Style Sheets#
Since Gaphor 2.0, diagrams can have a different look by means of style sheets. Style sheets use the Cascading Style Sheets (CSS) syntax. CSS is used to describe the presentation of a document written in a markup language, and is most commonly used with HTML for web pages.
On the W3C CSS home page, CSS is described as:
Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g., fonts, colors, spacing) to Web documents.
Its application goes well beyond web documents, though. Gaphor uses CSS to provide style elements to items in diagrams. CSS allows us, users of Gaphor, to change the visual appearance of our diagrams. Color and line styles can be changed to make it easier to read the diagrams.
Since we’re dealing with a diagram, and not a HTML document, some CSS features have been left out.
The style is part of the model, so everyone working on a model will have the same style. To edit the style press the tools page button at the top right corner in gaphor:
Here is a simple example of how to change the background color of a class:
class {
background-color: beige;
}
Or change the color of a component, only when it’s nested in a node:
node component {
background-color: skyblue;
}
The diagram itself is also expressed as a CSS node. It’s pretty easy to define a “dark” style:
diagram {
background-color: #343131;
}
* {
color: white;
text-color: white;
}
Here you already see the first custom attribute: text-color
. This property
allows you to control the color of the text drawn in an item. color
is used
for the lines (strokes) that make the layout of a diagram item.
Supported selectors#
Since we are dealing with diagrams and models, we do not need all the features of CSS. Below you’ll find a summary of all CSS features supported by Gaphor.
|
All items on the diagram, including the diagram itself. |
|
Any component item which is a descendant of a node. |
|
A component item which is a child of a node. |
|
A generalization item with a subject present. |
|
A class with name “Foo”. |
|
A diagram with a name starting with “draft”. |
|
A diagram with a name ends with “draft”. |
|
A diagram with a name containing the text “draft”. |
|
A diagram with a name of “draft” or “item”. |
|
A diagram with a name is “draft” or starts with “draft-“. |
|
The focused item. Other pseudo classes are:
|
|
A node containing no child nodes in the diagram. |
|
An item is at the top level of the diagram. This is only applicable for the diagram |
|
The item contains any of the provided selectors. E.g. |
|
Match any of the provided selectors. E.g. |
|
Negate the selector. E.g. |
The official specification of CSS3 attribute selectors.
Gaphor provides the
|=
attribute selector for the sake of completeness. It’s probably not very useful in this context, though.Please note that Gaphor CSS does not support IDs for diagram items, so the CSS syntax for IDs (
#some-id
) is not used. Also, class syntax (.some-class
) is not supported currently.
Style properties#
Gaphor supports a subset of CSS properties and some Gaphor specific properties.
The style sheet interpreter is relatively straight forward. All
widths, heights, and sizes are measured in pixels. You can’t use complex style
declarations, like the font
property in HTML/CSS which can contain font
family, size, weight.
Colors#
|
Examples:
|
|
Color used for lines. |
|
Color for text. |
|
Color opacity factor ( |
A color can be any CSS3 color code, as described in the CSS documentation. Gaphor supports all color notations:
rgb()
,rgba()
,hsl()
,hsla()
, Hex code (#ffffff
) and color names.
Text and fonts#
|
A single font name (e.g. |
|
An absolute size (e.g. |
|
Either |
|
Either |
|
Either |
|
Either |
|
Vertical alignment for text. Either |
|
Set vertical spacing for icon-like items (actors, start state). Example: |
font-family
can be only one font name, not a list of (fallback) names, as is used for HTML.font-size
can be a number or CSS absolute-size values. Only the valuesx-small
,small
,medium
,large
andx-large
are supported.
Drawing and spacing#
|
Radius for rectangles: |
|
Style for dashed lines: |
|
Content alignment for boxes. Either |
|
Either |
|
Set the width for lines: |
|
Set minimal height for an item: |
|
Set minimal width for an item: |
|
CSS style padding (top, right, bottom, left). Example: |
padding
is defined by integers in the range of 1 to 4. No unit (px, pt, em) needs to be used. All values are in pixel distance.dash-style
is a list of numbers (line, gap, line, gap, …)line-style
only has an effect when defined on adiagram
. A sloppiness factor can be provided in the range of -2 to 2.
Diagram styles#
Only a few properties can be defined on a diagram, namely background-color
and line-style
. You define the diagram style separately from the diagram item
styles. That way it’s possible to set the background color for diagrams
specifically. The line style can be the normal straight lines, or a more
playful “sloppy” style. For the sloppy style an optional wobliness factor can
be provided to set the level of line wobbliness. 0.5 is default, 0.0 is a
straight line. The value should be between -2.0 and 2.0. Values between 0.0 and
0.5 make for a subtle effect.
Gaphor supports dark and light mode since 2.16.0. Dark and light color schemes are exclusively used
for on-screen editing. When exporting images, only the default color scheme is applied.
