Add support for additional drawers

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

@@ -5,12 +5,13 @@ import android.graphics.Paint
 import android.graphics.RectF
 import android.text.StaticLayout
 import androidx.collection.ArrayMap
+import com.alamkanak.weekview.WeekView.DrawBase
 import java.util.Calendar
 import kotlin.math.max
 import kotlin.math.min
 
 internal class CalendarRenderer(
-    viewState: ViewState,
+    private val viewState: ViewState,
     eventChipsCacheProvider: EventChipsCacheProvider
 ) : Renderer {
 
@@ -29,9 +30,21 @@ internal class CalendarRenderer(
     override fun render(canvas: Canvas) {
         eventsUpdater.update()
 
+        drawAdditional(canvas, DrawBase.CANVAS)
         for (drawer in drawers) {
-            drawer.draw(canvas)
+            drawer.draw(canvas, viewState)
+            drawAdditional(canvas, drawer.base)
         }
+        drawAdditional(canvas, DrawBase.TOP)
+    }
+
+    private fun drawAdditional(canvas: Canvas, base: DrawBase) {
+        val drawers = viewState.additionalDrawers[base]
+        if (drawers.isNullOrEmpty()) return
+
+        val saveCount = canvas.save()
+        drawers.forEach { it.draw(canvas, viewState) }
+        canvas.restoreToCount(saveCount)
     }
 }
 
@@ -107,9 +120,10 @@ private class SingleEventsUpdater(
 
 private class DayBackgroundDrawer(
     private val viewState: ViewState
-) : Drawer {
+) : WeekView.Drawer {
+    override val base = DrawBase.BACKGROUND
 
-    override fun draw(canvas: Canvas) {
+    override fun draw(canvas: Canvas, bounds: WeekView.DrawBounds) {
         canvas.drawInBounds(viewState.calendarGridBounds) {
             viewState.dateRangeWithStartPixels.forEach { (date, startPixel) ->
                 drawDayBackground(date, startPixel, canvas)
@@ -167,9 +181,10 @@ private class DayBackgroundDrawer(
 
 private class BackgroundGridDrawer(
     private val viewState: ViewState
-) : Drawer {
+) : WeekView.Drawer {
+    override val base = DrawBase.GRID
 
-    override fun draw(canvas: Canvas) {
+    override fun draw(canvas: Canvas, bounds: WeekView.DrawBounds) {
         canvas.drawInBounds(viewState.calendarGridBounds) {
             if (viewState.showHourSeparators) {
                 drawHourLines()
@@ -201,7 +216,7 @@ private class BackgroundGridDrawer(
     private fun Canvas.drawHourLine(hour: Int) {
         val heightOfHour = (viewState.hourHeight * (hour - viewState.minHour))
         val verticalOffset = viewState.headerHeight + viewState.currentOrigin.y + heightOfHour
-        val horizontalOffset = if (viewState.isLtr) viewState.timeColumnWidth else 0f
+        val horizontalOffset = viewState.calendarGridBounds.left
 
         drawHorizontalLine(
             verticalOffset = verticalOffset,
@@ -216,11 +231,12 @@ private class SingleEventsDrawer(
     private val viewState: ViewState,
     private val chipsCacheProvider: EventChipsCacheProvider,
     private val eventLabels: ArrayMap<String, StaticLayout>
-) : Drawer {
+) : WeekView.Drawer {
+    override val base = DrawBase.EVENTS
 
     private val eventChipDrawer = EventChipDrawer(viewState)
 
-    override fun draw(canvas: Canvas) {
+    override fun draw(canvas: Canvas, bounds: WeekView.DrawBounds) {
         canvas.drawInBounds(viewState.calendarGridBounds) {
             for (date in viewState.dateRange) {
                 drawEventsForDate(date)
@@ -241,9 +257,10 @@ private class SingleEventsDrawer(
 
 private class NowLineDrawer(
     private val viewState: ViewState
-) : Drawer {
+) : WeekView.Drawer {
+    override val base = DrawBase.NOWLINE
 
-    override fun draw(canvas: Canvas) {
+    override fun draw(canvas: Canvas, bounds: WeekView.DrawBounds) {
         if (viewState.showNowLine.not()) {
             return
         }

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

@@ -136,7 +136,7 @@ private class HeaderUpdater(
 private class DateLabelsDrawer(
     private val viewState: ViewState,
     private val dateLabelLayouts: SparseArray<StaticLayout>
-) : Drawer {
+) : DrawerInternal {
 
     override fun draw(canvas: Canvas) {
         canvas.drawInBounds(viewState.headerBounds) {
@@ -240,7 +240,7 @@ private class AllDayEventsUpdater(
 internal class AllDayEventsDrawer(
     private val viewState: ViewState,
     private val allDayEventLayouts: ArrayMap<EventChip, StaticLayout>
-) : Drawer {
+) : DrawerInternal {
 
     private val eventChipDrawer = EventChipDrawer(viewState)
 
@@ -319,7 +319,7 @@ internal class AllDayEventsDrawer(
 private class HeaderDrawer(
     context: Context,
     private val viewState: ViewState
-) : Drawer {
+) : DrawerInternal {
 
     private val upArrow: Drawable by lazy {
         checkNotNull(ContextCompat.getDrawable(context, R.drawable.ic_arrow_up))

