Improve thumbnail performance.

library/src/main/java/com/bumptech/glide/request/target/DrawableImageViewTarget.java

@@ -5,6 +5,7 @@ import android.widget.ImageView;
 import com.bumptech.glide.request.GlideAnimation;
 
 public class DrawableImageViewTarget extends ViewTarget<ImageView, Drawable> {
+    private static final float SQUARE_RATIO_MARGIN = 0.05f;
     private final ImageView view;
 
     public DrawableImageViewTarget(ImageView view) {
@@ -14,6 +15,19 @@ public class DrawableImageViewTarget extends ViewTarget<ImageView, Drawable> {
 
     @Override
     public void onResourceReady(Drawable resource, GlideAnimation<Drawable> animation) {
+
+        //TODO: Try to generalize this to other sizes/shapes.
+        // This is a dirty hack that tries to make loading square thumbnails and then square full images less costly by
+        // forcing both the smaller thumb and the larger version to have exactly the same intrinsic dimensions. If a
+        // drawable is replaced in an ImageView by another drawable with different intrinsic dimensions, the ImageView
+        // requests a layout. Scrolling rapidly while replacing thumbs with larger images triggers lots of these calls
+        // and causes significant amounts of jank.
+        float viewRatio = view.getWidth() / (float) view.getHeight();
+        float drawableRatio = resource.getIntrinsicWidth() / (float) resource.getIntrinsicHeight();
+        if (Math.abs(viewRatio - 1f) <= SQUARE_RATIO_MARGIN && Math.abs(drawableRatio - 1f) <= SQUARE_RATIO_MARGIN) {
+            resource = new SquaringDrawable(resource, view.getWidth());
+        }
+
         if (animation == null || !animation.animate(view.getDrawable(), resource, view, this)) {
             view.setImageDrawable(resource);
         }

library/src/main/java/com/bumptech/glide/request/target/SquaringDrawable.java

+package com.bumptech.glide.request.target;
+
+import android.annotation.TargetApi;
+import android.graphics.Canvas;
+import android.graphics.ColorFilter;
+import android.graphics.PorterDuff;
+import android.graphics.Rect;
+import android.graphics.drawable.Drawable;
+
+/**
+ * A wrapper drawable to square the wrapped drawable so that it expands to fill a square with exactly the given side
+ * length. The goal of this drawable is to ensure that square thumbnail drawables always match the size of the view
+ * they will be displayed in to avoid a costly requestLayout call. This class should not be used with views or drawables
+ * that are not square.
+ */
+public class SquaringDrawable extends Drawable {
+    private final Drawable wrapped;
+    private int side;
+
+    public SquaringDrawable(Drawable wrapped, int side) {
+        this.wrapped = wrapped;
+        this.side = side;
+    }
+
+    @Override
+    public void setBounds(int left, int top, int right, int bottom) {
+        super.setBounds(left, top, right, bottom);
+        wrapped.setBounds(left, top, right, bottom);
+    }
+
+    @Override
+    public void setBounds(Rect bounds) {
+        super.setBounds(bounds);
+        wrapped.setBounds(bounds);
+    }
+    public void setChangingConfigurations(int configs) {
+        wrapped.setChangingConfigurations(configs);
+    }
+
+    @Override
+    public int getChangingConfigurations() {
+        return wrapped.getChangingConfigurations();
+    }
+
+    @Override
+    public void setDither(boolean dither) {
+        wrapped.setDither(dither);
+    }
+
+    @Override
+    public void setFilterBitmap(boolean filter) {
+        wrapped.setFilterBitmap(filter);
+    }
+
+    @TargetApi(11)
+    @Override
+    public Callback getCallback() {
+        return wrapped.getCallback();
+    }
+
+    @TargetApi(19)
+    @Override
+    public int getAlpha() {
+        return wrapped.getAlpha();
+    }
+
+    @Override
+    public void setColorFilter(int color, PorterDuff.Mode mode) {
+        wrapped.setColorFilter(color, mode);
+    }
+
+    @Override
+    public void clearColorFilter() {
+        wrapped.clearColorFilter();
+    }
+
+    @Override
+    public Drawable getCurrent() {
+        return wrapped.getCurrent();
+    }
+
+    @Override
+    public boolean setVisible(boolean visible, boolean restart) {
+        return wrapped.setVisible(visible, restart);
+    }
+
+    @Override
+    public int getIntrinsicWidth() {
+        return side;
+    }
+
+    @Override
+    public int getIntrinsicHeight() {
+        return side;
+    }
+
+    @Override
+    public int getMinimumWidth() {
+        return wrapped.getMinimumWidth();
+    }
+
+    @Override
+    public int getMinimumHeight() {
+        return wrapped.getMinimumHeight();
+    }
+
+    @Override
+    public boolean getPadding(Rect padding) {
+        return wrapped.getPadding(padding);
+    }
+
+    @Override
+    public void invalidateSelf() {
+        super.invalidateSelf();    //To change body of overridden methods use File | Settings | File Templates.
+        wrapped.invalidateSelf();
+    }
+
+    @Override
+    public void unscheduleSelf(Runnable what) {
+        super.unscheduleSelf(what);    //To change body of overridden methods use File | Settings | File Templates.
+        wrapped.unscheduleSelf(what);
+    }
+
+    @Override
+    public void scheduleSelf(Runnable what, long when) {
+        super.scheduleSelf(what, when);    //To change body of overridden methods use File | Settings | File Templates.
+        wrapped.scheduleSelf(what, when);
+    }
+
+    @Override
+    public void draw(Canvas canvas) {
+        wrapped.draw(canvas);
+    }
+
+    @Override
+    public void setAlpha(int i) {
+        wrapped.setAlpha(i);
+    }
+
+    @Override
+    public void setColorFilter(ColorFilter colorFilter) {
+        wrapped.setColorFilter(colorFilter);
+    }
+
+    @Override
+    public int getOpacity() {
+        return wrapped.getOpacity();
+    }
+}

