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Instead of traversing a single dual-element stack, use separate stacks for forward and backward. Record whether the jump was from a Note, so we select the right set of lines when we return to it. If nothing is selected, push the current top position on, instead of doing nothing at all. Correctly handle the case where somebody is trying to jump to the current position.
174 lines
6.0 KiB
C#
174 lines
6.0 KiB
C#
/*
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* Copyright 2019 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Text;
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namespace SourceGenWPF {
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/// <summary>
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/// Maintains a record of interesting places we've been.
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/// </summary>
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public class NavStack {
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// It's tempting to use a single stack, and just move a cursor up and down. However,
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// that doesn't quite work. We always want to record where you came from, so we're
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// pushing locations on when moving both forward and backward.
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//
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// If you move backward and then jump somewhere else, we want to discard the list of
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// previously-recorded forward places.
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//
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// Jumping to Notes is a little different from jumping to anything else, because we
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// want to highlight the note rather than the code at the associated offset. This
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// is especially important when moving upward through the file, or the note will be
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// off the top of the screen.
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// TODO(someday): change the back button to a pop-up list of locations (like the way
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// VS 2017 does it).
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/// <summary>
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/// Holds enough information to get us back where we were, in style.
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/// </summary>
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public class Location {
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public int Offset { get; set; }
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public bool IsNote { get; set; }
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public Location(int offset, bool isNote) {
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Offset = offset;
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IsNote = isNote;
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}
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public override string ToString() {
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return string.Format("[+{0:x6},{1}]", Offset, IsNote);
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}
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public static bool operator ==(Location a, Location b) {
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if (ReferenceEquals(a, b)) {
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return true; // same object, or both null
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}
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if (ReferenceEquals(a, null) || ReferenceEquals(b, null)) {
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return false; // one is null
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}
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return a.Offset == b.Offset && a.IsNote == b.IsNote;
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}
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public static bool operator !=(Location a, Location b) {
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return !(a == b);
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}
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public override bool Equals(object obj) {
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return obj is Location && this == (Location)obj;
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}
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public override int GetHashCode() {
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return Offset + (IsNote ? 65536 : 0);
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}
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}
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// Location stacks.
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private List<Location> mBackStack = new List<Location>();
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private List<Location> mFwdStack = new List<Location>();
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public NavStack() { }
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/// <summary>
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/// True if there is an opportunity to pop backward.
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/// </summary>
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public bool HasBackward {
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get {
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return mBackStack.Count > 0;
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}
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}
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/// <summary>
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/// True if there is an opportunity to push forward.
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/// </summary>
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public bool HasForward {
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get {
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return mFwdStack.Count > 0;
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}
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}
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/// <summary>
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/// Clears the stacks.
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/// </summary>
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public void Clear() {
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mBackStack.Clear();
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mFwdStack.Clear();
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}
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/// <summary>
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/// Pushes a new entry onto the back stack. Clears the forward stack.
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///
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/// If the same entry is already at the top of the stack, the entry will not be added.
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/// </summary>
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/// <param name="curLoc">Current location.</param>
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public void Push(Location curLoc) {
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if (mBackStack.Count > 0 && mBackStack[mBackStack.Count - 1] == curLoc) {
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Debug.WriteLine("Not re-pushing " + curLoc);
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return;
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}
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mBackStack.Add(curLoc);
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mFwdStack.Clear();
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//Debug.WriteLine("Stack now: " + this);
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}
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/// <summary>
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/// Pops the top element from the back stack, and pushes the current position
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/// onto the forward stack.
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/// </summary>
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/// <param name="fromLoc">Current location.</param>
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/// <returns>The location to move to.</returns>
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public Location MoveBackward(Location fromLoc) {
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if (mBackStack.Count == 0) {
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throw new Exception("Stack is empty");
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}
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Location toLoc = mBackStack[mBackStack.Count - 1];
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mBackStack.RemoveAt(mBackStack.Count - 1);
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mFwdStack.Add(fromLoc);
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return toLoc;
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}
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/// <summary>
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/// Pops the top element from the forward stack, and pushes the current position
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/// onto the back stack.
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/// </summary>
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/// <param name="fromLoc">Current location.</param>
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/// <returns>The location to move to.</returns>
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public Location MoveForward(Location fromLoc) {
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if (mFwdStack.Count == 0) {
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throw new Exception("Stack is empty");
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}
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Location toLoc = mFwdStack[mFwdStack.Count - 1];
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mFwdStack.RemoveAt(mFwdStack.Count - 1);
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mBackStack.Add(fromLoc);
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return toLoc;
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}
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public override string ToString() {
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StringBuilder sb = new StringBuilder();
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sb.Append("Back:");
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foreach (Location loc in mBackStack) {
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sb.Append(loc);
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}
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sb.Append(" Fwd:");
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foreach (Location loc in mFwdStack) {
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sb.Append(loc);
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}
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return sb.ToString();
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}
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}
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}
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