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Add a thin wrapper around Skia's PDF backend
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‎skiko/buildSrc/src/main/kotlin/tasks/configuration/CommonTasksConfiguration.kt‎

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@@ -27,6 +27,7 @@ fun skiaHeadersDirs(skiaDir: File): List<File> =
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skiaDir.resolve("include/utils"),
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skiaDir.resolve("include/codec"),
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skiaDir.resolve("include/svg"),
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skiaDir.resolve("include/docs"),
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skiaDir.resolve("modules/skottie/include"),
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skiaDir.resolve("modules/skparagraph/include"),
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skiaDir.resolve("modules/skshaper/include"),

‎skiko/src/commonMain/kotlin/org/jetbrains/skia/Document.kt‎

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package org.jetbrains.skia
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import org.jetbrains.skia.impl.*
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import org.jetbrains.skia.impl.Library.Companion.staticLoad
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/**
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* High-level API for creating a document-based canvas. To use:
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*
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* 1. Create a document, e.g., via `PDFDocument.make(...)`.
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* 2. For each page of content:
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* ```
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* canvas = doc.beginPage(...)
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* drawMyContent(canvas)
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* doc.endPage()
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* ```
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* 3. Close the document with `doc.close()`.
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*/
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class Document internal constructor(ptr: NativePointer, internal val _owner: Any) : RefCnt(ptr) {
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companion object {
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init {
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staticLoad()
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}
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}
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/**
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* Begins a new page for the document, returning the canvas that will draw
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* into the page. The document owns this canvas, and it will go out of
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* scope when endPage() or close() is called, or the document is deleted.
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* This will call endPage() if there is a currently active page.
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*
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* @throws IllegalArgumentException If no page can be created with the supplied arguments.
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*/
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fun beginPage(width: Float, height: Float, content: Rect? = null): Canvas {
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Stats.onNativeCall()
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try {
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val ptr = interopScope {
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_nBeginPage(_ptr, width, height, toInterop(content?.serializeToFloatArray()))
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}
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require(ptr != NullPointer) { "Document page was created with invalid arguments." }
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return Canvas(ptr, false, this)
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} finally {
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reachabilityBarrier(this)
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}
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}
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/**
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* Call endPage() when the content for the current page has been drawn
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* (into the canvas returned by beginPage()). After this call the canvas
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* returned by beginPage() will be out-of-scope.
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*/
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fun endPage() {
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Stats.onNativeCall()
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try {
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_nEndPage(_ptr)
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} finally {
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reachabilityBarrier(this)
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}
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}
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/**
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* Call close() when all pages have been drawn. This will close the file
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* or stream holding the document's contents. After close() the document
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* can no longer add new pages. Deleting the document will automatically
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* call close() if need be.
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*/
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override fun close() {
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// Deleting the document (which super.close() does) will automatically invoke SkDocument::close.
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super.close()
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}
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}
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@ExternalSymbolName("org_jetbrains_skia_Document__1nBeginPage")
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@ModuleImport("./skiko.mjs", "org_jetbrains_skia_Document__1nBeginPage")
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private external fun _nBeginPage(
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ptr: NativePointer, width: Float, height: Float, content: InteropPointer
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): NativePointer
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@ExternalSymbolName("org_jetbrains_skia_Document__1nEndPage")
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@ModuleImport("./skiko.mjs", "org_jetbrains_skia_Document__1nEndPage")
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private external fun _nEndPage(ptr: NativePointer)

‎skiko/src/commonMain/kotlin/org/jetbrains/skia/pdf/PDFCompressionLevel.kt‎

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package org.jetbrains.skia.pdf
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enum class PDFCompressionLevel(internal val skiaRepresentation: Int) {
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DEFAULT(-1),
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NONE(0),
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LOW_BUT_FAST(1),
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AVERAGE(6),
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HIGH_BUT_SLOW(9);
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}