library/src/main/java/com/bumptech/glide/request/target/Target.java

@@ -7,7 +7,7 @@ import com.bumptech.glide.request.Request;
 /**
  * An interface that Glide can load an image into
  *
- * @param <Z> The type of resource the target can display.
+ * @param <R> The type of resource the target can display.
  */
 public interface Target<R> {
 

samples/flickr/res/layout/flickr_photo_grid_item.xml

 <?xml version="1.0" encoding="utf-8"?>
 
 <ImageView xmlns:android="http://schemas.android.com/apk/res/android"
-    android:scaleType="centerCrop"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"/>

samples/flickr/src/main/java/com/bumptech/glide/samples/flickr/FlickrPhotoGrid.java

@@ -99,9 +99,8 @@ public class FlickrPhotoGrid extends SherlockFragment implements PhotoViewer {
         protected GenericRequestBuilder getRequestBuilder(Photo item) {
             return Glide.with(FlickrPhotoGrid.this)
                     .loadFromImage(item)
-                    .override(Api.THUMB_SIZE, Api.THUMB_SIZE)
-                    .priority(Priority.HIGH)
-                    .centerCrop();
+                    .override(Api.SQUARE_THUMB_SIZE, Api.SQUARE_THUMB_SIZE)
+                    .priority(Priority.HIGH);
         }
     }
 
@@ -150,8 +149,7 @@ public class FlickrPhotoGrid extends SherlockFragment implements PhotoViewer {
                     .loadFromImage(current)
                     .thumbnail(Glide.with(FlickrPhotoGrid.this)
                             .loadFromImage(current)
-                            .override(Api.THUMB_SIZE, Api.THUMB_SIZE)
-                            .centerCrop()
+                            .override(Api.SQUARE_THUMB_SIZE, Api.SQUARE_THUMB_SIZE)
                     )
                     .animate(R.anim.fade_in)
                     .centerCrop()

samples/flickr/src/main/java/com/bumptech/glide/samples/flickr/FlickrPhotoList.java

@@ -115,8 +115,9 @@ public class FlickrPhotoList extends SherlockFragment implements PhotoViewer {
             return Glide.with(FlickrPhotoList.this)
                     .loadFromImage(item)
                     .thumbnail(Glide.with(FlickrPhotoList.this)
-                            .loadFromImage(item)
-                            .override(Api.THUMB_SIZE, Api.THUMB_SIZE))
+                        .loadFromImage(item)
+                        .override(Api.SQUARE_THUMB_SIZE, Api.SQUARE_THUMB_SIZE)
+                    )
                     .centerCrop();
         }
     }
@@ -176,7 +177,7 @@ public class FlickrPhotoList extends SherlockFragment implements PhotoViewer {
                     .placeholder(new ColorDrawable(Color.GRAY))
                     .thumbnail(Glide.with(FlickrPhotoList.this)
                         .loadFromImage(current)
-                        .override(Api.THUMB_SIZE, Api.THUMB_SIZE))
+                        .override(Api.SQUARE_THUMB_SIZE, Api.SQUARE_THUMB_SIZE))
                     .centerCrop()
                     .crossFade(R.anim.fade_in, 150)
                     .into(viewHolder.imageView);

samples/flickr/src/main/java/com/bumptech/glide/samples/flickr/api/Api.java

@@ -45,7 +45,7 @@ public class Api {
         Collections.sort(SORTED_SIZE_KEYS);
     }
 
-    public static final int THUMB_SIZE = SORTED_SIZE_KEYS.get(0);
+    public static final int SQUARE_THUMB_SIZE = SORTED_SIZE_KEYS.get(0);
 
     private static String getSizeKey(int width, int height) {
         final int largestEdge = Math.max(width, height);