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[fanfix.git] / src / jexer / TWidget.java

/*
 * Jexer - Java Text User Interface
 *
 * The MIT License (MIT)
 *
 * Copyright (C) 2017 Kevin Lamonte
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * @author Kevin Lamonte [kevin.lamonte@gmail.com]
 * @version 1
 */
package jexer;

import java.io.IOException;
import java.util.List;
import java.util.ArrayList;

import jexer.backend.Screen;
import jexer.bits.ColorTheme;
import jexer.event.TCommandEvent;
import jexer.event.TInputEvent;
import jexer.event.TKeypressEvent;
import jexer.event.TMenuEvent;
import jexer.event.TMouseEvent;
import jexer.event.TResizeEvent;
import jexer.menu.TMenu;
import jexer.ttree.TTreeItem;
import jexer.ttree.TTreeView;
import jexer.ttree.TTreeViewWidget;
import static jexer.TKeypress.*;

/**
 * TWidget is the base class of all objects that can be drawn on screen or
 * handle user input events.
 */
public abstract class TWidget implements Comparable<TWidget> {

    // ------------------------------------------------------------------------
    // Variables --------------------------------------------------------------
    // ------------------------------------------------------------------------

    /**
     * Every widget has a parent widget that it may be "contained" in.  For
     * example, a TWindow might contain several TFields, or a TComboBox may
     * contain a TList that itself contains a TVScroller.
     */
    private TWidget parent = null;

    /**
     * Child widgets that this widget contains.
     */
    private List<TWidget> children;

    /**
     * The currently active child widget that will receive keypress events.
     */
    private TWidget activeChild = null;

    /**
     * If true, this widget will receive events.
     */
    private boolean active = false;

    /**
     * The window that this widget draws to.
     */
    private TWindow window = null;

    /**
     * Absolute X position of the top-left corner.
     */
    private int x = 0;

    /**
     * Absolute Y position of the top-left corner.
     */
    private int y = 0;

    /**
     * Width.
     */
    private int width = 0;

    /**
     * Height.
     */
    private int height = 0;

    /**
     * My tab order inside a window or containing widget.
     */
    private int tabOrder = 0;

    /**
     * If true, this widget can be tabbed to or receive events.
     */
    private boolean enabled = true;

    /**
     * If true, this widget will be rendered.
     */
    private boolean visible = true;

    /**
     * If true, this widget has a cursor.
     */
    private boolean cursorVisible = false;

    /**
     * Cursor column position in relative coordinates.
     */
    private int cursorX = 0;

    /**
     * Cursor row position in relative coordinates.
     */
    private int cursorY = 0;

    // ------------------------------------------------------------------------
    // Constructors -----------------------------------------------------------
    // ------------------------------------------------------------------------

    /**
     * Default constructor for subclasses.
     */
    protected TWidget() {
        children = new ArrayList<TWidget>();
    }

    /**
     * Protected constructor.
     *
     * @param parent parent widget
     */
    protected TWidget(final TWidget parent) {
        this(parent, true);
    }

    /**
     * Protected constructor.
     *
     * @param parent parent widget
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of widget
     * @param height height of widget
     */
    protected TWidget(final TWidget parent, final int x, final int y,
        final int width, final int height) {

        this(parent, true, x, y, width, height);
    }

    /**
     * Protected constructor used by subclasses that are disabled by default.
     *
     * @param parent parent widget
     * @param enabled if true assume enabled
     */
    protected TWidget(final TWidget parent, final boolean enabled) {
        this.enabled = enabled;
        this.parent = parent;
        this.window = parent.window;
        children = new ArrayList<TWidget>();

        // Do not add TStatusBars, they are drawn by TApplication
        if (this instanceof TStatusBar) {
        } else {
            parent.addChild(this);
        }
    }

    /**
     * Protected constructor used by subclasses that are disabled by default.
     *
     * @param parent parent widget
     * @param enabled if true assume enabled
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of widget
     * @param height height of widget
     */
    protected TWidget(final TWidget parent, final boolean enabled,
        final int x, final int y, final int width, final int height) {

        this.enabled = enabled;
        this.parent = parent;
        this.window = parent.window;
        children = new ArrayList<TWidget>();

        // Do not add TStatusBars, they are drawn by TApplication
        if (this instanceof TStatusBar) {
        } else {
            parent.addChild(this);
        }

        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }

    /**
     * Backdoor access for TWindow's constructor.  ONLY TWindow USES THIS.
     *
     * @param window the top-level window
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of window
     * @param height height of window
     */
    protected final void setupForTWindow(final TWindow window,
        final int x, final int y, final int width, final int height) {

        this.parent = window;
        this.window = window;
        this.x      = x;
        this.y      = y;
        this.width  = width;
        this.height = height;
    }

    // ------------------------------------------------------------------------
    // Event handlers ---------------------------------------------------------
    // ------------------------------------------------------------------------

