commit c50714de519939daaf9cb443f92724e85578c91e
Author: Axel Meyer <axel.meyer@durania.net>
Date:   Thu May 14 15:01:52 2026 +0200

    feat(P.3.6): lib-core.selection v0.1.0 — initial release
    
    Handle-Registry + Click/Drag-Box State-Machine + Selection-Set-API +
    alpha-tinted render-helpers. Release-edge detection internal via
    prev_click_down (no was_action_released in lib-core.input).
    
    See: meta/docs/superpowers/specs/2026-05-14-p3-6-lib-selection-design.md

diff --git a/README.md b/README.md
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index 0000000..aef5a76
--- /dev/null
+++ b/README.md
@@ -0,0 +1,45 @@
+# lib-core.selection — v0.1.0
+
+Click-Select + Drag-Box-Select + Selection-Set-State.
+
+## Quick Setup
+
+```lua
+local selection = require("lib-core.selection")
+local input     = require("lib-core.input")
+
+input.bind("lmb",        { "mouse_left" })
+input.bind("mod_add",    { "shift" })
+input.bind("mod_toggle", { "ctrl" })
+
+selection.bind_action("lmb")
+selection.bind_modifier_add("mod_add")
+selection.bind_modifier_toggle("mod_toggle")
+
+local handle = selection.register(function()
+    return { x = entity.x, y = entity.y, w = entity.w, h = entity.h }
+end)
+
+-- per-frame:
+function update(ctx, dt)  selection.update(dt)  end
+function render(ctx)
+    camera.begin()
+        -- entities…
+        selection.render_highlights()    -- world-space
+    camera.finish()
+    selection.render_drag_box()          -- screen-space
+end
+```
+
+## API
+
+- Registry: `register(aabb_fn) → handle`, `unregister(h)`, `count_registered()`
+- Set-Query: `list()`, `count()`, `contains(h)`, `is_empty()`
+- Set-Mutation: `add(h)`, `remove(h)`, `toggle(h)`, `clear()`
+- Bindings: `bind_action(name)`, `bind_modifier_add(name)`, `bind_modifier_toggle(name)`
+- State-Config: `set_drag_threshold(px)` / `drag_threshold()`, `set_enabled(bool)` / `enabled()`
+- State-Query: `drag_state() → "idle"|"ambiguous"|"dragging"`, `box_rect() → {x,y,w,h}|nil`
+- Visual: `set_drag_box_color(r,g,b,a)` / `drag_box_color()`, `set_highlight_color(r,g,b,a)` / `highlight_color()`
+- Per-Frame: `update(dt)`, `render_drag_box()`, `render_highlights()`
+
+See `meta/docs/superpowers/specs/2026-05-14-p3-6-lib-selection-design.md` for full design.
diff --git a/init.lua b/init.lua
new file mode 100644
index 0000000..151bcfa
--- /dev/null
+++ b/init.lua
@@ -0,0 +1,398 @@
+-- =====================================================================
+-- lib-core.selection v0.1.0 — Click-Select + Drag-Box-Select + Selection-Set-State
+-- See: meta/docs/superpowers/specs/2026-05-14-p3-6-lib-selection-design.md
+--
+-- Handle-Registry-Pattern (analog interaction): module registers AABB-callbacks,
+-- lib polls during hit-test. State-Machine (idle/ambiguous/dragging) für
+-- Click-vs-Drag-Disambiguation via pixel-threshold. Modifier-Bindings via
+-- action-names (mod_add, mod_toggle). AABB-Hit-Test (last-registered-wins).
+-- Render: alpha-tinted draw_rect helpers (kein Outline).
+--
+-- DEPRECATED-MVPs siehe Spec §7 + inline-comments unten.
+-- =====================================================================
+
+local input  = require("lib-core.input")
+local camera = require("lib-core.camera")
+
+-- Registry: array of {handle, aabb_fn}. Last-registered = end-of-array.
+local selectables = {}
+local next_handle = 1
+
+-- Selection-Set: table of handle → true.
+local selected = {}
+
+-- State-Machine.
+local drag_state      = "idle"   -- "idle" | "ambiguous" | "dragging"
+local press_x         = 0
+local press_y         = 0
+local cur_x           = 0
+local cur_y           = 0
+local drag_threshold  = 4         -- px
+local prev_click_down = false     -- release-edge detection
+
+-- Bindings.
