Everybody, I'm sorry.
And, Thank you for many Information.
After having changed screen resolution to 800x600, I also tested.
At that time, the OK/Cancel button was not able to be seen.
However, it begins only to have seen it from the screen because the size of the
window was large.
and, I tested for 120dpi.
The result was the same after all.
If the window was resized, the button was able to be seen.
more, I examined it.
And, The problem has been understood.
When a window size was resized before a window was displayed.
(maybe, To screen resolution by the system because the size of t