CommonLua/X/XScroll.lua

DefineClass.XScroll = {
	__parents = { "XPropControl" },
	properties = {
		{ category = "Scroll", id = "Min", editor = "number", default = 0 },
		{ category = "Scroll", id = "Max", editor = "number", default = 100 },
		{ category = "Scroll", id = "Scroll", editor = "number", default = 0, dont_save = true },
		{ category = "Scroll", id = "PageSize", editor = "number", default = 1 },
		{ category = "Scroll", id = "StepSize", editor = "number", default = 1 },
		{ category = "Scroll", id = "FullPageAtEnd", editor = "bool", default = false },
		{ category = "Scroll", id = "SnapToItems", editor = "bool", default = false },
		{ category = "Scroll", id = "AutoHide", editor = "bool", default = false, },
		{ category = "Scroll", id = "Horizontal", name = "Horizontal", editor = "bool", default = false, },
		{ category = "Scroll", id = "ThrottleTime", name = "Throttle time", editor = "number", default = 0, help = "Use -1 to update the value once per frame"},
		{ category = "Scroll", id = "ModifyObj", name = "Call ObjModified", editor = "bool", default = false, },
	},
	FoldWhenHidden = true,
	set_prop_thread = false,
}

function XScroll:SetScrollRange(min, max)
	max = Max(max, min)
	if self.Min == min and self.Max == max then return end
	self.Min = min
	self.Max = max
	self:SetScroll(self.Scroll)
end

function XScroll:SetStepSize(step)
	self.StepSize = Max(1, step)
end

function XScroll:ScrollIntoView()
end

function XScroll:ShouldShow()
	if not self.AutoHide then return true end
	local target = self:ResolveId(self.Target)
	assert(target, "What is this scroll scrolling if it has no target?")
	if not target then return end
	if self.Horizontal then
		return target.scroll_range_x - target.content_box:sizex() > 0
	end
	return target.scroll_range_y - target.content_box:sizey() > 0
end

function XScroll:SnapScrollPosition(current)
	current = current + (self.Min - current) % self.StepSize
	
	local scroll_end = self.Max - (self.FullPageAtEnd and self.PageSize or 0)
	return Clamp(current, self.Min, scroll_end)
end

function XScroll:DoSetScroll(current)
	if self.Scroll ~= current then
		self.Scroll = current
		self:Invalidate()
		return true
	end
end

function XScroll:SetScroll(current)
	if self.AutoHide then
		self:SetVisible(self:ShouldShow())
	end
	return self:DoSetScroll(self:SnapScrollPosition(current))
end

function XScroll:SetPageSize(page_size)
	page_size = page_size - page_size % self.StepSize
	local new_size = Max(page_size, 1)
	if self.PageSize == new_size then return end
	self.PageSize = new_size
	self:SetScroll(self.Scroll)
end

function XScroll:ScrollTo(current)
	if self:SetScroll(current) then
		local target = self:ResolveId(self.Target)
		if target then
			target:OnScrollTo(self.Scroll, self)
		end
		if self.BindTo ~= "" then
			local obj = ResolvePropObj(self.context)
			if self.ThrottleTime == 0 then
				SetProperty(obj, self.BindTo, self.Scroll)
				if self.ModifyObj then
					ObjModified(obj)
				end
			elseif not IsValidThread(self.set_prop_thread) then
				self.set_prop_thread = CreateRealTimeThread(function(self)
					repeat
						local value = self.Scroll
						SetProperty(obj, self.BindTo, self.Scroll)
						if self.ModifyObj then
							ObjModified(obj)
						end
						if self.ThrottleTime == -1 then
							WaitNextFrame()
						else
							Sleep(self.ThrottleTime)
						end
					until value == self.Scroll
					self.set_prop_thread = false
				end, self)
			else
			end
		end
		return true
	end
end

local eval = prop_eval

function XScroll:OnPropUpdate(context, prop_meta, value)
	if prop_meta then
		self:SetStepSize(eval(prop_meta.step, context, prop_meta) or self.StepSize)
		self:SetScrollRange(eval(prop_meta.min, context, prop_meta) or self.Min, eval(prop_meta.max, context, prop_meta) or self.Max)
	end
	assert(type(value) == "number")
	if type(value) == "number" then
		self:ScrollTo(value)
	end
end


