Fix backspacing over control visualizers (#16400)

During `!measureOnly` the old code would increment `distance` twice.
Now it doesn't. :)

Closes #16356

## Validation Steps Performed
See updated test instructions in `doc/COOKED_READ_DATA.md`

doc/COOKED_READ_DATA.md

@@ -15,6 +15,12 @@ All of the following ✅ marks must be fulfilled during manual testing:
   * Press tab: Autocomplete to "a😊b.txt" ✅
   * Navigate the cursor right past the "a"
   * Press tab twice: Autocomplete to "a😟b.txt" ✅
+* Execute `printf("    "); gets(buffer);` in C (or equivalent)
+  * Press Tab, A, Ctrl+V, Tab, A ✅
+  * The prompt is "        A^V     A" ✅
+  * Cursor navigation works ✅
+  * Backspacing/Deleting random parts of it works ✅
+  * It never deletes the initial 4 spaces ✅
 * Backspace deletes preceding glyphs ✅
 * Ctrl+Backspace deletes preceding words ✅
 * Escape clears input ✅

src/host/readDataCooked.cpp

@@ -938,22 +938,31 @@ ptrdiff_t COOKED_READ_DATA::_writeCharsImpl(const std::wstring_view& text, const
         const auto wch = *it;
         if (wch == UNICODE_TAB)
         {
-            const auto col = _getColumnAtRelativeCursorPosition(distance + cursorOffset);
-            const auto remaining = width - col;
-            distance += std::min(remaining, 8 - (col & 7));
             buf[0] = L'\t';
             len = 1;
         }
         else
         {
             // In the interactive mode we replace C0 control characters (0x00-0x1f) with ASCII representations like ^C (= 0x03).
-            distance += 2;
             buf[0] = L'^';
             buf[1] = gsl::narrow_cast<wchar_t>(wch + L'@');
             len = 2;
         }
 
-        if (!measureOnly)
+        if (measureOnly)
+        {
+            if (wch == UNICODE_TAB)
+            {
+                const auto col = _getColumnAtRelativeCursorPosition(distance + cursorOffset);
+                const auto remaining = width - col;
+                distance += std::min(remaining, 8 - (col & 7));
+            }
+            else
+            {
+                distance += 2;
+            }
+        }
+        else
         {
             distance += _writeCharsUnprocessed({ &buf[0], len });
         }