> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/web/get-started/samples/viewersnaptonearesttest.md).
# Snap To Nearest Point Sample Code
Automatically detect & snap-to nearest control point in PDF using JavaScript. Make measuring distances between two points in a drawing more intuitive for users
{% hint style="info" %}
**Requirements**
*These packages are required to use these features in production. Trial keys have unlimited access to all features*
Web SDKFull API
{% endhint %}
This JavaScript sample illustrates how to use the snap API to automatically detect and snap-to the nearest control point. This is commonly used to make measuring the distance between two points in a drawing or blueprint more intuitive for users. This sample works on all browsers (including IE11) and mobile devices without using plug-ins.
To see an example visit our [Measurement Demo](https://showcase.apryse.com/measurement-tools/).
### **Implementation steps**
Step 1: [Get started with WebViewer](/web/get-started/readme.md) in your preferred web stack
Step 2: [Enable the full API](/web/full-api/full-api-overview.md)
Step 3: Add the sample code provided in this guide
This full sample is one of many included in the [manual download of WebViewer.](/web/get-started/manually.md#1-download-webviewer)
{% tabs %}
{% tab title="JavaScript" %}
{% code lineNumbers="true" %}
```js
(() => {
let snapMode;
const getMouseLocation = e => {
const scrollElement = instance.Core.documentViewer.getScrollViewElement();
const scrollLeft = scrollElement.scrollLeft || 0;
const scrollTop = scrollElement.scrollTop || 0;
return {
x: e.pageX + scrollLeft,
y: e.pageY + scrollTop,
};
};
const mouseToPagePoint = e => {
const displayMode = instance.Core.documentViewer.getDisplayModeManager().getDisplayMode();
const windowPoint = getMouseLocation(e);
const page = displayMode.getSelectedPages(windowPoint, windowPoint);
const pageNumber = page.first !== null ? page.first : instance.Core.documentViewer.getCurrentPage();
return {
point: displayMode.windowToPage(windowPoint, pageNumber),
pageNumber,
};
};
const createSnapModesPanel = () => {
const snapModesPanel = {
tab: {
dataElement: 'snapModesPanelTab',
title: 'snapModesPanelTab',
img:
'',
},
panel: {
dataElement: 'snapModesPanel',
render: () => {
const { DEFAULT, POINT_ON_LINE, LINE_MID_POINT, LINE_INTERSECTION, PATH_ENDPOINT } = instance.Core.documentViewer.SnapMode;
const buttonContainer = document.createElement('div');
const map = {
Default: DEFAULT,
'Point On Line': POINT_ON_LINE,
'Line Midpoint': LINE_MID_POINT,
'Line Intersection': LINE_INTERSECTION,
'Path Endpoint': PATH_ENDPOINT,
};
Object.keys(map).forEach(key => {
const div = document.createElement('div');
div.style.margin = '0px 0px 12px 12px';
const radioBtn = document.createElement('input');
radioBtn.type = 'radio';
radioBtn.style.marginRight = '10px';
radioBtn.name = 'snapMode';
radioBtn.value = map[key];
radioBtn.id = key;
radioBtn.addEventListener('change', e => {
snapMode = parseInt(e.target.value, 10);
});
const label = document.createElement('label');
label.innerHTML = key;
label.for = key;
div.appendChild(radioBtn);
div.appendChild(label);
buttonContainer.appendChild(div);
});
// make the default radio button checked
buttonContainer.querySelector('input[id="Default"]').checked = true;
return buttonContainer;
},
},
};
instance.UI.setCustomPanel(snapModesPanel);
instance.UI.openElements([snapModesPanel.panel.dataElement]);
};
createSnapModesPanel();
instance.Core.documentViewer.addEventListener('pageComplete', () => {
const lineAnnot = new Core.Annotations.LineAnnotation();
lineAnnot.setStartPoint(0, 0);
lineAnnot.setEndPoint(0, 0);
lineAnnot.PageNumber = 1;
const annotationManager = instance.Core.documentViewer.getAnnotationManager();
annotationManager.addAnnotation(lineAnnot);
let timeout;
let shouldAddMouseMoveListener = true;
document.onmousemove = () => {
clearTimeout(timeout);
timeout = setTimeout(() => {
if (shouldAddMouseMoveListener) {
instance.Core.documentViewer.addEventListener('mouseMove', e => {
const result = mouseToPagePoint(e);
const pagePoint = result.point;
const pageNumber = result.pageNumber;
const oldPageNumber = lineAnnot.PageNumber;
lineAnnot.PageNumber = pageNumber;
lineAnnot.setStartPoint(pagePoint.x, pagePoint.y);
// refresh old page since line annotation has been removed from it
if (pageNumber !== oldPageNumber) {
annotationManager.drawAnnotations(oldPageNumber);
}
instance.Core.documentViewer.snapToNearest(pageNumber, pagePoint.x, pagePoint.y, snapMode).then(snapPoint => {
lineAnnot.setEndPoint(snapPoint.x, snapPoint.y);
annotationManager.redrawAnnotation(lineAnnot);
});
});
}
shouldAddMouseMoveListener = false;
}, 100);
};
});
})(window);
// eslint-disable-next-line spaced-comment
//# sourceURL=config.js
```
{% endcode %}
{% endtab %}
{% endtabs %}
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