Hide scrollbar on base form

I am having a slideshow in my base application, the program enters full screen mode to show the pictures. However, a scrollbar appears on the right side of the screen, even if there was no scrollbar before entering full screen.
If I set the picture size 1 px less than the height of the screen, it will not appear, but I prefer to show the picture filling the whole screen. I tried to fine adjust the size setting (since the measurement unit is 1/100 mm, not pixels), but didn’t find a value where the picture would appear right with no scrollbar.
I have looked through the properties of ThisComponent, ThisComponent.CurrentController.Frame.ComponentWindow and ThisComponent.CurrentController.Frame.ContainerWindow, and found nothing relevant.
If there is no property to set the scrollbar, another solution would be to set the size of the content. But I don’t find such setting either; I only find sizes of the window.

Another related question: text boxes on the form can either have scrollbars or not, but you cannot set them to automatic, so they will only appear, when the text exceeds the box area. Anybody has a solution?