    /**
     * Check if a mouse press/release event coordinate is contained in this
     * widget.
     *
     * @param mouse a mouse-based event
     * @return whether or not a mouse click would be sent to this widget
     */
    public final boolean mouseWouldHit(final TMouseEvent mouse) {

        if (!enabled) {
            return false;
        }

        if ((this instanceof TTreeItem)
            && ((y < 0) || (y > parent.getHeight() - 1))
        ) {
            return false;
        }

        if ((mouse.getAbsoluteX() >= getAbsoluteX())
            && (mouse.getAbsoluteX() <  getAbsoluteX() + width)
            && (mouse.getAbsoluteY() >= getAbsoluteY())
            && (mouse.getAbsoluteY() <  getAbsoluteY() + height)
        ) {
            return true;
        }
        return false;
    }

    /**
     * Method that subclasses can override to handle keystrokes.
     *
     * @param keypress keystroke event
     */
    public void onKeypress(final TKeypressEvent keypress) {

        if ((children.size() == 0)
            || (this instanceof TTreeView)
            || (this instanceof TText)
        ) {

            // Defaults:
            //   tab / shift-tab - switch to next/previous widget
            //   left-arrow or up-arrow: same as shift-tab
            if ((keypress.equals(kbTab))
                || (keypress.equals(kbDown))
            ) {
                parent.switchWidget(true);
                return;
            } else if ((keypress.equals(kbShiftTab))
                || (keypress.equals(kbBackTab))
                || (keypress.equals(kbUp))
            ) {
                parent.switchWidget(false);
                return;
            }
        }

        if ((children.size() == 0)
            && !(this instanceof TTreeView)
        ) {

            // Defaults:
            //   right-arrow or down-arrow: same as tab
            if (keypress.equals(kbRight)) {
                parent.switchWidget(true);
                return;
            } else if (keypress.equals(kbLeft)) {
                parent.switchWidget(false);
                return;
            }
        }

        // If I have any buttons on me AND this is an Alt-key that matches
        // its mnemonic, send it an Enter keystroke
        for (TWidget widget: children) {
            if (widget instanceof TButton) {
                TButton button = (TButton) widget;
                if (button.isEnabled()
                    && !keypress.getKey().isFnKey()
                    && keypress.getKey().isAlt()
                    && !keypress.getKey().isCtrl()
                    && (Character.toLowerCase(button.getMnemonic().getShortcut())
                        == Character.toLowerCase(keypress.getKey().getChar()))
                ) {

                    widget.onKeypress(new TKeypressEvent(kbEnter));
                    return;
                }
            }
        }

        // Dispatch the keypress to an active widget
        for (TWidget widget: children) {
            if (widget.active) {
                widget.onKeypress(keypress);
                return;
            }
        }
    }

    /**
     * Method that subclasses can override to handle mouse button presses.
     *
     * @param mouse mouse button event
     */
    public void onMouseDown(final TMouseEvent mouse) {
        // Default: do nothing, pass to children instead
        for (int i = children.size() - 1 ; i >= 0 ; i--) {
            TWidget widget = children.get(i);
            if (widget.mouseWouldHit(mouse)) {
                // Dispatch to this child, also activate it
                activate(widget);

                // Set x and y relative to the child's coordinates
                mouse.setX(mouse.getAbsoluteX() - widget.getAbsoluteX());
                mouse.setY(mouse.getAbsoluteY() - widget.getAbsoluteY());
                widget.onMouseDown(mouse);
                return;
            }
        }
    }

    /**
     * Method that subclasses can override to handle mouse button releases.
     *
     * @param mouse mouse button event
     */
    public void onMouseUp(final TMouseEvent mouse) {
        // Default: do nothing, pass to children instead
        for (int i = children.size() - 1 ; i >= 0 ; i--) {
            TWidget widget = children.get(i);
            if (widget.mouseWouldHit(mouse)) {
                // Dispatch to this child, also activate it
                activate(widget);

                // Set x and y relative to the child's coordinates
                mouse.setX(mouse.getAbsoluteX() - widget.getAbsoluteX());
                mouse.setY(mouse.getAbsoluteY() - widget.getAbsoluteY());
                widget.onMouseUp(mouse);
                return;
            }
        }
    }

    /**
     * Method that subclasses can override to handle mouse movements.
     *
     * @param mouse mouse motion event
     */
    public void onMouseMotion(final TMouseEvent mouse) {
        // Default: do nothing, pass it on to ALL of my children.  This way
        // the children can see the mouse "leaving" their area.
        for (TWidget widget: children) {
            // Set x and y relative to the child's coordinates
            mouse.setX(mouse.getAbsoluteX() - widget.getAbsoluteX());
            mouse.setY(mouse.getAbsoluteY() - widget.getAbsoluteY());
            widget.onMouseMotion(mouse);
        }
    }

