tachiyomi/app/src/main/res/layout/reader_activity.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:gravity="center">

    <FrameLayout
        android:id="@+id/reader_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/reader"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </FrameLayout>

        <ProgressBar
            android:id="@+id/please_wait"
            style="?android:attr/progressBarStyleLarge"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"/>

        <eu.kanade.tachiyomi.ui.reader.PageIndicatorTextView
            android:id="@+id/page_number"
            style="@style/TextAppearance.Regular.Caption"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center_horizontal"
            android:padding="4dp"
            android:textColor="@color/md_white_1000"
            android:textStyle="bold"
            android:shadowRadius="3"
            android:shadowDy="0"
            android:shadowDx="0"
            android:shadowColor="@color/md_black_1000"/>

    </FrameLayout>

    <FrameLayout
        android:id="@+id/reader_menu"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        android:visibility="invisible"
        tools:visibility="visible">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?colorPrimary"
            android:elevation="4dp"
            android:theme="?attr/actionBarTheme"/>

        <LinearLayout
            android:id="@+id/reader_menu_bottom"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:layout_gravity="bottom"
            android:gravity="center"
            android:background="?colorPrimary"
            android:orientation="horizontal"
            android:focusable="false"
            android:descendantFocusability="blocksDescendants">

            <ImageButton
                android:id="@+id/left_chapter"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="@dimen/material_layout_keylines_screen_edge_margin"
                android:background="?android:selectableItemBackground"
                app:srcCompat="@drawable/ic_skip_previous_white_24dp"/>

            <TextView
                android:id="@+id/left_page_text"
                android:layout_width="32dp"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:textSize="15sp"/>

            <SeekBar
                android:id="@+id/page_seekbar"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"/>

            <TextView
                android:id="@+id/right_page_text"
                android:layout_width="32dp"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:textSize="15sp"/>

            <ImageButton
                android:id="@+id/right_chapter"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:padding="@dimen/material_layout_keylines_screen_edge_margin"
                android:background="?android:selectableItemBackground"
                app:srcCompat="@drawable/ic_skip_next_white_24dp"/>

        </LinearLayout>

    </FrameLayout>

    <View
        android:id="@+id/brightness_overlay"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"/>

    <View
        android:id="@+id/color_overlay"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"/>

</FrameLayout>