-- some constants people might like to tweak
Text_color = {r=0, g=0, b=0}
Cursor_color = {r=1, g=0, b=0}
Highlight_color = {r=0.7, g=0.7, b=0.9}  -- selected text
Margin_top = 15
Margin_left = 25
Margin_right = 25
edit = {}
-- run in both tests and a real run

  local result = {
    lines = {{data=''}},  -- array of strings
    -- Lines can be too long to fit on screen, in which case they _wrap_ into
    -- multiple _screen lines_.
    -- rendering wrapped text lines needs some additional short-lived data per line:
    --   startpos, the index of data the line starts rendering from, can only be >1 for topmost line on screen
    line_cache = {},
    -- Given wrapping, any potential location for the text cursor can be described in two ways:
    -- * schema 1: As a combination of line index and position within a line (in utf8 codepoint units)
    -- * schema 2: As a combination of line index, screen line index within the line, and a position within the screen line.
    --
    -- Most of the time we'll only persist positions in schema 1, translating to
    -- schema 2 when that's convenient.
    --
    -- Make sure these coordinates are never aliased, so that changing one causes
    -- action at a distance.

    --   fragments: snippets of the line guaranteed to not straddle screen lines
    --   screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line

    --   screen_line_starting_pos: optional array of codepoint indices if it wraps over more than one screen line

    screen_top1 = {line=1, pos=1},  -- position of start of screen line at top of screen

    selection1 = {},
    -- some extra state to compute selection between mouse press and release
    old_cursor1 = nil,
    old_selection1 = nil,
    mousepress_shift = nil,
    -- cursor coordinates in pixels
    cursor_x = 0,
    cursor_y = 0,

    font_height = font_height,
    line_height = line_height,
    top = top,
    left = math.floor(left),
    right = math.floor(right),
    width = right-left,
    filename = love.filesystem.getSourceBaseDirectory()..'/lines.txt',  -- '/' should work even on Windows
    next_save = nil,
    -- undo
    history = {},
    next_history = 1,
    -- search
    search_term = nil,
    search_backup = nil,  -- stuff to restore when cancelling search
  }
  return result

function edit.check_locs(State)
  -- if State is inconsistent (i.e. file changed by some other program),
  --   throw away all cursor state entirely
  if edit.invalid1(State, State.screen_top1)

      or not Text.le1(State.screen_top1, State.cursor1) then
    State.screen_top1 = {line=1, pos=1}
    State.cursor1 = {line=1, pos=1}
  end
end
function edit.invalid1(State, loc1)
  if loc1.line > #State.lines then return true end
  local l = State.lines[loc1.line]
  if l.mode ~= 'text' then return false end  -- pos is irrelevant to validity for a drawing line
  return loc1.pos > #State.lines[loc1.line].data

end

    --   screen_line_starting_pos: optional array of codepoint indices if it wraps over more than one screen line