Basic safe rendering support for screen readers

Author: andyleejordan

PSReadLine/BasicEditing.cs

@@ -194,7 +194,8 @@ public static void BackwardDeleteChar(ConsoleKeyInfo? key = null, object arg = n
 
                 _singleton.RemoveTextToViRegister(startDeleteIndex, qty, BackwardDeleteChar, arg, !InViEditMode());
                 _singleton._current = startDeleteIndex;
-                _singleton.Render();
+                // Moves cursor to startDeleteIndex (backwards probably) and then deletes qty
+                _singleton.SafeRender($"\x1b[{qty}P", startDeleteIndex);
             }
         }
 
@@ -218,7 +219,8 @@ private void DeleteCharImpl(int qty, bool orExit)
                     {
                         _current = Math.Max(0, _buffer.Length + ViEndOfLineFactor);
                     }
-                    Render();
+                    // Deletes qty characters without moving the cursor
+                    _singleton.SafeRender($"\x1b[{qty}P");
                 }
             }
             else if (orExit)

PSReadLine/KillYank.cs

@@ -78,7 +78,8 @@ private void Kill(int start, int length, bool prepend)
             SaveEditItem(EditItemDelete.Create(killText, start));
             _buffer.Remove(start, length);
             _current = start;
-            Render();
+            // Deletes the rest of the line from start
+            SafeRender("\x1b[K", start);
             if (_killCommandCount > 0)
             {
                 if (prepend)

PSReadLine/PublicAPI.cs

@@ -83,7 +83,8 @@ public static void Insert(char c)
                 _singleton._buffer.Insert(_singleton._current, c);
             }
             _singleton._current += 1;
-            _singleton.Render();
+            // Renders the character (which moves the cursor forward one)
+            _singleton.SafeRender(c.ToString());
         }
 
         /// <summary>
@@ -105,7 +106,8 @@ public static void Insert(string s)
                 _singleton._buffer.Insert(_singleton._current, s);
             }
             _singleton._current += s.Length;
-            _singleton.Render();
+            // Renders the string (which moves the cursor forward the string's length)
+            _singleton.SafeRender(s);
         }
 
         /// <summary>
@@ -147,6 +149,8 @@ public static void Replace(int start, int length, string replacement, Action<Con
             var str = _singleton._buffer.ToString(start, length);
             _singleton.SaveEditItem(EditItemDelete.Create(str, start));
             _singleton._buffer.Remove(start, length);
+            // Moves cursor to start (backwards probably) and then deletes length
+            _singleton.SafeRender($"\x1b[{length}P", start);
             if (replacement != null)
             {
                 _singleton.SaveEditItem(EditItemInsertString.Create(replacement, start));
@@ -161,7 +165,8 @@ public static void Replace(int start, int length, string replacement, Action<Con
             if (useEditGroup)
             {
                 _singleton.EndEditGroup(instigator, instigatorArg); // Instigator is needed for VI undo
-                _singleton.Render();
+                // Renders the string (which moves the cursor forward the string's length)
+                _singleton.SafeRender(replacement);
             }
         }
 

PSReadLine/Render.cs

@@ -218,6 +218,24 @@ private void RenderWithPredictionQueryPaused()
             Render();
         }
 
+        private void SafeRender(string s, int? cursor = null)
+        {
+            // Render as usual if we're not supporting a screen reader
+            if (!_singleton.Options.ScreenReader)
+            {
+                Render();
+                return;
+            }
+
+            // Move the cursor if we have to
+            if (cursor.HasValue)
+                MoveCursor(cursor.Value);
+
+            // Directly write without re-rendering
+            // This means using ANSI escapes for movement
+            _console.Write(s);
+        }
+
         private void Render()
         {
             // If there are a bunch of keys queued up, skip rendering if we've rendered very recently.