Develop Reference

How to call a JS function or Python method when a glyph is completely rendered?

I am using bokeh as a Server Application. When I make a selection in a plot I do some actions in python and I update some sources (CDS). This changes are reflected in the plot. Is there a way to check when the glyphs are completely rendered (after the update)? I want to call a JavaScript function when all is completely loaded? With that function I want to call other python method to update the CDS again.
If I do not wait for this profiles to be rendered probably the application breaks, and that´s what I want to avoid. Actually I did some tests in the past and I had to create a huge CDS instead of several smaller CDS to make it work properly.
My Use Case. Why do I want to make this?
I have many tabs in my layout, they can be 10 for example. And each tab has some plots (3-6 plots). If I update the entire ColumnDataSource at the same time, it will take a while. Then I want to make it more fluent, so I would like to update only the data of the current visible tab, it will render faster and the user would receive an immediate response. I can disable the rest of the tabs temporarily to prevent malfunctions. At this moment I would need to call the JS or python method in order to update the content of the rest of the tabs.
Here a drawing of what I want to achieve in order to speed up the process:
About the data
Basically I have two DataFrames, one to build the cloud of points (around 5000 row and 130 columns) and I extract from the selected points another DataFrame to know which lines I should draw (360 columns and 5 to 15 rows), making some filters and selections. The algorythm I have used is in the answer of a question I have written time ago. With this amount of data the algorythm takes 6 or 7 seconds to finish.
Any other idea of how to improve the performance or how to split or the computing?

To improve the rendering speed you could try the webgl JavaScript API. This Bokeh documentation page Speeding up with WebGL explains how to do it. webgl supports circles, lines and most of the markers. Application:
p = Plot(output_backend="webgl") # for the glyph API
p = figure(output_backend="webgl") # for the plotting API
Please be aware that users report issues with webgl like plot stuttering, etc... but it may work in your case depend on which type of glyphs your plot contains.
Also make sure your data passed to the plot doesn't include NaN's as it is known to slow down Bokeh performance.
To my knowledge there is no attribute that indicates that rendering is completed or is still ongoing but you may think about some other alternatives to speed things up like combination of Bokeh with Datashader (pre-rendering large datasets into a fixed-size raster image) or Dask (speed up data reading from multiple sources like multiple csv files)
For example you could have one standard Bokeh plot where you make a
selection and let the other plots being generated as Datashader images
and embed them in Bokeh plots.
This example shows how to combine Bokeh + Datashader which significantly improves performance especially when over-plotting takes place. Please note that each time a single point is added to the plot entire canvas area will be re-drawn in the browser. This is how browsers work. Datashader can provide a single image so updating the plot is much quicker while you can still use Toolbar tools like zoom, pan etc....
Also the Python code implementation details counts. Using e.g. gridplot to link many plots can slow down performance so it is better to add them one by one to the document root, etc...

Time ago I made a trick to check if my design would work if I could trigger some function if the plots were rendered:
First I updated the current tab. This worked very well and fast.
Then I set a timeout to update the data of the rest of the tabs. But, in the meantime this second algorythm was being executed I could not work with the plots of the current tab because they were frozen.
So, the approach of triggering a function when everything is rendered is not a good idea, because even with such a callback the app would not work as I was expecting.

Can anyone tell me how to get the background animation effect used in Oculus Connect 3 website?

Oculus Connect 3
I know this site was built on react. I want to know more about how to get that background animation and mouse over effect. It's simply awesome to experience. Based on this I will decide to go with React or Angular 2.

If you open your browser's inspection tool (almost always F12) you can see the layout of the webpage. It contains a canvas element with the id "grid". The animation is made using this.
The animation itself looks like a simple node graph, where if you move your cursor the nodes close to the cursor try to stay away from it, thus creating an explosion-like effect.
If your cursor stays fix for 2-3 seconds, the animation starts using a point going randomly across the page instead.
I doubt this animation uses too much of any of the libraries you mentioned in your question, thus deciding which one of these you will be using based on this demo (which let's be honest, max 200 lines of vanilla JavaScript) is like deciding what you eat for breakfast based on the food statistics of Mongolia.
And also, animations like this are what scares off most users. I don't think you can show me any big multimedia or social network site, which has animation close to this.

