scrollbar.lua

--=========== Copyright © 2019, Planimeter, All rights reserved. ===========--
--
-- Purpose: Scrollbar class
--
--==========================================================================--

class "gui.scrollbar" ( "gui.box" )

local scrollbar = gui.scrollbar

function scrollbar:scrollbar( parent, name )
	gui.box.box( self, parent, name )
	self:setDisplay( "block" )
	self:setPosition( "absolute" )
	self.width       = 4
	self.height      = parent:getHeight()
	self.disabled    = false
	self.min         = 0
	self.max         = 0
	self.rangeWindow = 0
	self.value       = 0

	self:setUseFullscreenCanvas( true )
end

function scrollbar:draw()
	local length = self:getThumbLength()
	if ( length == self:getHeight() ) then
		return
	end

	local color = self:getScheme( "scrollbar.backgroundColor" )
	local width = self:getWidth()
	local x     = 0

	if ( self:isDisabled() ) then
		color = self:getScheme( "scrollbar.disabled.backgroundColor" )
	end

	love.graphics.setColor( color )
	love.graphics.rectangle( "fill", x, self:getThumbPos(), width, length )

	gui.box.draw( self )
end

accessor( scrollbar, "min" )
accessor( scrollbar, "max" )

function scrollbar:getRange()
	return self.min, self.max
end

accessor( scrollbar, "rangeWindow" )

function scrollbar:getThumbLength()
	local range = self:getMax() - self:getMin()
	local size  = self:getRangeWindow() / range
	return size * self:getHeight()
end

function scrollbar:getThumbPos()
	local min     = self:getMin()
	local range   = self:getMax() - min
	local percent = ( self:getValue() + min ) / range
	return percent * self:getHeight()
end

accessor( scrollbar, "value" )

function scrollbar:invalidateLayout()
	local parent = self:getParent()
	self:setPos( parent:getWidth() - self:getWidth(), 0 )
	self:setHeight( parent:getHeight() )
end

gui.accessor( scrollbar, "disabled", "is" )

local localX, localY = 0, 0

function scrollbar:mousepressed( x, y, button, istouch )
	if ( self.mouseover and button == 1 ) then
		self.mousedown = true
	end

	if ( self.mousedown and button == 1 ) then
		localX, localY = self:screenToLocal( x, y )

		local thumbPos = self:getThumbPos()
		if ( localY < thumbPos ) then
			self:pageUp()
			return
		elseif ( localY > thumbPos + self:getThumbLength() ) then
			self:pageDown()
			return
		end

		self.grabbedX  = localX
		self.grabbedY  = localY
	end
end

function scrollbar:mousereleased( x, y, button, istouch )
	self.mousedown = false
	self.grabbedX  = nil
	self.grabbedY  = nil
end

function scrollbar:onValueChanged( oldValue, newValue )
end

function scrollbar:pageDown()
	self:scrollDown( self:getRangeWindow() )
end

function scrollbar:pageUp()
	self:scrollUp( self:getRangeWindow() )
end

function scrollbar:scrollDown( value )
	self:setValue( self:getValue() + value )
end

function scrollbar:scrollUp( value )
	self:setValue( self:getValue() - value )
end

function scrollbar:scrollToBottom()
	self:setValue( self:getMax() )
end

function scrollbar:scrollToTop()
	self:setValue( self:getMin() )
end

local min, max = 0, 0
local range    = 0
local newRange = 0
local percent  = 0

local function updateRange( self, min, max )
	min, max = self:getRange()
	range    = max - min
	if ( range ~= 0 ) then
		newRange   = max - min
		percent    = ( self:getValue() + self:getMin() ) / range
		self.value = percent * newRange + self:getMin()
		if ( self.value > self:getMax() - self:getRangeWindow() ) then
			self.value = self:getMax() - self:getRangeWindow()
		end
	end
end

function scrollbar:setMin( min )
	updateRange( self, min, self:getMax() )
	self.min = min
end

function scrollbar:setMax( max )
	updateRange( self, self:getMin(), max )
	self.max = max
end

function scrollbar:setRange( min, max )
	self:setMin( min )
	self:setMax( max )
end

function scrollbar:setRangeWindow( rangeWindow )
	self.rangeWindow = rangeWindow
	local rangeSize  = self:getMax() - self:getMin()
	if ( rangeWindow > rangeSize ) then
		self.rangeWindow = rangeSize
	end
end

local oldValue   = 0
local deltaValue = 0

function scrollbar:setValue( value )
	oldValue   = self.value
	self.value = value
	if ( self.value < self.min ) then
		deltaValue = self.min - self.value
		self.value = self.min
		self:onValueChanged( oldValue, self.value )
		self:invalidate()
		return deltaValue
	elseif ( self.value > self.max - self.rangeWindow ) then
		deltaValue = self.max - self.rangeWindow - self.value
		self.value = self.max - self.rangeWindow
		self:onValueChanged( oldValue, self.value )
		self:invalidate()
		return deltaValue
	end
	self:onValueChanged( oldValue, self.value )
	self:invalidate()
	return 0
end

local mouseX, mouseY = 0, 0
local getPosition    = love.mouse.getPosition
local deltaX, deltaY = 0, 0

function scrollbar:update( dt )
	gui.panel.update( self, dt )

	if ( not self:isVisible() or self:isDisabled() ) then
		return
	end

	if ( not ( self.grabbedX or self.grabbedY ) ) then
		return
	end

	mouseX, mouseY = getPosition()
	localX, localY = self:screenToLocal( mouseX, mouseY )
	deltaX, deltaY = localX - self.grabbedX,
	                 localY - self.grabbedY

	if ( deltaX == 0 and deltaY == 0 ) then
		return
	end

	min, max      = self:getRange()
	range         = max - min
	deltaValue    = ( deltaY / self:getHeight() ) * range
	deltaValue    = self:setValue( self:getValue() + deltaValue )
	self.grabbedX = localX
	self.grabbedY = localY + ( deltaValue / range ) * self:getHeight()
end