Add Compose version of Drag2D

Drag2D:
- Moved android.support.drag2d.lib to a separate module, so that it may
  "easily" be referenced in other projects as a Java only source set

Drag2DCompose:
- Drag2D engine added as a module where the source is the relative path
  to Drag2d's engine directory
- The engine is implemented as an AnimationSpec, that's the baseline
  definition to drive animations in Compose
- Material2DMotionPreview shows usage of this AnimationSpec with a
  single draggable element

Author: oscar-ad

demoProjects/Drag2D/app/build.gradle

@@ -29,7 +29,7 @@ android {
 }
 
 dependencies {
-
+    implementation project(':engine')
     implementation 'androidx.appcompat:appcompat:1.6.1'
     implementation 'com.google.android.material:material:1.8.0'
 }

demoProjects/Drag2D/app/src/main/java/android/support/drag2d/DragCardActivity.java

@@ -41,7 +41,6 @@
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.AppCompatButton;
 import androidx.core.content.res.ResourcesCompat;
-import androidx.appcompat.widget.AppCompatSeekBar;
 
 import com.google.android.material.slider.Slider;
 

demoProjects/Drag2D/app/src/main/java/android/support/drag2d/MainActivity.java

@@ -22,7 +22,6 @@
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
-import android.graphics.PorterDuff;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.os.SystemClock;

demoProjects/Drag2D/engine/.gitignore

@@ -0,0 +1 @@
+/build

demoProjects/Drag2D/engine/build.gradle

@@ -0,0 +1,8 @@
+plugins {
+    id 'java-library'
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}

demoProjects/Drag2D/app/src/main/java/android/support/drag2d/lib/MaterialEasing.java renamed to demoProjects/Drag2D/engine/src/main/java/android/support/drag2d/lib/MaterialEasing.java

@@ -98,6 +98,14 @@ public float getY(float t) {
         return mvY.getPos(t);
     }
 
+    public float getVX(float t) {
+        return mvX.getV(t);
+    }
+
+    public float getVY(float t) {
+        return mvY.getV(t);
+    }
+
     public boolean isStillMoving(float t) {
         return mvX.getDuration() > t || mvY.getDuration() > t;
     }

demoProjects/Drag2D/app/src/main/java/android/support/drag2d/lib/MaterialVelocity.java renamed to demoProjects/Drag2D/engine/src/main/java/android/support/drag2d/lib/MaterialVelocity.java

@@ -14,3 +14,4 @@ dependencyResolutionManagement {
 }
 rootProject.name = "Drag2D"
 include ':app'
+include ':engine'