koreader/frontend/ui/widget/bbox.lua

require "math"
require "ui/widget/container"

--[[
BBoxWidget shows a bbox for page cropping
]]
BBoxWidget = InputContainer:new{
	page_bbox = nil,
	screen_bbox = nil,
	linesize = 2,
}

function BBoxWidget:init()
	self.page_bbox = self.document:getPageBBox(self.view.state.page)
	--DEBUG("used page bbox on page", self.view.state.page, self.page_bbox)
	if Device:isTouchDevice() then
		self.ges_events = {
			TapAdjust = {
				GestureRange:new{
					ges = "tap",
					range = self.view.dimen,
				}
			},
			PanAdjust = {
				GestureRange:new{
					ges = "pan",
					range = self.view.dimen,
					rate = 3.0, -- emit up to 3 evs per second
				}
			},
			HoldAdjust = {
				GestureRange:new{
					ges = "hold",
					range = self.view.dimen,
				}
			},
			ConfirmAdjust = {
				GestureRange:new{
					ges = "double_tap",
					range = self.view.dimen,
				}
			}
		}
	end
end

function BBoxWidget:getSize()
	return self.view.dimen
end

function BBoxWidget:paintTo(bb, x, y)
	-- As getScreenBBox uses view states, screen_bbox initialization is postponed.
	self.screen_bbox = self.screen_bbox or self:getScreenBBox(self.page_bbox)
	local bbox = self.screen_bbox
	-- top edge
	bb:invertRect(bbox.x0 + self.linesize, bbox.y0, bbox.x1 - bbox.x0, self.linesize)
	-- bottom edge
	bb:invertRect(bbox.x0 + self.linesize, bbox.y1, bbox.x1 - bbox.x0 - self.linesize, self.linesize)
	-- left edge
	bb:invertRect(bbox.x0, bbox.y0, self.linesize, bbox.y1 - bbox.y0 + self.linesize)
	-- right edge
	bb:invertRect(bbox.x1, bbox.y0 + self.linesize, self.linesize, bbox.y1 - bbox.y0)
end

-- transform page bbox to screen bbox
function BBoxWidget:getScreenBBox(page_bbox)
	local bbox = {}
	local scale = self.view.state.zoom
	local screen_offset = self.view.state.offset
	--DEBUG("screen offset in page_to_screen", screen_offset)
	bbox.x0 = math.round(page_bbox.x0 * scale + screen_offset.x)
	bbox.y0 = math.round(page_bbox.y0 * scale + screen_offset.y)
	bbox.x1 = math.round(page_bbox.x1 * scale + screen_offset.x)
	bbox.y1 = math.round(page_bbox.y1 * scale + screen_offset.y)
	return bbox
end

-- transform screen bbox to page bbox
function BBoxWidget:getPageBBox(screen_bbox)
	local bbox = {}
	local scale = self.view.state.zoom
	local screen_offset = self.view.state.offset
	--DEBUG("screen offset in screen_to_page", screen_offset)
	bbox.x0 = math.round((screen_bbox.x0 - screen_offset.x) / scale)
	bbox.y0 = math.round((screen_bbox.y0 - screen_offset.y) / scale)
	bbox.x1 = math.round((screen_bbox.x1 - screen_offset.x) / scale)
	bbox.y1 = math.round((screen_bbox.y1 - screen_offset.y) / scale)
	return bbox
end

function BBoxWidget:inPageArea(ges)
	local offset = self.view.state.offset
	local page_area = self.view.page_area
	local page_dimen = Geom:new{ x = offset.x, y = offset.y, h = page_area.h, w = page_area.w}
	return not ges.pos:notIntersectWith(page_dimen)
end

function BBoxWidget:adjustScreenBBox(ges)
	--DEBUG("adjusting crop bbox with pos", ges.pos)
	if not self:inPageArea(ges) then return end
	local bbox = self.screen_bbox
	local upper_left = Geom:new{ x = bbox.x0, y = bbox.y0}
	local upper_right = Geom:new{ x = bbox.x1, y = bbox.y0}
	local bottom_left = Geom:new{ x = bbox.x0, y = bbox.y1}
	local bottom_right = Geom:new{ x = bbox.x1, y = bbox.y1}
	local upper_center = Geom:new{ x = (bbox.x0 + bbox.x1) / 2, y = bbox.y0}
	local bottom_center = Geom:new{ x = (bbox.x0 + bbox.x1) / 2, y = bbox.y1}
	local right_center = Geom:new{ x = bbox.x1, y = (bbox.y0 + bbox.y1) / 2}
	local left_center = Geom:new{ x = bbox.x0, y = (bbox.y0 + bbox.y1) / 2}
	local anchors = {
		upper_left, upper_center, 	upper_right,
		left_center, 				right_center,
		bottom_left, bottom_center, bottom_right,
	}
	local _, nearest = math.tmin(anchors, function(a,b)
		return a:distance(ges.pos) > b:distance(ges.pos)
	end)
	--DEBUG("nearest anchor", nearest)
	if nearest == upper_left then
		upper_left.x = ges.pos.x
		upper_left.y = ges.pos.y
	elseif nearest == bottom_right then
		bottom_right.x = ges.pos.x
		bottom_right.y = ges.pos.y
	elseif nearest == upper_right then
		bottom_right.x = ges.pos.x
		upper_left.y = ges.pos.y
	elseif nearest == bottom_left then
		upper_left.x = ges.pos.x
		bottom_right.y = ges.pos.y
	elseif nearest == upper_center then
		upper_left.y = ges.pos.y
	elseif nearest == right_center then
		bottom_right.x = ges.pos.x
	elseif nearest == bottom_center then
		bottom_right.y = ges.pos.y
	elseif nearest == left_center then
		upper_left.x = ges.pos.x
	end
	self.screen_bbox = {
		x0 = math.round(upper_left.x), 
		y0 = math.round(upper_left.y),
		x1 = math.round(bottom_right.x),
		y1 = math.round(bottom_right.y)
	}
	
	UIManager.repaint_all = true
end

function BBoxWidget:getModifiedPageBBox()
	return self:getPageBBox(self.screen_bbox)
end

function BBoxWidget:onTapAdjust(arg, ges)
	self:adjustScreenBBox(ges)
	return true
end

function BBoxWidget:onPanAdjust(arg, ges)
	self:adjustScreenBBox(ges)
	return true
end

function BBoxWidget:onHoldAdjust(arg, ges)
	self:adjustScreenBBox(ges)
	return true
end

function BBoxWidget:onConfirmAdjust(arg, ges)
	if self:inPageArea(ges) then
		self.ui:handleEvent(Event:new("ConfirmPageCrop"))
	end
	return true
end