----- XScrollControl

DefineClass.XScrollControl = {
	__parents = { "XScroll" },
	properties = {
		{ category = "Scroll", id = "MinThumbSize", editor = "number", default = 15 },
	},
	current_pos = false,
	current_offset = false,
	ChildrenHandleMouse = false,
	touch = false
}


function XScrollControl:StartScroll(pt)
	if not self.enabled then return false end
	local pos = self.Horizontal and pt:x() - self.content_box:minx() or pt:y() - self.content_box:miny()
	local min, max = self:GetThumbRange()
	self.current_pos = min
	self.current_offset = pos - self.current_pos
	if self.current_offset < 0 or self.current_offset > max - min then
		self.current_offset = (max - min) / 2
	end
	return true
end

function XScrollControl:OnMouseButtonDown(pt, button)
	if button == "L" then
		if self:StartScroll(pt) then
			if not self.touch then
				self.desktop:SetMouseCapture(self)
			end
			self:OnMousePos(pt)
		end
		return "break"
	end
end

function XScrollControl:OnMousePos(pt)
	if not self.current_pos then return end
	local pos, size
	if self.Horizontal then
		pos = pt:x() - self.content_box:minx() - self.current_offset
		size = Max(1, self.content_box:sizex() - self:GetThumbSize())
	else
		pos = pt:y() - self.content_box:miny() - self.current_offset
		size = Max(1, self.content_box:sizey() - self:GetThumbSize())
	end
	pos = Clamp(pos, 0, size)
	self.current_pos = pos
	self:ScrollTo(self.Min + pos * Max(1, self.Max - self.Min - (self.FullPageAtEnd and self.PageSize or 0) + 1) / size)
	return "break"
end

function XScrollControl:OnMouseButtonUp(pt, button)
	if button == "L" then
		self:OnMousePos(pt)
		self.desktop:SetMouseCapture()
		return "break"
	end
end

function XScrollControl:OnCaptureLost()
	self.current_pos = false
	self.current_offset = false
end

function XScrollControl:OnTouchBegan(id, pt, touch)
	self.touch = true
	terminal.desktop:SetKeyboardFocus(false)
	self:OnMouseButtonDown(pt, "L")
	return "capture"
end

function XScrollControl:OnTouchMoved(id, pt, touch)
	return self:OnMousePos(pt)
end

function XScrollControl:OnTouchEnded()
	self.touch = false
	return "break"
end

function XScrollControl:OnTouchCancelled()
	self.touch = false
	return "break"
end

function XScrollControl:GetThumbSize()
	local area = self.Horizontal and self.content_box:sizex() or self.content_box:sizey()
	local page_size = area * self.PageSize / Max(1, self.Max - self.Min)
	return Clamp(page_size, self.MinThumbSize, area)
end

function XScrollControl:GetThumbRange()
	local thumb_size = self:GetThumbSize()
	local area = self.Horizontal and self.content_box:sizex() or self.content_box:sizey()
	local pos = self.current_pos or ((area - thumb_size) * (self.Scroll - self.Min) / Max(1, self.Max - self.Min - (self.FullPageAtEnd and self.PageSize or 0)))
	return pos, pos + thumb_size
end


----- XScrollBar

DefineClass.XScrollBar = {
	__parents = { "XScrollControl" },
	properties = {
		{ category = "Visual", id = "ScrollColor", name = "Scroll", editor = "color", default = RGBA(169, 169, 169, 255), },
		{ category = "Visual", id = "DisabledScrollColor", name = "Disabled scroll", editor = "color", default = RGBA(169, 169, 169, 96), },
	},
	FullPageAtEnd = true,
	Background = RGB(240, 240, 240),
	DisabledBackground = RGB(240, 240, 240),
}

function XScrollBar:DrawContent()
	local content_box = self.content_box
	if self.Horizontal then
		local x1, x2 = self:GetThumbRange()
		content_box = box(content_box:minx() + x1, content_box:miny(), content_box:minx() + x2, content_box:maxy())
	else
		local y1, y2 = self:GetThumbRange()
		content_box = box(content_box:minx(), content_box:miny() + y1, content_box:maxx(), content_box:miny() + y2)
	end
	UIL.DrawBorderRect(FitBoxInBox(content_box, self.content_box), 0, 0, 0, self.enabled and self.ScrollColor or self.DisabledScrollColor)
end


----- XScrollThumb

DefineClass.XScrollThumb = {
	__parents = { "XScrollControl" },
	properties = {
		{ category = "Scroll", id = "FixedSizeThumb", name = "Fixed size thumb", editor = "bool", default = true, },
	}
}

function XScrollThumb:DoSetScroll(scroll)
	if XScrollControl.DoSetScroll(self, scroll) then
		self:MoveThumb()
		return true
	end
	self:MoveThumb()
end

function XScrollThumb:Layout(x, y, width, height)
	XScrollControl.Layout(self, x, y, width, height)
	self:MoveThumb()
end

function XScrollThumb:GetThumbSize()
	if self.FixedSizeThumb then
		return self.Horizontal and self.idThumb.measure_width or self.idThumb.measure_height
	else
		return XScrollControl.GetThumbSize(self)
	end
end

function XScrollThumb:MoveThumb()
	if not self:HasMember("idThumb") then
		return
	end
	local x1, y1, x2, y2 = self.content_box:xyxy()
	local min, max = self:GetThumbRange()
	self.idThumb:SetDock("ignore")
	if self.Horizontal then
		self.idThumb:SetLayoutSpace(x1 + min, y1, max - min, y2 - y1)
	else
		self.idThumb:SetLayoutSpace(x1, y1 + min, x2 - x1, max - min)
	end
end


