Add `primary_selection`

2 files changed, 188 insertions, 0 deletions

diff --git a/README.md b/README.md
index 6841052..20b20d4 100644
--- a/README.md
+++ b/README.md
@@ -147,6 +147,7 @@ _Note: if you make a pull request, the table should be updated and kept in alpha
 | [`openfilelocation`](plugins/openfilelocation.lua?raw=1)                                                       | Opens the parent directory of the current file in the file manager                                                                                                                                                                                                                               |
 | [`openselected`](plugins/openselected.lua?raw=1)                                                               | Opens the selected filename or url                                                                                                                                                                                                                                                               |
 | [`pdfview`](plugins/pdfview.lua?raw=1)                                                                         | PDF preview for TeX files                                                                                                                                                                                                                                                                        |
+| [`primary_selection`](plugins/primary_selection.lua?raw=1)                                                     | Adds middle mouse click copy/paste (primary selection). To use this plugin, `xclip` must be installed.                                                                                                                                                                                           |
 | [`rainbowparen`](plugins/rainbowparen.lua?raw=1)                                                               | Show nesting of parentheses with rainbow colours                                                                                                                                                                                                                                                 |
 | [`regexreplacepreview`](plugins/regexreplacepreview.lua?raw=1)                                                 | Allows for you to write a regex and its replacement in one go, and live preview the results.                                                                                                                                                                                                     |
 | [`restoretabs`](plugins/restoretabs.lua?raw=1)                                                                 | Keep a list of recently closed tabs, and restore the tab in order on cntrl+shift+t.                                                                                                                                                                                                              |
diff --git a/plugins/primary_selection.lua b/plugins/primary_selection.lua
new file mode 100644
index 0000000..388caf0
--- /dev/null
+++ b/plugins/primary_selection.lua
@@ -0,0 +1,187 @@
+-- mod-version:3
+local core = require "core"
+local Doc = require "core.doc"
+local command = require "core.command"
+local keymap = require "core.keymap"
+local config = require "core.config"
+local common = require "core.common"
+
+local function string_to_cmd(s)
+  local result = {}
+  for match in s:gmatch("%g+") do
+    table.insert(result, match)
+  end
+  return result
+end
+
+config.plugins.primary_selection = common.merge({
+  command_in = { "xclip", "-in", "-selection", "primary" }, -- Command to use to copy the selection
+  command_out = { "xclip", "-out", "-selection", "primary" }, -- Command to use to obtain the selection
+  set_cursor = true, -- Set cursor on middle mouse click
+  min_copy_time = 0.150, -- How much time to delay setting the selection; in seconds
+  config_spec = {
+    name = "Primary selection",
+    {
+      label = "Command copy",
+      description = "Command to use to copy the selection.",
+      path = "_command_in",
+      type = "string",
+      default = "xclip -in -selection primary",
+      on_apply = function(value)
+        config.plugins.primary_selection.command_in = string_to_cmd(value)
+      end,
+    },
+    {
+      label = "Command paste",
+      description = "Command to use to obtain the selection.",
+      path = "_command_out",
+      type = "string",
+      default = "xclip -out -selection primary",
+      on_apply = function(value)
+        config.plugins.primary_selection.command_out = string_to_cmd(value)
+      end,
+    },
+    {
+      label = "Set cursor",
+      description = "Set cursor on middle mouse click.",
+      path = "set_cursor",
+      type = "toggle",
+      default = true,
+    },
+    {
+      label = "Copy timeout",
+      description = "How much time to delay setting the selection; in milliseconds.",
+      path = "min_copy_time_ms",
+      type = "number",
+      default = 150,
+      min = 0,
+      step = 50,
+      on_apply = function(value)
+        config.plugins.primary_selection.min_copy_time = value / 1000
+      end
+    },
+  }
+}, config.plugins.primary_selection)
+
+
+local last_selection_data
+--[[
+ = {
+  time = nil,
+  line1 = nil,
+  col1 = nil,
+  line2 = nil,
+  col2 = nil,
+  doc = nil,
+}
+]]
+
+local xclip_copy
+local function delayed_copy()
+  while true do
+    local data = last_selection_data
+    if not data then return end
+    local current_time = system.get_time()
+    local diff_time = current_time - data.time
+    -- Check if enough time has passed since last selection change
+    if diff_time >= config.plugins.primary_selection.min_copy_time then
+      if xclip_copy then xclip_copy:terminate() end
+      if not config.plugins.primary_selection.command_in
+       or #config.plugins.primary_selection.command_in == 0 then
+        core.warn("No primary selection copy command set")
+        break
+      end
+      xclip_copy = process.start(config.plugins.primary_selection.command_in)
+      if not xclip_copy then
+        core.warn("Unable to start copy command")
+        break
+      end
+      local text = data.doc:get_text(data.line1, data.col1, data.line2, data.col2)
+      local nbytes = #text
+      local total_written = 0
+      -- In some rare cases xclip isn't fast enough so we need to retry sending the data
+      local retry = 3
+      repeat
+        local written, err = xclip_copy:write(text)
+        if written == 0 or not written then
+          if retry > 0 then
+            retry = retry - 1
+          else
+            core.error("Error while setting primary selection. "..(err or ""))
+            break
+          end
+        else
+          retry = 3
+        end
+        total_written = total_written + written
+        text = string.sub(text, written + 1)
+      until total_written >= nbytes
+      xclip_copy:close_stream(process.STREAM_STDIN)
+      -- We need to leave the process running as killing it would destroy the copied buffer
+      break
+    end
+    coroutine.yield()
+  end
+  last_selection_data = nil
+end
+
+
+local doc_set_selections = Doc.set_selections
+function Doc:set_selections(...)
+  local result = doc_set_selections(self, ...)
+  local line1, col1, line2, col2
+  line1, col1, line2, col2 = self:get_selection()
+  if line1 ~= line2 or col1 ~= col2 then
+    if not last_selection_data then
+      -- Start "timer" to confirm the selection only after `min_copy_time` has passed
+      core.add_thread(delayed_copy)
+      last_selection_data = { }
+    end
+    -- We could extract the text here, but it is a potentially heavy operation,
+    -- so we do it only when we're actually confirming the selection.
+    -- The drawback is that if the selection is overwritten/deleted,
+    -- it is either never sent, or is different than expected.
+    -- TODO: Confirm the selection on text change.
+    last_selection_data.time  = system.get_time()
+    last_selection_data.line1 = line1
+    last_selection_data.col1  = col1
+    last_selection_data.line2 = line2
+    last_selection_data.col2  = col2
+    last_selection_data.doc   = self
+  end
+  return result
+end
+
+
+command.add("core.docview", {
+  ["primary-selection:paste"] = function(x, y, clicks, ...)
+    if not config.plugins.primary_selection.command_out
+     or #config.plugins.primary_selection.command_out == 0 then
+      core.warn("No primary selection paste command set")
+      return
+    end
+    if x and config.plugins.primary_selection.set_cursor then
+      -- TODO: There must be a better way to do this
+      core.on_event("mousepressed", "left", x, y, clicks, ...)
+      core.on_event("mousereleased", "left", x, y, clicks, ...)
+    end
+    local xclip = process.start(config.plugins.primary_selection.command_out)
+    if not xclip then
+      core.warn("Unable to start paste command")
+      return
+    end
+    local text = {}
+    repeat
+      local buffer = xclip:read_stdout()
+      table.insert(text, buffer or "")
+    until not buffer
+    if #text > 0 then
+      core.active_view.doc:text_input(table.concat(text))
+    end
+  end
+})
+
+keymap.add({
+  ["1mclick"] = "primary-selection:paste"
+})
+