Bugged ImGuiInputTextCallbackData::DeleteChars?

[ryobg]

What happens if we call, for example, DeleteChars (0, 5) when our CursorPos is somewhere in the middle of the string i.e. less than byte_count, but after pos? For example 2.

Answer: Out of this function we are left with dangling CursorPos == -3. Which may or may not trigger an assert out of the callback, depending how more we messed up with this out of order state. Selection is also going off btw.

Excerpt of the more important piece of code:

void ImGuiInputTextCallbackData::DeleteChars(int pos, int bytes_count)
{
    IM_ASSERT(pos + bytes_count <= BufTextLen);
    // ...
     if (CursorPos + bytes_count >= pos)
        CursorPos -= bytes_count;
    else if (CursorPos >= pos)
        CursorPos = pos;
    SelectionStart = SelectionEnd = CursorPos;
    //..
}

Direct link:

imgui/imgui_widgets.cpp

Line 3614 in 70289ab

void ImGuiInputTextCallbackData::DeleteChars(int pos, int bytes_count)

[ryobg]

Possible solution is to clamp it within a safe range during the first condition? Say:

CursorPos = ImMax (CursorPos - bytes_count, 0);

[ocornut]

Hello @ryobg, thanks a lot for reporting this!
I believe this code is incorrect and should always have been:

    if (CursorPos >= pos + bytes_count)
        CursorPos -= bytes_count;
    else if (CursorPos >= pos)
        CursorPos = pos;
   SelectionStart = SelectionEnd = CursorPos;

Fixed it now.

[ryobg]

Quick! Patched (its old) my code this way too. Good luck!