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Updated DropDown (markdown)

NeilFraser
2014-09-18 11:03:03 -07:00
parent 6e18a9ef90
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DropDown.md

@@ -1,32 +1,31 @@
**[Creating Custom Blocks](wiki/CustomBlocks): [Defining Blocks](wiki/DefiningBlocks): Drop-down Menus**
Drop-down menus can be somewhat complicated field elements used in creating blocks.
## Language Neutrality
```
input.appendField('hello');
var dropdown = new Blockly.FieldDropdown([['world', 'WORLD'], ['computer', 'CPU']]);
input.appendField(dropdown, 'MODE');
```
![https://blockly.googlecode.com/svn/wiki/appendFieldDropdown.png](https://blockly.googlecode.com/svn/wiki/appendFieldDropdown.png)
The ` FieldDropdown ` object is created with a list of menu options. Each option is made up of two strings. The first is the human-readable text to display. The second is a string constant which is used when saving the option to XML. This separation allows a dropdown menu's setting to be preserved between languages. For instance an English (` en/ `) version of a block may define ` [['left', 'LEFT'], ['right', 'RIGHT']] ` while a German (` de/ `) version of the same block would define ` [['links', 'LEFT'], ['rechts', 'RIGHT']] `.
## Prefix/Suffix Matching
If all the menu options of a ` FieldDropdown ` object share common prefix and/or suffix words, these words are automatically factored out and inserted as static text. For example, the same "hello world" code above could be rewritten like this:
```
var dropdown = new Blockly.FieldDropdown([['hello world', 'WORLD'], ['hello computer', 'CPU']]);
input.appendField(dropdown, 'MODE');
```
One advantage of this approach is that the block is easier for to translate into other languages. The earlier code has the strings ` 'hello' `, ` 'world' `, and ` 'computer' `, whereas the revised code has the strings ` 'hello world' ` and ` 'hello computer' `. Translators have a much easier time translating phrases than words in isolation.
Another advantage of this approach is that word order often changes between languages. Imagine a language that used ` 'world hello' ` and ` 'computer hello' `. The suffix matching algorithm will detect the common ` 'hello' ` and display it after the drop-down.
However, sometimes the prefix/suffix matching fails. There are some cases where two words should always go together and the prefix should not be factored out. For example ` 'drive red car' ` and ` 'drive red truck' ` should arguably only have ` 'drive' ` factored out, not ` 'drive red' `. The Unicode non-breaking space ` '\u00A0' ` may be used in place of a regular space to suppress the prefix/suffix matcher. Thus the above example can be fixed with ` 'drive red\u00A0car' ` and ` 'drive red\u00A0truck' `.
**[Creating Custom Blocks](wiki/CustomBlocks): [Defining Blocks](wiki/DefiningBlocks): Drop-down Menus**
Drop-down menus can be somewhat complicated field elements used in creating blocks.
## Language Neutrality
```
input.appendField('hello');
var dropdown = new Blockly.FieldDropdown([['world', 'WORLD'], ['computer', 'CPU']]);
input.appendField(dropdown, 'MODE');
```
![](appendFieldDropdown.png)
The ` FieldDropdown ` object is created with a list of menu options. Each option is made up of two strings. The first is the human-readable text to display. The second is a string constant which is used when saving the option to XML. This separation allows a dropdown menu's setting to be preserved between languages. For instance an English (` en/ `) version of a block may define ` [['left', 'LEFT'], ['right', 'RIGHT']] ` while a German (` de/ `) version of the same block would define ` [['links', 'LEFT'], ['rechts', 'RIGHT']] `.
## Prefix/Suffix Matching
If all the menu options of a ` FieldDropdown ` object share common prefix and/or suffix words, these words are automatically factored out and inserted as static text. For example, the same "hello world" code above could be rewritten like this:
```
var dropdown = new Blockly.FieldDropdown([['hello world', 'WORLD'], ['hello computer', 'CPU']]);
input.appendField(dropdown, 'MODE');
```
One advantage of this approach is that the block is easier for to translate into other languages. The earlier code has the strings ` 'hello' `, ` 'world' `, and ` 'computer' `, whereas the revised code has the strings ` 'hello world' ` and ` 'hello computer' `. Translators have a much easier time translating phrases than words in isolation.
Another advantage of this approach is that word order often changes between languages. Imagine a language that used ` 'world hello' ` and ` 'computer hello' `. The suffix matching algorithm will detect the common ` 'hello' ` and display it after the drop-down.
However, sometimes the prefix/suffix matching fails. There are some cases where two words should always go together and the prefix should not be factored out. For example ` 'drive red car' ` and ` 'drive red truck' ` should arguably only have ` 'drive' ` factored out, not ` 'drive red' `. The Unicode non-breaking space ` '\u00A0' ` may be used in place of a regular space to suppress the prefix/suffix matcher. Thus the above example can be fixed with ` 'drive red\u00A0car' ` and ` 'drive red\u00A0truck' `.
Another place where prefix/suffix matching fails is in languages that do not separate individual words with spaces. Chinese is a good example. The string