Added a case specifier to the theme API

This will allow themes to pull off some cool dirty tricks without
screwing anything up

theme/patterns.go

@@ -3,10 +3,28 @@ package theme
 import "image"
 import "git.tebibyte.media/sashakoshka/tomo/artist"
 
+// Case sepecifies what kind of element is using a pattern. It contains a
+// namespace parameter and an element parameter. The element parameter does not
+// necissarily need to match an element name, but if it can, it should. Both
+// parameters should be written in camel case. Themes can change their styling
+// based on this parameter for fine-grained control over the look and feel of
+// specific elements.
+type Case struct { Namespace, Element string } 
+ 
+// C can be used as shorthand to generate a case struct as used in PatternState.
+func C (namespace, element string) (c Case) {
+	return Case {
+		Namespace: namespace,
+		Element: element,
+	}
+}
+
 // PatternState lists parameters which can change the appearance of some
 // patterns. For example, passing a PatternState with Selected set to true may
 // result in a pattern that has a colored border within it.
 type PatternState struct {
+	Case
+
 	// On should be set to true if the element that is using this pattern is
 	// in some sort of "on" state, such as if a checkbox is checked or a
 	// switch is toggled on. This is only necessary if the element in