‎skiko/src/commonMain/kotlin/org/jetbrains/skia/pdf/PDFDateTime.kt‎

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package org.jetbrains.skia.pdf
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/**
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* @property year Year, e.g., 2025.
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* @property month Month between 1 and 12.
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* @property day Day between 1 and 31.
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* @property hour Hour between 0 and 23.
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* @property minute Minute between 0 and 59.
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* @property second Second between 0 and 59.
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* @property timeZoneMinutes The number of minutes that the time zone is ahead of or behind UTC.
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*/
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data class PDFDateTime(
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val year: Int,
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val month: Int,
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// Notice that we have omitted the dayOfWeek field here, as it is unused in Skia's PDF backend.
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val day: Int,
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val hour: Int,
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val minute: Int,
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val second: Int,
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val timeZoneMinutes: Int = 0
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) {
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init {
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require(month in 1..12) { "Month must be between 1 and 12." }
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require(day in 1..31) { "Day must be between 1 and 31." }
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require(hour in 0..23) { "Hour must be between 0 and 23." }
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require(minute in 0..59) { "Minute must be between 0 and 59." }
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require(second in 0..59) { "Second must be between 0 and 59." }
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}
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internal fun asArray() = intArrayOf(year, month, day, hour, minute, second, timeZoneMinutes)
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}

‎skiko/src/commonMain/kotlin/org/jetbrains/skia/pdf/PDFDocument.kt‎

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package org.jetbrains.skia.pdf
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import org.jetbrains.skia.Document
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import org.jetbrains.skia.ExternalSymbolName
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import org.jetbrains.skia.ModuleImport
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import org.jetbrains.skia.WStream
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import org.jetbrains.skia.impl.*
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import org.jetbrains.skia.impl.Library.Companion.staticLoad
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import org.jetbrains.skia.impl.Native.Companion.NullPointer
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object PDFDocument {
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init {
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staticLoad()
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}
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/**
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* Creates a PDF-backed document, writing the results into a WStream.
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*
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* PDF pages are sized in point units. 1 pt == 1/72 inch == 127/360 mm.
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*
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* @param out A PDF document will be written to this stream. The document may write
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* to the stream at anytime during its lifetime, until either close() is
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* called or the document is deleted.
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* @param metadata A PDFMetadata object. Any fields may be left empty.
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* @throws IllegalArgumentException If no PDF document can be created with the supplied arguments.
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*/
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fun make(out: WStream, metadata: PDFMetadata = PDFMetadata()): Document {
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Stats.onNativeCall()
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val ptr = try {
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interopScope {
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_nMakeDocument(
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getPtr(out),
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toInterop(metadata.title),
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toInterop(metadata.author),
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toInterop(metadata.subject),
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toInterop(metadata.keywords),
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toInterop(metadata.creator),
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toInterop(metadata.producer),
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toInterop(metadata.creation?.asArray()),
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toInterop(metadata.modified?.asArray()),
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toInterop(metadata.lang),
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metadata.rasterDPI,
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metadata.pdfA,
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metadata.encodingQuality,
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metadata.compressionLevel.skiaRepresentation
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)
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}
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} finally {
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reachabilityBarrier(out)
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}
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require(ptr != NullPointer) { "PDF document was created with invalid arguments." }
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return Document(ptr, out)
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}
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}
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@ExternalSymbolName("org_jetbrains_skia_pdf_PDFDocument__1nMakeDocument")
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@ModuleImport("./skiko.mjs", "org_jetbrains_skia_pdf_PDFDocument__1nMakeDocument")
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private external fun _nMakeDocument(
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wstreamPtr: NativePointer,
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title: InteropPointer,
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author: InteropPointer,
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subject: InteropPointer,
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keywords: InteropPointer,
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creator: InteropPointer,
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producer: InteropPointer,
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creation: InteropPointer,
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modified: InteropPointer,
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lang: InteropPointer,
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rasterDPI: Float,
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pdfA: Boolean,
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encodingQuality: Int,
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compressionLevel: Int
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): NativePointer

