Avoid starting identical requests.

If a request is already in progress we should only
cancel and restart it if the new request differs
from the in progress request in some way. Prior
to this change, we always cleared and restarted 
requests without checking to see if the request
parameters had changed. 

Progress toward #2194.

library/src/main/java/com/bumptech/glide/RequestBuilder.java

@@ -353,14 +353,18 @@ public <Y extends Target<TranscodeType>> Y into(@NonNull Y target) {
       throw new IllegalArgumentException("You must call #load() before calling #into()");
     }
 
-    Request previous = target.getRequest();
+    requestOptions.lock();
+    Request request = buildRequest(target);
 
+    Request previous = target.getRequest();
     if (previous != null) {
+      if (request.isEquivalentTo(previous)) {
+        request.recycle();
+        return target;
+      }
       requestManager.clear(target);
     }
 
-    requestOptions.lock();
-    Request request = buildRequest(target);
     target.setRequest(request);
     requestManager.track(target, request);
 

library/src/main/java/com/bumptech/glide/request/Request.java

@@ -57,4 +57,18 @@ public interface Request {
    * Recycles the request object and releases its resources.
    */
   void recycle();
+
+  /**
+   * Returns {@code true} if this {@link Request} is equivalent to the given {@link Request} (has
+   * all of the same options and sizes).
+   *
+   * <p>This method is identical to {@link #equals(Object)} except that it's specific to
+   * {@link Request} subclasses. We do not use {@link #equals(Object)} directly because we track
+   * {@link Request}s in collections like {@link java.util.Set} and it's perfectly legitimate to
+   * have two different {@link Request} objects for two different
+   * {@link com.bumptech.glide.request.target.Target}s (for example). Using a similar but different
+   * method let's us selectively compare {@link Request} objects to each other when it's useful in
+   * specific scenarios.
+   */
+  boolean isEquivalentTo(Request other);
 }

library/src/main/java/com/bumptech/glide/request/RequestOptions.java

@@ -1095,6 +1095,62 @@ public RequestOptions apply(RequestOptions other) {
     return selfOrThrowIfLocked();
   }
 
+
+  @Override
+  public boolean equals(Object o) {
+    if (o instanceof RequestOptions) {
+      RequestOptions other = (RequestOptions) o;
+      return Float.compare(other.sizeMultiplier, sizeMultiplier) == 0
+          && errorId == other.errorId
+          && Util.bothNullOrEqual(errorPlaceholder, other.errorPlaceholder)
+          && placeholderId == other.placeholderId
+          && Util.bothNullOrEqual(placeholderDrawable, other.placeholderDrawable)
+          && fallbackId == other.fallbackId
+          && Util.bothNullOrEqual(fallbackDrawable, other.fallbackDrawable)
+          && isCacheable == other.isCacheable
+          && overrideHeight == other.overrideHeight
+          && overrideWidth == other.overrideWidth
+          && isTransformationRequired == other.isTransformationRequired
+          && isTransformationAllowed == other.isTransformationAllowed
+          && useUnlimitedSourceGeneratorsPool == other.useUnlimitedSourceGeneratorsPool
+          && onlyRetrieveFromCache == other.onlyRetrieveFromCache
+          && diskCacheStrategy.equals(other.diskCacheStrategy)
+          && priority == other.priority
+          && options.equals(other.options)
+          && transformations.equals(other.transformations)
+          && resourceClass.equals(other.resourceClass)
+          && Util.bothNullOrEqual(signature, other.signature)
+          && Util.bothNullOrEqual(theme, other.theme);
+    }
+    return false;
+  }
+
+  @Override
+  public int hashCode() {
+    int hashCode = Util.hashCode(sizeMultiplier);
+    hashCode = Util.hashCode(errorId, hashCode);
+    hashCode = Util.hashCode(errorPlaceholder, hashCode);
+    hashCode = Util.hashCode(placeholderId, hashCode);
+    hashCode = Util.hashCode(placeholderDrawable, hashCode);
+    hashCode = Util.hashCode(fallbackId, hashCode);
+    hashCode = Util.hashCode(fallbackDrawable, hashCode);
+    hashCode = Util.hashCode(isCacheable, hashCode);
+    hashCode = Util.hashCode(overrideHeight, hashCode);
+    hashCode = Util.hashCode(overrideWidth, hashCode);
+    hashCode = Util.hashCode(isTransformationRequired, hashCode);
+    hashCode = Util.hashCode(isTransformationAllowed, hashCode);
+    hashCode = Util.hashCode(useUnlimitedSourceGeneratorsPool, hashCode);
+    hashCode = Util.hashCode(onlyRetrieveFromCache, hashCode);
+    hashCode = Util.hashCode(diskCacheStrategy, hashCode);
+    hashCode = Util.hashCode(priority, hashCode);
+    hashCode = Util.hashCode(options, hashCode);
+    hashCode = Util.hashCode(transformations, hashCode);
+    hashCode = Util.hashCode(resourceClass, hashCode);
+    hashCode = Util.hashCode(signature, hashCode);
+    hashCode = Util.hashCode(theme, hashCode);
+    return hashCode;
+  }
+
   /**
    * Throws if any further mutations are attempted.
    *

library/src/main/java/com/bumptech/glide/request/SingleRequest.java

@@ -80,7 +80,7 @@ private enum Status {
     PAUSED,
   }
 
-  private final String tag = String.valueOf(hashCode());
+  private final String tag = String.valueOf(super.hashCode());
   private final StateVerifier stateVerifier = StateVerifier.newInstance();
 
   private RequestCoordinator requestCoordinator;
@@ -551,6 +551,20 @@ private void onLoadFailed(GlideException e, int maxLogLevel) {
     }
   }
 
