How to use the Feathers ScrollText
Component
The ScrollText
is designed for displaying long passages of text. With longer text, TextFieldTextRenderer
may run into the maximum texture size limits. BitmapFontTextRenderer
may be a good alternative, but with enough characters, then it may begin to affect performance. ScrollText
provides the workaround of displaying text on the runtime's classic software-rendered display list.
The Basics
First, let's create a ScrollText
component, give it some text to display, and add it to the display list.
var scrollText:ScrollText = new ScrollText();
scrollText.text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";
this.addChild( scrollText );
As you can see, the ScrollText
is added to the Starling display list. This is merely an abstraction. Behind the scenes, a flash.text.TextField
is created and added to the classic display list. As you move and scale the ScrollText
instance on the Starling display list, the TextField
will be manipulated on the classic display list.
If we set the width
property, the ScrollText
content will automatically word wrap, and the height will grow.
scrollText.width = 200;
If we set both the width
and height
properties, the ScrollText
content will automatically allow scrolling if the content is taller than the height of the ScrollText
.
scrollText.width = 200;
scrollText.height = 200;
Skinning a ScrollText
For full details about what skin and style properties are available, see the ScrollText
API reference. We'll look at a few of the most common properties below.
Font Styles
ScrollText
may be styled with a flash.text.TextFormat
. You may use fonts installed on the target device or you may embed a font.
scrollText.textFormat = new TextFormat( "SomeEmbeddedFont", 12, true );
scrollText.embedFonts = true;
Use the isHTML
property to display the text as HTML, with the same capabilities as the htmlText
property of flash.text.TextField
.
scrollText.isHTML = true;
scrollText.text = "<font color=\"#ff0000\">Hello world</font>";
A number of other styling properties from flash.text.TextField
are available to use with ScrollText
, including antiAliasType
, backgroundColor
, borderColor
, gridFitType
, styleSheet
, sharpness
, thickness
, and others. See the ScrollText
API documentation for full details.
Targeting a ScrollText
in a theme
If you are creating a theme, you can set a function for the default styles like this:
getStyleProviderForClass( ScrollText ).defaultStyleFunction = setScrollTextStyles;
If you want to customize a specific scroll text to look different than the default, you may use a custom style name to call a different function:
text.styleNameList.add( "custom-scroll-text" );
You can set the function for the custom style name like this:
getStyleProviderForClass( ScrollText )
.setFunctionForStyleName( "custom-scroll-text", setCustomScrollTextStyles );
Trying to change the scroll text's styles and skins outside of the theme may result in the theme overriding the properties, if you set them before the scroll text was added to the stage and initialized. Learn to extend an existing theme to add custom skins.
If you aren't using a theme, then you may set any of the scroll text's properties directly.
Skinning the Scroll Bars
This section only explains how to access the horizontal scroll bar and vertical scroll bar sub-components. Please read How to use the Feathers ScrollBar
component (or SimpleScrollBar
) for full details about the skinning properties that are available on scroll bar components.
With a Theme
If you're creating a theme, you can target the Scroller.DEFAULT_CHILD_STYLE_NAME_HORIZONTAL_SCROLL_BAR
style name for the horizontal scroll bar and the Scroller.DEFAULT_CHILD_STYLE_NAME_VERTICAL_SCROLL_BAR
style name for the vertical scroll bar.
