Create at the tapped hour after a zoom (#148)

The week/day tap detector captured the hour height when pointerInput was
installed, and pointerInput only restarts when its keys change — so after a
pinch or a Settings hour-height change, taps were mapped against the old
spacing and created events at the wrong hour. Read the height (and the
callback) through rememberUpdatedState instead, and move the offset-to-minute
arithmetic into a tested tappedMinuteOfDay.

CHANGELOG.md

@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Tapping an empty slot in week or day view creates the event at the hour you
+  tapped, after the timeline has been zoomed. Pinching the day taller or shorter
+  — or changing **Hour height** in Settings — left the tap still being measured
+  against the old spacing, so the new event landed at some other hour entirely
+  ([#148]).
+
 ## [2.18.0] — 2026-07-31
 
 ### Added
@@ -1323,3 +1330,4 @@ automatically, with zero telemetry and no internet permission.
 [#57]: https://codeberg.org/jlmakiola/calendula/issues/57
 [#56]: https://codeberg.org/jlmakiola/calendula/issues/56
 [#114]: https://codeberg.org/jlmakiola/calendula/issues/114
+[#148]: https://codeberg.org/jlmakiola/calendula/issues/148

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/TimelineScale.kt

@@ -76,6 +76,18 @@ fun TimelineScale.hourHeight(viewportHeight: Dp): Dp = when (this) {
         .coerceAtLeast(fillHourHeight(viewportHeight))
 }
 
+/**
+ * The minute of the day a tap [offsetY] px down a timeline column means, snapped
+ * to the hour it landed in.
+ *
+ * [hourPx] must be the hour height the column is drawing at *now* — a tap
+ * detector that captured it when it was installed maps taps to a pre-pinch grid
+ * (#148). A zero or negative height (a viewport measured at nothing) has no grid
+ * to read, so it answers midnight rather than dividing by it.
+ */
+fun tappedMinuteOfDay(offsetY: Float, hourPx: Float): Int =
+    if (hourPx <= 0f) 0 else (offsetY / hourPx).toInt().coerceIn(0, 23) * 60
+
 /**
  * Shortest an event block may render, as a fraction of an hour. Blocks keep a
  * floor so a 15-minute event stays tappable, but the floor scales with the hour

app/src/main/java/de/jeanlucmakiola/calendula/ui/day/DayScreen.kt

@@ -45,6 +45,7 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
@@ -96,6 +97,7 @@ import de.jeanlucmakiola.calendula.ui.common.rememberTimelinePinchZoom
 import de.jeanlucmakiola.calendula.ui.common.formatHourLabel
 import de.jeanlucmakiola.calendula.ui.common.formatMinuteOfDay
 import de.jeanlucmakiola.calendula.ui.common.hourSeparatorLines
+import de.jeanlucmakiola.calendula.ui.common.tappedMinuteOfDay
 import de.jeanlucmakiola.calendula.ui.week.TimedBlock
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
@@ -577,6 +579,12 @@ private fun DayColumnCard(
     val hourPx = with(LocalDensity.current) { hourHeight.toPx() }
     val showHourLines = LocalShowHourLines.current
     val hourLineColor = MaterialTheme.colorScheme.outlineVariant
+    // The tap detector outlives the composition that installed it — a pinch or a
+    // Settings change moves the hour height without restarting it — so it reads
+    // the height and the callback through state handles instead of capturing
+    // them, or taps land on the scale the column had before the zoom (#148).
+    val currentHourPx = rememberUpdatedState(hourPx)
+    val currentOnCreateAt = rememberUpdatedState(onCreateAt)
     Card(
         // Plain rectangular column — the soft corners come from the outer
         // rounded scroll viewport, so inner rounding would look odd at the edges.
@@ -597,8 +605,10 @@ private fun DayColumnCard(
                 // only fires on the column background. Snaps to the tapped hour.
                 .pointerInput(date) {
                     detectTapGestures { offset ->
-                        val hour = (offset.y / hourPx).toInt().coerceIn(0, 23)
-                        onCreateAt(date, hour * 60)
+                        currentOnCreateAt.value(
+                            date,
+                            tappedMinuteOfDay(offset.y, currentHourPx.value),
+                        )
                     }
                 },
         ) {

