Wednesday, June 21, 2017

Memory issues according big canvas


I do not know, if I have a problem with Chrome, GWT or HTML/Canvas, please let me know, if I should ask somewhere else.
I build an application using GWT that shows something like a gantt chart with a lot of stuff around. The chart is painted into a canvas. When I create the canvas and draw my chart initially everything is fine (even with a quite big canvas with a size of 10000 px width and 2500 px hieght for example, Chrome task manager shows for example 150 MB memory usage and 50 MB JavaScriptMemory usage).
The problem starts during painting changes in the chart on my canvas. For example an existing rect should get another color because it is selected. For that I create a clipping area that fits to the selected rect.Afterwards the rect is repainted with the new color and if exists, some other objects, that collidates with the repainted rect, are repainted, too.
This works but sometimes this process uses a lot of memory. The JavaScriptMemory usage is nearly fixed but the "normal" memory usage (and if available the memory usage of the gpu process) increases dramatically, some 100 MB, sometimes more. What is the reason for that? If the cnavas is smaller, for example full hd size, the memory usage increase for such an operation is lower, sometimes "only" 30 MB. Why that? What is the best practise to do thinks like this? For example I read something about background canvas, multi canvas etc. Should I try it with such a strategy?

Thanks a lot for your help,


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