exposed-view

exposed-view 👁 👁️

Simple react-native View wrapper, to expose its position / size via colors.

Demo

Live Demo

Check this expo snack out.

Installation

If you use expo, use:

expo install exposed-view

Otherwise, for npm use:

npm i exposed-view --save

And for yarn use:

yarn add exposed-view

Usage

First, wrap your main app with the context provider, like so:

import { ExposedViewContextProvider } from "exposed-view";

export default function App() {
  return (
    <ExposedViewContextProvider exposeGlobal={true}>
      <MyApp />
    </ExposedViewContextProvider>
  );
}

After that, you can use the ExposedView component across your app, like so:

<ExposedView color={"steelblue"} style={{ width: 200, height: 200 }}>
  <Text style={{ fontSize: 14 }}>Some Container Text...</Text>
</ExposedView>

Global Toggle / "Kill-switch"

To make any exposing possible, make sure that at least one of the env variables EXPOSE_VIEW or EXPO_PUBLIC_EXPOSE_VIEW is set to "true" - otherwise it will render a normal react-native View instead, which doesn't include the coloring of course. The decision for this had performance reason for production environments - we recommend you to not set these env variables on production environments for simple deactivation of any visual highlighting of ExposedViews. Instead, your app will fall back to using standard View components instead. If you use this library inside an Expo Snack, this global toggle is automatically set to true, otherwise it could not be used there, since reading environment variables is not possible in Expo Snacks.

Props for ExposedViewContextProvider

The props you set here define the behaviour of all ExposedView components (see below) within your app.

prop	required	default	type	description
exposeGlobal	yes	-	boolean	Turn on or off any exposing functionality via this prop for every ExposedView component, that does NOT explicitely set its expose prop. Note: The kill-switch (mentioned above) must be considered too!
exposeOverride	no	undefined	boolean	This allows you to override ALL the ExposedView components in your app, as well as the exposeGlobal property above. It is recommended only if you want to temporarily turn on or off all exposing, without using the kill-switch mentioned above.
addAttributes	no	true	boolean	This allows you to add the attributes data-ev-x, data-ev-y, data-ev-width and data-ev-height to every container when used on web (via react-native-web). In other words, this exposes the position and dimensions of containers on the web, which can be helpful for debugging or e2e testing, for instance. Of course this properties are not available if no measurements are available.
showWarnings	no	false	boolean	Decides whether or not to show console.warns in case the highlighting css properties are overwritten by the View style itself, for instance, if a backgroundColor is set on an ExposedView it would warn, that in case of expose === true the highlighting backgroundColor would not be seen.
showDimensions	no	true	boolean	Decides whether or not to show dimensions, meaning width and height labels.
showPosition	no	true	boolean	Decides whether or not to show position, meaning x and y labels.
showUnit	no	false	boolean	Decides whether or not to show the px unit inside labels.
widthPosition	no	"bottom"	"top" | "bottom"	Decides where the width labels are shown.
heightPosition	no	"right"	"left" | "right"	Decides where the height labels are shown.
fontSize	no	12	number	Sets the fontSize of labels.
borderWidth	no	4	number	Sets the borderWidth for highlighting View components. In case a View has a borderWidth set already, this borderWidth gets ignored.
backgroundOpacity	no	0.55	number	Sets the opacity for the background of a highlighted View component - in other words, defines how much brighter the backgroundColor will be compared to the set color.
showPrefix	no	true	boolean	Decides if the prefixes like w, h, etc. should be shown inside labels or not.
prefixForWidth	no	"w"	string	Decides which prefix to show for width labels.
prefixForHeight	no	"h"	string	Decides which prefix to show for height labels.
prefixForX	no	"x"	string	Decides which prefix to show for x coordinate labels.
prefixForY	no	"y"	string	Decides which prefix to show for y coordinate labels.
colorForWidth	no	"#c9cba3"	string	Decides which color to use for width labels.
colorForHeight	no	"#ffe1a8"	string	Decides which color to use for height labels.
colorForX	no	"#e26d5c"	string	Decides which color to use for x coordinate labels.
colorForY	no	"#723d46"	string	Decides which color to use for y coordinate labels.

Props for ExposedView component

An <ExposedView /> accepts all props that the standard <View /> accepts.

It also accepts the optional expose prop, which has a higher priority than the global exposeGlobal setting on the context provider.

Besides that, the following one prop is mandatory: color (of type CSSProperties["color"]), which decides the "exposing" color for that ExposedView

Additionally, the following props are optional, and can be used, to override the corresponding setting from the ExposedViewContextProvider, for individual ExposedViews: showWarnings, showDimensions, showPosition, widthPosition, heightPosition, showUnit. The definition and behaviour of all these props can be seen in the table above.

Summary over switch hierarchy

Since there are multiple switch mechanisms that decide, whether a View is exposed or not, let's summarize it again:

• The exposeGlobal prop (required) on the context provider. It will switch on or off exposing for any ExposedView without an explicitly set expose prop.
• The expose prop (optional) on the ExposedView component.
• The exposeOverride prop (optional) on the context provider. If this is set (to either true or false) it will render the exposeGlobal props (1) as well as any set expose prop (2) useless. Only use it for temporary overriding.
• The EXPOSE_VIEW and EXPO_PUBLIC_EXPOSE_VIEW environment variables. If at least one of them is set to "true", it will activate the entire library. If none of them is set to "true", it will deactivate it, meaning any prop above (1-3) will be rendered useless.

Future ideas / improvements

• Add intelligent avoidance of labels (positions + dimensions) overflowing the screen edges?
• Make labels only appear on hover for web?
• Make labels have half opacity, and only show fully on hover for web?
• Add possibility to show defined width/height vs. effective px width/height?
• Make position values be relative to parent?
• Add warning icon if style prop overwriting occurs?

If you enjoy using this...