getStyleProviderForClass( ScrollBar )
.setFunctionForStyleName( Scroller.DEFAULT_CHILD_STYLE_NAME_HORIZONTAL_SCROLL_BAR, setHorizontalScrollBarStyles );
getStyleProviderForClass( ScrollBar )
.setFunctionForStyleName( Scroller.DEFAULT_CHILD_STYLE_NAME_VERTICAL_SCROLL_BAR, setVerticalScrollBarStyles );
You can override the default style names to use different ones in your theme, if you prefer:
scrollText.customHorizontalScrollBarStyleName = "custom-horizontal-scroll-bar";
scrollText.customVerticalScrollBarStyleName = "custom-vertical-scroll-bar";
You can set the function for the customHorizontalScrollBarStyleName
and the customVerticalScrollBarStyleName
like this:
getStyleProviderForClass( ScrollBar )
.setFunctionForStyleName( "custom-horizontal-scroll-bar", setCustomHorizontalScrollBarStyles, );
getStyleProviderForClass( ScrollBar )
.setFunctionForStyleName( "custom-vertical-scroll-bar", setCustomVerticalScrollBarStyles );
Without a Theme
If you are not using a theme, you can use horizontalScrollBarFactory
and verticalScrollBarFactory
to provide skins for the scroll bars:
scrollText.horizontalScrollBarFactory = function():ScrollBar
{
var scrollBar:ScrollBar = new ScrollBar();
scrollBar.direction = ScrollBar.DIRECTION_HORIZONTAL;
//skin the scroll bar here
scrollBar.trackLayoutMode = ScrollBar.TRACK_LAYOUT_MODE_SINGLE;
return scrollBar;
}
Alternatively, or in addition to the horizontalScrollBarFactory
and verticalScrollBarFactory
, you may use the horizontalScrollBarProperties
and the verticalScrollBarProperties
to pass skins to the scroll bars.
scrollText.horizontalScrollBarProperties.trackLayoutMode = ScrollBar.TRACK_LAYOUT_MODE_SINGLE;
In general, you should only pass skins to the scroll bars through horizontalScrollBarProperties
and verticalScrollBarProperties
if you need to change skins after the scroll bar is created. Using horizontalScrollBarFactory
and verticalScrollBarFactory
will provide slightly better performance, and your development environment will be able to provide code hinting thanks to stronger typing.
Customizing Scrolling Behavior
A number of properties are available to customize scrolling behavior and the scroll bars.
Interaction Modes
Scrolling containers provide two main interaction modes, which can be changed using the interactionMode
property.
By default, you can scroll using touch, just like you would on many mobile devices including smartphones and tablets. This mode allows you to grab the panel anywhere within its bounds and drag it around to scroll. This mode is defined by the constant, INTERACTION_MODE_TOUCH
.
Alternatively, you can set interactionMode
to INTERACTION_MODE_MOUSE
. This mode allows you to scroll using the horizontal or vertical scroll bar sub-components. You can also use the mouse wheel to scroll vertically.
Scroll Bar Display Mode
The scrollBarDisplayMode
property controls how and when scroll bars are displayed. This value may be overridden by the scroll policy, as explained below.
The default value is SCROLL_BAR_DISPLAY_MODE_FLOAT
, which displays the scroll bars above the view port's content, rather than affecting the size of the view port. When the scroll bars are floating, they fade out when the panel is not actively scrolling. This is a familiar behavior for scroll bars in the touch interaction mode. In the mouse interaction mode, the scroll bars will appear when the mouse hovers over them and then disappear when the hover ends.
To completely hide the scroll bars, but still allow scrolling, you can set scrollBarDisplayMode
to SCROLL_BAR_DISPLAY_MODE_NONE
.
Finally, if you want the scroll bars to always be visible outside of the content in a fixed position, you can set scrollBarDisplayMode
to SCROLL_BAR_DISPLAY_MODE_FIXED
. This is best for traditional desktop scrollable content.
Scroll Policies
The two previous properties control how scrolling works. The horizontalScrollPolicy
and verticalScrollPolicy
properties control whether scrolling is enabled or not.
The default scroll policy for both directions is SCROLL_POLICY_AUTO
. If the content's width is greater than the view port's width, the panel may scroll horizontally (same for height and vertical scrolling). If not, then the panel will not scroll in that direction. In addition to the scrollBarDisplayMode
, this can affect whether the scroll bar is visible or not.
You can completely disable scrolling in either direction, set the scroll policy to SCROLL_POLICY_OFF
. The scroll bar will not be visible, and the panel won't scroll, even if the content is larger than the view port.
Finally, you can ensure that scrolling is always enabled by setting the scroll policy to SCROLL_POLICY_ON
. If combined with hasElasticEdges
in the touch interaction mode, it will create a playful edge that always bounces back, even when the content is smaller than the view port. If using the mouse interaction mode, the scroll bar may always be visible under the same circumstances, though it may be disabled if the content is smaller than the view port.