+local click_action      = nil
+local mod_add_action    = nil
+local mod_toggle_action = nil
+
+-- Runtime-Toggle.
+local enabled_flag = true
+
+-- Visual settings (RGBA-tuples as {r,g,b,a} tables).
+local drag_box_rgba  = { 255, 255, 255, 32 }
+local highlight_rgba = {  60, 255,  80, 80 }
+
+-- ---------- internal helpers ----------
+
+local function check_string(arg_name, value)
+    if type(value) ~= "string" or value == "" then
+        error(string.format("selection.%s: must be non-empty string", arg_name))
+    end
+end
+
+local function find_selectable_index(handle)
+    for i, s in ipairs(selectables) do
+        if s.handle == handle then return i end
+    end
+    return nil
+end
+
+local function find_aabb_fn(handle)
+    for _, s in ipairs(selectables) do
+        if s.handle == handle then return s.aabb_fn end
+    end
+    return nil
+end
+
+local function clamp_color(name, v)
+    if type(v) ~= "number" or v < 0 or v > 255 then
+        error(string.format("selection.%s: color components must be 0..255", name))
+    end
+end
+
+local function resolve_mode()
+    if mod_toggle_action and input.is_action_down(mod_toggle_action) then
+        return "toggle"
+    end
+    if mod_add_action and input.is_action_down(mod_add_action) then
+        return "add"
+    end
+    return "replace"
+end
+
+local function commit_click(sx, sy, mode)
+    local wx, wy = camera.screen_to_world(sx, sy)
+    local hit = nil
+    -- Last-registered-wins: iterate in registration order, keep last match.
+    for _, s in ipairs(selectables) do
+        local a = s.aabb_fn()
+        if a and type(a) == "table"
+           and type(a.x) == "number" and type(a.y) == "number"
+           and type(a.w) == "number" and type(a.h) == "number" then
+            if wx >= a.x and wx <= a.x + a.w
+               and wy >= a.y and wy <= a.y + a.h then
+                hit = s.handle
+            end
+        end
+    end
+
+    if mode == "replace" then
+        selected = {}
+        if hit then selected[hit] = true end
+    elseif mode == "add" then
+        if hit then selected[hit] = true end
+    elseif mode == "toggle" then
+        if hit then
+            if selected[hit] then selected[hit] = nil
+            else                  selected[hit] = true end
+        end
+    end
+end
+
+local function commit_box(press_sx, press_sy, rel_sx, rel_sy, mode)
+    -- Project both screen corners to world (camera-state-aware).
+    local wx1, wy1 = camera.screen_to_world(press_sx, press_sy)
+    local wx2, wy2 = camera.screen_to_world(rel_sx, rel_sy)
+    local bxmin = math.min(wx1, wx2)
+    local bymin = math.min(wy1, wy2)
+    local bxmax = math.max(wx1, wx2)
+    local bymax = math.max(wy1, wy2)
+
+    local hits = {}
+    for _, s in ipairs(selectables) do
+        local a = s.aabb_fn()
+        if a and type(a) == "table"
+           and type(a.x) == "number" and type(a.y) == "number"
+           and type(a.w) == "number" and type(a.h) == "number" then
+            -- Any-overlap (AABB-intersection):
+            if not (a.x > bxmax or a.x + a.w < bxmin
+                    or a.y > bymax or a.y + a.h < bymin) then
+                hits[#hits + 1] = s.handle
+            end
+        end
+    end
+
+    if mode == "replace" then
+        selected = {}
+        for _, h in ipairs(hits) do selected[h] = true end
+    elseif mode == "add" then
+        for _, h in ipairs(hits) do selected[h] = true end
+    elseif mode == "toggle" then
+        for _, h in ipairs(hits) do
+            if selected[h] then selected[h] = nil
+            else                selected[h] = true end
+        end
+    end
+end
+
+-- ---------- public API ----------
+
+local M = {}
+
+-- Registry
+
+function M.register(aabb_fn)
+    if type(aabb_fn) ~= "function" then