+  @Override
+  public boolean isEquivalentTo(Request o) {
+    if (o instanceof SingleRequest) {
+      SingleRequest that = (SingleRequest) o;
+      return overrideWidth == that.overrideWidth
+          && overrideHeight == that.overrideHeight
+          && model.equals(that.model)
+          && transcodeClass.equals(that.transcodeClass)
+          && requestOptions.equals(that.requestOptions)
+          && priority == that.priority;
+    }
+    return false;
+  }
+
   private void logV(String message) {
     Log.v(TAG, message + " this: " + tag);
   }

library/src/main/java/com/bumptech/glide/request/ThumbnailRequestCoordinator.java

@@ -159,4 +159,14 @@ public void recycle() {
     full.recycle();
     thumb.recycle();
   }
+
+  @Override
+  public boolean isEquivalentTo(Request o) {
+    if (o instanceof ThumbnailRequestCoordinator) {
+      ThumbnailRequestCoordinator that = (ThumbnailRequestCoordinator) o;
+      return (full == null ? that.full == null : full.isEquivalentTo(that.full))
+          && (thumb == null ? that.thumb == null : thumb.isEquivalentTo(that.thumb));
+    }
+    return false;
+  }
 }

library/src/main/java/com/bumptech/glide/util/Util.java

@@ -15,6 +15,8 @@
  * A collection of assorted utility classes.
  */
 public final class Util {
+  private static final int HASH_MULTIPLIER = 31;
+  private static final int HASH_ACCUMULATOR = 17;
   private static final char[] HEX_CHAR_ARRAY = "0123456789abcdef".toCharArray();
   // 32 bytes from sha-256 -> 64 hex chars.
   private static final char[] SHA_256_CHARS = new char[64];
@@ -187,4 +189,33 @@ public static <T> List<T> getSnapshot(Collection<T> other) {
   public static boolean bothNullOrEqual(Object a, Object b) {
     return a == null ? b == null : a.equals(b);
   }
+
+  public static int hashCode(int value) {
+    return hashCode(value, HASH_ACCUMULATOR);
+  }
+
+  public static int hashCode(int value, int accumulator) {
+    return accumulator * HASH_MULTIPLIER + value;
+  }
+
+  public static int hashCode(float value) {
+    return hashCode(value, HASH_ACCUMULATOR);
+  }
+
+  public static int hashCode(float value, int accumulator) {
+    return hashCode(Float.floatToIntBits(value), accumulator);
+  }
+
+  public static int hashCode(Object object, int accumulator) {
+    return hashCode(object == null ? 0 : object.hashCode(), accumulator);
+  }
+
+  public static int hashCode(boolean value, int accumulator) {
+    return hashCode(value ? 1 : 0, accumulator);
+  }
+
+  public static int hashCode(boolean value) {
+    return hashCode(value, HASH_ACCUMULATOR);
+  }
+
 }

library/src/test/java/com/bumptech/glide/request/RequestOptionsTest.java

@@ -2,19 +2,29 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
+import android.app.Application;
 import android.graphics.Bitmap;
-
+import android.graphics.Color;
+import android.graphics.drawable.ColorDrawable;
+import android.graphics.drawable.Drawable;
+import android.graphics.drawable.GradientDrawable;
+import com.bumptech.glide.Priority;
 import com.bumptech.glide.load.MultiTransformation;
+import com.bumptech.glide.load.Option;
 import com.bumptech.glide.load.Transformation;
+import com.bumptech.glide.load.engine.DiskCacheStrategy;
 import com.bumptech.glide.load.resource.bitmap.CenterCrop;
 import com.bumptech.glide.load.resource.bitmap.CircleCrop;
-
+import com.bumptech.glide.signature.ObjectKey;
+import com.bumptech.glide.util.Util;
+import com.google.common.testing.EqualsTester;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Config;
 
 @RunWith(RobolectricTestRunner.class)
@@ -23,11 +33,14 @@ public class RequestOptionsTest {
 
   private RequestOptions options;
   @Mock private Transformation<Bitmap> transformation;
+  private Application app;
 
   @Before
   public void setUp() {
     MockitoAnnotations.initMocks(this);
     options = new RequestOptions();
+
+    app = RuntimeEnvironment.application;
   }
 
