18 User interface

Contents

18.1 Cursors: the 'cursor' property

Name: cursor
Value:[ [<uri> ,]* [ auto | crosshair | default | pointer | move | e-resize | ne-resize | nw-resize | n-resize | se-resize | sw-resize | s-resize | w-resize | text | wait | help | progress ] ] | inherit
Initial:auto
Applies to:all elements
Inherited:yes
Percentages:N/A
Media:visual, interactive
Computed value:as specified, except with any relative URLs converted to absolute

This property specifies the type of cursor to be displayed for the pointing device. Values have the following meanings:

auto
The UA determines the cursor to display based on the current context.
crosshair
A simple crosshair (e.g., short line segments resembling a "+" sign).
default
The platform-dependent default cursor. Often rendered as an arrow.
pointer
The cursor is a pointer that indicates a link.
move
Indicates something is to be moved.
e-resize, ne-resize, nw-resize, n-resize, se-resize, sw-resize, s-resize, w-resize
Indicate that some edge is to be moved. For example, the 'se-resize' cursor is used when the movement starts from the south-east corner of the box.
text
Indicates text that may be selected. Often rendered as an I-beam.
wait
Indicates that the program is busy and the user should wait. Often rendered as a watch or hourglass.
progress
A progress indicator. The program is performing some processing, but is different from 'wait' in that the user may still interact with the program. Often rendered as a spinning beach ball, or an arrow with a watch or hourglass.
help
Help is available for the object under the cursor. Often rendered as a question mark or a balloon.
<uri>
The user agent retrieves the cursor from the resource designated by the URI. If the user agent cannot handle the first cursor of a list of cursors, it should attempt to handle the second, etc. If the user agent cannot handle any user-defined cursor, it must use the generic cursor at the end of the list. Intrinsic sizes for cursors are calculated as for background images, except that a UA-defined rectangle is used in place of the rectangle that establishes the coordinate system for the 'background-image' property. This UA-defined rectangle should be based on the size of a typical cursor on the UA's operating system. If the resulting cursor size does not fit within this rectangle, the UA may proportionally scale the resulting cursor down until it fits within the rectangle.

Example(s):


:link,:visited { cursor: url(example.svg#linkcursor), url(hyper.cur), pointer }

This example sets the cursor on all hyperlinks (whether visited or not) to an external SVG cursor. User agents that do not support SVG cursors would simply skip to the next value and attempt to use the "hyper.cur" cursor. If that cursor format was also not supported, the UA would skip to the next value and simply render the 'pointer' cursor.

18.2 System Colors

Note. The System Colors are deprecated in the CSS3 Color Module [CSS3COLOR].

In addition to being able to assign pre-defined color values to text, backgrounds, etc., CSS2 introduced a set of named color values that allows authors to specify colors in a manner that integrates them into the operating system's graphic environment.

For systems that do not have a corresponding value, the specified value should be mapped to the nearest system value, or to a default color.

The following lists additional values for color-related CSS properties and their general meaning. Any color property (e.g., 'color' or 'background-color') can take one of the following names. Although these are case-insensitive, it is recommended that the mixed capitalization shown below be used, to make the names more legible.

ActiveBorder
Active window border.
ActiveCaption
Active window caption.
AppWorkspace
Background color of multiple document interface.
Background
Desktop background.
ButtonFace
Face color for three-dimensional display elements.
ButtonHighlight
Highlight color for three-dimensional display elements (for edges facing away from the light source).
ButtonShadow
Shadow color for three-dimensional display elements.
ButtonText
Text on push buttons.
CaptionText
Text in caption, size box, and scrollbar arrow box.
GrayText
Grayed (disabled) text. This color is set to #000 if the current display driver does not support a solid gray color.
Highlight
Item(s) selected in a control.
HighlightText
Text of item(s) selected in a control.
InactiveBorder
Inactive window border.
InactiveCaption
Inactive window caption.
InactiveCaptionText
Color of text in an inactive caption.
InfoBackground
Background color for tooltip controls.
InfoText
Text color for tooltip controls.
Menu
Menu background.
MenuText
Text in menus.
Scrollbar
Scroll bar gray area.
ThreeDDarkShadow
Dark shadow for three-dimensional display elements.
ThreeDFace
Face color for three-dimensional display elements.
ThreeDHighlight
Highlight color for three-dimensional display elements.
ThreeDLightShadow
Light color for three-dimensional display elements (for edges facing the light source).
ThreeDShadow
Dark shadow for three-dimensional display elements.
Window
Window background.
WindowFrame
Window frame.
WindowText
Text in windows.