    /**
     * Method that subclasses can override to handle mouse button
     * double-clicks.
     *
     * @param mouse mouse button event
     */
    public void onMouseDoubleClick(final TMouseEvent mouse) {
        // Default: do nothing, pass to children instead
        for (int i = children.size() - 1 ; i >= 0 ; i--) {
            TWidget widget = children.get(i);
            if (widget.mouseWouldHit(mouse)) {
                // Dispatch to this child, also activate it
                activate(widget);

                // Set x and y relative to the child's coordinates
                mouse.setX(mouse.getAbsoluteX() - widget.getAbsoluteX());
                mouse.setY(mouse.getAbsoluteY() - widget.getAbsoluteY());
                widget.onMouseDoubleClick(mouse);
                return;
            }
        }
    }

    /**
     * Method that subclasses can override to handle window/screen resize
     * events.
     *
     * @param resize resize event
     */
    public void onResize(final TResizeEvent resize) {
        // Default: change my width/height.
        if (resize.getType() == TResizeEvent.Type.WIDGET) {
            width = resize.getWidth();
            height = resize.getHeight();
        } else {
            // Let children see the screen resize
            for (TWidget widget: children) {
                widget.onResize(resize);
            }
        }
    }

    /**
     * Method that subclasses can override to handle posted command events.
     *
     * @param command command event
     */
    public void onCommand(final TCommandEvent command) {
        // Default: do nothing, pass to children instead
        for (TWidget widget: children) {
            widget.onCommand(command);
        }
    }

    /**
     * Method that subclasses can override to handle menu or posted menu
     * events.
     *
     * @param menu menu event
     */
    public void onMenu(final TMenuEvent menu) {
        // Default: do nothing, pass to children instead
        for (TWidget widget: children) {
            widget.onMenu(menu);
        }
    }

    /**
     * Method that subclasses can override to do processing when the UI is
     * idle.  Note that repainting is NOT assumed.  To get a refresh after
     * onIdle, call doRepaint().
     */
    public void onIdle() {
        // Default: do nothing, pass to children instead
        for (TWidget widget: children) {
            widget.onIdle();
        }
    }

    /**
     * Consume event.  Subclasses that want to intercept all events in one go
     * can override this method.
     *
     * @param event keyboard, mouse, resize, command, or menu event
     */
    public void handleEvent(final TInputEvent event) {
        /*
        System.err.printf("TWidget (%s) event: %s\n", this.getClass().getName(),
            event);
        */

        if (!enabled) {
            // Discard event
            // System.err.println("   -- discard --");
            return;
        }

        if (event instanceof TKeypressEvent) {
            onKeypress((TKeypressEvent) event);
        } else if (event instanceof TMouseEvent) {

            TMouseEvent mouse = (TMouseEvent) event;

            switch (mouse.getType()) {

            case MOUSE_DOWN:
                onMouseDown(mouse);
                break;

            case MOUSE_UP:
                onMouseUp(mouse);
                break;

            case MOUSE_MOTION:
                onMouseMotion(mouse);
                break;

            case MOUSE_DOUBLE_CLICK:
                onMouseDoubleClick(mouse);
                break;

            default:
                throw new IllegalArgumentException("Invalid mouse event type: "
                    + mouse.getType());
            }
        } else if (event instanceof TResizeEvent) {
            onResize((TResizeEvent) event);
        } else if (event instanceof TCommandEvent) {
            onCommand((TCommandEvent) event);
        } else if (event instanceof TMenuEvent) {
            onMenu((TMenuEvent) event);
        }

        // Do nothing else
        return;
    }

    // ------------------------------------------------------------------------
    // TWidget ----------------------------------------------------------------
    // ------------------------------------------------------------------------

    /**
     * Get parent widget.
     *
     * @return parent widget
     */
    public final TWidget getParent() {
        return parent;
    }

    /**
     * Get the list of child widgets that this widget contains.
     *
     * @return the list of child widgets
     */
    public List<TWidget> getChildren() {
        return children;
    }

    /**
     * Get active flag.
     *
     * @return if true, this widget will receive events
     */
    public final boolean isActive() {
        return active;
    }

    /**
     * Set active flag.
     *
     * @param active if true, this widget will receive events
     */
    public final void setActive(final boolean active) {
        this.active = active;
    }

    /**
     * Get the window this widget is on.
     *
     * @return the window
     */
    public final TWindow getWindow() {
        return window;
    }

    /**
     * Get X position.
     *
     * @return absolute X position of the top-left corner
     */
    public final int getX() {
        return x;
    }

    /**
     * Set X position.
     *
     * @param x absolute X position of the top-left corner
     */
    public final void setX(final int x) {
        this.x = x;
    }

    /**
     * Get Y position.
     *
     * @return absolute Y position of the top-left corner
     */
    public final int getY() {
        return y;
    }

    /**
     * Set Y position.
     *
     * @param y absolute Y position of the top-left corner
     */
    public final void setY(final int y) {
        this.y = y;
    }