----- XSleekScroll

DefineClass.XSleekScroll = {
	__parents = { "XScrollThumb" },
	FullPageAtEnd = true,
	FixedSizeThumb = false,
	Background = RGB(240, 240, 240),
	ThumbScale = point(500, 500)
}

function XSleekScroll:Init()
	XFrame:new({
		Id = "idThumb",
		Dock = "ignore",
		Image = "CommonAssets/UI/round-frame-20.tga",
		ImageScale = self.ThumbScale,
		FrameBox = box(9, 9, 9, 9),
		Background = RGBA(169, 169, 169, 255),
		DisabledBackground = RGBA(169, 169, 169, 96),
	}, self)
	self:SetHorizontal(self.Horizontal)
end

function XSleekScroll:SetHorizontal(horizontal)
	self.Horizontal = horizontal
	self.MinWidth = horizontal and 0 or 7
	self.MaxWidth = horizontal and 1000000 or 7
	self.MinHeight = horizontal and 7 or 0
	self.MaxHeight = horizontal and 7 or 1000000
	self:InvalidateMeasure()
	self:InvalidateLayout()
end

----- XRangeScroll

DefineClass.XRangeScroll = {
	__parents = { "XScrollThumb" },
	properties = {
		{ category = "Scroll", id = "Scroll", editor = "range", default = range(0, 0), dont_save = true, },
		{ category = "Scroll", id = "left_arrow_image", name = "Left Arrow", editor = "ui_image", default = "CommonAssets/UI/Controls/RangeSlider/arrowleft.tga", },
		{ category = "Scroll", id = "right_arrow_image", name = "Right Arrow", editor = "ui_image", default = "CommonAssets/UI/Controls/RangeSlider/arrowright.tga", },
		{ category = "Scroll", id = "up_arrow_image", name = "Up Arrow", editor = "ui_image", default = "CommonAssets/UI/Controls/RangeSlider/arrowup.tga", },
		{ category = "Scroll", id = "down_arrow_image", name = "Down Arrow", editor = "ui_image", default = "CommonAssets/UI/Controls/RangeSlider/arrowdown.tga", },
		{ category = "Scroll", id = "ThumbBackground", editor = "color", default = RGBA(169, 169, 169, 255), },
		{ category = "Scroll", id = "ThumbRolloverBackground", editor = "color", default = RGBA(180, 180, 180, 255), },
		{ category = "Scroll", id = "ThumbPressedBackground", editor = "color", default = RGBA(200, 200, 200, 255), },
		{ category = "Scroll", id = "horizontal_cursor", name = "Horizontal Cursor", editor = "ui_image", default = "CommonAssets/UI/Controls/resize03.tga", },
		{ category = "Scroll", id = "vertical_cursor", name = "Vertical Cursor", editor = "ui_image", default = "CommonAssets/UI/Controls/resize04.tga", },
		{ category = "Scroll", id = "ScrollColor", name = "Scroll", editor = "color", default = RGBA(169, 169, 169, 255), },
		{ category = "Scroll", id = "DisabledScrollColor", name = "Disabled scroll", editor = "color", default = RGBA(169, 169, 169, 96), },
	},
	Scroll = range(0, 0),
	MinThumbSize = 16,
	Background = RGB(240, 240, 240),
	ThumbScale = point(500, 500),
	mouse_in = false,
	idThumb = false,
}

function XRangeScroll:Init()
	local panel = XWindow:new({ Dock = "box" }, self)
	self.idPaddingPanel = panel
	XFrame:new({
		Id = "idThumbLeft",
		Dock = "ignore",
		ImageScale = self.ThumbScale,
		MinWidth = self.MinThumbSize * 2,
		Background = self.ThumbBackground,
		DisabledBackground = RGBA(169, 169, 169, 96),
		RolloverBackground = RGBA(0, 0, 0, 0),
	}, panel)
	XFrame:new({
		Id = "idThumbRight",
		Dock = "ignore",
		ImageScale = self.ThumbScale,
		MinWidth = self.MinThumbSize * 2,
		Background = self.ThumbBackground,
		DisabledBackground = RGBA(169, 169, 169, 96),
	}, panel)
	self.idThumb = self.idThumbLeft
	self:SetHorizontal(self.Horizontal)
end

