Resolve preview_cutoff (first attempt)

lua/telescope/config.lua

@@ -161,10 +161,18 @@ local layout_config_defaults = {
 
     horizontal = {
       prompt_position = "bottom",
-      preview_cutoff = 120,
+      preview_cutoff = {columns = 120},
     },
 
-    -- vertical = {},
+    vertical = {
+      prompt_position = "bottom",
+      preview_cutoff = {lines = 40},
+    },
+
+    center = {
+      preview_cutoff = {lines = 40},
+      height = 0.5
+    },
 }
 
 local layout_config_description = string.format([[

lua/telescope/config/resolve.lua

@@ -93,25 +93,25 @@ That's the next step to scrolling.
 local get_default = require('telescope.utils').get_default
 
 local resolver = {}
-local _resolve_map = {}
+local _resolve_len = {}
 
 -- Booleans
-_resolve_map[function(val) return val == false end] = function(_, val)
+_resolve_len[function(val) return val == false end] = function(_, val)
   return function(...)
     return val
   end
 end
 
 -- Percentages
-_resolve_map[function(val) return type(val) == 'number' and val >= 0 and val < 1 end] = function(selector, val)
+_resolve_len[function(val) return type(val) == 'number' and val >= 0 and val < 1 end] = function(selector, val)
   return function(...)
     local selected = select(selector, ...)
     return math.floor(val * selected)
   end
 end
 
 -- Numbers
-_resolve_map[function(val) return type(val) == 'number' and val >= 1 end] = function(selector, val)
+_resolve_len[function(val) return type(val) == 'number' and val >= 1 end] = function(selector, val)
   return function(...)
     local selected = select(selector, ...)
     return math.min(val, selected)
@@ -126,20 +126,20 @@ end
 --        function(self, max_columns, max_lines): number
 --
 --    Resulting number is used for this configuration value.
-_resolve_map[function(val) return type(val) == 'function' end] = function(_, val)
+_resolve_len[function(val) return type(val) == 'function' end] = function(_, val)
   return val
 end
 
 -- Add padding option
-_resolve_map[function(val) return type(val) == 'table' and val['padding'] ~= nil end] = function(selector, val)
+_resolve_len[function(val) return type(val) == 'table' and val['padding'] ~= nil end] = function(selector, val)
   local resolve_pad = function(value)
-    for k, v in pairs(_resolve_map) do
+    for k, v in pairs(_resolve_len) do
       if k(value) then
         return v(selector, value)
       end
     end
 
-    error('invalid configuration option for padding:' .. tostring(value))
+    error('invalid configuration option for padding: ' .. tostring(value))
   end
 
   return function(...)
@@ -169,13 +169,13 @@ end
 --- The returned function will have signature:
 ---     function(self, max_columns, max_lines): number
 resolver.resolve_height = function(val)
-  for k, v in pairs(_resolve_map) do
+  for k, v in pairs(_resolve_len) do
     if k(val) then
       return v(3, val)
     end
   end
 
-  error('invalid configuration option for height:' .. tostring(val))
+  error('invalid configuration option for height: ' .. tostring(val))
 end
 
 --- Converts input to a function that returns the width.
@@ -197,13 +197,73 @@ end
 --- The returned function will have signature:
 ---     function(self, max_columns, max_lines): number
 resolver.resolve_width = function(val)
-  for k, v in pairs(_resolve_map) do
+  for k, v in pairs(_resolve_len) do
     if k(val) then
       return v(2, val)
     end
   end
 
