progress indicators, bug fixes, after a while

public/assets/vendors/Flot/docs/composeImages.md

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+## jquery.flot.composeImages.js
+
+This plugin is used to expose a function used to overlap several canvases and
+SVGs, for the purpose of creating a snaphot out of them.
+
+### When composeImages is used:
+When multiple canvases and SVGs have to be overlapped into a single image
+and their offset on the page, must be preserved.
+
+### Where can be used:
+In creating a downloadable snapshot of the plots, axes, cursors etc of a graph.
+
+### How it works:
+The entry point is composeImages function. It expects an array of objects,
+which should be either canvases or SVGs (or a mix). It does a prevalidation
+of them, by verifying if they will be usable or not, later in the flow.
+After selecting only usable sources, it passes them to getGenerateTempImg
+function, which generates temporary images out of them. This function
+expects that some of the passed sources (canvas or SVG) may still have
+problems being converted to an image and makes sure the promises system,
+used by composeImages function, moves forward. As an example, SVGs with
+missing information from header or with unsupported content, may lead to
+failure in generating the temporary image. Temporary images are required
+mostly on extracting content from SVGs, but this is also where the x/y
+offsets are extracted for each image which will be added. For SVGs in
+particular, their CSS rules have to be applied.
+After all temporary images are generated, they are overlapped using
+getExecuteImgComposition function. This is where the destination canvas
+is set to the proper dimensions. It is then output by composeImages.
+This function returns a promise, which can be used to wait for the whole
+composition process. It requires to be asynchronous, because this is how
+temporary images load their data.