Color schemes can be defined with @media
queries. The official prefers-color-scheme = dark
query is supported,
as well as a more convenient dark-mode
.
/* The background you see in exported diagrams: */
diagram {
background-color: transparent;
}
/* Use a slightly grey background in the editor: */
@media light-mode {
diagram {
background-color: #e1e1e1;
}
}
/* And anthracite a slightly grey background in the editor: */
@media dark-mode {
diagram {
background-color: #393D47;
}
}
Variables#
Since Gaphor 2.16.0 you can use CSS variables in your style sheets.
This allows you to define often used values in a more generic way. Think of things like line dash style and colors.
The var()
function has some limitations:
Values can’t have a default value.
Variables can’t have a variable as their value.
Example:
diagram {
--bg-color: whitesmoke;
background-color: var(--bg-color);
}
diagram[diagramType=sd] {
--bg-color: rgb(200, 200, 255);
}
All diagrams have a white background. Sequence diagrams get a blue-ish background.
Working with model elements#
Gaphor has many model elements. How can you find out which item should be styled?
Gaphor only styles the elements that are in the model, so you should be explicit
on their names. For example: Component
inherits from Class
in the UML model,
but changing a color for Class
does not change it for Component
.
If you hover over a button the toolbox (bottom-left section), a popup will appear
with the item’s name and a shortcut. As a general rule, you can use the component
name, glued together as the name in the stylesheet.
A Component can be addressed as component
, Use Case as
usecase
. The name matching is case insensitive.
CSS names are written in lower case by default.
However, since the CSS element names are derived from names used within Gaphor, there are a few exceptions.
Profile |
Group |
Element |
CSS element |
---|---|---|---|
* |
* |
element name |
element name without spaces E.g. |
UML |
Classes |
all Association’s |
|
UML |
Components |
Device/Node |
|
UML |
Actions |
Decision/Merge Node |
|
UML |
Actions |
Fork/Join Node |
|
UML |
Actions |
Swimlane |
|
UML |
Interactions |
Reflexive message |
|
UML |
States |
Initial Pseudostate |
|
UML |
States |
History Pseudostate |
|
UML |
Profiles |
Metaclass |
|
C4 Model |
C4 Model |
Person |
|
C4 Model |
C4 Model |
Software System |
|
C4 Model |
C4 Model |
Component |
|
C4 Model |
C4 Model |
Container |
|
C4 Model |
C4 Model |
Container: Database |
|
SysML |
Blocks |
ValueType |
|
SysML |
Blocks |
Primitive |
|
SysML |
Requirements |
Derive Requirement |
|
RAAML |
FTA |
any AND/OR/… Gate |
|
Ideas#
Here are some ideas that go just beyond changing a color or a font. With the following examples we dig in to Gaphor’s model structure to reveal more information to the users.
To create your own expression you may want to use the Console ( → Tools → Console). Drop us a line on
Gitter and we would be happy to help you.
The drafts package#
All diagrams in the package “Drafts” should be drawn using sloppy lines:
diagram[owner.name=drafts] {
line-style: sloppy 0.3;
}
diagram[owner.name=drafts] * {
font-family: Purisa; /* Or use some other font that's installed on your system */
}
Unconnected relationships#
All items on a diagram that are not backed by a model element, should be drawn in a dark red color. This can be used to spot not-so-well connected relationships, such as Generalization, Implementation, and Dependency. These items will only be backed by a model element once you connect both line ends. This rule will exclude simple elements, like lines and boxes, which will never have a backing model element.
:not([subject], :is(line, box, ellipse, commentline)) {
color: firebrick;
}
Solid Control Flow lines#
In Gaphor, Control Flow lines follow the SysML styling: dashed. If you want, or need to strictly follow the official UML specifications, you can simply make those solid lines.
controlflow {
dash-style: 0;
}
Todo note highlight#
All comments beginning with the phrase “todo” can be highlighted in a different user-specific colour. This can be used to make yourself aware that you have to do some additional work to finalize the diagram.
comment[body^="TODO"] {
background-color: skyblue;
}
System Style Sheet#
* {
--opaque-background-color: white;
background-color: transparent;
color: black;
font-size: 14;
line-width: 2;
padding: 0;
}
*:drop {
color: #1a5fb4;
line-width: 3;
}
*:disabled {
opacity: 0.5;
}
@media light-mode {
* {
--opaque-background-color: #fafafa;
}
}
@media dark-mode {
* {
--opaque-background-color: #242424;
color: white;
}
*:drop {
color: #62a0ea;
}
}
dependency,
interfacerealization {
dash-style: 7 5;
}
dependency[on_folded_interface = true],
interfacerealization[on_folded_interface = true] {
dash-style: 0;
}
controlflow {
dash-style: 9 3;
}
proxyport,
activityparameternode,
executionspecification {
background-color: var(--opaque-background-color);
}