-  error('invalid configuration option for width:' .. tostring(val))
+  error('invalid configuration option for width: ' .. tostring(val))
+end
+
+
+
+local _resolve_cut = {}
+
+-- Booleans
+_resolve_cut[function(val) return val == false or val == true end] = function(val)
+  return function()
+    return val
+  end
+end
+
+-- Columns
+_resolve_cut[function(val) return type(val) == 'table' and val['columns'] ~= nil end] = function(val)
+  return function(_,max_columns,_)
+    return (val.columns <= max_columns)
+  end
+end
+
+-- Lines
+_resolve_cut[function(val) return type(val) == 'table' and val['lines'] ~= nil end] = function(val)
+  return function(_,_,max_lines)
+    return (val.lines <= max_lines)
+  end
+end
+
+--- Function
+_resolve_cut[function(val) return type(val) == 'function' end] = function(_, val)
+  return val
+end
+
+--- Converts input to a function that returns a boolean.
+--- The input must take one of four forms:
+--- 1. boolean:
+---     The cutoff is then a function that always returns the given boolean.
+--- 2. table of the form:
+---       {columns = `foo`} <br>
+---     where `foo` is a number >= 1. <br>
+---     The cutoff is then a function that is true when `max_columns` is greater than
+---     or equal to `foo` and is false otherwise.
+--- 3. table of the form:
+---       {lines = `foo`} <br>
+---     where `foo` is a number >= 1. <br>
+---     The cutoff is then a function that is true when `max_lines` is greater than
+---     or equal to `foo` and is false otherwise.
+--- 4. function <br>
+---     Must have signature:
+---       function(self, max_columns, max_lines): boolean
+---
+--- The returned function will have signature:
+---     function(self, max_columns, max_lines): boolean
+resolver.resolve_cutoff = function(val)
+  for k, v in pairs(_resolve_cut) do
+    if k(val) then
+      return v(val)
+    end
+  end
+
+  error('invalid configuration option for cutoff: ' .. tostring(val))
 end
 
 --- Win option always returns a table with preview, results, and prompt.

lua/telescope/pickers/layout_strategies.lua

@@ -241,7 +241,8 @@ end
 ---
 layout_strategies.horizontal = make_documented_layout('horizontal', vim.tbl_extend("error", shared_options, {
     preview_width = { "Change the width of Telescope's preview window", "See |resolver.resolve_width()|", },
-    preview_cutoff = "When columns are less than this value, the preview will be disabled",
+    preview_cutoff = {"Decides whether to display preview based on size of window.",
+      "See |resolver.resolve_cutoff|"},
     prompt_position = { "Where to place prompt window.", "Available Values: 'bottom', 'top'" },
 }), function(self, max_columns, max_lines, layout_config)
   local initial_options = p_window.get_initial_window_options(self)
@@ -257,11 +258,11 @@ layout_strategies.horizontal = make_documented_layout('horizontal', vim.tbl_exte
   local picker_height = resolve.resolve_height(height_opt)(self, max_columns, max_lines)
   local height_padding = math.floor((max_lines - picker_height)/2)
 
-  if self.previewer then
+  local prev_cutoff_func = resolve.resolve_cutoff(layout_config.preview_cutoff)
+  local has_preview = self.previewer and prev_cutoff_func(self, max_columns, max_lines)
+  if has_preview then
     preview.width = resolve.resolve_width(layout_config.preview_width or function(_, cols)
-      if not self.previewer or cols < layout_config.preview_cutoff then
-        return 0
-      elseif cols < 150 then
+      if cols < 150 then
         return math.floor(cols * 0.4)
       elseif cols < 200 then
         return 80
@@ -279,7 +280,7 @@ layout_strategies.horizontal = make_documented_layout('horizontal', vim.tbl_exte
   prompt.height = 1
   results.height = picker_height - prompt.height - 2
 
-  if self.previewer then
+  if has_preview then
     preview.height = picker_height
   else
     preview.height = 0
@@ -342,7 +343,8 @@ end)
 ---
 layout_strategies.center = make_documented_layout("center", vim.tbl_extend("error", shared_options, {
   -- TODO: Should this be based on rows here?
-  preview_cutoff = "When columns are less than this value, the preview will be disabled",
+  preview_cutoff = {"Decides whether to display preview based on size of window.",
+    "See |resolver.resolve_cutoff|"},
 }), function(self, max_columns, max_lines,layout_config)
   local initial_options = p_window.get_initial_window_options(self)
   local preview = initial_options.preview
@@ -375,9 +377,12 @@ layout_strategies.center = make_documented_layout("center", vim.tbl_extend("erro
   results.line = prompt.line + 1 + (bs)
 
   preview.line = 1
-  preview.height = math.floor(prompt.line - (2 + bs))
 
-  if not self.previewer or max_columns < layout_config.preview_cutoff then
+  local prev_cutoff_func = resolve.resolve_cutoff(layout_config.preview_cutoff)
+  local has_preview = self.previewer and prev_cutoff_func(self, max_columns, max_lines)
+  if has_preview then
+    preview.height = math.floor(prompt.line - (2 + bs))
+  else
     preview.height = 0
   end
 
