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-- undo/redo by managing the sequence of events in the current session
-- based on https://github.com/akkartik/mu1/blob/master/edit/012-editor-undo.mu
-- Incredibly inefficient; we make a copy of lines on every single keystroke.
-- The hope here is that we're either editing small files or just reading large files.
-- TODO: highlight stuff inserted by any undo/redo operation
-- TODO: coalesce multiple similar operations
function record_undo_event(data)
History[Next_history] = data
Next_history = Next_history+1
for i=Next_history,#History do
History[i] = nil
end
end
function undo_event()
if Next_history > 1 then
--? print('moving to history', Next_history-1)
Next_history = Next_history-1
local result = History[Next_history]
return result
end
end
function redo_event()
if Next_history <= #History then
--? print('restoring history', Next_history+1)
local result = History[Next_history]
Next_history = Next_history+1
return result
end
end
-- Copy all relevant global state.
-- Make copies of objects; the rest of the app may mutate them in place, but undo requires immutable histories.
function snapshot(s,e)
-- Snapshot everything by default, but subset if requested.
if s == nil and e == nil then
s = 1
e = #Lines
elseif e == nil then
e = s
end
-- compare with App.initialize_globals
local event = {
screen_top=deepcopy(Screen_top1),
selection=deepcopy(Selection1),
cursor=deepcopy(Cursor1),
current_drawing_mode=Drawing_mode,
previous_drawing_mode=Previous_drawing_mode,
lines={},
start_line=s,
end_line=e,
-- no filename; undo history is cleared when filename changes
}
-- deep copy lines without cached stuff like text fragments
for i=s,e do
local line = Lines[i]
if line.mode == 'text' then
table.insert(event.lines, {mode='text', data=line.data})
elseif line.mode == 'drawing' then
local points=deepcopy(line.points)
--? print('copying', line.points, 'with', #line.points, 'points into', points)
local shapes=deepcopy(line.shapes)
--? print('copying', line.shapes, 'with', #line.shapes, 'shapes into', shapes)
table.insert(event.lines, {mode='drawing', y=line.y, h=line.h, points=points, shapes=shapes, pending={}})
--? table.insert(event.lines, {mode='drawing', y=line.y, h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
else
print(line.mode)
assert(false)
end
end
return event
end
function patch(lines, from, to)
--? if #from.lines == 1 and #to.lines == 1 then
--? assert(from.start_line == from.end_line)
--? assert(to.start_line == to.end_line)
--? assert(from.start_line == to.start_line)
--? lines[from.start_line] = to.lines[1]
--? return
--? end
assert(from.start_line == to.start_line)
for i=from.end_line,from.start_line,-1 do
table.remove(lines, i)
end
assert(#to.lines == to.end_line-to.start_line+1)
for i=1,#to.lines do
table.insert(lines, to.start_line+i-1, to.lines[i])
end
end
-- https://stackoverflow.com/questions/640642/how-do-you-copy-a-lua-table-by-value/26367080#26367080
function deepcopy(obj, seen)
if type(obj) ~= 'table' then return obj end
if seen and seen[obj] then return seen[obj] end
local s = seen or {}
local result = setmetatable({}, getmetatable(obj))
s[obj] = result
for k,v in pairs(obj) do
result[deepcopy(k, s)] = deepcopy(v, s)
end
return result
end
function minmax(a, b)
return math.min(a,b), math.max(a,b)
end
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