Method GetWindowResizeBorderID

imgui_tiny_app/imgui/imgui.cpp:7200–7208

Borders (Left, Right, Up, Down)

// Borders (Left, Right, Up, Down)
ImGuiID ImGui::GetWindowResizeBorderID(ImGuiWindow* window, ImGuiDir dir)
{
    IM_ASSERT(dir >= 0 && dir < 4);
    int n = (int)dir + 4;
    ImGuiID id = window->DockIsActive ? window->DockNode->HostWindow->ID : window->ID;
    id = ImHashStr("#RESIZE", 0, id);
    id = ImHashData(&n, sizeof(int), id);
    return id;
}

// Handle resize for: Resize Grips, Borders, Gamepad
// Return true when using auto-fit (double-click on resize grip)