Add undo/redo infrastructure and buffer management additions.

UndoTree.cc

@@ -0,0 +1,47 @@
+#include "UndoTree.h"
+
+#include <cassert>
+
+
+void
+UndoTree::Begin(const UndoKind kind, const size_t row, const size_t col)
+{
+	if (this->pending != nullptr) {
+		if (this->pending->Kind() == kind) {
+			return;
+		}
+		this->Commit();
+	}
+
+	assert(this->pending == nullptr);
+	this->pending = new UndoNode(kind, row, col);
+	assert(this->pending != nullptr);
+}
+
+
+void
+UndoTree::Commit()
+{
+	if (this->pending == nullptr) {
+		return;
+	}
+
+	if (this->root == nullptr) {
+		assert(this->current == nullptr);
+
+		this->root    = this->pending;
+		this->current = this->pending;
+		this->pending = nullptr;
+
+		return;
+	}
+
+	assert(this->current != nullptr);
+	if (this->current->Next() != nullptr) {
+		this->current->DeleteNext();
+	}
+
+	this->current->Next(this->pending);
+	this->current = this->pending;
+	this->pending = nullptr;
+}