function XRangeScroll:OnMouseEnter(...)
	self.mouse_in = true
	return XScrollThumb.OnMouseEnter(self, ...)
end

function XRangeScroll:OnMousePos(pt, ...)
	if not self.current_pos then
		local closest_thumb, second_thumb = self:GetClosestThumb(pt)
		if closest_thumb and second_thumb then
			closest_thumb:SetBackground(self.ThumbRolloverBackground)
			second_thumb:SetBackground(self.ThumbBackground)
		end
	end
	return XScrollThumb.OnMousePos(self, pt, ...)
end

function XRangeScroll:OnMouseLeft(pt, ...)
	self.mouse_in = false
	if not self.current_pos then
		local closest_thumb = self:GetClosestThumb(pt)
		if closest_thumb then
			closest_thumb:SetBackground(self.ThumbBackground)
		end
	end
	return XScrollThumb.OnMouseLeft(self, pt, ...)
end

function XRangeScroll:DoSetScroll(current)
	local from, to
	if IsRange(current) then
		from, to = current.from, current.to
	else
		if self.idThumb == self.idThumbLeft then
			to = self.Scroll.to
			from = Min(current, to)
		else
			from = self.Scroll.from
			to = Max(current, from)
		end
	end
	if self.Scroll.from ~= from or self.Scroll.to ~= to then
		self.Scroll = range(from, to)
		self:InvalidateLayout()
		return true
	end
end

function XRangeScroll:SnapScrollPosition(current)
	if IsRange(current) then
		return current
	end
	return XScrollThumb.SnapScrollPosition(self, current)
end

function XRangeScroll:SetHorizontal(horizontal)
	self.Horizontal = horizontal
	self.MinWidth = horizontal and 0 or 7
	self.MaxWidth = horizontal and 1000000 or 7
	self.MinHeight = horizontal and 7 or 0
	self.MaxHeight = horizontal and 7 or 1000000
	if horizontal then
		self.idPaddingPanel:SetPadding(box(self.MinThumbSize, 0, self.MinThumbSize, 0))
		self.idThumbLeft:SetImage(self.left_arrow_image)
		self.idThumbRight:SetImage(self.right_arrow_image)
		self:SetMouseCursor(self.horizontal_cursor)
	else
		self.idPaddingPanel:SetPadding(box(0, self.MinThumbSize, 0, self.MinThumbSize))
		self.idThumbLeft:SetImage(self.down_arrow_image)
		self.idThumbRight:SetImage(self.up_arrow_image)
		self:SetMouseCursor(self.vertical_cursor)
	end
	self:InvalidateMeasure()
	self:InvalidateLayout()
end

function XRangeScroll:GetThumbRange()
	local thumb_size = self:GetThumbSize()
	local scroll
	if self.idThumb == self.idThumbLeft then
		scroll = self.Scroll.from
	else
		scroll = self.Scroll.to
	end
	local area = self.Horizontal and self.content_box:sizex() or self.content_box:sizey()
	local pos = self.current_pos or ((area - thumb_size) * (scroll - self.Min) / Max(1, self.Max - self.Min - (self.FullPageAtEnd and self.PageSize or 0)))
	return pos, pos + thumb_size
end

function XRangeScroll:GetClosestThumb(pt)
	if not self.enabled then return end
	local cboxl, cboxr = self.idThumbLeft.content_box, self.idThumbRight.content_box
	local mid_point
	if self.Horizontal then
		mid_point = cboxl:maxx() + (cboxr:minx() - cboxl:maxx()) / 2
	else
		mid_point = cboxl:maxy() + (cboxr:miny() - cboxl:maxy()) / 2
	end
	if pt:x() < mid_point then
		return self.idThumbLeft, self.idThumbRight
	else
		return self.idThumbRight, self.idThumbLeft
	end
end

function XRangeScroll:StartScroll(pt)
	local closest_thumb = self:GetClosestThumb(pt)
	if not closest_thumb then return end
	self.idThumb = closest_thumb
	closest_thumb:SetBackground(self.ThumbPressedBackground)
	return XScrollThumb.StartScroll(self, pt)
end

function XRangeScroll:OnCaptureLost()
	self.idThumbLeft:SetBackground(self.ThumbBackground)
	self.idThumbRight:SetBackground(self.ThumbBackground)
	return XScrollThumb.OnCaptureLost(self)
end

