removed the memory based limit of undo/redo as it was actually causin…

…g some integer underflow bugs

this resolves issue #23 and also makes undo/redo slightly more efficient to track

source/DocumentWidget.cpp

@@ -1546,22 +1546,11 @@ void DocumentWidget::addUndoItem(UndoInfo &&undo) {
  // Add the item to the beginning of the list
  undo_.emplace_front(std::move(undo));
 
- // Increment the operation and memory counts
- undoMemUsed_ += undo.oldText.size();
-
  // Trim the list if it exceeds any of the limits
  if (undo_.size() > UNDO_OP_LIMIT) {
  trimUndoList(UNDO_OP_TRIMTO);
  }
 
- if (undoMemUsed_ > UNDO_WORRY_LIMIT) {
- trimUndoList(UNDO_WORRY_TRIMTO);
- }
-
- if (undoMemUsed_ > UNDO_PURGE_LIMIT) {
- trimUndoList(UNDO_PURGE_TRIMTO);
- }
-
  if(MainWindow *window = MainWindow::fromDocument(this)) {
  window->undoAvailable(undo_.size() != 0);
  }
@@ -1589,11 +1578,6 @@ void DocumentWidget::removeUndoItem() {
  return;
  }
 
- const UndoInfo &undo = undo_.front();
-
- // Decrement the operation and memory counts
- undoMemUsed_ -= undo.oldText.size();
-
  // Remove and free the item
  undo_.pop_front();
 
@@ -1636,10 +1620,7 @@ void DocumentWidget::trimUndoList(size_t maxLength) {
  }
 
  // Trim off all subsequent entries
- while(it != undo_.end()) {
- undoMemUsed_ -= it->oldText.size();
- it = undo_.erase(it);
- }
+ undo_.erase(it, undo_.end());
 }
 
 void DocumentWidget::Undo() {

source/DocumentWidget.h

@@ -307,7 +307,6 @@ class DocumentWidget : public QWidget {
  int autoSaveCharCount_ = 0; // count of single characters typed since last backup file generated
  int autoSaveOpCount_ = 0; // count of editing operations ""
  size_t nMarks_ = 0; // number of active bookmarks
- size_t undoMemUsed_ = 0; // amount of memory (in bytes) dedicated to the undo list
  mode_t mode_ = 0; // permissions of file being edited
  time_t lastModTime_ = 0; // time of last modification to file
  uid_t uid_ = 0; // last recorded user id of the file

source/UndoInfo.h

@@ -8,15 +8,8 @@
  amounts of memory. These tuning parameters determine how much undo infor-
  mation is retained. Normally, the list is kept between UNDO_OP_LIMIT and
  UNDO_OP_TRIMTO in length (when the list reaches UNDO_OP_LIMIT, it is
- trimmed to UNDO_OP_TRIMTO then allowed to grow back to UNDO_OP_LIMIT).
- When there are very large amounts of saved text held in the list,
- UNDO_WORRY_LIMIT and UNDO_PURGE_LIMIT take over and cause the list to
- be trimmed back further to keep its size down. */
+ trimmed to UNDO_OP_TRIMTO then allowed to grow back to UNDO_OP_LIMIT). */
 
-constexpr auto UNDO_PURGE_LIMIT = 15000000u; // If undo list gets this large (in bytes), trim it to length of UNDO_PURGE_TRIMTO
-constexpr auto UNDO_PURGE_TRIMTO = 1u; // Amount to trim the undo list in a purge
-constexpr auto UNDO_WORRY_LIMIT = 2000000u; // If undo list gets this large (in bytes), trim it to length of UNDO_WORRY_TRIMTO
-constexpr auto UNDO_WORRY_TRIMTO = 5u; // Amount to trim the undo list when memory use begins to get serious
 constexpr auto UNDO_OP_LIMIT = 400u; // normal limit for length of undo list
 constexpr auto UNDO_OP_TRIMTO = 200u; // size undo list is normally trimmed to when it exceeds UNDO_OP_TRIMTO in length