/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.view;
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import android.graphics.Canvas;
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import android.graphics.Color;
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import android.graphics.Paint;
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import android.graphics.Rect;
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import android.graphics.RectF;
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/**
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* Helper class for drawing round scroll bars on round Wear devices.
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*/
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class RoundScrollbarRenderer {
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// The range of the scrollbar position represented as an angle in degrees.
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private static final int SCROLLBAR_ANGLE_RANGE = 90;
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private static final int MAX_SCROLLBAR_ANGLE_SWIPE = 16;
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private static final int MIN_SCROLLBAR_ANGLE_SWIPE = 6;
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private static final float WIDTH_PERCENTAGE = 0.02f;
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private static final int DEFAULT_THUMB_COLOR = 0xFFE8EAED;
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private static final int DEFAULT_TRACK_COLOR = 0x4CFFFFFF;
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private final Paint mThumbPaint = new Paint();
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private final Paint mTrackPaint = new Paint();
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private final RectF mRect = new RectF();
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private final View mParent;
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private final int mMaskThickness;
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public RoundScrollbarRenderer(View parent) {
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// Paints for the round scrollbar.
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// Set up the thumb paint
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mThumbPaint.setAntiAlias(true);
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mThumbPaint.setStrokeCap(Paint.Cap.ROUND);
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mThumbPaint.setStyle(Paint.Style.STROKE);
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// Set up the track paint
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mTrackPaint.setAntiAlias(true);
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mTrackPaint.setStrokeCap(Paint.Cap.ROUND);
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mTrackPaint.setStyle(Paint.Style.STROKE);
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mParent = parent;
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// Fetch the resource indicating the thickness of CircularDisplayMask, rounding in the same
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// way WindowManagerService.showCircularMask does. The scroll bar is inset by this amount so
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// that it doesn't get clipped.
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mMaskThickness = parent.getContext().getResources().getDimensionPixelSize(
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com.android.internal.R.dimen.circular_display_mask_thickness);
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}
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public void drawRoundScrollbars(Canvas canvas, float alpha, Rect bounds) {
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if (alpha == 0) {
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return;
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}
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// Get information about the current scroll state of the parent view.
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float maxScroll = mParent.computeVerticalScrollRange();
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float scrollExtent = mParent.computeVerticalScrollExtent();
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if (scrollExtent <= 0 || maxScroll <= scrollExtent) {
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return;
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}
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float currentScroll = Math.max(0, mParent.computeVerticalScrollOffset());
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float linearThumbLength = mParent.computeVerticalScrollExtent();
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float thumbWidth = mParent.getWidth() * WIDTH_PERCENTAGE;
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mThumbPaint.setStrokeWidth(thumbWidth);
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mTrackPaint.setStrokeWidth(thumbWidth);
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setThumbColor(applyAlpha(DEFAULT_THUMB_COLOR, alpha));
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setTrackColor(applyAlpha(DEFAULT_TRACK_COLOR, alpha));
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// Normalize the sweep angle for the scroll bar.
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float sweepAngle = (linearThumbLength / maxScroll) * SCROLLBAR_ANGLE_RANGE;
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sweepAngle = clamp(sweepAngle, MIN_SCROLLBAR_ANGLE_SWIPE, MAX_SCROLLBAR_ANGLE_SWIPE);
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// Normalize the start angle so that it falls on the track.
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float startAngle = (currentScroll * (SCROLLBAR_ANGLE_RANGE - sweepAngle))
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/ (maxScroll - linearThumbLength) - SCROLLBAR_ANGLE_RANGE / 2;
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startAngle = clamp(startAngle, -SCROLLBAR_ANGLE_RANGE / 2,
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SCROLLBAR_ANGLE_RANGE / 2 - sweepAngle);
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// Draw the track and the thumb.
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float inset = thumbWidth / 2 + mMaskThickness;
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mRect.set(
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bounds.left + inset,
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bounds.top + inset,
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bounds.right - inset,
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bounds.bottom - inset);
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canvas.drawArc(mRect, -SCROLLBAR_ANGLE_RANGE / 2, SCROLLBAR_ANGLE_RANGE, false,
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mTrackPaint);
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canvas.drawArc(mRect, startAngle, sweepAngle, false, mThumbPaint);
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}
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private static float clamp(float val, float min, float max) {
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if (val < min) {
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return min;
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} else if (val > max) {
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return max;
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} else {
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return val;
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}
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}
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private static int applyAlpha(int color, float alpha) {
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int alphaByte = (int) (Color.alpha(color) * alpha);
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return Color.argb(alphaByte, Color.red(color), Color.green(color), Color.blue(color));
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}
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private void setThumbColor(int thumbColor) {
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if (mThumbPaint.getColor() != thumbColor) {
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mThumbPaint.setColor(thumbColor);
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}
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}
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private void setTrackColor(int trackColor) {
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if (mTrackPaint.getColor() != trackColor) {
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mTrackPaint.setColor(trackColor);
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}
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}
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}
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