CCGUI scroll

--[[

    ComputerCraft GUI
    Scrollable element

--]]

ccgui = ccgui or {}

local ScrollSlider = common.newClass(ccgui.Slider)
function ScrollSlider:init()
    ccgui.Slider.init(self)

    self:on("beforepaint", self.sliderLayout, self, -1)
end
function ScrollSlider:sliderLayout()
    error("ScrollSlider:sliderLayout() not implemented")
end
function ScrollSlider:getStep()
    return 1
end
function ScrollSlider:getMinimum()
    return 0
end

local HorizontalSlider = common.newClass({
    horizontal  = true,
    arrowLabels = { "<", ">" }
}, ScrollSlider)
function HorizontalSlider:sliderLayout()
    -- Place below inner box of scroll element
    local sbox = self.parent:inner(self.parent.bbox)
    self.bbox = ccgui.newRectangle(sbox.x, sbox.y + sbox.h, sbox.w, 1)
end
function HorizontalSlider:getValue()
    return self.parent.scrollPosition.x
end
function HorizontalSlider:rawSetValue(newValue)
    self.parent.scrollPosition.x = newValue
    --self.parent:markRepaint()
end
function HorizontalSlider:getSpan()
    return self.parent:scrollVisible().x
end
function HorizontalSlider:getMaximum()
    return self.parent:scrollTotal().x
end

local VerticalSlider = common.newClass({
    horizontal = false,
    arrowLabels = { "^", "v" }
}, ScrollSlider)
function VerticalSlider:sliderLayout()
    -- Place at right of inner box of scroll element
    local sbox = self.parent:inner(self.parent.bbox)
    self.bbox = ccgui.newRectangle(sbox.x + sbox.w, sbox.y, 1, sbox.h)
end
function VerticalSlider:getValue()
    return self.parent.scrollPosition.y
end
function VerticalSlider:rawSetValue(newValue)
    self.parent.scrollPosition.y = newValue
    --self.parent:markRepaint()
end
function VerticalSlider:getSpan()
    return self.parent:scrollVisible().y
end
function VerticalSlider:getMaximum()
    return self.parent:scrollTotal().y
end

local ScrollElement = common.newClass({
    -- Orientation
    horizontal      = false,
    vertical        = true,
    -- Show scroll bars
    showScrollBars  = true,
    -- Mouse scroll
    mouseScroll     = false,
    -- Colors
    colorForeground = colours.grey,
    colorBar        = colours.grey,
    colorButton     = colours.lightGrey,
    -- Relative scroll position
    scrollPosition  = nil,
    -- Sliders
    sliderHoriz     = nil,
    sliderVerti     = nil
}, ccgui.Element)
ccgui.ScrollElement = ScrollElement

function ScrollElement:init()
    ccgui.Element.init(self)

    -- Scroll position
    self.scrollPosition = vector.new(0, 0)

    -- Orientation
    self.horizontal = not not self.horizontal
    self.vertical = not not self.vertical

    -- Sliders
    self.sliderHoriz = HorizontalSlider:new({
        parent          = self,
        colorForeground = self.colorForeground,
        colorBar        = self.colorBar,
        colorButton     = self.colorButton
    })
    self.sliderVerti = VerticalSlider:new({
        parent          = self,
        colorForeground = self.colorForeground,
        colorBar        = self.colorBar,
        colorButton     = self.colorButton
    })

    -- Mouse
    self:sinkEvent("mouse_click")
    self:sinkEvent("mouse_drag")
    self:on("mouse_scroll", self.scrollMouse, self)

    -- Paint
    self:on("paint", self.scrollPaint, self)
end

function ScrollElement:canScroll()
    return true
end

-- Relative visible scroll region
function ScrollElement:scrollVisible()
    error("ScrollElement:scrollVisible() not implemented")
end

-- Relative total scroll size
function ScrollElement:scrollTotal()
    error("ScrollElement:scrollTotal() not implemented")
end

-- Extra margins due to scroll bar
function ScrollElement:scrollBarMargins()
    if self.showScrollBars then
        local right, bottom = 0, 0
        if self.horizontal then
            bottom = 1
        end
        if self.vertical then
            right = 1
        end
        return ccgui.newMargins(0, right, bottom, 0)
    end

    return ccgui.newMargins(0)
end

function ScrollElement:inner(bbox)
    return ccgui.Element.inner(self, bbox):contract(self:scrollBarMargins())
end

function ScrollElement:outer(bbox)
    return ccgui.Element.outer(self, bbox:expand(self:scrollBarMargins()))
end

function ScrollElement:scrollPaint()
    if self.showScrollBars then
        if self.horizontal then
            self.sliderHoriz:paint()
        end
        if self.vertical then
            self.sliderVerti:paint()
        end
    end
end

function ScrollElement:scrollMouse(dir, x, y)
    if self.isVisible and self.mouseScroll and self:contains(x, y) then
        -- Prefer vertical over horizontal scrolling
        local slider = self.vertical and self.sliderVerti or self.sliderHorzi
        -- Step in scroll direction
        if dir < 0 then
            slider:prevStep()
        else
            slider:nextStep()
        end
    end
end

--[[

    Event sinking

]]--

function ScrollElement:sinkEvent(event)
    self:on(event, function(self, ...)
        if self.isVisible and self.showScrollBars then
            if self.horizontal then
                self.sliderHoriz:trigger(event, ...)
            end
            if self.vertical then
                self.sliderVerti:trigger(event, ...)
            end
        end
    end, self)
end