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Add local caching of "simple" Graphics State (ExtGState) data in PartialEvaluator.getOperatorList (issue 2813)

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This patch will help pathological cases the most, with issue 2813 being a particularily problematic example. While there's only *four* `/ExtGState` resources, there's a total `29062` of `setGState` operators. Even though parsing of a single `/ExtGState` resource is quite fast, having to re-parse them thousands of times does add up quite significantly.

For simplicity we'll only cache "simple" `/ExtGState` resource, since e.g. the general `SMask` case cannot be easily cached (without re-factoring other code, which may have undesirable effects on general parsing).

By caching "simple" `/ExtGState` resource, we thus improve performance by:
 - Not having to fetch/validate/parse the same `/ExtGState` data over and over.
 - Handling of repeated `setGState` operators becomes *synchronous* during the `OperatorList` building, instead of having to defer to the event-loop/microtask-queue since the `/ExtGState` parsing is done asynchronously.

---

Obviously I had intended to include (standard) benchmark results with this patch, but for reasons I don't understand the test run-time (even with `master`) of the document in issue 2813 is *a lot* slower than in the development viewer (making normal benchmarking infeasible).
However, testing this manually in the development viewer (using `pdfBug=Stats`) shows a *reduction* of `~10 %` in the rendering time of the PDF document in issue 2813.
This commit is contained in:
Jonas Jenwald 2020-07-11 13:52:11 +02:00
parent 6c39aff374
commit 90eb579713
3 changed files with 127 additions and 36 deletions
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44
test/unit/evaluator_spec.js
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@ -242,23 +242,35 @@ describe("evaluator", function () {
);
});
it("should execute if nested commands", function (done) {
const gState = new Dict();
gState.set("LW", 2);
gState.set("CA", 0.5);
const extGState = new Dict();
extGState.set("GS2", gState);
const resources = new ResourcesMock();
resources.ExtGState = extGState;
var stream = new StringStream("/F2 /GS2 gs 5.711 Tf");
runOperatorListCheck(
partialEvaluator,
stream,
new ResourcesMock(),
function (result) {
expect(result.fnArray.length).toEqual(3);
expect(result.fnArray[0]).toEqual(OPS.setGState);
expect(result.fnArray[1]).toEqual(OPS.dependency);
expect(result.fnArray[2]).toEqual(OPS.setFont);
expect(result.argsArray.length).toEqual(3);
expect(result.argsArray[0].length).toEqual(1);
expect(result.argsArray[1].length).toEqual(1);
expect(result.argsArray[2].length).toEqual(2);
done();
}
);
runOperatorListCheck(partialEvaluator, stream, resources, function (
result
) {
expect(result.fnArray.length).toEqual(3);
expect(result.fnArray[0]).toEqual(OPS.setGState);
expect(result.fnArray[1]).toEqual(OPS.dependency);
expect(result.fnArray[2]).toEqual(OPS.setFont);
expect(result.argsArray.length).toEqual(3);
expect(result.argsArray[0]).toEqual([
[
["LW", 2],
["CA", 0.5],
],
]);
expect(result.argsArray[1]).toEqual(["g_font_error"]);
expect(result.argsArray[2]).toEqual(["g_font_error", 5.711]);
done();
});
});
it("should skip if too few arguments", function (done) {
var stream = new StringStream("5 d0");