IGUIScrollBar.h

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/* Copyright (C) 2021 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
    A GUI Scrollbar, this class doesn't present all functionality
    to the scrollbar, it just controls the drawing and a wrapper
    for interaction with it.
*/

#ifndef INCLUDED_IGUISCROLLBAR
#define INCLUDED_IGUISCROLLBAR

#include "gui/CGUISprite.h"
#include "maths/Vector2D.h"
#include "ps/CStr.h"

class CCanvas2D;
class CGUI;
class IGUIScrollBarOwner;
struct SGUIMessage;

/**
 * The GUI Scroll-bar style. Tells us how scroll-bars look and feel.
 *
 * A scroll-bar style can choose whether to support horizontal, vertical
 * or both.
 *
 * @see IGUIScrollBar
 */
struct SGUIScrollBarStyle
{
    // CGUISpriteInstance makes this NONCOPYABLE implicitly, make it explicit
    NONCOPYABLE(SGUIScrollBarStyle);
    MOVABLE(SGUIScrollBarStyle);
    SGUIScrollBarStyle() = default;

    //--------------------------------------------------------
    /** @name General Settings */
    //--------------------------------------------------------
    //@{

    /**
     * Width of bar, also both sides of the edge buttons.
     */
    float m_Width;

    /**
     * Scrollable with the wheel.
     */
    bool m_ScrollWheel;

    /**
     * How much (in percent, 0.1f = 10%) to scroll each time
     * the wheel is admitted, or the buttons are pressed.
     */
    float m_ScrollSpeed;

    /**
     * Whether or not the edge buttons should appear or not. Sometimes
     * you actually don't want them, like perhaps in a combo box.
     */
    bool m_ScrollButtons;

    /**
     * Sometimes there is *a lot* to scroll, but to prevent the scroll "bar"
     * from being almost invisible (or ugly), you can set a minimum in pixel
     * size.
     */
    float m_MinimumBarSize;

    /**
     * Sometimes you would like your scroll bar to have a fixed maximum size
     * so that the texture does not get too stretched, you can set a maximum
     * in pixels.
     */
    float m_MaximumBarSize;

    /**
     * True if you want edge buttons, i.e. buttons that can be pressed in order
     * to scroll.
     */
    bool m_UseEdgeButtons;

    //@}
    //--------------------------------------------------------
    /** @name Vertical Sprites */
    //--------------------------------------------------------
    //@{

    CGUISpriteInstance m_SpriteButtonTop;
    CGUISpriteInstance m_SpriteButtonTopPressed;
    CGUISpriteInstance m_SpriteButtonTopDisabled;
    CGUISpriteInstance m_SpriteButtonTopOver;

    CGUISpriteInstance m_SpriteButtonBottom;
    CGUISpriteInstance m_SpriteButtonBottomPressed;
    CGUISpriteInstance m_SpriteButtonBottomDisabled;
    CGUISpriteInstance m_SpriteButtonBottomOver;

    CGUISpriteInstance m_SpriteBarVertical;
    CGUISpriteInstance m_SpriteBarVerticalOver;
    CGUISpriteInstance m_SpriteBarVerticalPressed;

    CGUISpriteInstance m_SpriteBackVertical;

    //@}
    //--------------------------------------------------------
    /** @name Horizontal Sprites */
    //--------------------------------------------------------
    //@{

    CGUISpriteInstance m_SpriteButtonLeft;
    CGUISpriteInstance m_SpriteButtonLeftPressed;
    CGUISpriteInstance m_SpriteButtonLeftDisabled;

    CGUISpriteInstance m_SpriteButtonRight;
    CGUISpriteInstance m_SpriteButtonRightPressed;
    CGUISpriteInstance m_SpriteButtonRightDisabled;

    CGUISpriteInstance m_SpriteBackHorizontal;
    CGUISpriteInstance m_SpriteBarHorizontal;

    //@}
};


/**
 * The GUI Scroll-bar, used everywhere there is a scroll-bar in the game.
 *
 * To include a scroll-bar to an object, inherent the object from
 * IGUIScrollBarOwner and call AddScrollBar() to add the scroll-bars.
 *
 * It's also important that the scrollbar is located within the parent
 * object's mouse over area. Otherwise the input won't be sent to the
 * scroll-bar.
 *
 * The class does not provide all functionality to the scroll-bar, many
 * things the parent of the scroll-bar, must provide. Like a combo-box.
 */
class IGUIScrollBar
{
public:
    NONCOPYABLE(IGUIScrollBar);

    IGUIScrollBar(CGUI& pGUI);
    virtual ~IGUIScrollBar();

public:
    /**
     * Draw the scroll-bar
     */
    virtual void Draw(CCanvas2D& canvas) = 0;

    /**
     * If an object that contains a scrollbar has got messages, send
     * them to the scroll-bar and it will see if the message regarded
     * itself.
     *
     * @see IGUIObject#HandleMessage()
     */
    virtual void HandleMessage(SGUIMessage& Message) = 0;

    /**
     * Set m_Pos with g_mouse_x/y input, i.e. when draggin.
     */
    virtual void SetPosFromMousePos(const CVector2D& mouse) = 0;

    /**
     * Hovering the scroll minus button
     *
     * @param mouse current mouse position
     * @return True if mouse positions are hovering the button
     */
    virtual bool HoveringButtonMinus(const CVector2D& UNUSED(mouse)) { return false; }

    /**
     * Hovering the scroll plus button
     *
     * @param mouse current mouse position
     * @return True if mouse positions are hovering the button
     */
    virtual bool HoveringButtonPlus(const CVector2D& UNUSED(mouse)) { return false; }