function XRangeScroll:MoveThumb()
	local x1, y1, x2, y2 = self.content_box:xyxy()
	local thumb_size = self:GetThumbSize()
	local area = self.Horizontal and self.content_box:sizex() or self.content_box:sizey()
	local posl = (area - thumb_size) * (self.Scroll.from - self.Min) / Max(1, self.Max - self.Min - (self.FullPageAtEnd and self.PageSize or 0))
	local posr = (area - thumb_size) * (self.Scroll.to - self.Min) / Max(1, self.Max - self.Min - (self.FullPageAtEnd and self.PageSize or 0))
	if self.Horizontal then
		self.idThumbLeft:SetLayoutSpace(x1 + posl, y1, thumb_size, y2 - y1)
		self.idThumbRight:SetLayoutSpace(x1 + posr, y1, thumb_size, y2 - y1)
	else
		self.idThumbLeft:SetLayoutSpace(x1, y1 + posl, x2 - x1, thumb_size)
		self.idThumbRight:SetLayoutSpace(x1, y1 + posr, x2 - x1, thumb_size)
	end
end

function XRangeScroll:DrawContent()
	XScrollThumb.DrawContent(self)
	local cboxl, cboxr = self.idThumbLeft.content_box, self.idThumbRight.content_box
	local minx, miny, maxx, maxy
	if self.Horizontal then
		minx, miny = cboxl:minx() + (cboxl:maxx() - cboxl:minx()) / 2, cboxl:miny()
		maxx, maxy = cboxr:minx() + (cboxr:maxx() - cboxr:minx()) / 2, cboxr:maxy()
	else
		minx, miny = cboxl:minx(), cboxl:miny() + (cboxl:maxy() - cboxl:miny()) / 2
		maxx, maxy = cboxr:maxx(), cboxr:miny() + (cboxr:maxy() - cboxr:miny()) / 2
	end
	local fill_box = box(minx, miny, maxx, maxy)
	UIL.DrawBorderRect(FitBoxInBox(fill_box, self.content_box), 0, 0, 0, self.enabled and self.ScrollColor or self.DisabledScrollColor)
end

----- XScrollArea

DefineClass.XScrollArea = {
	__parents = { "XControl" },
	properties = {
		{ category = "Scroll", id = "OffsetX", editor = "number", default = 0, dont_save = true, },
		{ category = "Scroll", id = "OffsetY", editor = "number", default = 0, dont_save = true, },
		{ category = "Scroll", id = "MinHSize", name = "Min horizontal size", editor = "bool", default = true, },
		{ category = "Scroll", id = "MinVSize", name = "Min vertical size", editor = "bool", default = true, },
		{ category = "Scroll", id = "HScroll", editor = "text", default = "", },
		{ category = "Scroll", id = "VScroll", editor = "text", default = "", },
		{ category = "Scroll", id = "MouseWheelStep", editor = "number", default = 80, },
		{ category = "Visual", id = "ShowPartialItems", editor = "bool", default = true, },
		{ category = "Visual", id = "ScrollInterpolationTime", editor = "number", min = 0, max = 500, slider = true, default = 0, },
		{ category = "Visual", id = "ScrollInterpolationEasing", editor = "choice", default = GetEasingIndex("Cubic in"), items = function(self) return GetEasingCombo() end, },
		{ category = "General", id = "MouseScroll", Name = "Scroll with mouse", editor = "bool", default = true, },
	},
	Clip = "parent & self",
	scroll_range_x = 0,
	scroll_range_y = 0,
	pending_scroll_into_view = false,
	pending_scroll_allow_interpolation = false,
	PendingOffsetX = 0,
	PendingOffsetY = 0,
}

function XScrollArea:Clear(keep_children)
	if not keep_children then
		self:DeleteChildren()
	end
	self:ScrollTo(0, 0)
	self.pending_scroll_into_view = false
end

function XScrollArea:ScrollTo(x, y, force, allow_interpolation)
	x = x or self.PendingOffsetX
	y = y or self.PendingOffsetY
	
	-- scrollbars might impose additional restrictions upon what scroll offets are allowed
	if self.PendingOffsetX ~= x then
		local scroll = self:ResolveId(self.HScroll)
		if scroll then
			x = scroll:SnapScrollPosition(x)
			scroll:SetScroll(x)
		end
	end
	if self.PendingOffsetY ~= y then
		local scroll = self:ResolveId(self.VScroll)
		if scroll then
			y = scroll:SnapScrollPosition(y)
			scroll:DoSetScroll(y)
		end
	end
	
