Tweak logo hiding transition for the Home sheet.

The transition at the bottom starts when the toolbar is in the center of the
visible part of the sheet, and keeps it centered throughout. The top transition
is symmetric to that.

Videos: https://photos.app.goo.gl/psMFW5kRuo0HEfba2

Bug: 759130
Change-Id: I91f518371915ee97fb4b99840e74b7fe8f130a71
Reviewed-on: https://chromium-review.googlesource.com/702259Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Commit-Queue: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506695}

chrome/android/java/src/org/chromium/chrome/browser/suggestions/SuggestionsBottomSheetContent.java

@@ -71,12 +71,6 @@ public class SuggestionsBottomSheetContent implements BottomSheet.BottomSheetCon
      */
     private boolean mIsAttachedToWindow;
 
-    // The sheet height fractions at which the logo transitions start and end.
-    private static final float LOGO_TRANSITION_BOTTOM_START = 0.3f;
-    private static final float LOGO_TRANSITION_BOTTOM_END = 0.1f;
-    private static final float LOGO_TRANSITION_TOP_START = 0.75f;
-    private static final float LOGO_TRANSITION_TOP_END = 0.95f;
-
     public SuggestionsBottomSheetContent(final ChromeActivity activity, final BottomSheet sheet,
             TabModelSelector tabModelSelector, SnackbarManager snackbarManager) {
         SuggestionsDependencyFactory depsFactory = SuggestionsDependencyFactory.getInstance();
@@ -99,21 +93,12 @@ public class SuggestionsBottomSheetContent implements BottomSheet.BottomSheetCon
         mRecyclerView = mView.findViewById(R.id.recycler_view);
         mRecyclerView.setBackgroundColor(backgroundColor);
 
-        TouchEnabledDelegate touchEnabledDelegate = new TouchEnabledDelegate() {
-            @Override
-            public void setTouchEnabled(boolean enabled) {
-                activity.getBottomSheet().setTouchEnabled(enabled);
-            }
-        };
-
+        TouchEnabledDelegate touchEnabledDelegate = activity.getBottomSheet()::setTouchEnabled;
         mContextMenuManager =
                 new ContextMenuManager(activity, navigationDelegate, touchEnabledDelegate);
         activity.getWindowAndroid().addContextMenuCloseListener(mContextMenuManager);
-        mSuggestionsUiDelegate.addDestructionObserver(new DestructionObserver() {
-            @Override
-            public void onDestroy() {
-                activity.getWindowAndroid().removeContextMenuCloseListener(mContextMenuManager);
-            }
+        mSuggestionsUiDelegate.addDestructionObserver(() -> {
+            activity.getWindowAndroid().removeContextMenuCloseListener(mContextMenuManager);
         });
 
         UiConfig uiConfig = new UiConfig(mRecyclerView);
@@ -153,8 +138,6 @@ public class SuggestionsBottomSheetContent implements BottomSheet.BottomSheetCon
                     mRecyclerView.scrollToPosition(0);
                     mRecyclerView.getScrollEventReporter().reset();
                 }
-
-
             }
 
             @Override
@@ -345,26 +328,28 @@ public class SuggestionsBottomSheetContent implements BottomSheet.BottomSheetCon
         mLogoView.setVisibility(View.VISIBLE);
         ViewUtils.setAncestorsShouldClipChildren(mControlContainerView, false);
 
-        // TODO(mvanouwerkerk): Consider using Material animation curves.
-        final float transitionFraction;
-        if (mLastSheetHeightFraction > LOGO_TRANSITION_TOP_START) {
-            float range = LOGO_TRANSITION_TOP_END - LOGO_TRANSITION_TOP_START;
-            transitionFraction =
-                    Math.min((mLastSheetHeightFraction - LOGO_TRANSITION_TOP_START) / range, 1.0f);
-        } else if (mLastSheetHeightFraction < LOGO_TRANSITION_BOTTOM_START) {
-            float range = LOGO_TRANSITION_BOTTOM_START - LOGO_TRANSITION_BOTTOM_END;
-            transitionFraction = Math.min(
-                    (LOGO_TRANSITION_BOTTOM_START - mLastSheetHeightFraction) / range, 1.0f);
-        } else {
-            transitionFraction = 0.0f;
-        }
-
         ViewGroup.MarginLayoutParams logoParams =
                 (ViewGroup.MarginLayoutParams) mLogoView.getLayoutParams();
+        float maxToolbarOffset = logoParams.height + logoParams.topMargin + logoParams.bottomMargin;
+
+        // Transform the sheet height fraction back to pixel scale.
+        float rangePx =
+                (mSheet.getFullRatio() - mSheet.getPeekRatio()) * mSheet.getSheetContainerHeight();
+        float sheetHeightPx = mLastSheetHeightFraction * rangePx;
+
+        // Calculate the transition fraction for hiding the logo: 0 means the logo is fully visible,
+        // 1 means it is fully invisible.
+        // The transition starts when the sheet is `2 * maxToolbarOffset` from the bottom or the
+        // top. This makes the toolbar stay vertically centered in the sheet during the
+        // bottom transition.
+        float transitionFraction =
+                Math.max(Math.max(1 - sheetHeightPx / (2 * maxToolbarOffset),
+                                 1 + (sheetHeightPx - rangePx) / (2 * maxToolbarOffset)),
+                        0);
+
         mLogoView.setTranslationY(logoParams.topMargin * -transitionFraction);
         mLogoView.setAlpha(Math.max(0.0f, 1.0f - (transitionFraction * 3.0f)));
 
-        float maxToolbarOffset = logoParams.height + logoParams.topMargin + logoParams.bottomMargin;
         float toolbarOffset = maxToolbarOffset * (1.0f - transitionFraction);
         mControlContainerView.setTranslationY(toolbarOffset);
         mToolbarPullHandle.setTranslationY(-toolbarOffset);