ctx.preview documentation for picker?

[kocv59]

Where is the documentation for ctx.preview for example ctx.preview:highlight and ctx.preview:set_lines? I want to preview part of the current file starting at some line.

[drowning-cat]

There is no documentation for preview methods:

https://github.com/folke/snacks.nvim/blob/bc0630e43be5699bb94dadc302c0d21615421d93/lua/snacks/picker/preview.lua

[dpetka2001]

These are actually the available previewers. The methods are in

snacks.nvim/lua/snacks/picker/core/preview.lua

Lines 266 to 284 in bc0630e

	function M:highlight(opts)
	opts = opts or {}
	local ft = opts.ft
	if not ft and opts.buf then
	local modeline = Snacks.picker.util.modeline(opts.buf)
	ft = modeline and modeline.ft
	end
	if not ft and (opts.file or opts.buf) then
	ft = vim.filetype.match({
	buf = opts.buf or self.win.buf,
	filename = opts.file,
	})
	end
	self:check_big()
	local lang = Snacks.util.get_lang(opts.lang or ft)
	if not (lang and pcall(vim.treesitter.start, self.win.buf, lang)) and ft then
	vim.bo[self.win.buf].syntax = ft
	end
	end

[kocv59]

Can documentation be added? I can't understand what to do looking at the code but documentation would help.

[drowning-cat]

To set a specific line and column for an item's file previewer, define item.pos = { line, col }. For example:

picker = {
  sources = {
    files = {
      transform = function(item)
        item.pos = { 2, 1 }
      end,

[kocv59]

How can I use it with pick()?

Snacks.picker.pick({
  finder = finder,
  format = format,
  confirm = confirm,
  preview = "file"
})

For example #2065.

[drowning-cat]

When defining an item inside a finder, you need to create an additional field called pos. If you look at #2065 (comment), you’ll see:

table.insert(headings, {
  file = vim.api.nvim_buf_get_name(bufnr),
  pos = { row + 1, col }, -- Position to preview/jump
  text = text,
  name = text,
  depth = id,
})

[kocv59]

I should use table.insert or transform that you showed before?

[drowning-cat]

You should use table.insert inside the finder function. Forget about the transform function — I only used it as an example of modifying items because it was easier than recreating finder from scratch just for a quick demonstration.

[amit152116]

I am building a custom Picker where I want to load the preview as the item is iterated. How to implement the preview function to do that. I can't load the preview with the results as the list is too big, and also, for each preview, I have to run a command via vim.fn.jobstart, which makes it very slow. here is the code snippet of picker

    Snacks.picker.pick {
      items = results,
      title = title,
      format = function(item, _)
        if not item or not item.display then return { { "" } } end

        -- Return TWO text segments, each with a different highlight group
        return {
          { "  ", "Icon" },
          { item.display, "PickWin" }, -- Highlight the topic name
        }
      end,
      layout = {
        preset = "default", -- or your preferred layout
        cycle = true,
        layout = {
          title = title,
        },
      },
      preview = function(ctx)
        if not ctx.item then return true end
        local item = ctx.item
        inspect(item)

        local prev_cmd = opts.preview_cmd

        local type = type(prev_cmd)
        if type == "string" then
          prev_cmd = { "ros2", prev_cmd, item.value }
        elseif type == "function" then
          prev_cmd = prev_cmd(item) or ""
        elseif type == "table" then
          prev_cmd = table.insert(prev_cmd, 1, "ros")
        end

        if prev_cmd == nil then return end

        JobRunner.run(prev_cmd, {
          on_complete = function(preview)
            if preview then
              -- Here I want to put the preview content in the picker. 
            end
          end,
        })
      end,
    }

[drowning-cat]

I would move this to another discussion. You need to provide a minimal example with the items filled in. In general, you can use ctx.preview:set_lines(lines). The only issue is that the text won’t be highlighted, as it depends on the filetype you’re displaying. Also, there is a cmd previewer; take a look at how the git_show previewer is implemented.