	-- defer actual scrolling to the next DrawWindow call (optimization for multiple scroll requests from mouse messages)
	local ret = false
	if self.PendingOffsetX ~= x or self.PendingOffsetY ~= y then
		self.PendingOffsetX = x
		self.PendingOffsetY = y
		self:Invalidate()
		ret = true
	end
	
	self.pending_scroll_allow_interpolation = allow_interpolation
	if force then
		self:DoScroll(self.PendingOffsetX, self.PendingOffsetY)
	end
	return ret
end

function XScrollArea:DoScroll(x, y)
	local dx = self.OffsetX - x
	local dy = self.OffsetY - y
	if dx ~= 0 or dy ~= 0 then
		-- scroll
		self.OffsetX = x
		self.OffsetY = y
		for _, win in ipairs(self) do
			if not win.Dock then
				local win_box = win.box
				win:SetBox(win_box:minx() + dx, win_box:miny() + dy, win_box:sizex(), win_box:sizey())
			end
		end
		if self.ScrollInterpolationTime > 0 and self.pending_scroll_allow_interpolation then
			self:AddInterpolation{
				id = "smooth_scroll",
				type = const.intRect,
				duration = self.ScrollInterpolationTime,
				easing = self.ScrollInterpolationEasing,
				originalRect = self.box,
				targetRect = self:GetInterpolatedBox("smooth_scroll", self.box - point(dx, dy)),
				interpolate_clip = const.interpolateClipOff,
				flags = const.intfInverse,
			}
			self.pending_scroll_allow_interpolation = false
		end
		
		-- finalization
		self:RecalcVisibility()
		if Platform.desktop then
			local pt = terminal.GetMousePos()
			if self:MouseInWindow(pt) then
				self.desktop:RequestUpdateMouseTarget()
			end
		end
	end
end

local irInside = const.irInside
local irIntersect = const.irIntersect
function XScrollArea:RecalcVisibility()
	local content = self.content_box
	local partial = self.ShowPartialItems
	for _, win in ipairs(self) do
		if not win.Dock then
			local intersect = content:Intersect2D(win.box)
			win:SetOutsideParent(intersect ~= irInside and not (intersect == irIntersect and partial))
		end
	end
end

function XScrollArea:OnScrollTo(pos, scroll)
	if scroll == self:ResolveId(self.VScroll) then
		self:ScrollTo(self.PendingOffsetX, pos)
	elseif scroll == self:ResolveId(self.HScroll) then
		self:ScrollTo(pos, self.PendingOffsetY)
	end
end

function XScrollArea:Measure(preferred_width, preferred_height)
	local measure_width = self:ResolveId(self.HScroll) and 1000000 or preferred_width
	local measure_height = self:ResolveId(self.VScroll) and 1000000 or preferred_height
	local width, height = XControl.Measure(self, measure_width, measure_height)
	self.scroll_range_x = width
	self.scroll_range_y = height
	if self.MinHSize then
		preferred_width = Min(preferred_width, width)
	end
	if self.MinVSize then
		preferred_height = Min(preferred_height, height)
	end
	return preferred_width, preferred_height
end

local function lAnyNonDockedWindows(self)
	for i, w in ipairs(self) do
		if not w.Dock then return true end
	end
end

function XScrollArea:Layout(x, y, width, height)
	-- can we accommodate the content better in our content box?
	local c_width, c_height = self.content_box:sizexyz()
	local offset_x, offset_y = self.PendingOffsetX, self.PendingOffsetY
	offset_x = Clamp(offset_x, 0, Max(0, self.scroll_range_x - c_width))
	offset_y = Clamp(offset_y, 0, Max(0, self.scroll_range_y - c_height))
	self:ScrollTo(offset_x, offset_y)
	-- layout
	width = self:ResolveId(self.HScroll) and Max(self.scroll_range_x, width) or width
	height = self:ResolveId(self.VScroll) and Max(self.scroll_range_y, height) or height
	if lAnyNonDockedWindows(self) then
		XWindowLayoutFuncs[self.LayoutMethod](self, x - self.OffsetX, y - self.OffsetY, width, height)
	end
	-- calc step for uniform layouts
	local h_step, v_step
	if self.LayoutMethod == "VList" and self.UniformRowHeight then
		local h_spacing, v_spacing = ScaleXY(self.scale, self.LayoutHSpacing, self.LayoutVSpacing)
		for _, win in ipairs(self) do
			if not win.Dock then
				v_step = Max(v_step, win.measure_height + v_spacing)
			end
		end
	end
	if self.LayoutMethod == "HList" and self.UniformColumnWidth then
		local h_spacing, v_spacing = ScaleXY(self.scale, self.LayoutHSpacing, self.LayoutVSpacing)
		for _, win in ipairs(self) do
			if not win.Dock then
				h_step = Max(h_step, win.measure_width + h_spacing)
			end
		end
	end
	-- setup scrollbars
	local scroll = self:ResolveId(self.HScroll)
	self.MouseWheelStep = v_step or self.MouseWheelStep
	if scroll then
		scroll:SetStepSize(h_step or 1)
		scroll:SetScrollRange(0, self.scroll_range_x)
		scroll:SetPageSize(self.content_box:sizex())
	end
	local scroll = self:ResolveId(self.VScroll)
	if scroll then
		scroll:SetStepSize(v_step or 1)
		scroll:SetScrollRange(0, self.scroll_range_y)
		scroll:SetPageSize(self.content_box:sizey())
	end
end

