## class Fl_Scroll

### Class Hierarchy

    Fl_Group
       |
       +----Fl_Scroll

### Include Files

    #include <FL/Fl_Scroll.H>

### Description

This container widget lets you maneuver around a set of widgets much larger than your window. If the child widgets are larger than the size of this object then scrollbars will appear so that you can scroll over to them:

If all of the child widgets are packed together into a solid rectangle then you want to set `box()` to `FL_NO_BOX` or one of the `_FRAME` types. This will result in the best output. However, if the child widgets are a sparse arrangment you must set `box()` to a real `_BOX` type. This can result in some blinking during redrawing, but that can be solved by using a `Fl_Double_Window`.

This widget can also be used to pan around a single child widget "canvas". This child widget should be of your own class, with a `draw()` method that draws the contents. The scrolling is done by changing the `x()` and `y()` of the widget, so this child must use the `x()` and `y()` to position it's drawing. To speed up drawing it should test `fl_push_clip()` .

Another very useful child is a single `Fl_Pack`, which is itself a group that packs it's children together and changes size to surround them. Filling the `Fl_Pack` with `Fl_Tabs` groups (and then putting normal widgets inside those) gives you a very powerful scrolling list of individually-openable panels.

Fluid lets you create these, but you can only lay out objects that fit inside the `Fl_Scroll` without scrolling. Be sure to leave space for the scrollbars, as Fluid won't show these either.

You cannot use `Fl_Window` as a child of this since the clipping is not conveyed to it when drawn, and it will draw over the scrollbars and neighboring objects.

`Fl_Scroll` widgets should not be nested. Having an Fl_Scroll inside another Fl_Scroll may result in drawing errors when resizing.

### Methods

- Fl_Scroll
- ~Fl_Scroll
- align
- position
- type
- xposition
- yposition

#### Fl_Scroll::Fl_Scroll(int x, int y, int w, int h, const char *label = 0)

Creates a new `Fl_Scroll` widget using the given position, size, and label string. The default boxtype is `FL_NO_BOX`.

#### virtual Fl_Scroll::~Fl_Scroll()

The destructor also deletes all the children. This allows a whole tree to be deleted at once, without having to keep a pointer to all the children in the user code. A kludge has been done so the `Fl_Scroll` and all of it's children can be automatic (local) variables, but you must declare the `Fl_Scroll` first, so that it is destroyed last.

#### void Fl_Widget::type(int)

By default you can scroll in both directions, and the scrollbars disappear if the data will fit in the area of the scroll. `type()` can change this:

- `0` - No scrollbars
- `Fl_Scroll::HORIZONTAL` - Only a horizontal scrollbar.
- `Fl_Scroll::VERTICAL` - Only a vertical scrollbar.
- `Fl_Scroll::BOTH` - The default is both scrollbars.
- `Fl_Scroll::HORIZONTAL_ALWAYS` - Horizontal scrollbar always on, vertical always off.
- `Fl_Scroll::VERTICAL_ALWAYS` - Vertical scrollbar always on, horizontal always off.
- `Fl_Scroll::BOTH_ALWAYS` - Both always on.

#### void Fl_Scroll::scrollbar.align(int)

This is used to change what side the scrollbars are drawn on. If the `FL_ALIGN_LEFT` bit is on, the vertical scrollbar is on the left. If the `FL_ALIGN_TOP` bit is on, the horizontal scrollbar is on the top. Note that only the alignment flags in `scrollbar` are considered. The flags in `hscrollbar` however are ignored.

#### int Fl_Scroll::xposition() const

Gets the current horizontal scrolling position.

#### int Fl_Scroll::yposition() const

Gets the current vertical scrolling position.

#### void Fl_Scroll::position(int w, int h)

Sets the upper-lefthand corner of the scrolling region.