pan_gesture.lua

-- Kazari, a touch gesture library.
--
-- Copyright (C) 2022 Miku AuahDark
--
-- This software is provided 'as-is', without any express or implied
-- warranty.  In no event will the authors be held liable for any damages
-- arising from the use of this software.
--
-- Permission is granted to anyone to use this software for any purpose,
-- including commercial applications, and to alter it and redistribute it
-- freely, subject to the following restrictions:
--
-- 1. The origin of this software must not be misrepresented; you must not
--    claim that you wrote the original software. If you use this software
--    in a product, an acknowledgment in the product documentation would be
--    appreciated but is not required.
-- 2. Altered source versions must be plainly marked as such, and must not be
--    misrepresented as being the original software.
-- 3. This notice may not be removed or altered from any source distribution.

---@type string
local path = (...):sub(1, -string.len(".pan_gesture") - 1)

---@type Kazari.BaseGesture
local BaseGesture = require(path..".base_gesture")
---@type Kazari.Util
local util = require(path..".util")

---Implements multi-finger pan gesture.
---@class Kazari.PanGesture: Kazari.BaseGesture
local PanGesture = {}
PanGesture.__index = PanGesture ---@private
PanGesture.__parent = BaseGesture ---@private

---@param minfingers integer
---@param maxfingers integer?
---@param clip boolean?
---@param constraint Kazari.AnyConstraint?
function PanGesture:init(minfingers, maxfingers, clip, constraint)
	maxfingers = maxfingers or minfingers
	assert(minfingers and minfingers > 0 and maxfingers >= minfingers, "number of touches must be greater than 0")

	---@type {[1]:any,[2]:number,[3]:number,[4]:number}[]
	self.touches = {} ---@private
	self.minCount = minfingers ---@private
	self.maxCount = maxfingers ---@private
	self.clipTouch = not not clip ---@private
	self.constraint = constraint ---@private
end

---@generic T
---@param context T
---@param func fun(context:T,x:number,y:number,dx:number,dy:number,pressure:number)
function PanGesture:onMove(context, func)
	self.onMoveCallback = func ---@private
	self.onMoveContext = context ---@private
end

---@generic T
---@param context T
---@param func fun(context:T,x:number,y:number,pressure:number)
function PanGesture:onMoveComplete(context, func)
	self.onMoveCompleteCallback = func
	self.onMoveCompleteContext = context
end

function PanGesture:getTouchCount()
	return #self.touches
end

---@param x number
---@param y number
---@param pressure number
function PanGesture:touchpressed(id, x, y, pressure)
	if #self.touches >= self.maxCount or not util.pointInConstraint(x, y, self.constraint) then
		return false
	end

	self.touches[#self.touches + 1] = {id, x, y, pressure}
	self:_update(false, 0, 0)
	return true
end

---@param x number
---@param y number
---@param dx number
---@param dy number
---@param pressure number
function PanGesture:touchmoved(id, x, y, dx, dy, pressure)
	-- Update gesture
	for _, v in ipairs(self.touches) do
		if v[1] == id then
			if self.clipTouch then
				x, y = util.ensurePointInside(x, y, self.constraint)
			end

			v[2], v[3], v[4] = x, y, pressure
			self:_update(false, dx, dy)
			return true
		end
	end

	return false
end

---@param x number
---@param y number
function PanGesture:touchreleased(id, x, y)
	for i, v in ipairs(self.touches) do
		if v[1] == id then
			if self.clipTouch then
				x, y = util.ensurePointInside(x, y, self.constraint)
			end

			v[2], v[3] = x, y
			self:_update(#self.touches <= self.minCount, 0, 0)
			table.remove(self.touches, i)
			return true
		end
	end

	return false
end

---@private
---@param finalize boolean
---@param dx number
---@param dy number
function PanGesture:_update(finalize, dx, dy)
	if #self.touches < self.minCount then
		return
	end

	-- Sum pressure
	local avgP = 0
	for _, v in ipairs(self.touches) do
		avgP = avgP + v[4]
	end

	-- Average
	avgP = avgP / #self.touches
	dx = dx / #self.touches
	dy = dy / #self.touches

	if (not self.lastX) or (not self.lastY) then
		self.lastX = 0 ---@private
		self.lastY = 0 ---@private
	end

	self.lastX = self.lastX + dx ---@private
	self.lastY = self.lastY + dy ---@private

	if self.onMoveCallback then
		self.onMoveCallback(self.onMoveContext, self.lastX, self.lastY, dx, dy, avgP)
	end

	if finalize then
		if self.onMoveCompleteCallback then
			self.onMoveCompleteCallback(self.onMoveContext, self.lastX, self.lastY, avgP)
		end

		self.lastX = nil ---@private
		self.lastY = nil ---@private
	end
end

function PanGesture:__tostring()
	return string.format("PanGesture<%p>(%d, %d, %s, %p)", self, self.minCount, self.maxCount, self.clipTouch, self.constraint)
end

setmetatable(PanGesture, {
	__call = function(_, minfingers, maxfingers, clip, constraint)
		local object = setmetatable({}, PanGesture)
		object:init(minfingers, maxfingers, clip, constraint)
		return object
	end
})

return PanGesture