    /**
     * Get the width.
     *
     * @return widget width
     */
    public final int getWidth() {
        return this.width;
    }

    /**
     * Change the width.
     *
     * @param width new widget width
     */
    public final void setWidth(final int width) {
        this.width = width;
    }

    /**
     * Get the height.
     *
     * @return widget height
     */
    public final int getHeight() {
        return this.height;
    }

    /**
     * Change the height.
     *
     * @param height new widget height
     */
    public final void setHeight(final int height) {
        this.height = height;
    }

    /**
     * Change the dimensions.
     *
     * @param x absolute X position of the top-left corner
     * @param y absolute Y position of the top-left corner
     * @param width new widget width
     * @param height new widget height
     */
    public final void setDimensions(final int x, final int y, final int width,
        final int height) {

        setX(x);
        setY(y);
        setWidth(width);
        setHeight(height);
    }

    /**
     * Get enabled flag.
     *
     * @return if true, this widget can be tabbed to or receive events
     */
    public final boolean isEnabled() {
        return enabled;
    }

    /**
     * Set enabled flag.
     *
     * @param enabled if true, this widget can be tabbed to or receive events
     */
    public final void setEnabled(final boolean enabled) {
        this.enabled = enabled;
        if (!enabled) {
            active = false;
            // See if there are any active siblings to switch to
            boolean foundSibling = false;
            if (parent != null) {
                for (TWidget w: parent.children) {
                    if ((w.enabled)
                        && !(this instanceof THScroller)
                        && !(this instanceof TVScroller)
                    ) {
                        parent.activate(w);
                        foundSibling = true;
                        break;
                    }
                }
                if (!foundSibling) {
                    parent.activeChild = null;
                }
            }
        }
    }

    /**
     * Set visible flag.
     *
     * @param visible if true, this widget will be drawn
     */
    public final void setVisible(final boolean visible) {
        this.visible = visible;
    }

    /**
     * See if this widget is visible.
     *
     * @return if true, this widget will be drawn
     */
    public final boolean isVisible() {
        return visible;
    }

    /**
     * Set visible cursor flag.
     *
     * @param cursorVisible if true, this widget has a cursor
     */
    public final void setCursorVisible(final boolean cursorVisible) {
        this.cursorVisible = cursorVisible;
    }

    /**
     * See if this widget has a visible cursor.
     *
     * @return if true, this widget has a visible cursor
     */
    public final boolean isCursorVisible() {
        // If cursor is out of my bounds, it is not visible.
        if ((cursorX >= width)
            || (cursorX < 0)
            || (cursorY >= height)
            || (cursorY < 0)
        ) {
            return false;
        }

        // If cursor is out of my window's bounds, it is not visible.
        if ((getCursorAbsoluteX() >= window.getAbsoluteX()
                + window.getWidth() - 1)
            || (getCursorAbsoluteX() < 0)
            || (getCursorAbsoluteY() >= window.getAbsoluteY()
                + window.getHeight() - 1)
            || (getCursorAbsoluteY() < 0)
        ) {
            return false;
        }
        return cursorVisible;
    }

    /**
     * Get cursor X value.
     *
     * @return cursor column position in relative coordinates
     */
    public final int getCursorX() {
        return cursorX;
    }

    /**
     * Set cursor X value.
     *
     * @param cursorX column position in relative coordinates
     */
    public final void setCursorX(final int cursorX) {
        this.cursorX = cursorX;
    }

    /**
     * Get cursor Y value.
     *
     * @return cursor row position in relative coordinates
     */
    public final int getCursorY() {
        return cursorY;
    }

    /**
     * Set cursor Y value.
     *
     * @param cursorY row position in relative coordinates
     */
    public final void setCursorY(final int cursorY) {
        this.cursorY = cursorY;
    }

    /**
     * Get this TWidget's parent TApplication.
     *
     * @return the parent TApplication
     */
    public TApplication getApplication() {
        return window.getApplication();
    }

    /**
     * Get the Screen.
     *
     * @return the Screen
     */
    public Screen getScreen() {
        return window.getScreen();
    }

    /**
     * Comparison operator.  For various subclasses it sorts on:
     * <ul>
     * <li>tabOrder for TWidgets</li>
     * <li>z for TWindows</li>
     * <li>text for TTreeItems</li>
     * </ul>
     *
     * @param that another TWidget, TWindow, or TTreeItem instance
     * @return difference between this.tabOrder and that.tabOrder, or
     * difference between this.z and that.z, or String.compareTo(text)
     */
    public final int compareTo(final TWidget that) {
        if ((this instanceof TWindow)
            && (that instanceof TWindow)
        ) {
            return (((TWindow) this).getZ() - ((TWindow) that).getZ());
        }
        if ((this instanceof TTreeItem)
            && (that instanceof TTreeItem)
        ) {
            return (((TTreeItem) this).getText().compareTo(
                ((TTreeItem) that).getText()));
        }
        return (this.tabOrder - that.tabOrder);
    }

