Stateful switch

README.md

@@ -83,6 +83,7 @@ Plugin | Description
 [`selectionhighlight`](plugins/selectionhighlight.lua?raw=1) | Highlights regions of code that match the current selection *([screenshot](https://user-images.githubusercontent.com/3920290/80710883-5f597c80-8ae7-11ea-97f0-76dfacc08439.png))*
 [`sort`](plugins/sort.lua?raw=1) | Sorts selected lines alphabetically
 [`spellcheck`](plugins/spellcheck.lua?raw=1) | Underlines misspelt words *([screenshot](https://user-images.githubusercontent.com/3920290/79923973-9caa7400-842e-11ea-85d4-7a196a91ca50.png))* *— note: on Windows a [`words.txt`](https://github.com/dwyl/english-words/blob/master/words.txt) dictionary file must be placed beside the exe*
+[`stateful_switch`](plugins/stateful_switch.lua?raw=1) | Improved switching between split panes which are displaying the same text file
 [`tabnumbers`](plugins/tabnumbers.lua?raw=1) | Displays tab numbers from 1–9 next to their names *([screenshot](https://user-images.githubusercontent.com/16415678/101285362-007a8500-37e5-11eb-869b-c10eb9d9d902.png))
 [`theme16`](https://github.com/monolifed/theme16)* | Theme manager with base16 themes
 [`titleize`](plugins/titleize.lua?raw=1) | Titleizes selected string (`hello world` => `Hello World`)

plugins/stateful_switch.lua

@@ -0,0 +1,106 @@
+local core = require "core"
+local command = require "core.command"
+local keymap = require "core.keymap"
+
+
+-- Keeps the line and column number where cursor was while switching
+-- between split panes. It is useful when working on a large
+-- text file in multiple panes.
+
+
+local function new_weak_table()
+  return setmetatable({ }, { __mode = "v" })
+end
+
+
+local function dv()
+  return core.active_view
+end
+
+
+local view_states = { }
+
+
+local function find_in_view_state(view_state, node, idx)
+  for k, v in pairs(view_state) do
+    if v.node == node and v.idx == idx then
+      return k
+    end
+  end
+
+  return -1
+end
+
+
+local function save_view_state()
+  local node = core.root_view:get_active_node()
+  local idx = node:get_view_idx(dv())
+  if dv().doc == nil then
+    return
+  end
+
+  local line, col = dv().doc:get_selection(false)
+
+  local ind = find_in_view_state(view_states, node, idx)
+
+  local state = new_weak_table()
+  state.node = node
+  state.idx = idx
+  state.line = line
+  state.col = col
+
+  if ind > -1 then
+    view_states[ind] = nil
+  end
+
+  table.insert(view_states, state)
+end
+
+
+local function restore_view_state()
+  local node = core.root_view:get_active_node()
+  local idx = node:get_view_idx(dv())
+
+  local ind = find_in_view_state(view_states, node, idx)
+  if ind > -1 then
+    local state = view_states[ind]
+    local line = state.line
+    local col = state.col
+
+    dv().doc:set_selection(line, col)
+    dv():scroll_to_line(line, true)
+  end
+end
+
+
+for _, dir in ipairs { "left", "right", "up", "down" } do
+  command.add(nil, {
+    ["stateful-switch:switch-to-" .. dir] = function ()
+      save_view_state()
+      command.perform("root:switch-to-" .. dir)
+      restore_view_state()
+    end
+  })
+end
+
+
+for _, dir in ipairs { "previous", "next" } do
+  command.add(nil, {
+    ["stateful-switch:switch-to-" .. dir .. "-tab"] = function ()
+      save_view_state()
+      command.perform("root:switch-to-" .. dir .. "-tab")
+      restore_view_state()
+    end
+  })
+end
+
+
+keymap.add({
+  ["alt+j"] = "stateful-switch:switch-to-left",
+  ["alt+l"] = "stateful-switch:switch-to-right",
+  ["alt+i"] = "stateful-switch:switch-to-up",
+  ["alt+k"] = "stateful-switch:switch-to-down",
+  ["ctrl+tab"] = "stateful-switch:switch-to-next-tab",
+  ["ctrl+shift+tab"] = "stateful-switch:switch-to-previous-tab"
+})
+