| Structure of a Drawing | Concepts | The User Interface |
Primitives can have properties that define how they are drawn.
Fill properties define how the area defined by a primitive is drawn. Often this is just a single color, but Sketch offers some more variety in the form of patterns.
Line properties define how the lines of a primitive are drawn. The most important line properties are probably color, width and dashes.
A primitive can usually have both, fill and line properties, but there is no need for a primitive to have any properties. You might just want to draw the outline but not the interior of a rectangle, for instance.
Some types of primitives even cannot have fill or line properties. An image object for instance has neither fill nor line properties and a text object doesn't have a line attribute (currently at least) but has an attribute that defines its font.
As an advanced feature, Sketch offers dynamic properties. These allow you to define logical properties to use instead of physical properties. Whenever you change the definition of a dynamic attribute, all objects that use that attribute are automatically updated. This is similar to logical markup versus physical markup in LaTeX or SGML.
Fill Properties define how the area of a primitive is filled.
The simplest case is just a single color that fills the area uniformly. Sketch offers more variety than that, though, in the form of patterns. A single color is then viewed as a very simple type of pattern.
A primitive may have empty fill properties or, phrased differently, no fill properties. In this case the area of the primitive is not changed all and the objects below the primitive are not obscured. Only its line is still drawn if it has line properties.
Sketch currently offers three kinds of pattern: solid, gradient and hatching pattern.
This is the simplest pattern: Just a single color that uniformly fills the area.
A gradient is the interpolation between two or more colors. A gradient pattern can be either linear, radial or conical.
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| Linear Gradient | Conical Gradient | Radial Gradient |
A primitive may either have no line properties (which means that only its area is filled if it has an area and nonempty fill properties) or one of each of the following properties:
Currently, this can only be a solid color or the empty pattern. An empty pattern means that no line is drawn. Future extensions will probably allow arbitrary patterns.
The line width. A width of zero means that the thinnest possible line is drawn.
Whether to draw a solid line or a dashed line. A line can have arbitrary dash patterns.
Dash patterns are represented by a list of numbers such as "5.0, 2.0, 1.0, 2.0". This list describes a pattern of a drawn segment of 5 units long, followed by a gap of 2 units, followed by a drawn segment of 1 unit and finally a gap of 2 units, after which the sequence starts over. The unit used is the line width. This means that a thicker line has longer dashes and gaps.
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| Structure of a Drawing | Concepts | The User Interface |