app/src/main/java/de/jeanlucmakiola/calendula/ui/week/WeekScreen.kt

@@ -51,6 +51,7 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
@@ -107,6 +108,7 @@ import de.jeanlucmakiola.calendula.ui.common.rememberTimelinePinchZoom
 import de.jeanlucmakiola.calendula.ui.common.formatHourLabel
 import de.jeanlucmakiola.calendula.ui.common.formatMinuteOfDay
 import de.jeanlucmakiola.calendula.ui.common.hourSeparatorLines
+import de.jeanlucmakiola.calendula.ui.common.tappedMinuteOfDay
 import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
 import de.jeanlucmakiola.calendula.ui.common.next
 import de.jeanlucmakiola.floret.time.isoWeekNumber
@@ -722,6 +724,12 @@ private fun DayColumnCard(
     val hourPx = with(LocalDensity.current) { hourHeight.toPx() }
     val showHourLines = LocalShowHourLines.current
     val hourLineColor = MaterialTheme.colorScheme.outlineVariant
+    // The tap detector outlives the composition that installed it — a pinch or a
+    // Settings change moves the hour height without restarting it — so it reads
+    // the height and the callback through state handles instead of capturing
+    // them, or taps land on the scale the column had before the zoom (#148).
+    val currentHourPx = rememberUpdatedState(hourPx)
+    val currentOnCreateAt = rememberUpdatedState(onCreateAt)
     Card(
         // Plain rectangular columns — the soft corners come from the outer
         // rounded scroll viewport, so inner rounding would look odd at the edges.
@@ -741,8 +749,10 @@ private fun DayColumnCard(
                 // blocks are consumed by their own handler first. Snaps to hour.
                 .pointerInput(date) {
                     detectTapGestures { offset ->
-                        val hour = (offset.y / hourPx).toInt().coerceIn(0, 23)
-                        onCreateAt(date, hour * 60)
+                        currentOnCreateAt.value(
+                            date,
+                            tappedMinuteOfDay(offset.y, currentHourPx.value),
+                        )
                     }
                 },
         ) {

app/src/test/java/de/jeanlucmakiola/calendula/ui/common/TimelineScaleTest.kt

@@ -126,4 +126,24 @@ class TimelineScaleTest {
             assertThat(parseTimelineScale(stored)).isEqualTo(TimelineScale.Regular)
         }
     }
+
+    @Test
+    fun `a tap creates at the hour it landed in, at whatever scale`() {
+        // Same point on the same column reads as a different hour once the
+        // timeline has been pinched — which is the whole of #148: the tap has to
+        // be measured against the height the column is drawing at now.
+        assertThat(tappedMinuteOfDay(offsetY = 500f, hourPx = 100f)).isEqualTo(5 * 60)
+        assertThat(tappedMinuteOfDay(offsetY = 500f, hourPx = 50f)).isEqualTo(10 * 60)
+        // Within an hour it snaps back to that hour's start.
+        assertThat(tappedMinuteOfDay(offsetY = 599f, hourPx = 100f)).isEqualTo(5 * 60)
+    }
+
+    @Test
+    fun `a tap outside the day stays inside it`() {
+        assertThat(tappedMinuteOfDay(offsetY = -20f, hourPx = 56f)).isEqualTo(0)
+        assertThat(tappedMinuteOfDay(offsetY = 99_999f, hourPx = 56f)).isEqualTo(23 * 60)
+        // A viewport measured at nothing has no grid to read — midnight, not a
+        // division by zero.
+        assertThat(tappedMinuteOfDay(offsetY = 500f, hourPx = 0f)).isEqualTo(0)
+    }
 }