feat: Add flat press animation

neumorphism/src/main/java/soup/neumorphism/NeumorphButton.kt

@@ -156,6 +156,7 @@ open class NeumorphButton @JvmOverloads constructor(
 
     override fun setTranslationZ(translationZ: Float) {
         super.setTranslationZ(translationZ)
+        val elevation = elevation
         if (isInitialized) {
             shapeDrawable.setTranslationZ(translationZ)
         }

neumorphism/src/main/java/soup/neumorphism/NeumorphShapeDrawable.kt

@@ -11,6 +11,7 @@ import androidx.annotation.StyleRes
 import soup.neumorphism.internal.drawable.NeumorphShadow
 import soup.neumorphism.internal.shape.Shape
 import soup.neumorphism.internal.shape.ShapeFactory
+import kotlin.math.abs
 
 
 open class NeumorphShapeDrawable : Drawable {
@@ -309,13 +310,9 @@ open class NeumorphShapeDrawable : Drawable {
             drawBackgroundBitmap(canvas)
         }
 
-        val elevation = drawableState.shadowElevation
-        val z = drawableState.shadowElevation + drawableState.translationZ
-
-        val pressPercentage = z / elevation
-        shadowPaint.alpha = (255 * pressPercentage).toInt()
-
-        shadow?.draw(canvas, shadowPaint)
+        val minTranslationZ = -18.74f
+        val pressPercentage = abs(drawableState.translationZ) / abs(minTranslationZ)
+        shadow?.draw(canvas, pressPercentage)
 
         if (hasStroke()) {
             drawStrokeShape(canvas)

neumorphism/src/main/java/soup/neumorphism/internal/shape/NeumorphBasinShape.kt

@@ -26,8 +26,8 @@ class NeumorphBasinShape(
         bounds
     )
 
-    override fun draw(canvas: Canvas, paint: Paint?) {
-        outerShadow.draw(canvas, paint)
-        innerShadow.draw(canvas, null)
+    override fun draw(canvas: Canvas, pressPercentage: Float) {
+        outerShadow.draw(canvas, pressPercentage)
+        innerShadow.draw(canvas, pressPercentage)
     }
 }

neumorphism/src/main/java/soup/neumorphism/internal/shape/NeumorphShape.kt → neumorphism/src/main/java/soup/neumorphism/internal/shape/NeumorphFlatShape.kt

@@ -8,27 +8,29 @@ import soup.neumorphism.internal.drawable.NeumorphInnerShadow
 import soup.neumorphism.internal.drawable.NeumorphOuterShadow
 import soup.neumorphism.internal.drawable.NeumorphShadow
 
-class NeumorphShape(
+class NeumorphFlatShape(
     private val appearance: NeumorphShadow.Style,
     private val theme: NeumorphShadow.Theme,
-    private val bounds: Rect,
-    private val isOuterShadow: Boolean
+    private val bounds: Rect
 ) : Shape {
 
     private val shadow: NeumorphShadow
-        get() = if (isOuterShadow) NeumorphOuterShadow(appearance, theme, bounds)
-        else NeumorphInnerShadow(appearance, theme, bounds)
+        get() = NeumorphOuterShadow(appearance, theme, bounds)
 
     private val shadowBitmap: Bitmap by lazy {
         shadow.drawToBitmap()
     }
 
-    override fun draw(canvas: Canvas, paint: Paint?) {
+    private val shadowPaint = Paint()
+
+    override fun draw(canvas: Canvas, pressPercentage: Float) {
+        val pressOffset = 1 - pressPercentage
+        shadowPaint.alpha = (255 * pressOffset).toInt()
         canvas.drawBitmap(
             shadowBitmap,
             0f,
             0f,
-            paint
+            shadowPaint
         )
     }
 }

neumorphism/src/main/java/soup/neumorphism/internal/shape/NeumorphPressedShape.kt

@@ -0,0 +1,27 @@
+package soup.neumorphism.internal.shape
+
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import android.graphics.Paint
+import android.graphics.Rect
+import soup.neumorphism.internal.drawable.NeumorphInnerShadow
+import soup.neumorphism.internal.drawable.NeumorphOuterShadow
+import soup.neumorphism.internal.drawable.NeumorphShadow
+
+class NeumorphPressedShape(
+    private val appearance: NeumorphShadow.Style,
+    private val theme: NeumorphShadow.Theme,
+    private val bounds: Rect
+) : Shape {
+
+    private val shadow: NeumorphShadow
+        get() = NeumorphInnerShadow(appearance, theme, bounds)
+
+    private val shadowBitmap: Bitmap by lazy {
+        shadow.drawToBitmap()
+    }
+
+    override fun draw(canvas: Canvas, pressPercentage: Float) {
+        canvas.drawBitmap(shadowBitmap, 0f, 0f, null)
+    }
+}

neumorphism/src/main/java/soup/neumorphism/internal/shape/Shape.kt

@@ -6,5 +6,5 @@ import android.graphics.Path
 import android.graphics.Rect
 
 interface Shape {
-    fun draw(canvas: Canvas, paint: Paint?)
+    fun draw(canvas: Canvas, pressPercentage: Float)
 }

neumorphism/src/main/java/soup/neumorphism/internal/shape/ShapeFactory.kt

@@ -27,18 +27,16 @@ object ShapeFactory {
     ): Shape {
 
         val shape = when (shapeType) {
-            ShapeType.FLAT -> NeumorphShape(
+            ShapeType.FLAT -> NeumorphFlatShape(
                 appearance,
                 theme,
-                bounds,
-                isOuterShadow = true
+                bounds
             )
 
-            ShapeType.PRESSED -> NeumorphShape(
+            ShapeType.PRESSED -> NeumorphPressedShape(
                 appearance,
                 theme,
-                bounds,
-                isOuterShadow = false
+                bounds
             )
 
             ShapeType.BASIN -> NeumorphBasinShape(