119 lines
4.0 KiB
Lua
119 lines
4.0 KiB
Lua
-- undo/redo by managing the sequence of events in the current session
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-- based on https://github.com/akkartik/mu1/blob/master/edit/012-editor-undo.mu
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-- Incredibly inefficient; we make a copy of lines on every single keystroke.
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-- The hope here is that we're either editing small files or just reading large files.
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-- TODO: highlight stuff inserted by any undo/redo operation
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-- TODO: coalesce multiple similar operations
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function record_undo_event(State, data)
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State.history[State.next_history] = data
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State.next_history = State.next_history+1
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for i=State.next_history,#State.history do
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State.history[i] = nil
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end
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end
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function undo_event(State)
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if State.next_history > 1 then
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--? print('moving to history', State.next_history-1)
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State.next_history = State.next_history-1
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local result = State.history[State.next_history]
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return result
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end
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end
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function redo_event(State)
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if State.next_history <= #State.history then
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--? print('restoring history', State.next_history+1)
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local result = State.history[State.next_history]
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State.next_history = State.next_history+1
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return result
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end
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end
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-- Copy all relevant global state.
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-- Make copies of objects; the rest of the app may mutate them in place, but undo requires immutable histories.
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function snapshot(State, s,e)
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-- Snapshot everything by default, but subset if requested.
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assert(s, 'failed to snapshot operation for undo history')
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if e == nil then
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e = s
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end
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assert(#State.lines > 0, 'failed to snapshot operation for undo history')
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if s < 1 then s = 1 end
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if s > #State.lines then s = #State.lines end
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if e < 1 then e = 1 end
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if e > #State.lines then e = #State.lines end
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-- compare with App.initialize_globals
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local event = {
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screen_top=deepcopy(State.screen_top1),
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selection=deepcopy(State.selection1),
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cursor=deepcopy(State.cursor1),
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current_drawing_mode=Drawing_mode,
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previous_drawing_mode=State.previous_drawing_mode,
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lines={},
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start_line=s,
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end_line=e,
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-- no filename; undo history is cleared when filename changes
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}
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-- deep copy lines without cached stuff like text fragments
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for i=s,e do
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local line = State.lines[i]
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if line.mode == 'text' then
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table.insert(event.lines, {mode='text', data=line.data}) -- I've forgotten: should we deepcopy(line.data)?
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elseif line.mode == 'drawing' then
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table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
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else
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assert(false, ('unknown line mode %s'):format(line.mode))
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end
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end
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return event
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end
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function patch(lines, from, to)
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--? if #from.lines == 1 and #to.lines == 1 then
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--? assert(from.start_line == from.end_line)
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--? assert(to.start_line == to.end_line)
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--? assert(from.start_line == to.start_line)
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--? lines[from.start_line] = to.lines[1]
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--? return
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--? end
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assert(from.start_line == to.start_line, 'failed to patch undo operation')
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for i=from.end_line,from.start_line,-1 do
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table.remove(lines, i)
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end
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assert(#to.lines == to.end_line-to.start_line+1, 'failed to patch undo operation')
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for i=1,#to.lines do
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table.insert(lines, to.start_line+i-1, to.lines[i])
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end
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end
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function patch_placeholders(line_cache, from, to)
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assert(from.start_line == to.start_line, 'failed to patch undo operation')
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for i=from.end_line,from.start_line,-1 do
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table.remove(line_cache, i)
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end
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assert(#to.lines == to.end_line-to.start_line+1, 'failed to patch undo operation')
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for i=1,#to.lines do
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table.insert(line_cache, to.start_line+i-1, {})
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end
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end
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-- https://stackoverflow.com/questions/640642/how-do-you-copy-a-lua-table-by-value/26367080#26367080
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function deepcopy(obj, seen)
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if type(obj) ~= 'table' then return obj end
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if seen and seen[obj] then return seen[obj] end
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local s = seen or {}
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local result = setmetatable({}, getmetatable(obj))
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s[obj] = result
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for k,v in pairs(obj) do
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result[deepcopy(k, s)] = deepcopy(v, s)
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end
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return result
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end
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function minmax(a, b)
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return math.min(a,b), math.max(a,b)
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end
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