    /**
     * Get scroll-position
     */
    float GetPos() const { return m_Pos; }

    /**
     * Set scroll-position by hand
     */
    virtual void SetPos(float f) { m_Pos = f; UpdatePosBoundaries(); }

    /**
     * Get the value of m_Pos that corresponds to the bottom of the scrollable region
     */
    float GetMaxPos() const { return std::max(0.f, m_ScrollRange - m_ScrollSpace); }

    /**
     * Scrollbars without height shouldn't be visible
     */
    bool IsVisible() const { return GetMaxPos() != 0.f; }

    /**
     * Increase scroll one step
     */
    virtual void ScrollPlus() { m_Pos += 30.f; UpdatePosBoundaries(); }

    /**
     * Decrease scroll one step
     */
    virtual void ScrollMinus() { m_Pos -= 30.f; UpdatePosBoundaries(); }

    /**
     * Increase scroll three steps
     */
    virtual void ScrollPlusPlenty() { m_Pos += 90.f; UpdatePosBoundaries(); }

    /**
     * Decrease scroll three steps
     */
    virtual void ScrollMinusPlenty() { m_Pos -= 90.f; UpdatePosBoundaries(); }

    /**
     * Set host object, must be done almost at creation of scroll bar.
     * @param pOwner Pointer to host object.
     */
    void SetHostObject(IGUIScrollBarOwner* pOwner) { m_pHostObject = pOwner; }

    /**
     * Set Width
     * @param width Width
     */
    void SetWidth(float width) { m_Width = width; }

    /**
     * Set X Position
     * @param x Position in this axis
     */
    void SetX(float x) { m_X = x; }

    /**
     * Set Y Position
     * @param y Position in this axis
     */
    void SetY(float y) { m_Y = y; }

    /**
     * Set Z Position
     * @param z Position in this axis
     */
    void SetZ(float z) { m_Z = z; }

    /**
     * Set Length of scroll bar
     * @param length Length
     */
    void SetLength(float length) { m_Length = length; }

    /**
     * Set content length
     * @param range Maximum scrollable range
     */
    void SetScrollRange(float range) { m_ScrollRange = std::max(range, 1.f); SetupBarSize(); UpdatePosBoundaries(); }

    /**
     * Set space that is visible in the scrollable control.
     * @param space Visible area in the scrollable control.
     */
    void SetScrollSpace(float space) { m_ScrollSpace = space; SetupBarSize(); UpdatePosBoundaries(); }

    /**
     * Set bar pressed
     * @param b True if bar is pressed
     */
    void SetBarPressed(bool b) { m_BarPressed = b; }

    /**
     * Set Scroll bar style string
     * @param style String with scroll bar style reference name
     */
    void SetScrollBarStyle(const CStr& style) { m_ScrollBarStyle = style; }

    /**
     * Get style used by the scrollbar
     * @return Scroll bar style struct.
     */
    const SGUIScrollBarStyle* GetStyle() const;

    /**
     * Get the rectangle of the actual BAR. not the whole scroll-bar.
     * @return Rectangle, CRect
     */
    virtual CRect GetBarRect() const = 0;

    /**
     * Get the rectangle of the outline of the scrollbar, every component of the
     * scroll-bar should be inside this area.
     * @return Rectangle, CRect
     */
    virtual CRect GetOuterRect() const = 0;

protected:
    /**
     * Sets up bar size
     */
    void SetupBarSize();

    /**
     * Call every time m_Pos has been updated.
     */
    void UpdatePosBoundaries();

protected:
    //@}
    //--------------------------------------------------------
    /** @name Settings */
    //--------------------------------------------------------
    //@{

    /**
     * Width of the scroll bar
     */
    float m_Width;

    /**
     * Absolute X Position
     */
    float m_X;

    /**
     * Absolute Y Position
     */
    float m_Y;

    /**
     * Absolute Z Position
     */
    float m_Z;

    /**
     * Total length of scrollbar, including edge buttons.
     */
    float m_Length;

    /**
     * Content that can be scrolled, in pixels
     */
    float m_ScrollRange;

    /**
     * Content that can be viewed at a time, in pixels
     */
    float m_ScrollSpace;

    /**
     * Use input from the scroll-wheel? True or false.
     */
    float m_BarSize;

    /**
     * Scroll bar style reference name
     */
    CStr m_ScrollBarStyle;

    /**
     * Pointer to scroll bar style used.
     */
    SGUIScrollBarStyle* m_pStyle;

    /**
     * Host object, prerequisite!
     */
    IGUIScrollBarOwner* m_pHostObject;

    /**
     * Reference to CGUI object, these cannot work stand-alone
     */
    CGUI& m_pGUI;

    /**
     * Mouse position when bar was pressed
     */
    CVector2D m_BarPressedAtPos;

    //@}
    //--------------------------------------------------------
    /** @name States */
    //--------------------------------------------------------
    //@{

    /**
     * If the bar is currently being pressed and dragged.
     */
    bool m_BarPressed;

    /**
     * Bar being hovered or not
     */
    bool m_BarHovered;

    /**
     * Scroll buttons hovered
     */
    bool m_ButtonMinusHovered, m_ButtonPlusHovered;

    /**
     * Scroll buttons pressed
     */
    bool m_ButtonMinusPressed, m_ButtonPlusPressed;

    /**
     * Position of scroll bar, 0 means scrolled all the way to one side.
     * It is measured in pixels, it is up to the host to make it actually
     * apply in pixels.
     */
    float m_Pos;

    /**
     * Position from 0.f to 1.f it had when the bar was pressed.
     */
    float m_PosWhenPressed;

    //@}
};

#endif // INCLUDED_IGUISCROLLBAR