logic layer

inc/logic/logic.focus.lua

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+--- @section Focus
+
+local FOCUS_DEFAULT_SPEED = 5
+
+local active = false
+local closing = false
+local driven = false
+local center_x = 0
+local center_y = 0
+local radius = 0
+local speed = FOCUS_DEFAULT_SPEED
+local on_complete = nil
+local driven_initial_r = 0
+local driven_max_r = 0
+
+local function max_radius(cx, cy)
+  local dx = math.max(cx, Config.screen.width - cx)
+  local dy = math.max(cy, Config.screen.height - cy)
+  return math.sqrt(dx * dx + dy * dy)
+end
+
+--- Starts a focus overlay that reveals content through an expanding circle.
+--- @within Focus
+--- @param cx number The x-coordinate of the circle center.
+--- @param cy number The y-coordinate of the circle center.
+--- @param[opt] params table Optional parameters: `speed` (number) expansion rate in pixels/frame, `initial_radius` (number) starting radius in pixels (default 0), `on_complete` (function) callback when overlay disperses.
+function Focus.start(cx, cy, params)
+  params = params or {}
+  active = true
+  closing = false
+  driven = false
+  center_x = cx
+  center_y = cy
+  radius = params.initial_radius or 0
+  speed = params.speed or FOCUS_DEFAULT_SPEED
+  on_complete = params.on_complete
+end
+
+--- Starts a closing focus overlay that hides content by shrinking the visible circle.
+--- @within Focus
+--- @param cx number The x-coordinate of the circle center.
+--- @param cy number The y-coordinate of the circle center.
+--- @param[opt] params table Optional parameters: `speed` (number) shrink rate in pixels/frame, `on_complete` (function) callback when screen is fully covered.
+function Focus.close(cx, cy, params)
+  params = params or {}
+  active = true
+  closing = true
+  driven = false
+  center_x = cx
+  center_y = cy
+  radius = max_radius(cx, cy)
+  speed = params.speed or FOCUS_DEFAULT_SPEED
+  on_complete = params.on_complete
+end
+
+--- Starts a driven focus overlay whose radius is controlled externally via Focus.set_percentage().
+--- The radius maps linearly from initial_radius (at 0%) to the screen corner distance (at 100%).
+--- @within Focus
+--- @param cx number The x-coordinate of the circle center.
+--- @param cy number The y-coordinate of the circle center.
+--- @param[opt] params table Optional parameters: `initial_radius` (number) radius at 0% (default 0).
+function Focus.start_driven(cx, cy, params)
+  params = params or {}
+  active = true
+  closing = false
+  driven = true
+  center_x = cx
+  center_y = cy
+  driven_initial_r = params.initial_radius or 0
+  driven_max_r = max_radius(cx, cy)
+  radius = driven_initial_r
+  on_complete = nil
+end
+
+--- Sets the visible radius as a percentage of the full screen extent.
+--- Only has effect when the overlay is in driven mode (started via Focus.start_driven).
+--- @within Focus
+--- @param pct number A value from 0 to 1 (0 = initial_radius, 1 = full screen).
+function Focus.set_percentage(pct)
+  if not driven then return end
+  radius = driven_initial_r + pct * (driven_max_r - driven_initial_r)
+end
+
+--- Checks whether the focus overlay is currently active.
+--- @within Focus
+--- @return boolean Whether the focus overlay is active.
+function Focus.is_active()
+  return active
+end
+
+--- Stops the focus overlay immediately.
+--- @within Focus
+function Focus.stop()
+  active = false
+  closing = false
+  driven = false
+  radius = 0
+  on_complete = nil
+end
+
+--- Updates the focus overlay animation. No-op in driven mode.
+--- @within Focus
+function Focus.update()
+  if not active then return end
+  if driven then return end
+
+  if closing then
+    radius = radius - speed
+    if radius <= 0 then
+      local cb = on_complete
+      Focus.stop()
+      if cb then cb() end
+    end
+  else
+    radius = radius + speed
+    if radius >= max_radius(center_x, center_y) then
+      local cb = on_complete
+      Focus.stop()
+      if cb then cb() end
+    end
+  end
+end
+
+--- Draws the focus overlay (black screen with circular cutout).
+--- Must be called after all other drawing to appear on top of every visual layer.
+--- @within Focus
+function Focus.draw()
+  if not active then return end
+
+  local cx = center_x
+  local cy = center_y
+  local r = radius
+  local w = Config.screen.width
+  local h = Config.screen.height
+  local color = Config.colors.black
+
+  if closing and r <= 0 then
+    rect(0, 0, w, h, color)
+    return
+  end
+
+  local top = math.max(0, math.floor(cy - r))
+  local bottom = math.min(h - 1, math.ceil(cy + r))
+
+  if top > 0 then
+    rect(0, 0, w, top, color)
+  end
+
+  if bottom < h - 1 then
+    rect(0, bottom + 1, w, h - bottom - 1, color)
+  end
+
+  for y = top, bottom do
+    local dy = y - cy
+    local half_w = math.sqrt(math.max(0, r * r - dy * dy))
+    local left = math.floor(cx - half_w)
+    local right = math.ceil(cx + half_w)
+
+    if left > 0 then
+      rect(0, y, left, 1, color)
+    end
+    if right < w then
+      rect(right, y, w - right, 1, color)
+    end
+  end
+end