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// Copyright (C) 2003 Mooffie <mooffie@typo.co.il>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
#include "undo.h"
#include "dbg.h"
#define DEFAULT_LIMIT 4000
#define RESERVE 1000
UndoStack::UndoStack()
{
top = 0;
merge_small_ops = false;
bytes_size = 0;
bytes_size_limit = DEFAULT_LIMIT;
truncated = false;
}
void UndoStack::clear()
{
stack.clear();
bytes_size = 0;
top = 0;
truncated = false;
}
// get_prev_op() - returns a pointer to the last operation made to the buffer.
// returns NULL if the undo stack is empty.
UndoOp* UndoStack::get_prev_op()
{
if (top == 0)
return NULL;
return &stack[--top];
}
// get_next_op() - returns a pointer to the last operation that was undone.
UndoOp *UndoStack::get_next_op()
{
if (top == stack.size())
return NULL;
return &stack[top++];
}
void UndoStack::set_size_limit(size_t limit)
{
bytes_size_limit = limit;
clear();
}
void UndoStack::update_size_up(int chars_count)
{
bytes_size += chars_count * sizeof(unichar);
}
void UndoStack::update_size_up(const UndoOp &op)
{
bytes_size += op.calc_size();
}
void UndoStack::update_size_down(const UndoOp &op)
{
bytes_size -= op.calc_size();
}
// truncate_undo() - called when the stack size is too big. it erases the
// old operations.
void UndoStack::truncate_undo()
{
unsigned new_size = bytes_size_limit;
// we have to reserve some space in order not to reach the
// size-limit very soon.
if (new_size > RESERVE)
new_size -= RESERVE;
else
new_size = 0;
unsigned i = 0;
while (i < stack.size() && bytes_size > new_size) {
update_size_down(stack[i++]);
}
stack.erase(stack.begin(), stack.begin() + i);
top -= i;
truncated = true;
}
// merge() - merges a new operation with the last operation. returns false if
// that was not possible.
//
// An example: suppose the last operation was to insert "a" into the buffer.
// If the user now types "b", merge() will change the last operation to record
// an insertion of "ab".
//
// However, if the user moves the cursor to a different location before typing
// "b", such a merge is not possible, because "a" and "b" are not adjacent.
bool UndoOp::merge(const UndoOp &op)
{
if (type != op.type)
return false;
if (op.inserted_text.len() + op.deleted_text.len() != 1)
return false;
if (point.para != op.point.para)
return false;
switch (type) {
case opInsert:
if (op.point.pos == point.pos + inserted_text.len()) {
inserted_text.append(op.inserted_text);
return true;
}
break;
case opDelete:
if (op.point.pos == point.pos) {
deleted_text.append(op.deleted_text);
return true;
}
if (op.point.pos == point.pos - 1) {
point.pos--;
deleted_text.insert(deleted_text.begin(),
op.deleted_text.begin(),
op.deleted_text.end());
return true;
}
break;
default:
break;
}
return false;
}
// erase_redo_ops() - erases the operations that were undone.
void UndoStack::erase_redo_ops()
{
for (unsigned i = top; i < stack.size(); i++)
update_size_down(stack[i]);
stack.erase(stack.begin() + top, stack.end());
}
// record_op() - records an operation on the stack.
void UndoStack::record_op(const UndoOp &op)
{
if (disabled())
return;
// recording an opearation erases the recordings of all the operations
// that were undone till now.
if (is_redo_available())
erase_redo_ops();
if (undo_size_too_big())
truncate_undo();
// first try to merge this operation with the previous one. if that
// fails, record it as a separate operation.
if (merge_small_ops && !stack.empty() && stack.back().merge(op)) {
update_size_up(1); // one character was recorded
} else {
stack.push_back(op);
update_size_up(op);
top++;
}
}
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