evan
97abf037b8
Follows the submodule: on_touch_down and friends become onTouchDown, the last snake_case left in the surface now that handlers are table fields rather than globals. main.lua declares SlateApp, this card's contract with its apps, and every app composes what it fills -- PaintApp is SlateApp plus TouchHandlers, Home is SlateApp alone -- which is also the only static record of the features an app needs.
74 lines
1.8 KiB
Lua
74 lines
1.8 KiB
Lua
local ui = require "ui"
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-- One node for the whole canvas: every pixel is content, so the app takes the touch
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-- callbacks raw rather than asking the tree what was hit. It wants the firmware's noise
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-- threshold and no gesture slop -- a three pixel stroke is a stroke, not a mis-tap.
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local BRUSH = 2
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---@class PaintApp : SlateApp, TouchHandlers
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local M = {}
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local canvas, area
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local lastX, lastY
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local function inside(x, y)
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return area and x >= area.x and x < area.x + area.w and y >= area.y and y < area.y + area.h
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end
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function M.init()
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log.info "paint ready"
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end
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function M.node()
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-- The painter runs on every repaint, and a repaint is what clearing means here: the
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-- tree fills the box with the background before calling it, so this only has to
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-- remember where the box landed.
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canvas = ui.custom {
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w = "fill",
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h = "fill",
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paint = function(_, x, y, w, h)
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area = { x = x, y = y, w = w, h = h }
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end,
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}
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return ui.box {
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w = "fill",
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h = "fill",
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ui.box {
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row = true,
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pad = 8,
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ui.button {
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label = "clear",
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on_click = function()
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lastX = nil
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ui.invalidate(canvas)
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end,
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},
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},
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canvas,
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}
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end
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function M.onTouchDown(x, y)
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if not inside(x, y) then
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return
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end
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lastX, lastY = x, y
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screen.fillCircle(x, y, BRUSH, ui.theme.accent)
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end
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-- Strokes are joined with a line because the poll rate, not the finger, decides the gap:
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-- a fast swipe reports points tens of pixels apart and dots alone would look dotted.
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function M.onTouchMove(x, y)
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if not lastX or not inside(x, y) then
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return
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end
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screen.drawLine(lastX, lastY, x, y, ui.theme.accent)
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screen.fillCircle(x, y, BRUSH, ui.theme.accent)
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lastX, lastY = x, y
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end
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function M.onTouchUp()
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lastX = nil
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end
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return M
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