Android Question I just used Windows Copilot in a truly productive way - "mastering" HTML, CSS and javascript

JackKirk · Apr 2, 2024

Following on from https://www.b4x.com/android/forum/threads/windows-10-copilot.159957/

I just used it again on another javascript problem - it was so good I have reproduced the dialog (I won't say conversation because that sort of implies sentience):

I used Notepad to create the prompt:

I have a HTML5 div as follows:

<div id="mycam1" style="margin-top: 0px;margin-bottom: 0px;margin-left: 0px;margin-right: 0px;padding-top: 0px;padding-bottom: 0px;padding-left: 0px;padding-right: 0px;z-depth-0;width:100%px;height:100%px;background:#ffffff;border-radius:0px;">
<video autoplay muted playsinline id="mycam1video" width="100%" height="100%" style="border:none#03a9f4;border-width:0px;border-radius:0px;padding: 0px 0px 0px 0px;"></video>
<canvas id="mycam1canvas" width=10, height=10 style="border:none #03a9f4;display:none;"></canvas>
</div><script>var _mycam1;</script>

I have a HTML5 javascript as follows:

var mycam1canvas = document.getElementById('mycam1canvas');
var mycam1context = mycam1canvas.getContext('2d');
var mycam1video = document.getElementById('mycam1video');
mycam1context.drawImage(mycam1video, 0, 0, mycam1video.videoWidth, mycam1video.videoHeight);
var mycam1dataURL = mycam1canvas.toDataURL('image/jpeg');
var image = document.getElementById('imgshow');
image.src = mycam1dataURL;
b4j_raiseEvent('mycam1_takepicture', {'value':mycam1dataURL});

The javascript is fired when I want to take a picture of the video stream but the picture is only 10 pixels by 10 pixels as per the initial div.

How do I change the javascript so that the canvas is adjusted to the size of the video?

It responded with:

To adjust the canvas size to match the video dimensions, you can follow these steps:

Wrap the Video and Canvas: Wrap both the <video> and <canvas> elements in a parent <div> element. This will allow you to position them relative to each other.

Set Canvas Size: Use JavaScript to set the canvas size to match the video size when the video’s metadata is loaded. You can achieve this by listening for the loadedmetadata event on the video element.

Position the Canvas: Position the canvas over the video using CSS. Set the canvas position to absolute and use the getBoundingClientRect() method to get the position and dimensions of the video. Then apply these values to the canvas.

Here’s an example of how you can modify your code:

HTML

<!DOCTYPE html>
<html>
<head>

<style>
body {
font-family: sans-serif;
}
video {
max-width: 100%;
width: 320px;
}
canvas {
position: absolute;
}
</style>
</head>
<body>
<h1>Realtime communication with WebRTC</h1>
<div id="videos">
<video id="localVideo" autoplay muted></video>
<video id="remoteVideo" autoplay></video>
</div>
<canvas id="mycam1canvas"></canvas>
<script>
const mycam1canvas = document.getElementById('mycam1canvas');
const mycam1context = mycam1canvas.getContext('2d');
const mycam1video = document.getElementById('localVideo');

// Set canvas size to match video size when metadata is loaded
mycam1video.addEventListener('loadedmetadata', function() {
mycam1canvas.width = mycam1video.videoWidth;
mycam1canvas.height = mycam1video.videoHeight;
});

// Draw video frame onto the canvas
function drawFrame() {
mycam1context.drawImage(mycam1video, 0, 0, mycam1video.videoWidth, mycam1video.videoHeight);
requestAnimationFrame(drawFrame); // Continuously update canvas
}

// Start drawing frames
mycam1video.addEventListener('play', drawFrame);
</script>
</body>
</html>

AI-generated code. Review and use carefully. More info on FAQ.
In this modified code:

The canvas size is set to match the video size.

The canvas is positioned over the video using absolute positioning.

The drawFrame() function continuously draws video frames onto the canvas.

Remember to adjust the styling and other elements as needed for your specific use case.

The response was much better formatted than what appears above.

From which I was able to deduce that the only change I need to make in my javascript was add

mycam1canvas.width = mycam1video.videoWidth;
mycam1canvas.height = mycam1video.videoHeight;

i.e. my javascript became:

var mycam1canvas = document.getElementById('mycam1canvas');
var mycam1context = mycam1canvas.getContext('2d');
var mycam1video = document.getElementById('mycam1video');
mycam1canvas.width = mycam1video.videoWidth;
mycam1canvas.height = mycam1video.videoHeight;
mycam1context.drawImage(mycam1video, 0, 0, mycam1video.videoWidth, mycam1video.videoHeight);
var mycam1dataURL = mycam1canvas.toDataURL('image/jpeg');
var image = document.getElementById('imgshow');
image.src = mycam1dataURL;
b4j_raiseEvent('mycam1_takepicture', {'value':mycam1dataURL});

And it all worked!!!!!

