Text Class: Buttons, Textfields, Labels

Grzegorz Kraszewski

Introduction

The Text class is the most commonly used one for creating gadgets. This is because it not only creates plain labels (also called "static text" in other GUI engines), but also framed read-only text gadgets and textual buttons. In fact MUI has no special class for buttons, a button is just a Text object with a proper frame and background and user input activated. This versatility has a disadvantage of allowing for creatinon of style guide nonconformant interfaces.

The Text class uses the MUI Text Rendering Engine for text output. It allows for multiline text, using styles (bold, italic), colors and inlined images. These features should be used sparingly to keep user interfaces consistent and comfortable to use. The rendering engine is controlled by inserting escape sequences in the text. Another engine feature is aligning the text inside the object rectangle (left, right, centered).

Common Attributes

• MUIA_Background and MUIA_Frame are attributes inherited from the Area class. They specify a background and frame used for an object.
• MUIA_Text_Contents specifies the text. It may contain formatting engine escape sequences. The text is buffered internally, so the value of this attribute may point to a local variable or a dynamically allocated buffer.
• MUIA_Text_PreParse may be considered a fixed prefix, which is always added at the start of text before rendering. It is usually used for applying a constant styles and formatting, for example setting it to "\33c" will always center the text. This attribute simplifies text handling when the text displayed is not constant (for example is loaded from a locale catalog).
• MUIA_Font is another attribute inherited from the Area class and specifies a font to be used for text rendeding. In most cases it is one of fonts predefined by user in MUI settings.

For more attributes and detailed descriptions refer to the Text class autodoc in the SDK.

Labels

Labels are the simplest form of Text instances. They have no frame and inherit their background from the parent object. They use the standard MUI font in most cases, so MUIA_Font needs not to be specified. An important (and often forgotten) detail is a proper text baseline align when a label is used with some framed gadget containing text as well (a String gadget for example). The default MUI behaviour for vertical text positioning is to center it. If the framed gadget uses uneven vertical padding, baselines of the label and the gadget may be unaligned. A special attribute MUIA_FramePhantomHoriz solves this problem. It is specified for a label and its value should be the frame type of the associated gadget. Then the label gets an invisible frame of this type (frame horizontal parts to be exact, hence the attribute name) and the text is layouted accordingly. As a result the label and the gadget text are always aligned vertically, assuming they use the same font.