Join selection transitions (#30)

* Add joining range-to-range animations

* Set cell ranges in CellMoveToCell

* Fix TickCallback

* Join move-cell-to-cell transitions

* Join move-cell-to-cell and range-to-range transitions

* Add docs

* Fix joining cell-move-to-cell transitions

* Small refactor

* Fix docs

* Generalize models

* Remove hasTransition()

* Refactor

* Fix docs

README.md

@@ -165,10 +165,7 @@ There's a description of methods of `SelectionManager` and what they are expecte
   arguments. Note that, rangeEnd is **inclusive**. measureManager should be used to determine bounds of a cell.
 - `updateConfiguration(measureManager)` - updates internal measurements and computation based on measureManager results
   of both previousState and currentState. Change of measureManager result means that cells might be moved or resized.
-- `hasTransition()` - returns whether there's a transition between previousState and currentState.
-- `createTransition(measureManager, options)` - creates a transitive state between previousState and currentState. It's
-  only called if hasTransition() returns true.
-- `options` is used to stylize the selection as selection state shouldn't contain any style-related information.
+- `createTransition(measureManager, options)` - creates a transitive state between previousState and currentState
 
 Selection renderer is responsible for drawing simple selection state or transitive state, that is created to save information about transition between two selection states. When selection is to be drawn, the canvas' matrix is translated in such way that coordinates will be relative to the grid's leftmost point on top.
 

library/src/main/java/com/github/pelmenstar1/rangecalendar/CellMeasureManager.kt

@@ -8,6 +8,11 @@ import android.graphics.PointF
  * **API surface of this class is not stable and new members might be added or removed.**
  */
 interface CellMeasureManager {
+    enum class CoordinateRelativity {
+        VIEW,
+        GRID
+    }
+
     /**
      * Width of cell (in pixels).
      */
@@ -24,15 +29,15 @@ interface CellMeasureManager {
     val roundRadius: Float
 
     /**
-     * Gets x-axis value of the coordinate that specifies left corner of the cell.
+     * Gets x-axis value of the coordinate that specifies left corner of the cell. The coordinate is relative to the grid.
      *
      * @param cellIndex index of the cell, should be in range 0..41
      * @throws IllegalArgumentException if [cellIndex] is out of the range 0..41
      */
     fun getCellLeft(cellIndex: Int): Float
 
     /**
-     * Gets y-axis value of the coordinate that specifies top corner of the cell.
+     * Gets y-axis value of the coordinate that specifies top corner of the cell. The coordinate is relative to the grid.
      *
      * @param cellIndex index of the cell, should be in range 0..41
      * @throws IllegalArgumentException if [cellIndex] is out of the range 0..41
@@ -50,6 +55,7 @@ interface CellMeasureManager {
 
     /**
      * Gets points on the calendar view and cell's index nearest to the point by cell [distance]. The point is set to [outPoint].
+     * The coordinates of the point are relative to the grid.
      *
      * @param distance cell distance, expected to be non-negative
      * @param outPoint the resulting point is set to this point
@@ -59,9 +65,17 @@ interface CellMeasureManager {
     fun getCellAndPointByDistance(distance: Float, outPoint: PointF): Int
 
     /**
-     * Gets index of a cell nearest to a point with specified coordinates. If there's no such cell, returns `-1`
+     * Gets 'cell distance' using a point ([x], [y]) relative to the grid.
+     * The [x] can be arbitrary but the [y] **must** be aligned to the row's top point.
+     *
+     * @see getCellDistance
+     */
+    fun getCellDistanceByPoint(x: Float, y: Float): Float
+
+    /**
+     * Gets index of a cell nearest to a point with specified coordinates. If there's no such cell, returns `-1`.
      */
-    fun getCellAt(x: Float, y: Float): Int
+    fun getCellAt(x: Float, y: Float, relativity: CoordinateRelativity): Int
 
     /**
      * Returns the absolute value of a dimension specified by the [anchor].