    /**
     * See if this widget should render with the active color.
     *
     * @return true if this widget is active and all of its parents are
     * active.
     */
    public final boolean isAbsoluteActive() {
        if (parent == this) {
            return active;
        }
        return (active && parent.isAbsoluteActive());
    }

    /**
     * Returns the cursor X position.
     *
     * @return absolute screen column number for the cursor's X position
     */
    public final int getCursorAbsoluteX() {
        return getAbsoluteX() + cursorX;
    }

    /**
     * Returns the cursor Y position.
     *
     * @return absolute screen row number for the cursor's Y position
     */
    public final int getCursorAbsoluteY() {
        return getAbsoluteY() + cursorY;
    }

    /**
     * Compute my absolute X position as the sum of my X plus all my parent's
     * X's.
     *
     * @return absolute screen column number for my X position
     */
    public final int getAbsoluteX() {
        assert (parent != null);
        if (parent == this) {
            return x;
        }
        if ((parent instanceof TWindow)
            && !(parent instanceof TMenu)
            && !(parent instanceof TDesktop)
        ) {
            // Widgets on a TWindow have (0,0) as their top-left, but this is
            // actually the TWindow's (1,1).
            return parent.getAbsoluteX() + x + 1;
        }
        return parent.getAbsoluteX() + x;
    }

    /**
     * Compute my absolute Y position as the sum of my Y plus all my parent's
     * Y's.
     *
     * @return absolute screen row number for my Y position
     */
    public final int getAbsoluteY() {
        assert (parent != null);
        if (parent == this) {
            return y;
        }
        if ((parent instanceof TWindow)
            && !(parent instanceof TMenu)
            && !(parent instanceof TDesktop)
        ) {
            // Widgets on a TWindow have (0,0) as their top-left, but this is
            // actually the TWindow's (1,1).
            return parent.getAbsoluteY() + y + 1;
        }
        return parent.getAbsoluteY() + y;
    }

    /**
     * Get the global color theme.
     *
     * @return the ColorTheme
     */
    public final ColorTheme getTheme() {
        return window.getApplication().getTheme();
    }

    /**
     * Draw my specific widget.  When called, the screen rectangle I draw
     * into is already setup (offset and clipping).
     */
    public void draw() {
        // Default widget draws nothing.
    }

    /**
     * Called by parent to render to TWindow.
     */
    public final void drawChildren() {
        // Set my clipping rectangle
        assert (window != null);
        assert (getScreen() != null);
        Screen screen = getScreen();

        // Special case: TStatusBar is drawn by TApplication, not anything
        // else.
        if (this instanceof TStatusBar) {
            return;
        }

        screen.setClipRight(width);
        screen.setClipBottom(height);

        int absoluteRightEdge = window.getAbsoluteX() + window.getWidth();
        int absoluteBottomEdge = window.getAbsoluteY() + window.getHeight();
        if (!(this instanceof TWindow) && !(this instanceof TVScroller)) {
            absoluteRightEdge -= 1;
        }
        if (!(this instanceof TWindow) && !(this instanceof THScroller)) {
            absoluteBottomEdge -= 1;
        }
        int myRightEdge = getAbsoluteX() + width;
        int myBottomEdge = getAbsoluteY() + height;
        if (getAbsoluteX() > absoluteRightEdge) {
            // I am offscreen
            screen.setClipRight(0);
        } else if (myRightEdge > absoluteRightEdge) {
            screen.setClipRight(screen.getClipRight()
                - (myRightEdge - absoluteRightEdge));
        }
        if (getAbsoluteY() > absoluteBottomEdge) {
            // I am offscreen
            screen.setClipBottom(0);
        } else if (myBottomEdge > absoluteBottomEdge) {
            screen.setClipBottom(screen.getClipBottom()
                - (myBottomEdge - absoluteBottomEdge));
        }

        // Set my offset
        screen.setOffsetX(getAbsoluteX());
        screen.setOffsetY(getAbsoluteY());

        // Draw me
        draw();

        // Continue down the chain
        for (TWidget widget: children) {
            if (widget.isVisible()) {
                widget.drawChildren();
            }
        }
    }

    /**
     * Repaint the screen on the next update.
     */
    public final void doRepaint() {
        window.getApplication().doRepaint();
    }

    /**
     * Add a child widget to my list of children.  We set its tabOrder to 0
     * and increment the tabOrder of all other children.
     *
     * @param child TWidget to add
     */
    private void addChild(final TWidget child) {
        children.add(child);

        if ((child.enabled)
            && !(child instanceof THScroller)
            && !(child instanceof TVScroller)
        ) {
            for (TWidget widget: children) {
                widget.active = false;
            }
            child.active = true;
            activeChild = child;
        }
        for (int i = 0; i < children.size(); i++) {
            children.get(i).tabOrder = i;
        }
    }