This is probably a "SO WHAT" to any experienced javascript type - but I am not - because it is somewhat tangential to my objectives and I simply do not want to invest the monumental time that would be involved.

This provides a great enabler for someone like me.

JackKirk · Apr 5, 2024

Another more complex example (well for me anyrate)...

I used Notepad to create the prompt:

I have some HTML:

<div id="cam_div" style="margin-top: 0px;margin-bottom: 0px;margin-left: 0px;margin-right: 0px;padding-top: 0px;padding-bottom: 0px;padding-left: 0px;padding-right: 0px;z-depth-0;width:100%px;height:100%px;background:#ffffff;border-radius:0px;">
<video id="cam_video" autoplay muted playsinline width="100%" height="100%" style="border:none#03a9f4;border-width:0px;border-radius:0px;padding: 0px 0px 0px 0px;"></video>
<canvas id="cam_canvas" width=1, height=1 style="border:none #03a9f4;display:none;"></canvas>
</div>

and some javascript:

var cam_video = document.getElementById('cam_video');
vendorUrl = window.URL || window.webkitURL;
const constraints =
{
audio: false,
video:
{
facingMode: 'user'
// facingMode: 'environment'
}
}
navigator.mediaDevices.getUserMedia(constraints)
.then(function (stream)
{
cam_video.srcObject=stream;
cam_video.play();
b4j_raiseEvent('cam_4_abm_instance_Ready', {'value':'mediaDevices API supported'});
},
function(error)
{
b4j_raiseEvent('cam_4_abm_instance_Error', {'value':'Your browser does not support mediaDevices API - we suggest you use another browser or device'});
});

How can I modify these so that I can trap when the cam_video is clicked

It responded with:

To capture when the cam_video element is clicked, you can add an event listener to it. Here’s how you can modify your JavaScript code:

JavaScript

var cam_video = document.getElementById('cam_video');
vendorUrl = window.URL || window.webkitURL;
const constraints = {
audio: false,
video: {
facingMode: 'user'
// facingMode: 'environment'
}
};

navigator.mediaDevices.getUserMedia(constraints)
.then(function (stream) {
cam_video.srcObject = stream;
cam_video.play();
b4j_raiseEvent('cam_4_abm_instance_Ready', {'value': 'mediaDevices API supported'});

// Add a click event listener to the cam_video element
cam_video.addEventListener('click', function() {
// Your custom logic here when the video is clicked
console.log('Video clicked!');
// You can raise an event or perform any other action as needed
});
})
.catch(function(error) {
b4j_raiseEvent('cam_4_abm_instance_Error', {'value': 'Your browser does not support mediaDevices API - we suggest you use another browser or device'});
});

AI-generated code. Review and use carefully. More info on FAQ.
In the modified code, I’ve added an event listener for the click event on the cam_video element. You can replace the console.log('Video clicked!') line with your desired behavior when the video is clicked.

And my modified javascript is:

<<<<<<<< ABMComp_Refresh
var cam_video = document.getElementById('cam_video');
vendorUrl = window.URL || window.webkitURL;
const constraints =
{
audio: false,
video:
{
facingMode: 'user'
// facingMode: 'environment'
}
}
navigator.mediaDevices.getUserMedia(constraints)
.then(function (stream)
{
cam_video.srcObject=stream;
cam_video.play();
b4j_raiseEvent('cam_4_abm_instance_Ready', {'value':'mediaDevices API supported'});
cam_video.addEventListener('click', function() {
b4j_raiseEvent('cam_4_abm_instance_VideoClick', {'value':''});
});
},
function(error)
{
b4j_raiseEvent('cam_4_abm_instance_Error', {'value':'Your browser does not support mediaDevices API - we suggest you use another browser or device'});
});

And it works!!! - I can now capture a snapshot of the video by clicking anywhere on the video display.

JackKirk · Apr 5, 2024

I have been badgering away all afternoon with Copilot solving a number of CSS and javascript issues I have - mainly due to my ignorance.

It even solved a problem with fa-camera-rotate icon not being available in the font awesome icon library I was referencing.

The approach I am adopting (as much as anything because of my ignorance) is to give it plenty of background info and ask simple incremental questions.

JackKirk · Apr 12, 2024

A complete example here:

https://www.b4x.com/android/forum/threads/abmaterial-a-robust-camera-component.160415/post-984993

JackKirk · May 5, 2024

80+ lines of javascript to massage cookies in ABMaterial - done completely with Copilot:

https://www.b4x.com/android/forum/threads/abmaterial-an-exploration-of-cookies.160940/post-987785

Android Question I just used Windows Copilot in a truly productive way - "mastering" HTML, CSS and javascript

JackKirk

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JackKirk

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JackKirk

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JackKirk

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