function XScrollArea:UpdateLayout()
	XControl.UpdateLayout(self)
	if self.pending_scroll_into_view then
		local content_box = self.content_box
		for _, child_or_box in ipairs(self.pending_scroll_into_view) do
			if IsBox(child_or_box) then
				child_or_box = Offset(child_or_box, content_box:minx() - self.OffsetX, content_box:miny() - self.OffsetY)
			end
			self:ScrollIntoView(child_or_box)
		end
		self.pending_scroll_into_view = false
	end
	
	self.layout_update = false
	if self.PendingOffsetX == self.OffsetX and self.PendingOffsetY == self.OffsetY then
		-- recalc visibility after layout if there is no pending scroll
		-- scrolling recalcs visibility
		self:RecalcVisibility()
		XControl.UpdateLayout(self)
	end
end

function XScrollArea:ScrollIntoView(child_or_box, boxOnTop)
	if not child_or_box or not IsBox(child_or_box) and child_or_box.window_state == "destroying" then
		return
	end
	
	local content_box = self.content_box
	if self.layout_update then
		self.pending_scroll_into_view = self.pending_scroll_into_view or {}
		-- store boxes in relative coordinates, so that further scrolling or moving the control won't affect them
		if IsBox(child_or_box) then
			child_or_box = Offset(child_or_box, self.OffsetX - content_box:minx(), self.OffsetY - content_box:miny())
		end
		table.insert(self.pending_scroll_into_view, child_or_box)
		return
	end
	
	--[[local parent_scroll_area = GetParentOfKind(self.parent, "XScrollArea")
	if parent_scroll_area then
		parent_scroll_area:ScrollIntoView(child_or_box)
	end]]
	
	local child_box = IsBox(child_or_box) and child_or_box or child_or_box.box
	
	local HScroll = self:ResolveId(self.HScroll)
	if HScroll then HScroll:ScrollIntoView(child_box:minx() - content_box:minx() + self.OffsetX) end
	
	local VScroll = self:ResolveId(self.VScroll)
	if VScroll then VScroll:ScrollIntoView(child_box:miny() - content_box:miny() + self.OffsetY) end
	
	local offset_x, offset_y = self.PendingOffsetX, self.PendingOffsetY
	child_box = Offset(child_box, self.OffsetX - offset_x, self.OffsetY - offset_y)
	if child_box:minx() < content_box:minx() then
		offset_x = offset_x - content_box:minx() + child_box:minx()
	elseif child_box:maxx() > content_box:maxx() then
		offset_x = offset_x - content_box:maxx() + child_box:maxx()
	end
	if child_box:miny() < content_box:miny() then
		offset_y = offset_y - content_box:miny() + child_box:miny()
	elseif child_box:maxy() > content_box:maxy() then
		local childOffset
		if boxOnTop then
			childOffset = Min(child_box:miny() + content_box:sizey(), content_box:miny() + self.scroll_range_y - offset_y)
		else
			childOffset = child_box:maxy()
		end
		offset_y = offset_y - content_box:maxy() + childOffset
	end
	self:ScrollTo(offset_x, offset_y, not "force", "allow_interpolation")
end

function XScrollArea:ScrollUp()
	local horizontal = (self.HScroll or "") ~= ""
	local vertical = (self.VScroll or "") ~= ""
	local x, y = self.PendingOffsetX, self.PendingOffsetY
	if vertical or not horizontal then
		local max = Max(0, self.scroll_range_y - self.content_box:sizey())
		y = Clamp(y - self.MouseWheelStep, 0, max)
	else
		local max = Max(0, self.scroll_range_x - self.content_box:sizex())
		x = Clamp(x - self.MouseWheelStep, 0, max)
	end
	return self:ScrollTo(x, y, not "force", "allow_interpolation")
end

function XScrollArea:ScrollDown()
	local horizontal = (self.HScroll or "") ~= ""
	local vertical = (self.VScroll or "") ~= ""
	local x, y = self.PendingOffsetX, self.PendingOffsetY
	if vertical or not horizontal then
		local max = Max(0, self.scroll_range_y - self.content_box:sizey())
		y = Clamp(y + self.MouseWheelStep, 0, max)
	else
		local max = Max(0, self.scroll_range_x - self.content_box:sizex())
		x = Clamp(x + self.MouseWheelStep, 0, max)
	end
	return self:ScrollTo(x, y, not "force", "allow_interpolation")
end