    /**
     * Switch the active child.
     *
     * @param child TWidget to activate
     */
    public final void activate(final TWidget child) {
        assert (child.enabled);
        if ((child instanceof THScroller)
            || (child instanceof TVScroller)
        ) {
            return;
        }

        if (child != activeChild) {
            if (activeChild != null) {
                activeChild.active = false;
            }
            child.active = true;
            activeChild = child;
        }
    }

    /**
     * Switch the active child.
     *
     * @param tabOrder tabOrder of the child to activate.  If that child
     * isn't enabled, then the next enabled child will be activated.
     */
    public final void activate(final int tabOrder) {
        if (activeChild == null) {
            return;
        }
        TWidget child = null;
        for (TWidget widget: children) {
            if ((widget.enabled)
                && !(widget instanceof THScroller)
                && !(widget instanceof TVScroller)
                && (widget.tabOrder >= tabOrder)
            ) {
                child = widget;
                break;
            }
        }
        if ((child != null) && (child != activeChild)) {
            activeChild.active = false;
            assert (child.enabled);
            child.active = true;
            activeChild = child;
        }
    }

    /**
     * Switch the active widget with the next in the tab order.
     *
     * @param forward if true, then switch to the next enabled widget in the
     * list, otherwise switch to the previous enabled widget in the list
     */
    public final void switchWidget(final boolean forward) {

        // Only switch if there are multiple enabled widgets
        if ((children.size() < 2) || (activeChild == null)) {
            return;
        }

        int tabOrder = activeChild.tabOrder;
        do {
            if (forward) {
                tabOrder++;
            } else {
                tabOrder--;
            }
            if (tabOrder < 0) {

                // If at the end, pass the switch to my parent.
                if ((!forward) && (parent != this)) {
                    parent.switchWidget(forward);
                    return;
                }

                tabOrder = children.size() - 1;
            } else if (tabOrder == children.size()) {
                // If at the end, pass the switch to my parent.
                if ((forward) && (parent != this)) {
                    parent.switchWidget(forward);
                    return;
                }

                tabOrder = 0;
            }
            if (activeChild.tabOrder == tabOrder) {
                // We wrapped around
                break;
            }
        } while ((!children.get(tabOrder).enabled)
            && !(children.get(tabOrder) instanceof THScroller)
            && !(children.get(tabOrder) instanceof TVScroller));

        assert (children.get(tabOrder).enabled);

        activeChild.active = false;
        children.get(tabOrder).active = true;
        activeChild = children.get(tabOrder);
    }

    /**
     * Returns my active widget.
     *
     * @return widget that is active, or this if no children
     */
    public TWidget getActiveChild() {
        if ((this instanceof THScroller)
            || (this instanceof TVScroller)
        ) {
            return parent;
        }

        for (TWidget widget: children) {
            if (widget.active) {
                return widget.getActiveChild();
            }
        }
        // No active children, return me
        return this;
    }

    // ------------------------------------------------------------------------
    // Other TWidget constructors ---------------------------------------------
    // ------------------------------------------------------------------------

    /**
     * Convenience function to add a label to this container/window.
     *
     * @param text label
     * @param x column relative to parent
     * @param y row relative to parent
     * @return the new label
     */
    public final TLabel addLabel(final String text, final int x, final int y) {
        return addLabel(text, x, y, "tlabel");
    }

    /**
     * Convenience function to add a label to this container/window.
     *
     * @param text label
     * @param x column relative to parent
     * @param y row relative to parent
     * @param colorKey ColorTheme key color to use for foreground text.
     * Default is "tlabel"
     * @return the new label
     */
    public final TLabel addLabel(final String text, final int x, final int y,
        final String colorKey) {

        return new TLabel(this, text, x, y, colorKey);
    }

    /**
     * Convenience function to add a label to this container/window.
     *
     * @param text label
     * @param x column relative to parent
     * @param y row relative to parent
     * @param colorKey ColorTheme key color to use for foreground text.
     * Default is "tlabel"
     * @param useWindowBackground if true, use the window's background color
     * @return the new label
     */
    public final TLabel addLabel(final String text, final int x, final int y,
        final String colorKey, final boolean useWindowBackground) {

        return new TLabel(this, text, x, y, colorKey, useWindowBackground);
    }

    /**
     * Convenience function to add a button to this container/window.
     *
     * @param text label on the button
     * @param x column relative to parent
     * @param y row relative to parent
     * @param action action to call when button is pressed
     * @return the new button
     */
    public final TButton addButton(final String text, final int x, final int y,
        final TAction action) {

        return new TButton(this, text, x, y, action);
    }

    /**
     * Convenience function to add a checkbox to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param label label to display next to (right of) the checkbox
     * @param checked initial check state
     * @return the new checkbox
     */
    public final TCheckBox addCheckBox(final int x, final int y,
        final String label, final boolean checked) {