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

@@ -6,7 +6,7 @@ internal interface Updater {
     fun update()
 }
 
-internal interface Drawer {
+internal interface DrawerInternal {
     fun draw(canvas: Canvas)
 }
 

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

@@ -8,21 +8,21 @@ import android.graphics.Typeface
 import android.os.Build
 import android.text.TextPaint
 import android.view.View
-import java.util.Calendar
+import java.util.*
 import kotlin.math.ceil
 import kotlin.math.max
 import kotlin.math.min
 
 typealias DateFormatter = (Calendar) -> String
 typealias TimeFormatter = (Int) -> String
 
-internal class ViewState {
+internal class ViewState : WeekView.DrawBounds {
 
     // View
-    var viewWidth: Int = 0
-    var viewHeight: Int = 0
+    override var viewWidth: Int = 0
+    override var viewHeight: Int = 0
 
-    var isLtr: Boolean = true
+    override var isLtr: Boolean = true
 
     // Calendar state
     var firstVisibleDate: Calendar = today()
@@ -64,7 +64,7 @@ internal class ViewState {
     var eventMarginVertical: Int = 0
     var singleDayHorizontalPadding: Int = 0
 
-    var hourHeight: Float = 0f
+    override var hourHeight: Float = 0f
     var minHourHeight: Float = 0f
     var maxHourHeight: Float = 0f
     var effectiveMinHourHeight: Float = 0f
@@ -95,6 +95,8 @@ internal class ViewState {
 
     var typeface: Typeface = Typeface.DEFAULT
 
+    var additionalDrawers: Map<WeekView.DrawBase, List<WeekView.Drawer>> = emptyMap()
+
     var timeColumnWidth: Float = 0f
     var timeColumnTextHeight: Float = 0f
 
@@ -134,13 +136,13 @@ internal class ViewState {
 
     // In LTR: Dates in the past have origin.x > 0, dates in the future have origin.x < 0
     // In RTL: Dates in the past have origin.x < 0, dates in the future have origin.x > 0
-    var currentOrigin = PointF(0f, 0f)
+    override var currentOrigin = PointF(0f, 0f)
 
     val headerBackgroundPaint = Paint()
 
     val headerBackgroundWithShadowPaint = Paint()
 
-    val dayWidth: Float
+    override val dayWidth: Float
         get() = (viewWidth - timeColumnWidth) / numberOfVisibleDays
 
     val drawableDayWidth: Float
@@ -237,7 +239,7 @@ internal class ViewState {
 
     private val _calendarGridBounds: RectF = RectF()
 
-    val calendarGridBounds: RectF
+    override val calendarGridBounds: RectF
         get() = _calendarGridBounds.apply {
             left = if (isLtr) timeColumnWidth else 0f
             top = headerHeight

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

@@ -4,6 +4,7 @@ import android.annotation.SuppressLint
 import android.content.Context
 import android.content.res.Configuration
 import android.graphics.Canvas
+import android.graphics.PointF
 import android.graphics.RectF
 import android.graphics.Typeface
 import android.os.Parcelable
@@ -1354,6 +1355,53 @@ class WeekView @JvmOverloads constructor(
             invalidate()
         }
 
+    /*
+     ***********************************************************************************************
+     *
+     *   Custom drawers
+     *
+     ***********************************************************************************************
+     */
+
+    /**
+     * Bounds available to [Drawer] to draw on the [Canvas] during rendering.
+     */
+    @PublicApi
+    interface DrawBounds {
+        val calendarGridBounds: RectF
+        val currentOrigin: PointF
+        val viewWidth: Int
+        val viewHeight: Int
+        val dayWidth: Float
+        val hourHeight: Float
+        val isLtr: Boolean
+    }
+
+    @PublicApi
+    enum class DrawBase {
+        CANVAS, BACKGROUND, GRID, EVENTS, NOWLINE, TOP;
+    }
+
+    @PublicApi
+    interface Drawer {
+        fun draw(canvas: Canvas, bounds: DrawBounds)
+        val base: DrawBase
+    }
+
+    /**
+     * Additional drawers that will be draw on the view during rendering.
+     *
+     * Each drawer will draw on top of the layer specified by [Drawer.base]. Drawers with the same
+     * base will draw in the order specified in the list.
+     */
+    @PublicApi
+    var additionalDrawers: List<Drawer>
+        get() = viewState.additionalDrawers.values.flatten()
+        set(value) {
+            viewState.additionalDrawers = value.groupBy { it.base }
+            invalidate()
+        }
+
     /*
      ***********************************************************************************************
      *

sample/src/main/AndroidManifest.xml

@@ -78,6 +78,14 @@
                 android:name="android.support.PARENT_ACTIVITY"
                 android:value=".ui.main.MainActivity" />
         </activity>
+        <activity
+            android:name=".ui.CustomDrawersActivity"
+            android:label="@string/week_view"
+            android:parentActivityName=".ui.main.MainActivity">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value=".ui.main.MainActivity" />
+        </activity>
     </application>
 
 </manifest>