// Copyright 2012 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.android_webview;
import android.view.View;
import android.view.View.MeasureSpec;
/**
* Helper methods used to manage the layout of the View that contains AwContents.
*/
public class AwLayoutSizer {
public static final int FIXED_LAYOUT_HEIGHT = 0;
// These are used to prevent a re-layout if the content size changes within a dimension that is
// fixed by the view system.
private boolean mWidthMeasurementIsFixed;
private boolean mHeightMeasurementIsFixed;
// Size of the rendered content, as reported by native.
private int mContentHeightCss;
private int mContentWidthCss;
// Page scale factor. This is set to zero initially so that we don't attempt to do a layout if
// we get the content size change notification first and a page scale change second.
private float mPageScaleFactor = 0.0f;
// The page scale factor that was used in the most recent onMeasure call.
private float mLastMeasuredPageScaleFactor = 0.0f;
// Whether to postpone layout requests.
private boolean mFreezeLayoutRequests;
// Did we try to request a layout since the last time mPostponeLayoutRequests was set to true.
private boolean mFrozenLayoutRequestPending;
private double mDIPScale;
// Was our height larger than the AT_MOST constraint the last time onMeasure was called?
private boolean mHeightMeasurementLimited;
// If mHeightMeasurementLimited is true then this contains the height limit.
private int mHeightMeasurementLimit;
// The most recent width and height seen in onSizeChanged.
private int mLastWidth;
private int mLastHeight;
// Used to prevent sending multiple setFixedLayoutSize notifications with the same values.
private int mLastSentFixedLayoutSizeWidth = -1;
private int mLastSentFixedLayoutSizeHeight = -1;
// Callback object for interacting with the View.
private Delegate mDelegate;
public interface Delegate {
void requestLayout();
void setMeasuredDimension(int measuredWidth, int measuredHeight);
void setFixedLayoutSize(int widthDip, int heightDip);
boolean isLayoutParamsHeightWrapContent();
}
/**
* Default constructor. Note: both setDelegate and setDIPScale must be called before the class
* is ready for use.
*/
public AwLayoutSizer() {
}
public void setDelegate(Delegate delegate) {
mDelegate = delegate;
}
public void setDIPScale(double dipScale) {
mDIPScale = dipScale;
}
/**
* Postpone requesting layouts till unfreezeLayoutRequests is called.
*/
public void freezeLayoutRequests() {
mFreezeLayoutRequests = true;
mFrozenLayoutRequestPending = false;
}
/**
* Stop postponing layout requests and request layout if such a request would have been made
* had the freezeLayoutRequests method not been called before.
*/
public void unfreezeLayoutRequests() {
mFreezeLayoutRequests = false;
if (mFrozenLayoutRequestPending) {
mFrozenLayoutRequestPending = false;
mDelegate.requestLayout();
}
}
/**
* Update the contents size.
* This should be called whenever the content size changes (due to DOM manipulation or page
* load, for example).
* The width and height should be in CSS pixels.
*/
public void onContentSizeChanged(int widthCss, int heightCss) {
doUpdate(widthCss, heightCss, mPageScaleFactor);
}
/**
* Update the contents page scale.
* This should be called whenever the content page scale factor changes (due to pinch zoom, for
* example).
*/
public void onPageScaleChanged(float pageScaleFactor) {
doUpdate(mContentWidthCss, mContentHeightCss, pageScaleFactor);
}
private void doUpdate(int widthCss, int heightCss, float pageScaleFactor) {
// We want to request layout only if the size or scale change, however if any of the
// measurements are 'fixed', then changing the underlying size won't have any effect, so we
// ignore changes to dimensions that are 'fixed'.
final int heightPix = (int) (heightCss * mPageScaleFactor * mDIPScale);
boolean pageScaleChanged = mPageScaleFactor != pageScaleFactor;
boolean contentHeightChangeMeaningful = !mHeightMeasurementIsFixed &&
(!mHeightMeasurementLimited || heightPix < mHeightMeasurementLimit);
boolean pageScaleChangeMeaningful =
!mWidthMeasurementIsFixed || contentHeightChangeMeaningful;
boolean layoutNeeded = (mContentWidthCss != widthCss && !mWidthMeasurementIsFixed) ||
(mContentHeightCss != heightCss && contentHeightChangeMeaningful) ||
(pageScaleChanged && pageScaleChangeMeaningful);
mContentWidthCss = widthCss;
mContentHeightCss = heightCss;
mPageScaleFactor = pageScaleFactor;
if (layoutNeeded) {
if (mFreezeLayoutRequests) {
mFrozenLayoutRequestPending = true;
} else {
mDelegate.requestLayout();
}
} else if (pageScaleChanged && mLastWidth != 0) {
// Because the fixed layout size is directly impacted by the pageScaleFactor we must
// update it even if the physical size of the view doesn't change.
updateFixedLayoutSize(mLastWidth, mLastHeight, mPageScaleFactor);
}
}
/**
* Calculate the size of the view.
* This is designed to be used to implement the android.view.View#onMeasure() method.