d3 drag behavior low performance on chrome with huge dataset

I implemented d3 slider control allowing to navigate through data serie displayed along time axis.
I'm trying to isolate/solve problem with drag events coming too seldom (more than one second interval), when data set is large enough (entire data array is inlined in html page, so page weights about 13 megabytes).
http://javaeedemo.pragmasoft.cloudbees.net/test/isolated-test1.html
Drag looks jumpy in chrome, but is smooth in firefox.
data array has only about 300 elements, and elements contains lot of data including nested arrays, but I only use one property in every element named 'end'.
I tried to reduce data array size, leaving same amount of elements, but only left 'end' property in every element, so this change doesn't impact functionality, only page size.
http://javaeedemo.pragmasoft.cloudbees.net/test/isolated-test2.html
With these changes drag looks much more smoothly on chrome.
Appreciate any help, including ideas about how to isolate problem. I tried to use Chrome Timeline, what I see there is that my onDrag handler executes very fast (matter of 1 ms) yet I still have substantial gaps between onmousemove calls.
Added:
I managed to find some almost working solution - I added drag behavior event listeners to raw mouse events instead, like
//var dragBehavior = d3.behavior.drag()
// .on("dragstart", onDrag.bind(this))
g.on("mousedown", onDragStart.bind(this));
...
Now it works much more smoothly, which makes me thinking that problem is somewhere in drag behavior code. isolated-test3.html has workaround to compare:
Of course I'd prefer using drag behavior, as it solves number of problems and supports touch events as well.

Link Elements to Keep Their Appearance In Sync

I'm developing an iPad app using PhoneGap and jQuery Mobile and I'd like to create a preview pane in a carousel. The preview pane would include a smaller version of each of the other panes, scaled so they fit inside the single pane. The panes are not static and can be updated at any time using WebSockets, and the preview should be updated simultaneously. There can also be any number of panes (although to keep things simple, assume an upper limit of 9). For performance purposes, assume each pane can have upwards of 200 DOM objects attached to it. To make it slightly more complicated, the carousel can exist on more than one different page.
I've been contemplating the best way to go about implementing this preview pane, and, before inventing a pair of Complicator's Gloves, would like to hear back from the community on any possible better strategies.
A couple methods I have been considering include:
Cloning each pane and then using a CSS transform to scale it to an appropriate size, based on how many panes there are, and then attaching the clones to the preview pane.
Store each pane as a jQuery object in a variable and draw each pane and the preview pane using that object (possibly necessitating redrawing the entire carousel every time there is an update, depending on how much effort I want to make identifying and updating deltas).
Repositioning all the panes so that they exist inside the preview pane when the preview pane is active (this might break the carousel, or at least make it look slightly bizarre as a user swipes a pane over but hasn't actually moved on to that pane yet).
Is there anything I'm missing? It would be nice if there was an easy way to "link" two elements together to make one mirror the other, but apply different CSS to one or the other (for zooming). I suppose it might be possible to do this by creating an event that would fire and then adding a listener to its clone, which would then copy the html of the updated element to itself (probably wouldn't be too terribly to difficult to write a jquery plugin to manage this).
Any better suggestions?

I am not sure what phonegap allows for as far as rendering options go, but my first instinct would be to take a screen shot of the relevant pane. Perhaps phonegap has this built in?
Another option is a javascript library which will clone the DOM and create an HTML5 canvas element. You can either then display the canvas natively, or convert the canvas data in to image data.
Here is one such library: http://html2canvas.hertzen.com/
Given the large number of elements needed, I would hesitate to clone those over and over again. However, if live previews are a necessity, that might be more efficient than using image files or the canvas. You could fire off the canvas draw function after major changes, but probably wouldn't want to do it after the end of every frame of animation.

HTML 5 Canvas vs Divs for scrolling pane

I'm making an TV Guide. See http://i.tv/guide for an example implementation using Canvas.
I need to make lots of little boxes representing each show. I need to be able to scroll them around, both vertically (channels) and horizontally (time). To make it with Canvas, my understanding is that the only way to implement scrolling is to intercept the correct events, and redraw the canvas smoothly with new offsets many times a second.
If I were to use divs, I could slap scrollbars on it and let it scroll normally. I could position them once, and let the scrolling move them around, rather than re-calculating their new offsets.
Which should I pick for this kind of project? If I use divs will it be too slow? Some lineups have 500 channels. I want to display up to 4 hours at once.
Thanks!

I would strongly recommend using plain HTML in preference to canvas, for interactive elements. Apart from the speed issue (divs are usually going to be faster than drawing it all manually yourself), HTML is designed to offer accessibility and usability features for free, which you'd have to do a lot of work to get even partially from canvas.
The canvas-based guide as linked has the following drawbacks:
very slow to render/scroll, for me;
impervious to keyboard navigation;
no HTML link actions (like middle-click-link-to-open-in-new-tab or right-click-bookmark);
text not copy/pastable;
a dead loss for accessibility tools like screen-readers;
reduced browser compatibility;
invisible to search engines.
Use canvas for pretty graphical and interactive effects you can't achieve with plain HTML. To be honest I don't even see any of that on i.tv's site; I have no idea why they have implemented it in this seemingly-crazy way.

Doing it with DIV's wont have issues with speed. Browsers rendering engines are built to render elements. DOM rendering is faster than canvas rendering in a lot of cases, take isogenicengine they use DOM based rendering to render thousands of elements to make games You should implement it based on your technical ability. Both technologies will be able to do what you want. Personally I would choose canvas but I see no issue with DOM rendering.
Good Luck.