config/lua: add simple layout API (#14258)

Adds a simple layout lua api

4 files changed, 225 insertions, 0 deletions

diff --git a/example/layouts/columns.lua b/example/layouts/columns.lua
new file mode 100644
index 00000000..dc907cd4
--- /dev/null
+++ b/example/layouts/columns.lua
@@ -0,0 +1,12 @@
+hl.layout.register("columns", {
+    recalculate = function(ctx)
+        local n = #ctx.targets
+        if n == 0 then
+            return
+        end
+
+        for i, target in ipairs(ctx.targets) do
+            target:place(ctx:column(i, n))
+        end
+    end,
+})
diff --git a/example/layouts/grid.lua b/example/layouts/grid.lua
new file mode 100644
index 00000000..10a0cab1
--- /dev/null
+++ b/example/layouts/grid.lua
@@ -0,0 +1,14 @@
+hl.layout.register("grid", {
+    recalculate = function(ctx)
+        local n = #ctx.targets
+        if n == 0 then
+            return
+        end
+
+        local cols = math.ceil(math.sqrt(n))
+
+        for i, target in ipairs(ctx.targets) do
+            target:place(ctx:grid_cell(i, cols))
+        end
+    end,
+})
diff --git a/example/layouts/manual.lua b/example/layouts/manual.lua
new file mode 100644
index 00000000..1ba2ebd0
--- /dev/null
+++ b/example/layouts/manual.lua
@@ -0,0 +1,144 @@
+local state = {
+    order = {},
+    split = {},
+    default_split = "h",
+}
+
+local function target_id(target)
+    local window = target.window
+    return window and tostring(window.stable_id) or tostring(target.index)
+end
+
+local function active_id(ctx)
+    for _, target in ipairs(ctx.targets) do
+        local window = target.window
+        if window and window.active then
+            return target_id(target)
+        end
+    end
+
+    return state.order[#state.order]
+end
+
+local function index_of(tbl, value)
+    for i, v in ipairs(tbl) do
+        if v == value then
+            return i
+        end
+    end
+end
+
+local function sync_order(ctx)
+    local present = {}
+    local targets = {}
+
+    for _, target in ipairs(ctx.targets) do
+        local id = target_id(target)
+        present[id] = true
+        targets[id] = target
+    end
+
+    local old_order = state.order
+    state.order = {}
+
+    for _, id in ipairs(old_order) do
+        if present[id] then
+            table.insert(state.order, id)
+        else
+            state.split[id] = nil
+        end
+    end
+
+    local focused = active_id(ctx)
+    for _, target in ipairs(ctx.targets) do
+        local id = target_id(target)
+        if not index_of(state.order, id) then
+            local after = focused and index_of(state.order, focused)
+            table.insert(state.order, after and (after + 1) or (#state.order + 1), id)
+        end
+    end
+
+    return targets
+end
+
+local function place_chain(ctx, targets, ids, area, i)
+    if i > #ids then
+        return
+    end
+
+    local target = targets[ids[i]]
+    if not target then
+        return
+    end
+
+    if i == #ids then
+        target:place(area)
+        return
+    end
+
+    local split = state.split[ids[i]] or state.default_split
+    if split == "v" then
+        target:place(ctx:split(area, "top", 0.5))
+        place_chain(ctx, targets, ids, ctx:split(area, "bottom", 0.5), i + 1)
+    else
+        target:place(ctx:split(area, "left", 0.5))
+        place_chain(ctx, targets, ids, ctx:split(area, "right", 0.5), i + 1)
+    end
+end
+
+local function move_active(ctx, delta)
+    local id = active_id(ctx)
+    local i = id and index_of(state.order, id)
+    local j = i and (i + delta)
+
+    if not i or j < 1 or j > #state.order then
+        return
+    end
+
+    state.order[i], state.order[j] = state.order[j], state.order[i]
+end
+
+hl.layout.register("manual", {
+    recalculate = function(ctx)
+        local targets = sync_order(ctx)
+        place_chain(ctx, targets, state.order, ctx.area, 1)
+    end,
+
+    layout_msg = function(ctx, msg)
+        local id = active_id(ctx)
+        local command = msg:match("^(%S+)")
+
+        if command == "splith" or command == "h" then
+            if id then
+                state.split[id] = "h"
+            end
+        elseif command == "splitv" or command == "v" then
+            if id then
+                state.split[id] = "v"
+            end
+        elseif command == "splittoggle" or command == "toggle" then
+            if id then
+                state.split[id] = state.split[id] == "v" and "h" or "v"
+            end
+        elseif command == "promote" then
+            local i = id and index_of(state.order, id)
+            if i then
+                table.remove(state.order, i)
+                table.insert(state.order, 1, id)
+            end
+        elseif command == "swapnext" then
+            move_active(ctx, 1)
+        elseif command == "swapprev" then
+            move_active(ctx, -1)
+        elseif command == "rotate" then
+            for k, v in pairs(state.split) do
+                state.split[k] = v == "v" and "h" or "v"
+            end
+            state.default_split = state.default_split == "v" and "h" or "v"
+        else
+            return "manual: expected splith, splitv, splittoggle, promote, swapnext, swapprev, or rotate"
+        end
+
+        return true
+    end,
+})
diff --git a/example/layouts/spiral.lua b/example/layouts/spiral.lua
new file mode 100644
index 00000000..e97f4dbd
--- /dev/null
+++ b/example/layouts/spiral.lua
@@ -0,0 +1,55 @@
+local state = {
+    ratio = 0.58,
+    offset = 0,
+}
+
+local sides = { "left", "top", "right", "bottom" }
+local opposite = {
+    left = "right",
+    right = "left",
+    top = "bottom",
+    bottom = "top",
+}
+
+local function clamp(x, min, max)
+    return math.max(min, math.min(max, x))
+end
+
+hl.layout.register("spiral", {
+    recalculate = function(ctx)
+        local n = #ctx.targets
+        if n == 0 then
+            return
+        end
+
+        local area = ctx.area
+
+        for i, target in ipairs(ctx.targets) do
+            if i == n then
+                target:place(area)
+            else
+                local side = sides[((i - 1 + state.offset) % #sides) + 1]
+                target:place(ctx:split(area, side, state.ratio))
+                area = ctx:split(area, opposite[side], 1.0 - state.ratio)
+            end
+        end
+    end,
+
+    layout_msg = function(ctx, msg)
+        local command, arg = msg:match("^(%S+)%s*(.*)$")
+
+        if command == "ratio" then
+            state.ratio = clamp(tonumber(arg) or state.ratio, 0.1, 0.9)
+        elseif command == "grow" then
+            state.ratio = clamp(state.ratio + 0.05, 0.1, 0.9)
+        elseif command == "shrink" then
+            state.ratio = clamp(state.ratio - 0.05, 0.1, 0.9)
+        elseif command == "rotate" then
+            state.offset = (state.offset + 1) % #sides
+        else
+            return "spiral: expected ratio <0.1..0.9>, grow, shrink, or rotate"
+        end
+
+        return true
+    end,
+})