+        error("selection.register: aabb_fn must be a function")
+    end
+    local h = next_handle
+    next_handle = next_handle + 1
+    selectables[#selectables + 1] = { handle = h, aabb_fn = aabb_fn }
+    return h
+end
+
+function M.unregister(handle)
+    local idx = find_selectable_index(handle)
+    if idx then
+        table.remove(selectables, idx)
+        selected[handle] = nil   -- also remove from selection if present
+    end
+    -- silent no-op if handle unknown
+end
+
+function M.count_registered()
+    return #selectables
+end
+
+-- Set-Query
+
+function M.list()
+    local out = {}
+    for h, _ in pairs(selected) do
+        out[#out + 1] = h
+    end
+    return out
+end
+
+function M.count()
+    local n = 0
+    for _ in pairs(selected) do n = n + 1 end
+    return n
+end
+
+function M.contains(handle)
+    return selected[handle] == true
+end
+
+function M.is_empty()
+    return next(selected) == nil
+end
+
+-- Set-Mutation (programmatic)
+
+function M.add(handle)
+    if find_aabb_fn(handle) == nil then
+        error("selection.add: handle not registered")
+    end
+    selected[handle] = true
+end
+
+function M.remove(handle)
+    selected[handle] = nil
+end
+
+function M.toggle(handle)
+    if find_aabb_fn(handle) == nil then
+        error("selection.toggle: handle not registered")
+    end
+    if selected[handle] then selected[handle] = nil
+    else                     selected[handle] = true end
+end
+
+function M.clear()
+    selected = {}
+end
+
+-- Bindings
+
+function M.bind_action(action_name)
+    check_string("bind_action", action_name)
+    click_action = action_name
+end
+
+function M.bind_modifier_add(action_name)
+    check_string("bind_modifier_add", action_name)
+    mod_add_action = action_name
+end
+
+function M.bind_modifier_toggle(action_name)
+    check_string("bind_modifier_toggle", action_name)
+    mod_toggle_action = action_name
+end
+
+-- State-Machine-Config
+
+function M.set_drag_threshold(px)
+    if type(px) ~= "number" or px <= 0 then
+        error("selection.set_drag_threshold: must be positive number")
+    end
+    drag_threshold = px
+end
+
+function M.drag_threshold()
+    return drag_threshold
+end
+
+function M.set_enabled(b)
+    if type(b) ~= "boolean" then
+        error("selection.set_enabled: must be boolean")
+    end
+    enabled_flag = b
+end
+
+function M.enabled()
+    return enabled_flag
+end
+
+-- State-Machine-Query
+
+function M.drag_state()
+    return drag_state
+end
+
+function M.box_rect()
+    if drag_state ~= "dragging" then return nil end
+    local bx = math.min(press_x, cur_x)
+    local by = math.min(press_y, cur_y)
+    local bw = math.abs(cur_x - press_x)
+    local bh = math.abs(cur_y - press_y)
+    return { x = bx, y = by, w = bw, h = bh }
+end
+
+-- Visual-Config
+
+function M.set_drag_box_color(r, g, b, a)
+    clamp_color("set_drag_box_color.r", r)
+    clamp_color("set_drag_box_color.g", g)
+    clamp_color("set_drag_box_color.b", b)
+    clamp_color("set_drag_box_color.a", a)
+    drag_box_rgba = { r, g, b, a }
+end
+
+function M.drag_box_color()
+    return { drag_box_rgba[1], drag_box_rgba[2], drag_box_rgba[3], drag_box_rgba[4] }
+end
+
+function M.set_highlight_color(r, g, b, a)
+    clamp_color("set_highlight_color.r", r)
+    clamp_color("set_highlight_color.g", g)
+    clamp_color("set_highlight_color.b", b)
+    clamp_color("set_highlight_color.a", a)
+    highlight_rgba = { r, g, b, a }
+end
+
+function M.highlight_color()
+    return { highlight_rgba[1], highlight_rgba[2], highlight_rgba[3], highlight_rgba[4] }
+end
+
+-- Per-Frame
+
+function M.update(dt)
+    if not enabled_flag then return end
+    if click_action == nil then return end
+
+    -- Release-edge detection (lib-core.input has no was_action_released).