[amit152116]

Here is the full method :

local function ros2_picker(cmd, opts)
  opts = opts or {}

  local title = string.format("  ROS2 %s", opts.title or cmd)

  opts.on_complete = function(results)
    if not results or #results == 0 then return end

    Snacks.picker.pick {
      items = results,
      title = title,
      format = function(item, _)
        if not item or not item.display then return { { "" } } end

        -- Return TWO text segments, each with a different highlight group
        return {
          { "  ", "Icon" },
          { item.display, "PickWin" }, -- Highlight the topic name
        }
      end,
      layout = {
        preset = "default", -- or your preferred layout
        cycle = true,
        layout = {
          title = title,
        },
      },
      preview = function(ctx)
        if not ctx.item then return true end
        local item = ctx.item
        inspect(item)

        local prev_cmd = opts.preview_cmd

        local type = type(prev_cmd)
        if type == "string" then
          prev_cmd = { "ros2", prev_cmd, item.value }
        elseif type == "function" then
          prev_cmd = prev_cmd(item) or ""
        elseif type == "table" then
          prev_cmd = table.insert(prev_cmd, 1, "ros")
        end

        if prev_cmd == nil then return end

        JobRunner.run(prev_cmd, {
          on_complete = function(preview)
            if preview then
              Snacks.notify(preview, { level = "info", title = title })
            end
          end,
        })
      end,
    }
  end

  JobRunner.stream("ros2 " .. cmd, opts)
end

I am running a command ros2 interface list --only-msgs which gives the results list as

{ {
    display = "/diagnostics",
    idx = 1,
    preview = { "/diagnostics" },
    score = 1000,
    value = "/diagnostics"
  }, {
    display = "/mavros/actuator_control",
    idx = 2,
    preview = { "/mavros/actuator_control" },
    score = 1000,
    value = "/mavros/actuator_control"
  }, {
    display = "/mavros/adsb/send",
    idx = 3,
    preview = { "/mavros/adsb/send" },
    score = 1000,
    value = "/mavros/adsb/send"
  }, {
    display = "/mavros/adsb/vehicle",
    idx = 4,
    preview = { "/mavros/adsb/vehicle" },
    score = 1000,
    value = "/mavros/adsb/vehicle"
  }, {
    display = "/mavros/altitude",
    idx = 5,
    preview = { "/mavros/altitude" },
    score = 1000,
    value = "/mavros/altitude"
  }, {
    display = "/mavros/battery",
    idx = 6,
    preview = { "/mavros/battery" },
    score = 1000,
    value = "/mavros/battery"
  }, {
    display = "/mavros/cam_imu_sync/cam_imu_stamp",
    idx = 7,
    preview = { "/mavros/cam_imu_sync/cam_imu_stamp" },
    score = 1000,
    value = "/mavros/cam_imu_sync/cam_imu_stamp"
  }}

Then, for the preview of the item, I am running the command ros2 interface show {item.value}, which I want to show in the preview window. How to show the output of the command in the preview window when the item cursor is on that item.

And outpout of send command is :

Type: diagnostic_msgs/msg/DiagnosticArray

Publisher count: 2

Node name: mavros_router
Node namespace: /mavros
Topic type: diagnostic_msgs/msg/DiagnosticArray
Endpoint type: PUBLISHER
GID: 01.0f.22.6d.5b.d0.6d.fb.00.00.00.00.00.00.21.03.00.00.00.00.00.00.00.00
QoS profile:
Reliability: RELIABLE
History (Depth): UNKNOWN
Durability: VOLATILE
Lifespan: Infinite
Deadline: Infinite
Liveliness: AUTOMATIC
Liveliness lease duration: Infinite

Node name: mavros
Node namespace: /mavros
Topic type: diagnostic_msgs/msg/DiagnosticArray
Endpoint type: PUBLISHER
GID: 01.0f.22.6d.5b.d0.6d.fb.00.00.00.00.00.00.37.03.00.00.00.00.00.00.00.00
QoS profile:
Reliability: RELIABLE
History (Depth): UNKNOWN
Durability: VOLATILE
Lifespan: Infinite
Deadline: Infinite
Liveliness: AUTOMATIC
Liveliness lease duration: Infinite

Subscription count: 0

[drowning-cat]

Doesn't work?

if preview then
  ctx.preview:set_lines(preview)
  ctx.preview:highlight({ ft = "yaml" })
else
  ctx.preview:notify("No preview", "error")
end

[amit152116]

Yes, it is working. There was some issue with the preview data. Thanks for the help.

[kocv59]

@amit152116 Can you show the full working method?