*/
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int contentHeightPix = (int) (mContentHeightCss * mPageScaleFactor * mDIPScale);
int contentWidthPix = (int) (mContentWidthCss * mPageScaleFactor * mDIPScale);
int measuredHeight = contentHeightPix;
int measuredWidth = contentWidthPix;
mLastMeasuredPageScaleFactor = mPageScaleFactor;
// Always use the given size unless unspecified. This matches WebViewClassic behavior.
mWidthMeasurementIsFixed = (widthMode != MeasureSpec.UNSPECIFIED);
mHeightMeasurementIsFixed = (heightMode == MeasureSpec.EXACTLY);
mHeightMeasurementLimited =
(heightMode == MeasureSpec.AT_MOST) && (contentHeightPix > heightSize);
mHeightMeasurementLimit = heightSize;
if (mHeightMeasurementIsFixed || mHeightMeasurementLimited) {
measuredHeight = heightSize;
}
if (mWidthMeasurementIsFixed) {
measuredWidth = widthSize;
}
if (measuredHeight < contentHeightPix) {
measuredHeight |= View.MEASURED_STATE_TOO_SMALL;
}
if (measuredWidth < contentWidthPix) {
measuredWidth |= View.MEASURED_STATE_TOO_SMALL;
}
mDelegate.setMeasuredDimension(measuredWidth, measuredHeight);
}
/**
* Notify the AwLayoutSizer that the size of the view has changed.
* This should be called by the Android view system after onMeasure if the view's size has
* changed.
*/
public void onSizeChanged(int w, int h, int ow, int oh) {
mLastWidth = w;
mLastHeight = h;
updateFixedLayoutSize(mLastWidth, mLastHeight, mLastMeasuredPageScaleFactor);
}
/**
* Notify the AwLayoutSizer that the layout pass requested via Delegate.requestLayout has
* completed.
* This should be called after onSizeChanged regardless of whether the size has changed or not.
*/
public void onLayoutChange() {
updateFixedLayoutSize(mLastWidth, mLastHeight, mLastMeasuredPageScaleFactor);
}
private void setFixedLayoutSize(int widthDip, int heightDip) {
if (widthDip == mLastSentFixedLayoutSizeWidth &&
heightDip == mLastSentFixedLayoutSizeHeight)
return;
mLastSentFixedLayoutSizeWidth = widthDip;
mLastSentFixedLayoutSizeHeight = heightDip;
mDelegate.setFixedLayoutSize(widthDip, heightDip);
}
// This needs to be called every time either the physical size of the view is changed or the
// pageScale is changed. Since we need to ensure that this is called immediately after
// onSizeChanged we can't just wait for onLayoutChange. At the same time we can't only make this
// call from onSizeChanged, since onSizeChanged won't fire if the view's physical size doesn't
// change.
private void updateFixedLayoutSize(int w, int h, float pageScaleFactor) {
boolean wrapContentForHeight = mDelegate.isLayoutParamsHeightWrapContent();
// If the WebView's size in the Android view system depends on the size of its contents then
// the viewport size cannot be directly calculated from the WebView's physical size as that
// can result in the layout being unstable (for example loading the following contents
// <div style="height:150%">a</a>
// would cause the WebView to indefinitely attempt to increase its height by 50%).
// If both the width and height are fixed (specified by the parent View) then content size
// changes will not cause subsequent layout passes and so we don't need to do anything
// special.
// We assume the width is 'fixed' if the parent View specified an EXACT or an AT_MOST
// measureSpec for the width (in which case the AT_MOST upper bound is the width).
// That means that the WebView will ignore LayoutParams.width set to WRAP_CONTENT and will
// instead try to take up as much width as possible. This is necessary because it's not
// practical to do web layout without a set width.
// For height the behavior is different because for a given width it is possible to
// calculate the minimum height required to display all of the content. As such the WebView
// can size itself vertically to match the content height. Because certain container views
// (LinearLayout with a WRAP_CONTENT height, for example) can result in onMeasure calls with
// both EXACTLY and AT_MOST height measureSpecs it is not possible to infer the sizing
// policy for the whole subtree based on the parameters passed to the onMeasure call.
// For that reason the LayoutParams.height property of the WebView is used. This behaves
// more predictably and means that toggling the fixedLayoutSize mode (which can have
// significant impact on how the web contents is laid out) is a direct consequence of the
// developer's choice. The downside is that it could result in the Android layout being
// unstable if a parent of the WebView has a wrap_content height while the WebView itself
// has height set to match_parent. Unfortunately addressing this edge case is costly so it
// will have to stay as is (this is compatible with Classic behavior).
if ((mWidthMeasurementIsFixed && !wrapContentForHeight) || pageScaleFactor == 0) {
setFixedLayoutSize(0, 0);
return;
}
final double dipAndPageScale = pageScaleFactor * mDIPScale;
final int contentWidthPix = (int) (mContentWidthCss * dipAndPageScale);
int widthDip = (int) Math.ceil(w / dipAndPageScale);
// Make sure that we don't introduce rounding errors if the viewport is to be exactly as
// wide as the contents.
if (w == contentWidthPix) {
widthDip = mContentWidthCss;
}
// This is workaround due to the fact that in wrap content mode we need to use a fixed
// layout size independent of view height, otherwise things like <div style="height:120%">
// cause the webview to grow indefinitely. We need to use a height independent of the
// webview's height. 0 is the value used in WebViewClassic.
setFixedLayoutSize(widthDip, FIXED_LAYOUT_HEIGHT);
}
}