fix memory leak in CompositeWithOpaqueBackground (#4150)

Found with Leak canary: The transformation ends up in Glide's memory
cache and leaks whole Activities through the view -> context reference.

This fixes the problem by removing the background detection logic (so
the view reference is no longer needed) and setting the background
directly instead. Looks exactly as before.

app/src/main/java/com/keylesspalace/tusky/adapter/StatusBaseViewHolder.java

@@ -335,9 +335,13 @@ private void setAvatar(String url,
             avatarRadius = avatarRadius36dp;
         }
 
-        ImageLoadingHelper.loadAvatar(url, avatar, avatarRadius,
+        ImageLoadingHelper.loadAvatar(
+            url,
+            avatar,
+            avatarRadius,
             statusDisplayOptions.animateAvatars(),
-            Collections.singletonList(new CompositeWithOpaqueBackground(avatar)));
+            Collections.singletonList(new CompositeWithOpaqueBackground(MaterialColors.getColor(avatar, android.R.attr.colorBackground)))
+        );
     }
 
     protected void setMetaData(@NonNull StatusViewData.Concrete statusViewData, @NonNull StatusDisplayOptions statusDisplayOptions, @NonNull StatusActionListener listener) {

app/src/main/java/com/keylesspalace/tusky/util/CompositeWithOpaqueBackground.kt

@@ -24,12 +24,6 @@ import android.graphics.ColorMatrix
 import android.graphics.ColorMatrixColorFilter
 import android.graphics.Paint
 import android.graphics.Shader
-import android.graphics.drawable.ColorDrawable
-import android.graphics.drawable.Drawable
-import android.util.TypedValue
-import android.view.View
-import androidx.annotation.AttrRes
-import androidx.core.content.ContextCompat
 import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool
 import com.bumptech.glide.load.resource.bitmap.BitmapTransformation
 import com.bumptech.glide.util.Util
@@ -48,25 +42,26 @@ import java.security.MessageDigest
  * Fix this, by:
  *
  * - Creating a mask that matches the partially transparent areas of the image
- * - Creating a new bitmap that, in the areas that match the mask, contains the same background
- *   drawable as the [ImageView].
+ * - Creating a new bitmap that, in the areas that match the mask, contains a background color
  * - Composite the original image over the top
  *
  * So the partially transparent areas on the original image are composited over the original
  * background, the fully transparent areas on the original image are left transparent.
  */
-class CompositeWithOpaqueBackground(val view: View) : BitmapTransformation() {
+class CompositeWithOpaqueBackground(val backgroundColor: Int) : BitmapTransformation() {
+
     override fun equals(other: Any?): Boolean {
         if (other is CompositeWithOpaqueBackground) {
-            return other.view == view
+            return other.backgroundColor == backgroundColor
         }
         return false
     }
 
-    override fun hashCode() = Util.hashCode(ID.hashCode(), view.hashCode())
+    override fun hashCode() = Util.hashCode(ID.hashCode(), backgroundColor.hashCode())
+
     override fun updateDiskCacheKey(messageDigest: MessageDigest) {
         messageDigest.update(ID_BYTES)
-        messageDigest.update(ByteBuffer.allocate(4).putInt(view.hashCode()).array())
+        messageDigest.update(ByteBuffer.allocate(4).putInt(backgroundColor.hashCode()).array())
     }
 
     override fun transform(
@@ -78,20 +73,9 @@ class CompositeWithOpaqueBackground(val view: View) : BitmapTransformation() {
         // If the input bitmap has no alpha channel then there's nothing to do
         if (!toTransform.hasAlpha()) return toTransform
 
-        // Get the background drawable for this view, falling back to the given attribute
-        val backgroundDrawable = view.getFirstNonNullBackgroundOrAttr(android.R.attr.colorBackground)
-        backgroundDrawable ?: return toTransform
-
         // Convert the background to a bitmap.
         val backgroundBitmap = pool.get(outWidth, outHeight, Bitmap.Config.ARGB_8888)
-        when (backgroundDrawable) {
-            is ColorDrawable -> backgroundBitmap.eraseColor(backgroundDrawable.color)
-            else -> {
-                val backgroundCanvas = Canvas(backgroundBitmap)
-                backgroundDrawable.setBounds(0, 0, outWidth, outHeight)
-                backgroundDrawable.draw(backgroundCanvas)
-            }
-        }
+        backgroundBitmap.eraseColor(backgroundColor)
 
         // Convert the alphaBitmap (where the alpha channel has 8bpp) to a mask of 1bpp
         // TODO: toTransform.extractAlpha(paint, ...) could be used here, but I can't find any
@@ -143,24 +127,5 @@ class CompositeWithOpaqueBackground(val view: View) : BitmapTransformation() {
             )
             isAntiAlias = false
         }
-
-        /**
-         * @param attr attribute reference for the default drawable if no background is set on
-         *      this view or any of its ancestors.
-         * @return The first non-null background drawable from this view, or its ancestors,
-         *      falling back to the attribute resource given by `attr` if none of the views have a
-         *      background.
-         */
-        fun View.getFirstNonNullBackgroundOrAttr(@AttrRes attr: Int): Drawable? =
-            background ?: (parent as? View)?.getFirstNonNullBackgroundOrAttr(attr) ?: run {
-                val v = TypedValue()
-                context.theme.resolveAttribute(attr, v, true)
-                // TODO: On API 29 can use v.isColorType here
-                if (v.type >= TypedValue.TYPE_FIRST_COLOR_INT && v.type <= TypedValue.TYPE_LAST_COLOR_INT) {
-                    ColorDrawable(v.data)
-                } else {
-                    ContextCompat.getDrawable(context, v.resourceId)
-                }
-            }
     }
 }