NTP, peeking card and heading hiding constraints

chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java
index 28ec164bb7f56cc8b4abbc45f595964659421568..a9d0f3263db8f207cdf6ccad99c51763b1f6a0cd 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetHeaderViewHolder.java
@@ -50,6 +50,18 @@ public class SnippetHeaderViewHolder extends NewTabPageViewHolder {
     }
 
     /**
+     * Only allow the header to transition if the user has not scrolled on the page beyond the
+     * |mMaxPeekPadding + mMaxSnippetHeaderHeight|. There will only ever be one peeking card on the
+     * page and only when there is enough space to show the peeking card on the first screen at the
+     * bottom.
+     * @return

[Michael van Ouwerkerk, 2016/07/15 15:05:28]

Also same as for the other one: either document @return or delete it.

[mcwilliams, 2016/07/18 15:11:45]

Done.

+     */
+    private boolean allowHeaderToTransition() {

[Michael van Ouwerkerk, 2016/07/15 15:05:28]

Same as for the other method, I think "isHeaderAllowedToTransition" would be
more readable.

[PEConn, 2016/07/15 15:08:23]

(again, maybe isHeaderTransitionAllowed instead)

[mcwilliams, 2016/07/18 15:11:45]

Done.

+        return mRecyclerView.computeVerticalScrollOffset()
+                <= mMaxSnippetHeaderHeight + mMaxPeekPadding;
+    }
+
+    /**
      * Update the view for the fade in/out and heading height.
      */
     public void updateDisplay() {
@@ -58,11 +70,15 @@ public class SnippetHeaderViewHolder extends NewTabPageViewHolder {
         int snippetHeaderTop = itemView.getTop();
         int recyclerViewHeight = mRecyclerView.getHeight();
 
-        // Check if snippet header top is within range to start showing. Set the header height, this
-        // is a percentage of how much is scrolled. The balance of the scroll will
-        // be used to display the peeking card.
-        int amountScrolled = (recyclerViewHeight - mMaxPeekPadding) - snippetHeaderTop;
-        if (mHeader.isVisible()) {
+        if (!mHeader.isVisible()) {
+            headerHeight = 0;
+        } else if (!allowHeaderToTransition()) {
+            headerHeight = mMaxSnippetHeaderHeight;
+        } else {
+            // Check if snippet header top is within range to start showing. Set the header height,
+            // this is a percentage of how much is scrolled. The balance of the scroll will be used
+            // to display the peeking card.
+            int amountScrolled = (recyclerViewHeight - mMaxPeekPadding) - snippetHeaderTop;
             headerHeight = MathUtils.clamp((int) (amountScrolled * SCROLL_HEADER_HEIGHT_PERCENTAGE),
                     0, mMaxSnippetHeaderHeight);
         }