Started the header file for attributed strings, drawing text layouts, and the new text system in general.

common/ui_attrstr.h

@@ -0,0 +1,30 @@
+typedef struct uiAttributedString uiAttributedString;
+
+_UI_ENUM(uiAttribute) {
+	// TODO
+};
+
+// @role uiAttributedString constructor
+// uiNewAttributedString() creates a new uiAttributedString from
+// initialString. The string will be entirely unattributed.
+_UI_EXTERN uiAttributedString *uiNewAttributedString(const char *initialString);
+
+// @role uiAttributedString destructor
+// uiFreeAttributedString() destroys the uiAttributedString s.
+_UI_EXTERN void uiFreeAttributedString(uiAttributedString *s);
+
+// uiAttributedStringString() returns the textual content of s as a
+// '\0'-terminated UTF-8 string. The returned pointer is valid until
+// the next change to the textual content of s.
+_UI_EXTERN const char *uiAttributedStringString(uiAttributedString *s);
+
+// uiAttributedStringLength() returns the number of UTF-8 bytes in
+// the textual content of s, excluding the terminating '\0'.
+_UI_EXTERN size_t uiAttributedStringLen(uiAttributedString *s);
+
+_UI_EXTERN void uiAttributedStringAppendUnattributed(uiAttributedString *s, const char *str);
+_UI_EXTERN void uiAttributedStringInsertAtUnattributed(uiAttributedString *s, const char *str, size_t at);
+_UI_EXTERN void uiAttributedStringDelete(uiAttributedString *s, size_t start, size_t end);
+_UI_EXTERN size_t uiAttributedStringNumGraphemes(uiAttributedString *s);
+_UI_EXTERN size_t uiAttributedStringByteIndexToGrapheme(uiAttributedString *s, size_t pos);
+_UI_EXTERN size_t uiAttributedStringGraphemeToByteIndex(uiAttributedString *s, size_t pos);