   @Test
@@ -146,4 +159,101 @@ public void testApplyMultiTransform() {
     assertThat(options.getTransformations().get(Bitmap.class))
       .isInstanceOf(MultiTransformation.class);
   }
+
+  @Test
+  public void testEqualsHashCode() {
+    Drawable first = new ColorDrawable(Color.RED);
+    Drawable second = new GradientDrawable();
+    assertThat(first).isNotEqualTo(second);
+    assertThat(Util.bothNullOrEqual(first, second)).isFalse();
+    new EqualsTester()
+        .addEqualityGroup(
+            new RequestOptions().sizeMultiplier(.7f),
+            new RequestOptions().sizeMultiplier(.7f))
+        .addEqualityGroup(new RequestOptions().sizeMultiplier(0.8f))
+        .addEqualityGroup(new RequestOptions().error(1), new RequestOptions().error(1))
+        .addEqualityGroup(new RequestOptions().error(2))
+        .addEqualityGroup(new RequestOptions().error(first), new RequestOptions().error(first))
+        .addEqualityGroup(new RequestOptions().error(second))
+        .addEqualityGroup(new RequestOptions().placeholder(1), new RequestOptions().placeholder(1))
+        .addEqualityGroup(new RequestOptions().placeholder(2))
+        .addEqualityGroup(
+            new RequestOptions().placeholder(first),
+            new RequestOptions().placeholder(first))
+        .addEqualityGroup(new RequestOptions().placeholder(second))
+        .addEqualityGroup(new RequestOptions().fallback(1), new RequestOptions().fallback(1))
+        .addEqualityGroup(new RequestOptions().fallback(2))
+        .addEqualityGroup(
+            new RequestOptions().fallback(first),
+            new RequestOptions().fallback(first))
+        .addEqualityGroup(new RequestOptions().fallback(second))
+        .addEqualityGroup(
+            new RequestOptions().skipMemoryCache(true),
+            new RequestOptions().skipMemoryCache(true))
+        .addEqualityGroup(
+            new RequestOptions(),
+            new RequestOptions().skipMemoryCache(false),
+            new RequestOptions().theme(null),
+            new RequestOptions().onlyRetrieveFromCache(false),
+            new RequestOptions().useUnlimitedSourceGeneratorsPool(false))
+        .addEqualityGroup(
+            new RequestOptions().override(100),
+            new RequestOptions().override(100, 100))
+        .addEqualityGroup(
+            new RequestOptions().override(200),
+            new RequestOptions().override(200, 200))
+        .addEqualityGroup(
+            new RequestOptions().override(100, 200),
+            new RequestOptions().override(100, 200))
+        .addEqualityGroup(
+            new RequestOptions().override(200, 100),
+            new RequestOptions().override(200, 100))
+        .addEqualityGroup(
+            new RequestOptions().centerCrop(),
+            new RequestOptions().centerCrop())
+        .addEqualityGroup(
+            new RequestOptions().optionalCenterCrop(),
+            new RequestOptions().optionalCenterCrop())
+        .addEqualityGroup(new RequestOptions().fitCenter())
+        .addEqualityGroup(new RequestOptions().circleCrop())
+        .addEqualityGroup(new RequestOptions().centerInside())
+        .addEqualityGroup(
+            new RequestOptions().useUnlimitedSourceGeneratorsPool(true),
+            new RequestOptions().useUnlimitedSourceGeneratorsPool(true))
+        .addEqualityGroup(
+            new RequestOptions().onlyRetrieveFromCache(true),
+            new RequestOptions().onlyRetrieveFromCache(true))
+        .addEqualityGroup(
+            new RequestOptions().diskCacheStrategy(DiskCacheStrategy.ALL),
+            new RequestOptions().diskCacheStrategy(DiskCacheStrategy.ALL))
+        .addEqualityGroup(
+            new RequestOptions().diskCacheStrategy(DiskCacheStrategy.NONE))
+        .addEqualityGroup(
+            new RequestOptions().priority(Priority.HIGH),
+            new RequestOptions().priority(Priority.HIGH))
+        .addEqualityGroup(
+            new RequestOptions().priority(Priority.LOW))
+        .addEqualityGroup(
+            new RequestOptions().set(Option.<Boolean>memory("test"), true),
+            new RequestOptions().set(Option.<Boolean>memory("test"), true))
+        .addEqualityGroup(
+            new RequestOptions().set(Option.<Boolean>memory("test"), false))
+        .addEqualityGroup(
+            new RequestOptions().set(Option.<Boolean>memory("test2"), true))
+        .addEqualityGroup(
+            new RequestOptions().decode(Integer.class),
+            new RequestOptions().decode(Integer.class))
+        .addEqualityGroup(
+            new RequestOptions().decode(Float.class))
+        .addEqualityGroup(
+            new RequestOptions().signature(new ObjectKey("test")),
+            new RequestOptions().signature(new ObjectKey("test")))
+        .addEqualityGroup(
+            new RequestOptions().signature(new ObjectKey("test2")))
+        .addEqualityGroup(
+            new RequestOptions().theme(app.getTheme()),
+            new RequestOptions().theme(app.getTheme()))
+        .testEquals();
+  }
+
 }