+    local cur_down = input.is_action_down(click_action)
+    local released = (prev_click_down and not cur_down)
+    prev_click_down = cur_down
+
+    local mx, my = engine.input.get_mouse_pos()
+
+    if drag_state == "idle" then
+        if input.was_action_pressed(click_action) then
+            press_x, press_y = mx, my
+            cur_x,   cur_y   = mx, my
+            drag_state = "ambiguous"
+        end
+    elseif drag_state == "ambiguous" then
+        cur_x, cur_y = mx, my
+        local dx, dy = cur_x - press_x, cur_y - press_y
+        if (dx * dx + dy * dy) >= (drag_threshold * drag_threshold) then
+            drag_state = "dragging"
+        end
+    elseif drag_state == "dragging" then
+        cur_x, cur_y = mx, my
+    end
+
+    if released and drag_state ~= "idle" then
+        local mode = resolve_mode()
+        if drag_state == "ambiguous" then
+            commit_click(press_x, press_y, mode)
+        else  -- "dragging"
+            commit_box(press_x, press_y, cur_x, cur_y, mode)
+        end
+        drag_state = "idle"
+    end
+end
+
+-- Render-Helpers
+--
+-- CONVENTION (not enforced):
+--   render_highlights() MUSS zwischen camera.begin()/camera.finish() aufgerufen werden.
+--   render_drag_box()   MUSS AUSSERHALB camera.begin/finish aufgerufen werden.
+
+function M.render_drag_box()
+    if drag_state ~= "dragging" then return end
+    local bx = math.min(press_x, cur_x)
+    local by = math.min(press_y, cur_y)
+    local bw = math.abs(cur_x - press_x)
+    local bh = math.abs(cur_y - press_y)
+    local c = engine.render.rgba(drag_box_rgba[1], drag_box_rgba[2],
+                                  drag_box_rgba[3], drag_box_rgba[4])
+    engine.render.draw_rect(bx, by, bw, bh, c)
+end
+
+function M.render_highlights()
+    if next(selected) == nil then return end
+    local c = engine.render.rgba(highlight_rgba[1], highlight_rgba[2],
+                                  highlight_rgba[3], highlight_rgba[4])
+    for handle, _ in pairs(selected) do
+        local aabb_fn = find_aabb_fn(handle)
+        if aabb_fn then
+            local a = aabb_fn()
+            if a and type(a) == "table"
+               and type(a.x) == "number" and type(a.y) == "number"
+               and type(a.w) == "number" and type(a.h) == "number" then
+                engine.render.draw_rect(a.x, a.y, a.w, a.h, c)
+            end
+        end
+    end
+end
+
+-- DEPRECATED-MVP: was_action_released in lib-core.input (currently tracked internally
+--                 via prev_click_down — promote to input-lib when 2nd consumer needs it)
+-- DEPRECATED-MVP: pixel-perfect click hit-test (needs sprite-API + opacity-mask)
+-- DEPRECATED-MVP: register(aabb_fn, z) z-order disambiguator
+-- DEPRECATED-MVP: on_changed(fn) observer-callback (polling-API sufficient for RTS-MVP)
+-- DEPRECATED-MVP: capability-/interface-based deps (oneOf-resolver — own architectural slice)
+-- DEPRECATED-MVP: lib-core.drag extraction (when 2nd consumer appears: inventory-DnD,
+--                 map-editor-paint, area-pick minigame)
+-- DEPRECATED-MVP: draw_rect_outline engine-add (when alpha-fill aesthetic insufficient)
+-- DEPRECATED-MVP: spatial-index (Quadtree/Grid) when N > ~1000 selectables
+-- DEPRECATED-MVP: selection.first() / iter() for stable iteration order
+-- DEPRECATED-MVP: per-selectable highlight-color (when friend/enemy distinction needed)
+-- DEPRECATED-MVP: window-focus-loss drag-state reset
+-- DEPRECATED-MVP: double-click-select-all-of-type (RTS polish)
+-- DEPRECATED-MVP: drag-beyond-window-edge auto-cam-pan (couples to camera-lib)
+
+return M
diff --git a/manifest.lib b/manifest.lib
new file mode 100644
index 0000000..59e36f1
--- /dev/null
+++ b/manifest.lib
@@ -0,0 +1 @@
+{"id":"lib-core.selection","version":"0.1.0","api_min":"0.1","deps":[{"id":"lib-core.input","version":"0.3.0"},{"id":"lib-core.camera","version":"0.3.0"}]}
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