        return new TCheckBox(this, x, y, label, checked);
    }

    /**
     * Convenience function to add a combobox to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible combobox width, including the down-arrow
     * @param values the possible values for the box, shown in the drop-down
     * @param valuesIndex the initial index in values, or -1 for no default
     * value
     * @param valuesHeight the height of the values drop-down when it is
     * visible
     * @param updateAction action to call when a new value is selected from
     * the list or enter is pressed in the edit field
     * @return the new combobox
     */
    public final TComboBox addComboBox(final int x, final int y,
        final int width, final List<String> values, final int valuesIndex,
        final int valuesHeight, final TAction updateAction) {

        return new TComboBox(this, x, y, width, values, valuesIndex,
            valuesHeight, updateAction);
    }

    /**
     * Convenience function to add a spinner to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param upAction action to call when the up arrow is clicked or pressed
     * @param downAction action to call when the down arrow is clicked or
     * pressed
     * @return the new spinner
     */
    public final TSpinner addSpinner(final int x, final int y,
        final TAction upAction, final TAction downAction) {

        return new TSpinner(this, x, y, upAction, downAction);
    }

    /**
     * Convenience function to add a calendar to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param updateAction action to call when the user changes the value of
     * the calendar
     * @return the new calendar
     */
    public final TCalendar addCalendar(final int x, final int y,
        final TAction updateAction) {

        return new TCalendar(this, x, y, updateAction);
    }

    /**
     * Convenience function to add a progress bar to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of progress bar
     * @param value initial value of percent complete
     * @return the new progress bar
     */
    public final TProgressBar addProgressBar(final int x, final int y,
        final int width, final int value) {

        return new TProgressBar(this, x, y, width, value);
    }

    /**
     * Convenience function to add a radio button group to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param label label to display on the group box
     * @return the new radio button group
     */
    public final TRadioGroup addRadioGroup(final int x, final int y,
        final String label) {

        return new TRadioGroup(this, x, y, label);
    }

    /**
     * Convenience function to add a text field to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @return the new text field
     */
    public final TField addField(final int x, final int y,
        final int width, final boolean fixed) {

        return new TField(this, x, y, width, fixed);
    }

    /**
     * Convenience function to add a text field to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @param text initial text, default is empty string
     * @return the new text field
     */
    public final TField addField(final int x, final int y,
        final int width, final boolean fixed, final String text) {

        return new TField(this, x, y, width, fixed, text);
    }

    /**
     * Convenience function to add a text field to this container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @param text initial text, default is empty string
     * @param enterAction function to call when enter key is pressed
     * @param updateAction function to call when the text is updated
     * @return the new text field
     */
    public final TField addField(final int x, final int y,
        final int width, final boolean fixed, final String text,
        final TAction enterAction, final TAction updateAction) {

        return new TField(this, x, y, width, fixed, text, enterAction,
            updateAction);
    }

    /**
     * Convenience function to add a scrollable text box to this
     * container/window.
     *
     * @param text text on the screen
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @param colorKey ColorTheme key color to use for foreground text
     * @return the new text box
     */
    public final TText addText(final String text, final int x,
        final int y, final int width, final int height, final String colorKey) {

        return new TText(this, text, x, y, width, height, colorKey);
    }

    /**
     * Convenience function to add a scrollable text box to this
     * container/window.
     *
     * @param text text on the screen
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @return the new text box
     */
    public final TText addText(final String text, final int x, final int y,
        final int width, final int height) {

        return new TText(this, text, x, y, width, height, "ttext");
    }

    /**
     * Convenience function to add an editable text area box to this
     * container/window.
     *
     * @param text text on the screen
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @return the new text box
     */
    public final TEditorWidget addEditor(final String text, final int x,
        final int y, final int width, final int height) {

        return new TEditorWidget(this, text, x, y, width, height);
    }

    /**
     * Convenience function to spawn a message box.
     *
     * @param title window title, will be centered along the top border
     * @param caption message to display.  Use embedded newlines to get a
     * multi-line box.
     * @return the new message box
     */
    public final TMessageBox messageBox(final String title,
        final String caption) {

        return getApplication().messageBox(title, caption, TMessageBox.Type.OK);
    }

    /**
     * Convenience function to spawn a message box.
     *
     * @param title window title, will be centered along the top border
     * @param caption message to display.  Use embedded newlines to get a
     * multi-line box.
     * @param type one of the TMessageBox.Type constants.  Default is
     * Type.OK.
     * @return the new message box
     */
    public final TMessageBox messageBox(final String title,
        final String caption, final TMessageBox.Type type) {

        return getApplication().messageBox(title, caption, type);
    }

    /**
     * Convenience function to spawn an input box.
     *
     * @param title window title, will be centered along the top border
     * @param caption message to display.  Use embedded newlines to get a
     * multi-line box.
     * @return the new input box
     */
    public final TInputBox inputBox(final String title, final String caption) {

