Add support to fitBottomStart scaleType

Summary: Introducing fitBottomStart scaleType which scales the child to fit inside the parent, aspect ratio is preserved and child is aligned to bottom-left.

Reviewed By: kirwan

Differential Revision: D5543561

fbshipit-source-id: 21cc7879e45f69ac309e616cf5b1d55070afb109

Author: Victor Laguna

drawee/src/main/java/com/facebook/drawee/drawable/ScalingUtils.java

@@ -86,8 +86,16 @@ public interface ScaleType {
      */
     static final ScaleType FOCUS_CROP = ScaleTypeFocusCrop.INSTANCE;
 
+    /**
+     * Scales the child so that it fits entirely inside the parent. At least one dimension (width or
+     * height) will fit exactly. Aspect ratio is preserved. Child is aligned to the bottom-left
+     * corner of the parent.
+     */
+    static final ScaleType FIT_BOTTOM_START = ScaleTypeFitBottomStart.INSTANCE;
+
     /**
      * Gets transformation matrix based on the scale type.
+     *
      * @param outTransform out matrix to store result
      * @param parentBounds parent bounds
      * @param childWidth child width
@@ -212,6 +220,33 @@ public String toString() {
     }
   }
 
+  private static class ScaleTypeFitBottomStart extends AbstractScaleType {
+
+    public static final ScaleType INSTANCE = new ScaleTypeFitBottomStart();
+
+    @Override
+    public void getTransformImpl(
+        Matrix outTransform,
+        Rect parentRect,
+        int childWidth,
+        int childHeight,
+        float focusX,
+        float focusY,
+        float scaleX,
+        float scaleY) {
+      float scale = Math.min(scaleX, scaleY);
+      float dx = parentRect.left;
+      float dy = parentRect.top + (parentRect.height() - childHeight * scale);
+      outTransform.setScale(scale, scale);
+      outTransform.postTranslate((int) (dx + 0.5f), (int) (dy + 0.5f));
+    }
+
+    @Override
+    public String toString() {
+      return "fit_bottom_start";
+    }
+  }
+
   private static class ScaleTypeFitCenter extends AbstractScaleType {
 
     public static final ScaleType INSTANCE = new ScaleTypeFitCenter();

drawee/src/main/java/com/facebook/drawee/generic/GenericDraweeHierarchyInflater.java

@@ -255,6 +255,8 @@ private static ScaleType getScaleTypeFromXml(
         return ScaleType.CENTER_CROP;
       case 7: // focusCrop
         return ScaleType.FOCUS_CROP;
+      case 8: // fitBottomStart
+        return ScaleType.FIT_BOTTOM_START;
       default:
         // this method is supposed to be called only when XML attribute is specified.
         throw new RuntimeException("XML attribute not specified!");

drawee/src/main/res/values/attrs.xml

@@ -30,6 +30,7 @@
       <enum name="centerInside" value="5" />
       <enum name="centerCrop" value="6" />
       <enum name="focusCrop" value="7" />
+      <enum name="fitBottomStart" value="8" />
     </attr>
 
     <!-- A drawable to be be used as a retry image. -->
@@ -45,6 +46,7 @@
       <enum name="centerInside" value="5" />
       <enum name="centerCrop" value="6" />
       <enum name="focusCrop" value="7" />
+      <enum name="fitBottomStart" value="8" />
     </attr>
 
     <!-- A drawable to be be used as a failure image. -->
@@ -60,6 +62,7 @@
       <enum name="centerInside" value="5" />
       <enum name="centerCrop" value="6" />
       <enum name="focusCrop" value="7" />
+      <enum name="fitBottomStart" value="8" />
     </attr>
 
     <!-- A drawable to be be used as a progress bar. -->
@@ -75,6 +78,7 @@
       <enum name="centerInside" value="5" />
       <enum name="centerCrop" value="6" />
       <enum name="focusCrop" value="7" />
+      <enum name="fitBottomStart" value="8" />
     </attr>
     <!-- Progress bar Auto Rotate interval in milliseconds -->
     <attr name="progressBarAutoRotateInterval" format="integer"/>
@@ -90,6 +94,7 @@
       <enum name="centerInside" value="5" />
       <enum name="centerCrop" value="6" />
       <enum name="focusCrop" value="7" />
+      <enum name="fitBottomStart" value="8" />
     </attr>
 
     <!-- A drawable or color to be used as a background. -->

drawee/src/test/java/com/facebook/drawee/drawable/ScalingUtilsTest.java

@@ -175,6 +175,19 @@ public void testFocusCrop_FocusBottomRight() {
     test(0.80f, 0.80f,   10,   -4, 500, 400, 1.00f, 1.00f, ScaleType.FOCUS_CROP);
   }
 
+  @Test
+  public void testFitBottomStart() {
+    test(1.60f, 1.60f, 10, 75, 250, 150, ScaleType.FIT_BOTTOM_START);
+    test(0.50f, 0.50f, 10, 215, 800, 200, ScaleType.FIT_BOTTOM_START);
+    test(0.50f, 0.50f, 10, 115, 800, 400, ScaleType.FIT_BOTTOM_START);
+    test(2.00f, 2.00f, 10, 15, 200, 150, ScaleType.FIT_BOTTOM_START);
+    test(1.00f, 1.00f, 10, 15, 400, 300, ScaleType.FIT_BOTTOM_START);
+    test(0.50f, 0.50f, 10, 15, 800, 600, ScaleType.FIT_BOTTOM_START);
+    test(1.50f, 1.50f, 10, 15, 200, 200, ScaleType.FIT_BOTTOM_START);
+    test(0.75f, 0.75f, 10, 15, 200, 400, ScaleType.FIT_BOTTOM_START);
+    test(0.75f, 0.75f, 10, 15, 500, 400, ScaleType.FIT_BOTTOM_START);
+  }
+
   private void test(
       // expected
       float scaleX,