PDF text: dual-layer + single-layer rendering with PdfTextMode option#579
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andiwand wants to merge 5 commits into
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PDF text: dual-layer + single-layer rendering with PdfTextMode option#579andiwand wants to merge 5 commits into
andiwand wants to merge 5 commits into
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Introduces a `PdfTextMode` enum with two values: - `dual_layer`: visual (PUA glyphs, paint order) + transparent Unicode selection/search layer. Default. - `single_layer`: single combined layer with frequency-based Unicode mapping, similar to pdf2htmlEX. The active mode is controlled by `HtmlConfig::pdf_text_mode`. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Mq2d2eFjjCL8cHpU9pHugq
Replaces the single-glyph-per-absolute-span approach with two modes,
both using line blocks (position:absolute on the line div, margin-left
on inline run spans) instead of per-glyph absolute positioning.
Dual-layer mode (default, PdfTextMode::dual_layer):
- Visual layer (<div class="vis" aria-hidden>): paint-order glyph
rendering. Fonts re-encoded to PUA. Invisible text omitted.
- Selection layer (<div class="sel">): transparent real-Unicode text.
Runs grouped into line blocks by baseline; space detection inserts
gap spans. Each run span is display:inline-block with CSS justify
(text-align:justify; text-align-last:justify; text-justify:inter-
character) so characters fill the PDF advance without JavaScript.
- Similar approach to pdf.js.
Single-layer mode (PdfTextMode::single_layer):
- One combined layer per page in paint order.
- Pre-pass frequency analysis: counts (uchar, glyph) co-occurrences
per font, then picks the most-frequent glyph as the cmap entry —
so the common case wins, not first-come-first-serve.
- Clean runs (all uchar→glyph pairs match the winner) render the real
Unicode directly in the embedded font — natively selectable.
- Unclean runs paint glyphs via ::before{content:attr(data-g)} with
a zero-width display:inline-block overlay span for selectability.
- PUA-only chars (no Unicode mapping) remain visible but unselectable.
- Similar approach to pdf2htmlEX.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mq2d2eFjjCL8cHpU9pHugq
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Shared static methods (`px_decl`, `ascent_em`, `glyph_run_str`, `escape_markup`) and a template `handle_graphic_element` replace the copy-pasted lambdas in both rendering modes (-60 lines, cleaner diffs). The single-layer `add_class` captures `styles` from scope to match the dual-layer signature; `AtomicStyles styles` is moved up before the pre- pass so the capture is valid. Two dual-layer correctness fixes (from code-review): - Add letter-spacing/word-spacing to visual runs when Tc/Tw are non-zero, so embedded glyphs space correctly for PDFs with custom char/word spacing. - Move vis_prev_* state updates inside the `if (!invisible)` block so invisible/clip-mode runs do not shift the next visible run's position. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Mq2d2eFjjCL8cHpU9pHugq
Adds a standalone test that translates style-various-1.pdf through both dual_layer and single_layer modes and asserts the output document.html contains the expected marker classes (vis+sel for dual, line-block t for single). Prevents silent regressions if a mode is broken. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Mq2d2eFjjCL8cHpU9pHugq
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Summary
Combines the prototypes from #577 and #578 into a single implementation with a user-selectable mode.
PdfTextModeenum toHtmlConfig(dual_layerdefault,single_layeropt-in)position:absoluteon the line<div>,margin-lefton inline run<span>s) rather than per-glyph absolute positioning — forward-compatible with future paragraph groupingDual-layer mode (
PdfTextMode::dual_layer, default)Similar approach to pdf.js:
<div class="vis" aria-hidden="true">): paint-order glyph rendering using fonts re-encoded to the Private Use Area. Invisible text (Tr 3/7) omitted.<div class="sel">): transparent real-Unicode text in reading order. Runs grouped into per-baseline line blocks; gap detection insertsdisplay:inline-blockspacer spans. Each run span uses CSStext-align:justify; text-align-last:justify; text-justify:inter-characterto spread characters to match the PDF advance — no JavaScript.Single-layer mode (
PdfTextMode::single_layer)Similar approach to pdf2htmlEX:
(uchar, glyph)co-occurrences per font across all pages, then picks the most-frequent glyph for each Unicode character as the cmap winner (common case wins, not first-come-first-serve).::before{content:attr(data-g)}CSS generated content with a zero-widthdisplay:inline-block; overflow:hiddenoverlay<span>carrying the real Unicode for selection.Test plan
style-various-1.pdf):class="vis" aria-hidden+class="sel"divs present; visual spans contain PUA bytes; selection spans contain readable Unicode--singleflag on CLI):gl+ovclasses present;data-gattributes contain PUA bytes; inline text contains readable Unicode