46 lines
1.8 KiB
Dart
46 lines
1.8 KiB
Dart
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// lib/editor/pdf/pdf_document_source.dart
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//
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// A minimal abstraction over a paginated document (a pdfrx PdfDocument in
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// production) consumed by the layout + render layer. Keeping the layout math
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// behind this seam lets continuous-single windowing (layout/page_viewport.dart)
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// and tiling be unit-tested against a fake source — no pdfium, no GPU, no real
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// PDF (the production pdfrx adapter is a thin device-side wrapper added with the
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// viewport widget / page_tile renderer, which are device-gated).
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import 'dart:ui' show Size;
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import '../layout/page_viewport.dart';
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/// Read-only page geometry for a paginated document.
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abstract class PageDocumentSource {
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/// Number of pages (>= 0).
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int get pageCount;
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/// Intrinsic size of page [index] in PDF points (width/height > 0).
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Size pageSize(int index);
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}
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/// Builds continuous-single stacking metrics by fitting every page to a single
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/// [columnWidth] (fit-to-width, the continuous-single mode): each page's
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/// laid-out height is `columnWidth × (pageHeight / pageWidth)`, preserving its
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/// aspect ratio. [gap] is inserted between pages (content units).
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///
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/// Pages reporting a non-positive width are treated as zero-height (defensive;
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/// real pages always have a positive width) so a malformed page can't throw.
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///
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/// Returns the metrics needed by [PageStackMetrics.visibleRange]; pair this with
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/// the device-gated page-mounting widget.
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PageStackMetrics pageStackMetricsForWidth(
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PageDocumentSource source,
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double columnWidth, {
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double gap = 0.0,
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}) {
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assert(columnWidth >= 0);
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final heights = List<double>.generate(source.pageCount, (i) {
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final size = source.pageSize(i);
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if (size.width <= 0) return 0.0;
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return columnWidth * (size.height / size.width);
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});
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return PageStackMetrics(pageHeights: heights, gap: gap);
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}
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