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[ReactNative] PixelRatio docs

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Summary:
Update docs for `PixelRatio` in preparation for open sourcing React Native for Android.

See http://stackoverflow.com/questions/11581649/about-android-image-and-asset-sizes
This commit is contained in:
Martin Konicek
2015-07-27 09:25:19 -07:00
parent 09bb761b25
commit b7253dc604
1 changed files with 12 additions and 3 deletions
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15
Libraries/Utilities/PixelRatio.js
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@@ -20,9 +20,11 @@ var Dimensions = require('Dimensions');
*
* ### Displaying a line that's as thin as the device permits
*
* A width of 1 is actually pretty thick on an iPhone 4+, we can do one that's
* thinner using a width of `1 / PixelRatio.get()`. It's a technique that works
* on all the devices independent of their pixel density.
* A width of 1 is actually pretty thick on devices with high pixel density
* (such as iPhone 4+ and many Android devices), we can make one that's
* thinner using a width of `1 / PixelRatio.get()`.
* It's a technique that works on all the devices independent of their
* pixel density.
*
* ```
* style={{ borderWidth: 1 / PixelRatio.get() }}
@@ -46,12 +48,18 @@ class PixelRatio {
/**
* Returns the device pixel density. Some examples:
*
* - PixelRatio.get() === 1
* - mdpi Android devices (160 dpi)
* - PixelRatio.get() === 1.5
* - hdpi Android devices (240 dpi)
* - PixelRatio.get() === 2
* - iPhone 4, 4S
* - iPhone 5, 5c, 5s
* - iPhone 6
* - xhdpi Android devices (320 dpi)
* - PixelRatio.get() === 3
* - iPhone 6 plus
* - xxhdpi Android devices (480 dpi)
* - PixelRatio.get() === 3.5
* - Nexus 6
*/
@@ -68,6 +76,7 @@ class PixelRatio {
*
* Currently this is only implemented on Android and reflects the user preference set in
* Settings > Display > Font size, on iOS it will always return the default pixel ratio.
* @platform android
*/
static getFontScale(): number {
return Dimensions.get('window').fontScale || PixelRatio.get();