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fix(select): pre-selected option correctly floats label #2125

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merged 3 commits into from
Feb 7, 2018
Merged

fix(select): pre-selected option correctly floats label #2125

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1a5695a
fix(select): pre-selected option correctly floats label
dpraul Jan 30, 2018
677e31c
docs(select): update pre-selected option with FOUC explanation
dpraul Feb 7, 2018
350f47c
Merge branch 'master' into fix/select/pre-selected-option
dpraul Feb 7, 2018
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9 changes: 8 additions & 1 deletion packages/mdc-select/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@ style dependencies for both the mdc-list and mdc-menu for this component to func
```html
<div class="mdc-select" role="listbox">
<div class="mdc-select__surface" tabindex="0">
<div class="mdc-select__label">Pick a Food Group</div>
<div class="mdc-select__label mdc-select__label--float-above">Pick a Food Group</div>
<div class="mdc-select__selected-text"></div>
<div class="mdc-select__bottom-line"></div>
</div>
Expand Down Expand Up @@ -129,6 +129,13 @@ style dependencies for both the mdc-list and mdc-menu for this component to func
</div>
```

#### Preventing [FOUC](https://en.wikipedia.org/wiki/Flash_of_unstyled_content)
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This section should be removed. It doesn't really address the FOUC issue. It seems like this section duplicates the Select with pre-selected option section example, and they should be merged under that section.

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Oops, looks like I fat-fingered the markdown here - meant to nest the Preventing FOUC section under the Select with pre-selected option.

Should I fix the nesting so that it provides context to the Select with pre-selected option section, or just remove the Preventing FOUC section altogether?

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Change it to

When dealing with the select component that has pre-selected values, you'll want to ensure that you
render `mdc-select__label` with the `mdc-select__label--float-above` modifier class and the selected option with `aria-selected`. This will
ensure that the label moves out of the way of the select's value and prevents a Flash Of
Un-styled Content (**FOUC**).

so that it more closely matches the text field explanation for pre-filled values. Also, it should be above the example on Line 99.


Because `MDCSelect` updates its UI based on the values it reads in when it is instantiated, there is
potential for an incorrect first render before the script containing the `MDCSelect` initialization
logic executes. To avoid this, you can manually add the `mdc-select__label--float-above` class to the
label element whenever you are initializing the component with an option pre-selected

#### Disabled select

```html
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8 changes: 3 additions & 5 deletions packages/mdc-select/foundation.js
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Original file line number Diff line number Diff line change
Expand Up @@ -106,10 +106,6 @@ export default class MDCSelectFoundation extends MDCFoundation {
};
this.cancelHandler_ = () => {
this.close_();

if (this.selectedIndex_ === -1) {
this.adapter_.removeClassFromLabel(cssClasses.LABEL_FLOAT_ABOVE);
}
};
}

Expand Down Expand Up @@ -157,6 +153,9 @@ export default class MDCSelectFoundation extends MDCFoundation {
if (this.selectedIndex_ >= 0) {
selectedTextContent = this.adapter_.getTextForOptionAtIndex(this.selectedIndex_).trim();
this.adapter_.setAttrForOptionAtIndex(this.selectedIndex_, 'aria-selected', 'true');
this.adapter_.addClassToLabel(cssClasses.LABEL_FLOAT_ABOVE);
} else {
this.adapter_.removeClassFromLabel(cssClasses.LABEL_FLOAT_ABOVE);
}
this.adapter_.setSelectedTextContent(selectedTextContent);
}
Expand Down Expand Up @@ -214,7 +213,6 @@ export default class MDCSelectFoundation extends MDCFoundation {
const focusIndex = this.selectedIndex_ < 0 ? 0 : this.selectedIndex_;

this.setMenuStylesForOpenAtIndex_(focusIndex);
this.adapter_.addClassToLabel(cssClasses.LABEL_FLOAT_ABOVE);
this.adapter_.addClassToBottomLine(cssClasses.BOTTOM_LINE_ACTIVE);
this.adapter_.addClass(OPEN);
this.animationRequestId_ = requestAnimationFrame(() => {
Expand Down