        return getApplication().inputBox(title, caption);
    }

    /**
     * Convenience function to spawn an input box.
     *
     * @param title window title, will be centered along the top border
     * @param caption message to display.  Use embedded newlines to get a
     * multi-line box.
     * @param text initial text to seed the field with
     * @return the new input box
     */
    public final TInputBox inputBox(final String title, final String caption,
        final String text) {

        return getApplication().inputBox(title, caption, text);
    }

    /**
     * Convenience function to add a password text field to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @return the new text field
     */
    public final TPasswordField addPasswordField(final int x, final int y,
        final int width, final boolean fixed) {

        return new TPasswordField(this, x, y, width, fixed);
    }

    /**
     * Convenience function to add a password text field to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @param text initial text, default is empty string
     * @return the new text field
     */
    public final TPasswordField addPasswordField(final int x, final int y,
        final int width, final boolean fixed, final String text) {

        return new TPasswordField(this, x, y, width, fixed, text);
    }

    /**
     * Convenience function to add a password text field to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width visible text width
     * @param fixed if true, the text cannot exceed the display width
     * @param text initial text, default is empty string
     * @param enterAction function to call when enter key is pressed
     * @param updateAction function to call when the text is updated
     * @return the new text field
     */
    public final TPasswordField addPasswordField(final int x, final int y,
        final int width, final boolean fixed, final String text,
        final TAction enterAction, final TAction updateAction) {

        return new TPasswordField(this, x, y, width, fixed, text, enterAction,
            updateAction);
    }

    /**
     * Convenience function to add a scrollable tree view to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of tree view
     * @param height height of tree view
     * @return the new tree view
     */
    public final TTreeViewWidget addTreeViewWidget(final int x, final int y,
        final int width, final int height) {

        return new TTreeViewWidget(this, x, y, width, height);
    }

    /**
     * Convenience function to add a scrollable tree view to this
     * container/window.
     *
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of tree view
     * @param height height of tree view
     * @param action action to perform when an item is selected
     * @return the new tree view
     */
    public final TTreeViewWidget addTreeViewWidget(final int x, final int y,
        final int width, final int height, final TAction action) {

        return new TTreeViewWidget(this, x, y, width, height, action);
    }

    /**
     * Convenience function to spawn a file open box.
     *
     * @param path path of selected file
     * @return the result of the new file open box
     * @throws IOException if a java.io operation throws
     */
    public final String fileOpenBox(final String path) throws IOException {
        return getApplication().fileOpenBox(path);
    }

    /**
     * Convenience function to spawn a file open box.
     *
     * @param path path of selected file
     * @param type one of the Type constants
     * @return the result of the new file open box
     * @throws IOException if a java.io operation throws
     */
    public final String fileOpenBox(final String path,
        final TFileOpenBox.Type type) throws IOException {

        return getApplication().fileOpenBox(path, type);
    }
    /**
     * Convenience function to add a directory list to this container/window.
     *
     * @param path directory path, must be a directory
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @return the new directory list
     */
    public final TDirectoryList addDirectoryList(final String path, final int x,
        final int y, final int width, final int height) {

        return new TDirectoryList(this, path, x, y, width, height, null);
    }

    /**
     * Convenience function to add a directory list to this container/window.
     *
     * @param path directory path, must be a directory
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @param action action to perform when an item is selected
     * @return the new directory list
     */
    public final TDirectoryList addDirectoryList(final String path, final int x,
        final int y, final int width, final int height, final TAction action) {

        return new TDirectoryList(this, path, x, y, width, height, action);
    }

    /**
     * Convenience function to add a directory list to this container/window.
     *
     * @param strings list of strings to show
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @return the new directory list
     */
    public final TList addList(final List<String> strings, final int x,
        final int y, final int width, final int height) {

        return new TList(this, strings, x, y, width, height, null);
    }

    /**
     * Convenience function to add a directory list to this container/window.
     *
     * @param strings list of strings to show
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @param enterAction action to perform when an item is selected
     * @return the new directory list
     */
    public final TList addList(final List<String> strings, final int x,
        final int y, final int width, final int height,
        final TAction enterAction) {

        return new TList(this, strings, x, y, width, height, enterAction);
    }

    /**
     * Convenience function to add a directory list to this container/window.
     *
     * @param strings list of strings to show
     * @param x column relative to parent
     * @param y row relative to parent
     * @param width width of text area
     * @param height height of text area
     * @param enterAction action to perform when an item is selected
     * @param moveAction action to perform when the user navigates to a new
     * item with arrow/page keys
     * @return the new directory list
     */
    public final TList addList(final List<String> strings, final int x,
        final int y, final int width, final int height,
        final TAction enterAction, final TAction moveAction) {

        return new TList(this, strings, x, y, width, height, enterAction,
            moveAction);
    }

}