Combine date label handling for single-line and multi-line (alamkanak#151)

* Combine single-line and multi-line day label drawing into one

* Simplify header row updating

Author: thellmund

core/src/main/java/com/alamkanak/weekview/DayLabelDrawer.kt

@@ -0,0 +1,38 @@
+package com.alamkanak.weekview
+
+import android.graphics.Canvas
+import java.util.Calendar
+
+internal class DayLabelsDrawer<T>(
+    private val config: WeekViewConfigWrapper,
+    private val cache: WeekViewCache<T>
+) : Drawer {
+
+    override fun draw(
+        drawingContext: DrawingContext,
+        canvas: Canvas
+    ) {
+        val left = config.timeColumnWidth
+        val top = 0f
+        val right = canvas.width.toFloat()
+        val bottom = config.getTotalHeaderHeight()
+
+        canvas.drawInRect(left, top, right, bottom) {
+            drawingContext.dateRangeWithStartPixels.forEach { (date, startPixel) ->
+                drawLabel(date, startPixel, this)
+            }
+        }
+    }
+
+    private fun drawLabel(day: Calendar, startPixel: Float, canvas: Canvas) {
+        val key = day.toEpochDays()
+        val textLayout = cache.dateLabelLayouts[key]
+
+        canvas.withTranslation(
+            x = startPixel + config.widthPerDay / 2,
+            y = config.headerRowPadding.toFloat()
+        ) {
+            textLayout.draw(this)
+        }
+    }
+}

core/src/main/java/com/alamkanak/weekview/DayLabelsDrawer.kt

@@ -0,0 +1,76 @@
+package com.alamkanak.weekview
+
+import android.text.StaticLayout
+import android.util.SparseArray
+import java.util.Calendar
+
+internal class HeaderRowUpdater<T>(
+    private val config: WeekViewConfigWrapper,
+    private val cache: WeekViewCache<T>,
+    private val eventsCacheWrapper: EventsCacheWrapper<T>
+) : Updater {
+
+    private var previousHorizontalOrigin: Float? = null
+    private val previousAllDayEventIds = mutableSetOf<Long>()
+
+    private val eventsCache: EventsCache<T>
+        get() = eventsCacheWrapper.get()
+
+    override fun isRequired(drawingContext: DrawingContext): Boolean {
+        val didScrollHorizontally = previousHorizontalOrigin != config.currentOrigin.x
+        val currentTimeColumnWidth = config.timeTextWidth + config.timeColumnPadding * 2
+        val didTimeColumnChange = currentTimeColumnWidth != config.timeColumnWidth
+        val allDayEvents = eventsCache[drawingContext.dateRange]
+            .filter { it.isAllDay }
+            .map { it.id }
+            .toSet()
+        val didEventsChange = allDayEvents.hashCode() != previousAllDayEventIds.hashCode()
+        return (didScrollHorizontally || didTimeColumnChange || didEventsChange).also {
+            previousAllDayEventIds.clear()
+            previousAllDayEventIds += allDayEvents
+        }
+    }
+
+    override fun update(drawingContext: DrawingContext) {
+        val dateLabels = updateDateLabels(drawingContext)
+        updateHeaderHeight(drawingContext, dateLabels)
+    }
+
+    private fun updateDateLabels(drawingContext: DrawingContext): List<StaticLayout> {
+        val textLayouts = drawingContext.dateRange.map { date ->
+            date.toEpochDays() to calculateStaticLayoutForDate(date)
+        }.toMap()
+
+        cache.dateLabelLayouts.clear()
+        cache.dateLabelLayouts += textLayouts
+
+        return textLayouts.values.toList()
+    }
+
+    private fun updateHeaderHeight(
+        drawingContext: DrawingContext,
+        dateLabels: List<StaticLayout>
+    ) {
+        val maximumLayoutHeight = dateLabels.map { it.height.toFloat() }.max() ?: 0f
+        config.headerTextHeight = maximumLayoutHeight
+        drawingContext.refreshHeaderHeight()
+    }
+
+    private fun DrawingContext.refreshHeaderHeight() {
+        val visibleEvents = eventsCache[dateRange].filter { it.isAllDay }
+        config.hasEventInHeader = visibleEvents.isNotEmpty()
+        config.refreshHeaderHeight()
+    }
+
+    private fun calculateStaticLayoutForDate(date: Calendar): StaticLayout {
+        val dayLabel = config.dateFormatter(date)
+        return dayLabel.toTextLayout(
+            textPaint = if (date.isToday) config.todayHeaderTextPaint else config.headerTextPaint,
+            width = config.totalDayWidth.toInt()
+        )
+    }
+
+    private operator fun <E> SparseArray<E>.plusAssign(elements: Map<Int, E>) {
+        elements.entries.forEach { put(it.key, it.value) }
+    }
+}

core/src/main/java/com/alamkanak/weekview/HeaderRowHeightUpdater.kt

@@ -1,7 +1,10 @@
 package com.alamkanak.weekview
 
+import android.os.Build.VERSION.SDK_INT
+import android.text.Layout
 import android.text.SpannableStringBuilder
 import android.text.StaticLayout
+import android.text.TextPaint
 import android.text.style.StyleSpan
 
 internal val StaticLayout.lineHeight: Int
@@ -10,3 +13,25 @@ internal val StaticLayout.lineHeight: Int
 internal fun SpannableStringBuilder.setSpan(
     styleSpan: StyleSpan
 ) = setSpan(styleSpan, 0, length, 0)
+
+internal fun CharSequence.toTextLayout(
+    textPaint: TextPaint,
+    width: Int,
+    alignment: Layout.Alignment = Layout.Alignment.ALIGN_NORMAL,
+    spacingMultiplier: Float = 1f,
+    spacingExtra: Float = 0f,
+    includePad: Boolean = false
+) = if (SDK_INT >= 23) {
+    StaticLayout.Builder
+        .obtain(this, 0, length, textPaint, width)
+        .setAlignment(alignment)
+        .setLineSpacing(spacingExtra, spacingMultiplier)
+        .setIncludePad(includePad)
+        .build()
+} else {
+    @Suppress("DEPRECATION")
+    StaticLayout(this, textPaint, width, alignment, spacingMultiplier, spacingExtra, includePad)
+}
+
+internal val StaticLayout.maxLineLength: Float
+    get() = (0 until lineCount).map { getLineWidth(it) }.max() ?: 0f