Cache a few things to speed up canvas rendering.

[jpobst]

Caching a few values and a scratch surface can give us some nice wins, particularly for rendering a zoomed in canvas.

Original

Method	Mean	Error	StdDev	Allocated
RenderOneToOne	2.159 ms	0.0388 ms	0.0363 ms	242 B
RenderManyOneToOne	9.597 ms	0.1060 ms	0.0940 ms	824 B
RenderZoomIn	42.322 ms	0.2513 ms	0.2350 ms	29,294 B
RenderManyZoomIn	404.774 ms	3.2200 ms	3.0120 ms	29,600 B
RenderZoomOut	8.205 ms	0.1055 ms	0.0987 ms	272 B
RenderManyZoomOut	76.499 ms	0.7711 ms	0.7213 ms	1,574 B

PR

Method	Mean	Error	StdDev	Allocated
RenderOneToOne	2.144 ms	0.0155 ms	0.0145 ms	250 B
RenderManyOneToOne	9.529 ms	0.0866 ms	0.0810 ms	832 B
RenderZoomIn	22.584 ms	0.1647 ms	0.1460 ms	28,358 B
RenderManyZoomIn	123.765 ms	0.7484 ms	0.7001 ms	29,637 B
RenderZoomOut	8.179 ms	0.0824 ms	0.0771 ms	280 B
RenderManyZoomOut	65.336 ms	0.3871 ms	0.3432 ms	983 B

[cameronwhite]

This is great, thanks!!

[cameronwhite]

Thinking about this more, I wonder if the zoom in/out drawing could be done purely in Cairo by setting up a suitable transform for the source surface? The filtering behaviour would probably be different, but this could make it easy to draw straight onto the final surface with the layer's opacity / blend mode

[jpobst]

I was wondering about that, especially for 'Zoom Out'.

I think 'Zoom In' is a bit trickier because most zoom functions apply a smoothing algorithm, and we want our 'Zoom In' to just show big, chunky pixels instead of being smoothed.

[cameronwhite]

Looking through the Cairo docs, it looks like that might be doable by setting up the "fast" or "nearest" filter for the source surface pattern

[cameronwhite]

I've got this mostly working, I'll upload a PR for it shortly!