Fix 2 menu completion issues that happen when we need to scroll screen buffer (PowerShell#2949)

Author: daxian-dbw

PSReadLine/Completion.cs

@@ -445,15 +445,8 @@ public void DrawMenu(Menu previousMenu, bool menuSelect)
  SaveCursor();
  }
 
- // Move cursor to the start of the first line after our input.
- var bufferEndPoint = Singleton.ConvertOffsetToPoint(Singleton._buffer.Length);
- console.SetCursorPosition(bufferEndPoint.X, bufferEndPoint.Y);
- // Top must be initialized before calling AdjustForPossibleScroll, otherwise
- // on the last line of the buffer, the scroll operation causes Top to point
- // past the buffer, which in turn causes the menu to be printed twice.
- this.Top = bufferEndPoint.Y + 1;
- AdjustForPossibleScroll(1);
- MoveCursorDown(1);
+ PreviousTop = Top;
+ MoveCursorToStartDrawingPosition(console);
 
  var bufferWidth = console.BufferWidth;
  var columnWidth = this.ColumnWidth;
@@ -514,7 +507,7 @@ public void DrawMenu(Menu previousMenu, bool menuSelect)
  }
 
  // if the menu has moved, we need to clear the lines under it
- if (bufferEndPoint.Y < PreviousTop)
+ if (Top < PreviousTop)
  {
  // In either of the following two cases, we will need to move the cursor to the next line:
  // - if extra rows from previous menu were cleared, then we know the current line was erased
@@ -528,11 +521,9 @@ public void DrawMenu(Menu previousMenu, bool menuSelect)
  MoveCursorDown(1);
  }
 
- Singleton.WriteBlankLines(PreviousTop - bufferEndPoint.Y);
+ Singleton.WriteBlankLines(PreviousTop - Top);
  }
 
- PreviousTop = bufferEndPoint.Y;
-
  if (menuSelect)
  {
  RestoreCursor();
@@ -797,7 +788,7 @@ private void PossibleCompletionsImpl(CommandCompletion completions, bool menuSel
  }
  else
  {
- menu.DrawMenu(null, menuSelect:false);
+ menu.DrawMenu(null, menuSelect: false);
  InvokePrompt(key: null, arg: _console.CursorTop);
  }
  }
@@ -879,7 +870,6 @@ private void MenuCompleteImpl(Menu menu, CommandCompletion completions)
 
  if (topAdjustment != 0)
  {
- menu.Top += topAdjustment;
  menu.DrawMenu(null, menuSelect: true);
  }
  if (topAdjustment > 0)
@@ -963,7 +953,7 @@ private void MenuCompleteImpl(Menu menu, CommandCompletion completions)
  {
  var newMenu = menuStack.Pop();
 
- newMenu.DrawMenu(menu, menuSelect:true);
+ newMenu.DrawMenu(menu, menuSelect: true);
  previousSelection = -1;
 
  menu = newMenu;
@@ -1025,7 +1015,7 @@ private void MenuCompleteImpl(Menu menu, CommandCompletion completions)
  {
  var newMenu = CreateCompletionMenu(newMatches);
 
- newMenu.DrawMenu(menu, menuSelect:true);
+ newMenu.DrawMenu(menu, menuSelect: true);
  previousSelection = -1;
 
  // Remember the current menu for when we see Backspace.

PSReadLine/DisplayBlockBase.cs

@@ -23,6 +23,16 @@ protected void MoveCursorDown(int cnt)
  }
  }
 
+ protected void AdjustForActualScroll(int scrollCnt)
+ {
+ if (scrollCnt > 0)
+ {
+ Top -= scrollCnt;
+ _singleton._initialY -= scrollCnt;
+ _savedCursorTop -= scrollCnt;
+ }
+ }
+
  protected void AdjustForPossibleScroll(int cnt)
  {
  IConsole console = Singleton._console;
@@ -35,6 +45,34 @@ protected void AdjustForPossibleScroll(int cnt)
  }
  }
 
+ protected void MoveCursorToStartDrawingPosition(IConsole console)
+ {
+ // Calculate the coord to place the cursor at the end of current input.
+ Point bufferEndPoint = Singleton.ConvertOffsetToPoint(Singleton._buffer.Length);
+ // Top must be initialized before any possible adjustion by 'AdjustForPossibleScroll' or 'AdjustForActualScroll',
+ // otherwise its value would be corrupted and cause rendering issue.
+ Top = bufferEndPoint.Y + 1;
+
+ if (bufferEndPoint.Y == console.BufferHeight)
+ {
+ // The input happens to end at the very last cell of the current buffer, so 'bufferEndPoint' is pointing to
+ // the first cell at one line below the current buffer, and thus we need to scroll up the buffer.
+ console.SetCursorPosition(console.BufferWidth - 1, console.BufferHeight - 1);
+ // We scroll the buffer by 2 lines here, so the cursor is placed at the start of the first line after 'bufferEndPoint'.
+ MoveCursorDown(2);
+ bufferEndPoint.Y -= 2;
+ AdjustForActualScroll(2);
+ }
+ else
+ {
+ // Move the cursor to the end of our input.
+ console.SetCursorPosition(bufferEndPoint.X, bufferEndPoint.Y);
+ // Move cursor to the start of the first line after our input (after 'bufferEndPoint').
+ AdjustForPossibleScroll(1);
+ MoveCursorDown(1);
+ }
+ }
+
  private int _savedCursorLeft;
  private int _savedCursorTop;
 

PSReadLine/DynamicHelp.cs

@@ -241,21 +241,11 @@ public void DrawMultilineBlock()
 
  multilineItems = 0;
 
- this.SaveCursor();
-
- // Move cursor to the start of the first line after our input.
- var bufferEndPoint = Singleton.ConvertOffsetToPoint(Singleton._buffer.Length);
- console.SetCursorPosition(bufferEndPoint.X, bufferEndPoint.Y);
- // Top must be initialized before calling AdjustForPossibleScroll, otherwise
- // on the last line of the buffer, the scroll operation causes Top to point
- // past the buffer, which in turn causes the menu to be printed twice.
- this.Top = bufferEndPoint.Y + 1;
- AdjustForPossibleScroll(1);
- MoveCursorDown(1);
+ SaveCursor();
+ MoveCursorToStartDrawingPosition(console);
 
  var bufferWidth = console.BufferWidth;
-
- var items = this.ItemsToDisplay;
+ var items = ItemsToDisplay;
 
  for (var index = 0; index < items.Count; index++)
  {
@@ -282,7 +272,7 @@ public void DrawMultilineBlock()
  }
  }
 
- this.RestoreCursor();
+ RestoreCursor();
  }
 
  public void Clear()