "mediumblue" to 0x0000CD, "mediumorchid" to 0xBA55D3,
+        "mediumpurple" to 0x9370DB, "mediumseagreen" to 0x3CB371, "mediumslateblue" to 0x7B68EE,
+        "mediumspringgreen" to 0x00FA9A, "mediumturquoise" to 0x48D1CC,
+        "mediumvioletred" to 0xC71585, "midnightblue" to 0x191970, "mintcream" to 0xF5FFFA,
+        "mistyrose" to 0xFFE4E1, "moccasin" to 0xFFE4B5, "navajowhite" to 0xFFDEAD,
+        "navy" to 0x000080, "oldlace" to 0xFDF5E6, "olive" to 0x808000,
+        "olivedrab" to 0x6B8E23, "orange" to 0xFFA500, "orangered" to 0xFF4500,
+        "orchid" to 0xDA70D6, "palegoldenrod" to 0xEEE8AA, "palegreen" to 0x98FB98,
+        "paleturquoise" to 0xAFEEEE, "palevioletred" to 0xDB7093, "papayawhip" to 0xFFEFD5,
+        "peachpuff" to 0xFFDAB9, "peru" to 0xCD853F, "pink" to 0xFFC0CB,
+        "plum" to 0xDDA0DD, "powderblue" to 0xB0E0E6, "purple" to 0x800080,
+        "red" to 0xFF0000, "rosybrown" to 0xBC8F8F, "royalblue" to 0x4169E1,
+        "saddlebrown" to 0x8B4513, "salmon" to 0xFA8072, "sandybrown" to 0xF4A460,
+        "seagreen" to 0x2E8B57, "seashell" to 0xFFF5EE, "sienna" to 0xA0522D,
+        "silver" to 0xC0C0C0, "skyblue" to 0x87CEEB, "slateblue" to 0x6A5ACD,
+        "slategray" to 0x708090, "slategrey" to 0x708090, "snow" to 0xFFFAFA,
+        "springgreen" to 0x00FF7F, "steelblue" to 0x4682B4, "tan" to 0xD2B48C,
+        "teal" to 0x008080, "thistle" to 0xD8BFD8, "tomato" to 0xFF6347,
+        "turquoise" to 0x40E0D0, "violet" to 0xEE82EE, "wheat" to 0xF5DEB3,
+        "white" to 0xFFFFFF, "whitesmoke" to 0xF5F5F5, "yellow" to 0xFFFF00,
+        "yellowgreen" to 0x9ACD32,
+    )
+}