console.lua: bind Shift+UP and DOWN to scroll the log

We don't know how many log lines wrap, so scrolling the log with page up
and down with wrapped lines would skip lines, and those are also already
bound to history navigation.

This therefore only implements scrolling of one item at a time. While
not perfect because when the item is wrapped it scrolls multiple lines,
it is usable.

The number of log lines kept in memory is increased from 100 to 1000.

Closes #14718.

Author: guidocella

DOCS/man/console.rst

@@ -81,6 +81,12 @@ PGDN
 Ctrl+r
     Search the command history. See `SELECT`_ for the key bindings in this mode.
 
+Shift+UP
+    Scroll the log one line up.
+
+Shift+DOWN
+    Scroll the log one line down.
+
 INSERT
     Toggle insert mode.
 

player/lua/console.lua

@@ -90,7 +90,9 @@ local searching_history = false
 local history_paths = {}
 local histories_to_save = {}
 
+local MAX_LOG_LINES = 1000
 local log_buffers = {}
+local log_offset = 0
 local key_bindings = {}
 local dont_bind_up_down = false
 local global_margins = { t = 0, b = 0 }
@@ -747,7 +749,9 @@ local function render()
 
     local log_ass = ""
     local log_buffer = log_buffers[id] or {}
-    for i = #log_buffer - math.min(max_lines, #log_buffer) + 1, #log_buffer do
+    log_offset = math.max(math.min(log_offset, #log_buffer - max_lines), 0)
+    for i = #log_buffer - math.min(max_lines, #log_buffer) - log_offset + 1,
+            #log_buffer - log_offset do
         log_ass = log_ass .. style .. log_buffer[i].style ..
                   ass_escape(log_buffer[i].text) .. "\\N"
     end
@@ -1314,6 +1318,15 @@ local function clear_log_buffer()
     render()
 end
 
+local function scroll_log(amount)
+    if selectable_items then
+        return
+    end
+
+    log_offset = log_offset + amount
+    render()
+end
+
 -- Returns a string of UTF-8 text from the clipboard (or the primary selection)
 local function get_clipboard(clip)
     if platform == "x11" then
@@ -1479,6 +1492,8 @@ local function get_bindings()
         { "down",        function() move_history(1) end         },
         { "ctrl+n",      function() move_history(1) end         },
         { "wheel_down",  function() move_history(1, true) end   },
+        { "shift+up",    function() scroll_log(1) end           },
+        { "shift+down",  function() scroll_log(-1) end          },
         { "wheel_left",  function() end                         },
         { "wheel_right", function() end                         },
         { "ctrl+left",   prev_word                              },
@@ -1653,6 +1668,7 @@ mp.register_script_message("get-input", function (script_name, args)
         selectable_items = nil
         unbind_mouse()
         id = args.id or script_name .. prompt
+        log_offset = 0
         completion_buffer = {}
         autoselect_completion = args.autoselect_completion
 
@@ -1675,7 +1691,7 @@ mp.register_script_message("get-input", function (script_name, args)
     mp.commandv("script-message-to", input_caller, "input-event", "opened")
 end)
 
--- Add a line to the log buffer (which is limited to 100 lines)
+-- Add a line to the log buffer
 mp.register_script_message("log", function (message)
     local log_buffer = log_buffers[id]
     message = utils.parse_json(message)
@@ -1687,14 +1703,18 @@ mp.register_script_message("log", function (message)
                          message.terminal_style or "",
     }
 
-    if #log_buffer > 100 then
+    if #log_buffer > MAX_LOG_LINES then
         table.remove(log_buffer, 1)
     end
 
     if not open then
         return
     end
 
+    if log_offset > 0 then
+        log_offset = log_offset + 1
+    end
+
     if not update_timer:is_enabled() then
         render()
         update_timer:resume()