[philip-tam]

Summary

Makes page content look noticeably crisper at every zoom level and makes the zoom percentages behave like other PDF viewers.

Rendering

• Zoom tiles refined on settle. Between 150% and 300% a single 300%-quality coverage tile was shown shrunk by a non-integer factor (e.g. 1.5x at 200%), softening thin strokes; only exactly 300% was 1:1. The cached tile still shows instantly, then an exact zoom * dpr tile replaces it (tileNeedsExactRender).
• Whole device pixels. The page bitmap and tiles are drawn with a rounded transform translation; a fractional offset made the canvas bilinearly blend every pixel with its neighbours, softening all text even when the bitmap was at the exact screen resolution.
• Continuous view at device resolution. Pages were rendered at plain doc.scale and shown in a canvas with a floored CSS size, so the bitmap was resampled by a fraction of a pixel (uneven grey table rules/text at most zoom levels, and upscaled by dpr on high-DPI screens). They now render at scale * devicePixelRatio and the canvas is sized from the bitmap (1:1).
• Page sharpening preference (Page Display: Off / Light / Medium / Strong / Maximum, default Medium): a light 3x3 unsharp mask on freshly rendered page and tile bitmaps. Measured on the same text at the same size, PDFium's output had lighter ink and ~20% weaker edges than a hinted text renderer; this closes most of that gap. Flat areas are untouched; changing the level flushes the bitmap caches. ~70 ms for a normal view, ~270 ms worst case for a 12 Mpx bitmap.

Zoom

• 100% is now resolution based. A Page Display preference ("Screen resolution for 100% zoom", default 110 dpi) defines it: 1 PDF point = dpi/72 CSS px (96 would match browsers). The status bar shows/accepts the percentage in that unit and Actual Size uses it. The internal scale (doc.scale / viewport.zoom) is unchanged, so saved state and MCP app_set_zoom keep their meaning.
• Round zoom steps. +/- buttons, keys, Ctrl+wheel and trackpad pinch (single-page and continuous view) step through 10, 25, 33, 50, 67, 75, 100, 125, 150, 200, 300, 400, 600, 800 ... instead of x1.25 / smooth zoom.

Notes for review: the 110 dpi default changes what "100%" looks like for everyone (it is a preference; 96 gives browser size). New i18n keys are added for en/nl only, like the neighbouring Page Display keys.

Test plan

• New unit tests: zoom-display (percent/scale conversion, dpi clamping, step ladder), render-sharpen (flat areas, edges, alpha, border), tileNeedsExactRender
• Full npm run test:unit passes; vite build passes
• Manually checked on a multi-page text/table PDF: table rules and small text are crisp in single-page view at 123-200% after settling; continuous view and Ctrl+wheel stepping to be re-verified with the final build

[philip-tam]

Hi @mojtabakarimi, when you have a moment, could you review this PR? I merged the latest main into the branch (the unit test list now lives in scripts/unit-testlijst.txt, so I registered the two new test files there), so it is mergeable again and CI is re-running. All unit tests and the build pass locally.

The main review points are the new 110 dpi default for 100% zoom (a preference; 96 gives browser size) and the continuous-view render path (now 1:1 at device resolution). Happy to adjust anything. Thanks!