function XScrollArea:ScrollLeft()
	local horizontal = (self.HScroll or "") ~= ""
	local vertical = (self.VScroll or "") ~= ""
	local x, y = self.PendingOffsetX, self.PendingOffsetY
	if not vertical or horizontal then
		local max = Max(0, self.scroll_range_x - self.content_box:sizex())
		x = Clamp(x - self.MouseWheelStep, 0, max)
	else
		local max = Max(0, self.scroll_range_y - self.content_box:sizey())
		y = Clamp(y - self.MouseWheelStep, 0, max)
	end
	return self:ScrollTo(x, y, not "force", "allow_interpolation")
end

function XScrollArea:ScrollRight()
	local horizontal = (self.HScroll or "") ~= ""
	local vertical = (self.VScroll or "") ~= ""
	local x, y = self.PendingOffsetX, self.PendingOffsetY
	if not vertical or horizontal then
		local max = Max(0, self.scroll_range_x - self.content_box:sizex())
		x = Clamp(x + self.MouseWheelStep, 0, max)
	else
		local max = Max(0, self.scroll_range_y - self.content_box:sizey())
		y = Clamp(y + self.MouseWheelStep, 0, max)
	end
	return self:ScrollTo(x, y, not "force", "allow_interpolation")
end

function XScrollArea:OnMouseWheelForward()
	if not self.MouseScroll then return end
	if self:ScrollUp() or not GetParentOfKind(self.parent, "XScrollArea") then
		return "break"
	end
end

function XScrollArea:OnMouseWheelBack()
	if not self.MouseScroll then return end
	if self:ScrollDown() or not GetParentOfKind(self.parent, "XScrollArea") then
		return "break"
	end
end


---- Touch

function XScrollArea:OnTouchBegan(id, pos, touch)
	terminal.desktop:SetKeyboardFocus(false)
	touch.start_pos = pos
	touch.start_time = RealTime()
	return "capture"
end

function XScrollArea:OnTouchMoved(id, pos, touch)
	if touch.capture == self then
		local horizontal = (self.HScroll or "") ~= ""
		local vertical = (self.VScroll or "") ~= ""
		local last_pos = touch.last_pos or touch.start_pos
		local diff = pos - last_pos
		local x, y = self.PendingOffsetX, self.PendingOffsetY
		if vertical then
			local max = Max(0, self.scroll_range_y - self.content_box:sizey())
			y = Clamp(y - diff:y(), 0, max)
		end
		if horizontal then
			local max = Max(0, self.scroll_range_x - self.content_box:sizex())
			x = Clamp(x - diff:x(), 0, max)
		end
		touch.last_pos = pos
		if self:ScrollTo(x, y) or not GetParentOfKind(self.parent, "XScrollArea") then
			return "break"
		end
	end
end

local function empty_func() end
function XScrollArea:DrawWindow(clip_box)
	if self.PendingOffsetX ~= self.OffsetX or self.PendingOffsetY ~= self.OffsetY then
		self.Invalidate = empty_func
		self:DoScroll(self.PendingOffsetX, self.PendingOffsetY)
		-- Do full layout before drawing, making sure virtual items entering the view are (immediately) displayed correctly;
		-- UpdateMeasure/UpdateLayout won't do anything unless a newly "spawned" XVirtualContent child changed measure
		self:UpdateMeasure(self.parent.content_box:size():xy())
		XControl.UpdateLayout(self) -- use base method to prevent a call to RecalcVisibility
		self.Invalidate = nil
	end
	XControl.DrawWindow(self, clip_box)
end


----- XFitContent

DefineClass.XFitContent = {
	__parents = { "XControl" },
	properties = {
		{ category = "Visual", id = "Fit", name = "Fit", editor = "choice", default = "none", items = {"none", "width", "height", "smallest", "largest", "both"}, },
	},
}

local one = point(1000, 1000)
function XFitContent:UpdateMeasure(max_width, max_height)
	if not self.measure_update then return end
	local fit = self.Fit
	if fit == "none" then
		XControl.UpdateMeasure(self, max_width, max_height)
		return
	end
	for _, child in ipairs(self) do
		child:SetOutsideScale(one)
	end
	self.scale = one
	XControl.UpdateMeasure(self, 1000000, 1000000)
	local content_width, content_height = ScaleXY(self.parent.scale, self.measure_width, self.measure_height)
	assert(content_width > 0 and content_height > 0)
	if content_width == 0 or content_height == 0 then
		XControl.UpdateMeasure(self, max_width, max_height)
		return
	end
	if fit == "smallest" or fit == "largest" then
		local space_is_wider = max_width * content_height >= max_height * content_width
		fit = space_is_wider == (fit == "largest") and "width" or "height"
	end
	local scale_x = max_width * 1000 / content_width
	local scale_y = max_height * 1000 / content_height
	if fit == "width" then
		scale_y = scale_x
	elseif fit == "height" then
		scale_x = scale_y
	end
	self:SetScaleModifier(point(scale_x, scale_y))
	XControl.UpdateMeasure(self, max_width, max_height)
end