Refactor OverlayPanel height calculations

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.compositor.bottombar;
 
 import android.content.Context;
 import android.graphics.Color;
 import android.view.ViewGroup;
 
@@ skipping 141 matching lines @@
      */
     protected abstract void closePanel(StateChangeReason reason, boolean animate);
 
     /**
      * Event notification that the Panel did get closed.
      * @param reason The reason the panel is closing.
      */
     protected abstract void onClosed(StateChangeReason reason);
 
     /**
-     * @return The absolute amount in DP that the top controls have shifted off screen.
-     */
-    protected abstract float getTopControlsOffsetDp();
-
-    /**
      * TODO(mdjones): This method should be removed from this class.
      * @return The resource id that contains how large the top controls are.
      */
     protected abstract int getControlContainerHeightResource();
 
     /**
      * Handles when the Panel's container view size changes.
      * @param width The new width of the Panel's container view.
      * @param height The new height of the Panel's container view.
      * @param previousWidth The previous width of the Panel's container view.
      */
     protected abstract void handleSizeChanged(float width, float height, float previousWidth);
 
     // ============================================================================================
     // Layout Integration
     // ============================================================================================
 
     private float mLayoutWidth;
     private float mLayoutHeight;
+    private float mLayoutYOffset;
 
     private float mMaximumWidth;
     private float mMaximumHeight;
 
     private boolean mIsFullWidthSizePanelForTesting;
     private boolean mOverrideIsFullWidthSizePanelForTesting;
 
     /**
      * Called when the size of the view has changed.
      *
      * @param width  The new width in dp.
      * @param height The new width in dp.
+     * @param visibleViewportOffsetY The Y offset of the content in dp.
      */
-    public void onSizeChanged(float width, float height) {
-        if (width == mLayoutWidth && height == mLayoutHeight) return;
+    public void onSizeChanged(float width, float height, float visibleViewportOffsetY) {

[Changwan Ryu, 2016/07/07 03:29:32]

How about renaming it as onLayoutChanged? I don't feel that viewport offset is
part of 'size'.

[mdjones, 2016/07/07 18:33:40]

I renamed this method up to the SceneOverlay interface; I can change the names
there too if you want.

+        if (width == mLayoutWidth && height == mLayoutHeight
+                && visibleViewportOffsetY == mLayoutYOffset) {
+            return;
+        }
 
         float previousLayoutWidth = mLayoutWidth;
 
         mLayoutWidth = width;
         mLayoutHeight = height;
+        mLayoutYOffset = visibleViewportOffsetY;
 
         mMaximumWidth = calculateOverlayPanelWidth();
         mMaximumHeight = getPanelHeightFromState(PanelState.MAXIMIZED);
 
         handleSizeChanged(width, height, previousLayoutWidth);
     }
 
     /**
      * @return Whether the Panel is in full width size.
      */
@@ skipping 35 matching lines @@
     }
 
     /**
      * @return The height of the Chrome toolbar in dp.
      */
     public float getToolbarHeight() {
         return mToolbarHeight;
     }
 
     /**
-     * @param y The y coordinate.
-     * @return The Y coordinate relative the fullscreen height.
-     */
-    public float getFullscreenY(float y) {
-        return y + (mToolbarHeight - getTopControlsOffsetDp()) / mPxToDp;
-    }
-
-    /**
      * @return Whether the Panel is showing.
      */
     public boolean isShowing() {
         return mHeight > 0;
     }
 
     /**
      * @return Whether the Overlay Panel is opened. That is, whether the current height is greater
      * than the peeking height.
      */
     public boolean isPanelOpened() {
         return mHeight > getBarContainerHeight();
     }
 
     /**
      * @return The fullscreen width.
      */
     private float getFullscreenWidth() {
         return mLayoutWidth;
     }
 
     /**
      * @return The height of the tab the panel is displayed on top of.
      */
     public float getTabHeight() {
-        // NOTE(mdjones): This value will always be the same for a particular orientation; it is
-        // the content height + visible toolbar height.
-        return mLayoutHeight + (getToolbarHeight() - getTopControlsOffsetDp());
+        return mLayoutHeight;
     }
 
     /**
      * @return The maximum width of the Overlay Panel in pixels.
      */
     public int getMaximumWidthPx() {
         return Math.round(mMaximumWidth / mPxToDp);
     }
 
     /**
@@ skipping 785 matching lines @@
      * consideration the Toolbar height, and adjust the offset accordingly, in order to
      * move the Toolbar out of the view as the Panel expands.
      *
      * @return The target offset Y.
      */
     private float calculateBasePageTargetY() {
         // Only a fullscreen wide Panel should offset the base page. A small panel should
         // always return zero to ensure the Base Page remains in the same position.
         if (!isFullWidthSizePanel()) return 0.f;
 
-        // Start with the desired offset.
-        float offset = calculateBasePageDesiredOffset();
+        // Start with the desired offset taking viewport offset into consideration and make sure
+        // the result is <= 0 so the page moves up and not down.
+        float offset = Math.min(calculateBasePageDesiredOffset() - mLayoutYOffset, 0.0f);
 
-        // Make sure offset is negative to prevent Base Page from moving down,
-        // because there's nothing to render above the Page.
-        offset = Math.min(offset, 0.f);
-        // If visible, the Toolbar will be hidden. Therefore, we need to adjust
-        // the offset to account for this difference.
-        offset -= (mToolbarHeight - getTopControlsOffsetDp());
         // Make sure the offset is not greater than the expanded height, because
         // there's nothing to render below the Page.
         offset = Math.max(offset, -getExpandedHeight());
 
         return offset;
     }
 
     /**
      * @return The Y coordinate to apply to the Base Page in order to keep the selection
      *         in view when the Overlay Panel is in EXPANDED state.
@@ skipping 67 matching lines @@
      * Overrides the FullWidthSizePanel state for testing.
      *
      * @param isFullWidthSizePanel Whether the Panel has a full width size.
      */
     @VisibleForTesting
     public void setIsFullWidthSizePanelForTesting(boolean isFullWidthSizePanel) {
         mOverrideIsFullWidthSizePanelForTesting = true;
         mIsFullWidthSizePanelForTesting = isFullWidthSizePanel;
     }
 }