Example(s):

For example, to set the foreground and background colors of a paragraph to the same foreground and background colors of the user's window, write the following:


p { color: WindowText; background-color: Window }

18.3 User preferences for fonts

As for colors, authors may specify fonts in a way that makes use of a user's system resources. Please consult the 'font' property for details.

18.4 Dynamic outlines: the 'outline' property

At times, style sheet authors may want to create outlines around visual objects such as buttons, active form fields, image maps, etc., to make them stand out. CSS 2.1 outlines differ from borders in the following ways:

  1. Outlines do not take up space.
  2. Outlines may be non-rectangular.

The outline properties control the style of these dynamic outlines.

Name: outline
Value:[ <'outline-color'> || <'outline-style'> || <'outline-width'> ] | inherit
Initial:see individual properties
Applies to:all elements
Inherited:no
Percentages:N/A
Media:visual, interactive
Computed value:see individual properties
Name: outline-width
Value:<border-width> | inherit
Initial:medium
Applies to:all elements
Inherited:no
Percentages:N/A
Media:visual, interactive
Computed value:absolute length; '0' if the outline style is 'none'
Name: outline-style
Value:<border-style> | inherit
Initial:none
Applies to:all elements
Inherited:no
Percentages:N/A
Media:visual, interactive
Computed value:as specified
Name: outline-color
Value:<color> | invert | inherit
Initial:invert
Applies to:all elements
Inherited:no
Percentages:N/A
Media:visual, interactive
Computed value:as specified

The outline created with the outline properties is drawn "over" a box, i.e., the outline is always on top, and does not influence the position or size of the box, or of any other boxes. Therefore, displaying or suppressing outlines does not cause reflow or overflow.

The outline may be drawn starting just outside the border edge.

Outlines may be non-rectangular. For example, if the element is broken across several lines, the outline is the minimum outline that encloses all the element's boxes. In contrast to borders, the outline is not open at the line box's end or start, but is always fully connected if possible.

The 'outline-width' property accepts the same values as 'border-width'.

The 'outline-style' property accepts the same values as 'border-style', except that 'hidden' is not a legal outline style.

The 'outline-color' accepts all colors, as well as the keyword 'invert'. 'Invert' is expected to perform a color inversion on the pixels on the screen. This is a common trick to ensure the focus border is visible, regardless of color background.

Conformant UAs may ignore the 'invert' value on platforms that do not support color inversion of the pixels on the screen. If the UA does not support the 'invert' value then the initial value of the 'outline-color' property is the value of the 'color' property, similar to the initial value of the 'border-top-color' property.

The 'outline' property is a shorthand property, and sets all three of 'outline-style', 'outline-width', and 'outline-color'.

Note. The outline is the same on all sides. In contrast to borders, there is no 'outline-top' or 'outline-left' property.

This specification does not define how multiple overlapping outlines are drawn, or how outlines are drawn for boxes that are partially obscured behind other elements.

Note. Since the outline does not affect formatting (i.e., no space is left for it in the box model), it may well overlap other elements on the page.

Example(s):

Here's an example of drawing a thick outline around a BUTTON element:


button { outline : thick solid}

Scripts may be used to dynamically change the width of the outline, without provoking a reflow.

18.4.1 Outlines and the focus

Graphical user interfaces may use outlines around elements to tell the user which element on the page has the focus. These outlines are in addition to any borders, and switching outlines on and off should not cause the document to reflow. The focus is the subject of user interaction in a document (e.g., for entering text, selecting a button, etc.). User agents supporting the interactive media group must keep track of where the focus lies and must also represent the focus. This may be done by using dynamic outlines in conjunction with the :focus pseudo-class.

Example(s):

For example, to draw a thick black line around an element when it has the focus, and a thick red line when it is active, the following rules can be used:


:focus  { outline: thick solid black }
:active { outline: thick solid red }

18.5 Magnification

The CSS working group considers that the magnification of a document or portions of a document should not be specified through style sheets. User agents may support such magnification in different ways (e.g., larger images, louder sounds, etc.)

When magnifying a page, UAs should preserve the relationships between positioned elements. For example, a comic strip may be composed of images with overlaid text elements. When magnifying this page, a user agent should keep the text within the comic strip balloon.