From 7d1a8292b6c7db7401af05f75e6d9992fc8ed28a Mon Sep 17 00:00:00 2001
From: haorenW1025 <whz861025@gmail.com>
Date: Thu, 17 Sep 2020 00:20:45 +0800
Subject: [PATCH] feat: add scrolling in preview window (#47)

* feat: add scrolling in preview window

refactor into two layers

* remove redundant code

* add error message for scroll_fn and send_input

* consider count for preview scrolling
---
 README.md                    |  3 +++
 lua/telescope/actions.lua    |  8 ++++++++
 lua/telescope/pickers.lua    |  6 ++++++
 lua/telescope/previewers.lua | 36 +++++++++++++++++++++++++++++++++++-
 4 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 7573484..77f717b 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,9 @@ j      k     next | previous (in normal mode)
 <C-v>        go to file selection as a vertical split
 <C-t>        go to a file in a new tab
 
+<C-u>        scroll up in preview window
+<C-d>        scroll down in preview window
+
 <C-c>        close telescope
 <Esc>        close telescope (in normal mode)
 ```
diff --git a/lua/telescope/actions.lua b/lua/telescope/actions.lua
index 50c9fe2..224a3e4 100644
--- a/lua/telescope/actions.lua
+++ b/lua/telescope/actions.lua
@@ -34,6 +34,14 @@ function actions.get_selected_entry(prompt_bufnr)
   return actions.get_current_picker(prompt_bufnr):get_selection()
 end
 
+function actions.preview_scrolling_up(prompt_bufnr)
+  actions.get_current_picker(prompt_bufnr).previewer:scroll_fn(-30)
+end
+
+function actions.preview_scrolling_down(prompt_bufnr)
+  actions.get_current_picker(prompt_bufnr).previewer:scroll_fn(30)
+end
+
 -- TODO: It seems sometimes we get bad styling.
 local function goto_file_selection(prompt_bufnr, command)
   local picker = actions.get_current_picker(prompt_bufnr)
diff --git a/lua/telescope/pickers.lua b/lua/telescope/pickers.lua
index 66973f7..bf88b63 100644
--- a/lua/telescope/pickers.lua
+++ b/lua/telescope/pickers.lua
@@ -42,6 +42,9 @@ local default_mappings = {
     ["<C-x>"] = actions.goto_file_selection_split,
     ["<C-v>"] = actions.goto_file_selection_vsplit,
     ["<C-t>"] = actions.goto_file_selection_tabedit,
+
+    ["<C-u>"] = actions.preview_scrolling_up,
+    ["<C-d>"] = actions.preview_scrolling_down,
   },
 
   n = {
@@ -57,6 +60,9 @@ local default_mappings = {
 
     ["<Down>"] = actions.move_selection_next,
     ["<Up>"] = actions.move_selection_previous,
+
+    ["<C-u>"] = actions.preview_scrolling_up,
+    ["<C-d>"] = actions.preview_scrolling_down,
   },
 }
 
diff --git a/lua/telescope/previewers.lua b/lua/telescope/previewers.lua
index 5798bac..462b65e 100644
--- a/lua/telescope/previewers.lua
+++ b/lua/telescope/previewers.lua
@@ -11,7 +11,7 @@ local Previewer = {}
 Previewer.__index = Previewer
 
 -- TODO: Should play with these some more, ty @clason
-local bat_options = " --style=plain --paging=never --color=always "
+local bat_options = " --style=plain --color=always "
 
 local previewer_ns = vim.api.nvim_create_namespace('telescope.previewers')
 
@@ -28,6 +28,8 @@ function Previewer:new(opts)
     state = nil,
     _setup_func = opts.setup,
     _teardown_func = opts.teardown,
+    _send_input = opts.send_input,
+    _scroll_fn = opts.scroll_fn,
     preview_fn = opts.preview_fn,
   }, Previewer)
 end
@@ -55,6 +57,22 @@ function Previewer:teardown()
   end
 end
 
+function Previewer:send_input(input)
+  if self._send_input then
+    self:_send_input(input)
+  else
+    vim.api.nvim_err_writeln("send_input is not defined for this previewer")
+  end
+end
+
+function Previewer:scroll_fn(direction)
+  if self._scroll_fn then
+    self:_scroll_fn(direction)
+  else
+    vim.api.nvim_err_writeln("scroll_fn is not defined for this previewer")
+  end
+end
+
 previewers.new = function(...)
   return Previewer:new(...)
 end
@@ -186,6 +204,22 @@ previewers.cat = defaulter(function(opts)
       }
     end,
 
+    send_input = function(self, input)
+      termcode = vim.api.nvim_replace_termcodes(input, true, false, true)
+      if self.state.termopen_id then
+        pcall(vim.fn.chansend, self.state.termopen_id, termcode)
+      end
+    end,
+
+    scroll_fn = function(self, direction)
+      if not self.state then
+        return
+      end
+      if direction > 0 then input = "d" else input = "u" end
+      local count = math.abs(direction)
+      self:send_input(count..input)
+    end,
+
     teardown = function(self)
       if not self.state then
         return