Performance

Drawing setsare notdocuments.

A 500-page issue at A1 is routinely hundreds of megabytes of dense vector content. Most viewers load it all or die trying. ScaleSet PDF reads only what you look at.

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G-200

Only the sheets near you exist; only what you can see is drawn

SHEET G-200.1

Measured

The numbers.

Measured on the generated 800-page, 49.1 MB sample set with npm run perf.

1.1MB

read to open a 49 MB, 800-sheet set and paint the first sheet

480ms

until the first sheet is on screen

129ms

to jump from sheet 1 to sheet 601

5ms

for 500 hit tests across 4,000 markups on one sheet

npm run perf · 800 pages · 49.1 MB

SHEET G-200.2

How

Four things keep
it responsive.

01 · Range reading

Read only what you look at

Opening reads the cross-reference tables and the pages you look at, through pdf.js range requests over the app's own file access. The rest of the file is never touched until you go there.

Open1.1 MB of 49.1 MB, 19 range requests
First paint480 ms

G-200.2

OPEN · 800 PAGES

01Cross-reference tables read
02Page 1 requested, nothing else
03First sheet painted at 480 ms
04Total read: 1.1 MB of 49.1 MB

02 · Virtualisation

Three pages exist, wherever you are

Only the pages near the viewport exist at all. On page 1 or page 601, three pages are mounted. Rendering work is cancelled the moment you scroll past it, and page objects are leased so a background thumbnail cannot be torn down mid-draw.

G-200.3

ON PAGE 601

01Pages 600, 601 and 602 exist
02Every other page is a placeholder
03Rendering cancelled as you scroll past
04Thumbnails leased, never torn down mid-draw
05Jump from page 1: 129 ms

03 · Two-layer raster

Sharp at 1200%, without the memory

A pixel-capped whole-page canvas sits underneath, with a full-resolution canvas covering only the visible slice. Zooming to 1200% costs about 4 MP of raster instead of about 4,000 MP, and panning never shows blank paper.

Zoom to 1200%detail painted in 259 ms
Raster held3.8 MP

G-200.4

AT 1200%

01Base canvas: whole page, pixel-capped
02Detail canvas: the visible slice only
03Raster held: 3.8 MP
04Panning: never blank paper

04 · Spatial index

4,000 markups, no slowdown

Viewport queries, hit-testing and lasso selection use a uniform grid rather than scanning every markup. The flatten export runs in a worker, so a 400-page export never freezes the window.

500 hit tests5 ms with 4,000 markups
Overlay rebuild54 ms with 4,000 markups

G-200.5

4,000 MARKUPS

01Uniform grid over the sheet
02Only cells under the cursor are asked
03500 hit tests in 5 ms
04Overlay rebuilt in 54 ms

SHEET G-200.6

The full log

npm run perf.

PERF800-page, 49.1 MB generated sample

Measure	Result
Open (metadata ready)	255 ms
First page painted	480 ms
Bytes read to open + paint page 1	1.1 MB of 49.1 MB (19 range requests)
Jump to page 601	129 ms
Sustained scroll	17 ms/frame
Zoom to 1200% (detail tile painted)	259 ms
Raster held in memory at 1200%	3.8 MP
Overlay rebuild, 4,000 markups	54 ms
500 hit tests, 4,000 markups	5 ms
JS heap	14 MB

SHEET G-501

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