@@ -386,7 +391,7 @@ layout_strategies.center = make_documented_layout("center", vim.tbl_extend("erro
   preview.col = results.col
 
   return {
-    preview = self.previewer and preview.width > 0 and preview,
+    preview = self.previewer and preview.height > 0 and preview,
     results = results,
     prompt = prompt
   }
@@ -416,7 +421,10 @@ end)
 ---@eval { ["description"] = require("telescope.pickers.layout_strategies")._format("vertical") }
 ---
 layout_strategies.vertical = make_documented_layout("vertical", vim.tbl_extend("error", shared_options, {
-  preview_height = { "Change the height of Telescope's preview window", "See |resolver.resolve_height()|" },
+  preview_height = { "Change the height of Telescope's preview window",
+    "See |resolver.resolve_height()|" },
+  preview_cutoff = {"Decides whether to display preview based on size of window.",
+    "See |resolver.resolve_cutoff|"},
 }), function(self, max_columns, max_lines, layout_config)
 
   local initial_options = p_window.get_initial_window_options(self)
@@ -425,24 +433,26 @@ layout_strategies.vertical = make_documented_layout("vertical", vim.tbl_extend("
   local prompt = initial_options.prompt
 
   local width_opt = layout_config.width
-  local picker_width = resolve.resolve_width(width_opt)(self,max_columns,max_lines)
+  local picker_width = resolve.resolve_width(width_opt)(self, max_columns, max_lines)
   local width_padding = math.floor((max_columns - picker_width)/2)
 
   local height_opt = layout_config.height
-  local picker_height = resolve.resolve_height(height_opt)(self,max_columns,max_lines)
+  local picker_height = resolve.resolve_height(height_opt)(self, max_columns, max_lines)
   local height_padding = math.floor((max_lines - picker_height)/2)
 
-  if not self.previewer then
-    preview.width = 0
-  else
+  local prev_cutoff_func = resolve.resolve_cutoff(layout_config.preview_cutoff)
+  local has_preview = self.previewer and prev_cutoff_func(self, max_columns, max_lines)
+  if has_preview then
     preview.width = picker_width
+  else
+    preview.width = 0
   end
   results.width = picker_width
   prompt.width = picker_width
 
   local preview_total = 0
   preview.height = 0
-  if self.previewer then
+  if has_preview then
     preview.height = resolve.resolve_height(
       layout_config.preview_height or 0.5
     )(self, max_columns, picker_height)
@@ -455,7 +465,7 @@ layout_strategies.vertical = make_documented_layout("vertical", vim.tbl_extend("
 
   results.col, preview.col, prompt.col = width_padding, width_padding, width_padding
 
-  if self.previewer then
+  if has_preview then
     if not layout_config.mirror then
       preview.line = height_padding
       results.line = preview.line + preview.height + 2
@@ -471,7 +481,7 @@ layout_strategies.vertical = make_documented_layout("vertical", vim.tbl_extend("
   end
 
   return {
-    preview = self.previewer and preview.width > 0 and preview,
+    preview = self.previewer and preview.height > 0 and preview,
     results = results,
     prompt = prompt
   }
@@ -568,7 +578,7 @@ layout_strategies.bottom_pane = make_documented_layout('bottom_pane', vim.tbl_ex
   local prompt = initial_options.prompt
   local preview = initial_options.preview
 
-  local result_height = resolve.resolve_height(layout_config.height)(self,max_columns,max_lines) or 25
+  local result_height = resolve.resolve_height(layout_config.height)(self, max_columns, max_lines) or 25
 
   local prompt_width = max_columns
   local col = 0

lua/telescope/themes.lua

@@ -35,7 +35,7 @@ function themes.get_dropdown(opts)
     sorting_strategy = "ascending",
     layout_strategy = "center",
     layout_config = {
-      preview_cutoff = 1, -- Preview should always show (unless previewer = false)
+      preview_cutoff = true, -- Preview should always show (unless previewer = false)
 
       width = function(_, max_columns, _)
         return math.min(max_columns - 3, 80)