Difference between revisions of "Text Class: Buttons, Textfields, Labels"
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''Grzegorz Kraszewski'' | ''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. | ||
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| + | 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). | ||
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| + | ==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. | ||
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| + | For more attributes and detailed descriptions refer to the ''Text'' class autodoc in the SDK. | ||
==Labels== | ==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. | ||
==Textfields== | ==Textfields== | ||
| + | <!-- | ||
The ''Text'' MUI class is used not only for creating static texts or labels (like in the [["Hello world!" in MUI|"Hello World!" example]]), but also framed readonly text gadgets and textual buttons. All these object differ only in attributes. A read-only framed text field has a specific background and frame: | The ''Text'' MUI class is used not only for creating static texts or labels (like in the [["Hello world!" in MUI|"Hello World!" example]]), but also framed readonly text gadgets and textual buttons. All these object differ only in attributes. A read-only framed text field has a specific background and frame: | ||
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return obj; | return obj; | ||
} | } | ||
| + | --> | ||
==Buttons== | ==Buttons== | ||
| + | <!-- | ||
As said above, a text button is an instance of the ''Text'' class too. It has more attributes than a plain label however. ''MUIA_Text_PreParse'' attribute centers the text in the object using a control code of the [[MUI text engine]]. After setting a frame and a background, a proper font is also specified with ''MUIA_Font''. Forgetting this attribute is one of common interface design errors. Next four attributes are related to user input. ''MUIA_InputMode'' attribute defines type of button (push or toggle one). ''MUIA_CycleChain'' makes the button reachable with keyboard. Incomplete keyboard support for GUI is another common error and should be avoided. All gadgets receiving user input should have ''MUIA_CycleChain'' set. Most important gadgets should be also reachable with single keys. ''MUIA_ControlChar'' sets a key, which activates the gadget. For textual gadgets a letter of this key should be also underlined with ''MUIA_Text_HiChar''. It implies that the character used should be present in the gadget label. Both these attributes should be set to small letters. ''MUIA_ControlChar'' set to a capital letter will force user to press ''SHIFT''. ''MUIA_Text_HiChar'' is case insensitive. Digits can be also used for control characters, if button labels contain them. Using other characters is strongly discouraged. | As said above, a text button is an instance of the ''Text'' class too. It has more attributes than a plain label however. ''MUIA_Text_PreParse'' attribute centers the text in the object using a control code of the [[MUI text engine]]. After setting a frame and a background, a proper font is also specified with ''MUIA_Font''. Forgetting this attribute is one of common interface design errors. Next four attributes are related to user input. ''MUIA_InputMode'' attribute defines type of button (push or toggle one). ''MUIA_CycleChain'' makes the button reachable with keyboard. Incomplete keyboard support for GUI is another common error and should be avoided. All gadgets receiving user input should have ''MUIA_CycleChain'' set. Most important gadgets should be also reachable with single keys. ''MUIA_ControlChar'' sets a key, which activates the gadget. For textual gadgets a letter of this key should be also underlined with ''MUIA_Text_HiChar''. It implies that the character used should be present in the gadget label. Both these attributes should be set to small letters. ''MUIA_ControlChar'' set to a capital letter will force user to press ''SHIFT''. ''MUIA_Text_HiChar'' is case insensitive. Digits can be also used for control characters, if button labels contain them. Using other characters is strongly discouraged. | ||
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return obj; | return obj; | ||
} | } | ||
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Revision as of 11:01, 5 January 2011
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.