‎skiko/src/commonMain/kotlin/org/jetbrains/skia/pdf/PDFMetadata.kt‎

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package org.jetbrains.skia.pdf
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/**
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* Optional metadata to be passed into the PDF factory function.
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*
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* @property title The document's title.
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* @property author The name of the person who created the document.
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* @property subject The subject of the document.
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* @property keywords Keywords associated with the document.
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* Commas may be used to delineate keywords within the string.
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* @property creator If the document was converted to PDF from another format,
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* the name of the conforming product that created the
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* original document from which it was converted.
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* @property producer The product that is converting this document to PDF.
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* @property creation The date and time the document was created.
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* The zero default value represents an unknown/unset time.
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* @property modified The date and time the document was most recently modified.
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* The zero default value represents an unknown/unset time.
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* @property lang The natural language of the text in the PDF.
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* @property rasterDPI The DPI (pixels-per-inch) at which features without native PDF support
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* will be rasterized (e.g. draw image with perspective, draw text with
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* perspective, ...). A larger DPI would create a PDF that reflects the
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* original intent with better fidelity, but it can make for larger PDF
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* files too, which would use more memory while rendering, and it would be
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* slower to be processed or sent online or to printer.
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* @property pdfA If true, include XMP metadata, a document UUID, and sRGB output intent
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* information. This adds length to the document and makes it
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* non-reproducible, but are necessary features for PDF/A-2b conformance
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* @property encodingQuality Encoding quality controls the trade-off between size and quality. By
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* default this is set to 101 percent, which corresponds to lossless
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* encoding. If this value is set to a value <= 100, and the image is
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* opaque, it will be encoded (using JPEG) with that quality setting.
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* @property compressionLevel PDF streams may be compressed to save space.
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* Use this to specify the desired compression vs time tradeoff.
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*/
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data class PDFMetadata(
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val title: String? = null,
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val author: String? = null,
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val subject: String? = null,
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val keywords: String? = null,
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val creator: String? = null,
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val producer: String? = "Skia/PDF",
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val creation: PDFDateTime? = null,
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val modified: PDFDateTime? = null,
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val lang: String? = null,
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val rasterDPI: Float = 72f,
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val pdfA: Boolean = false,
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val encodingQuality: Int = 101,
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val compressionLevel: PDFCompressionLevel = PDFCompressionLevel.DEFAULT
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)

‎skiko/src/commonTest/kotlin/org/jetbrains/skia/pdf/PDFDocumentTest.kt‎

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package org.jetbrains.skia.pdf
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import org.jetbrains.skia.Color
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import org.jetbrains.skia.OutputWStream
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import org.jetbrains.skia.Paint
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import org.jetbrains.skia.Rect
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import java.io.ByteArrayOutputStream
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import kotlin.test.*
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class PDFDocumentTest {
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@Test
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fun makeWithNullMetadata() {
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val metadata = PDFMetadata(producer = null, compressionLevel = PDFCompressionLevel.NONE)
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val baos = ByteArrayOutputStream()
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PDFDocument.make(OutputWStream(baos), metadata).use { doc ->
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assertNotNull(doc.beginPage(100f, 250f), "Canvas is null.")
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doc.endPage()
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}
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val pdf = baos.toString(Charsets.UTF_8)
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assertDoesNotContain(pdf, "/Title")
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assertDoesNotContain(pdf, "/Author")
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assertDoesNotContain(pdf, "/Subject")
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assertDoesNotContain(pdf, "/Keywords")
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assertDoesNotContain(pdf, "/Creator")
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assertDoesNotContain(pdf, "/Producer")
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assertDoesNotContain(pdf, "/CreationDate")
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assertDoesNotContain(pdf, "/ModDate")
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assertDoesNotContain(pdf, "/Lang")
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}
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@Test
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fun makeWithNonNullMetadata() {
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val metadata = PDFMetadata(
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title = "My Novel",
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author = "Johann Wolfgang von Goethe",
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subject = "Literature",
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keywords = "Some,Important,Keywords",
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creator = "Skiko Test Suite",
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producer = "Skia",
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creation = PDFDateTime(2023, 7, 26, 13, 37, 42),
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modified = PDFDateTime(2024, 5, 12, 10, 20, 30, 150),
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lang = "de-DE",
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compressionLevel = PDFCompressionLevel.NONE
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)
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val baos = ByteArrayOutputStream()
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PDFDocument.make(OutputWStream(baos), metadata).use { doc ->
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assertNotNull(doc.beginPage(100f, 250f), "Canvas is null.")
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doc.endPage()
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}
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val pdf = baos.toString(Charsets.UTF_8)
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assertContains(pdf, "/Title (${metadata.title})")
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assertContains(pdf, "/Author (${metadata.author})")
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assertContains(pdf, "/Subject (${metadata.subject})")
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assertContains(pdf, "/Keywords (${metadata.keywords})")
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assertContains(pdf, "/Creator (${metadata.creator})")
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assertContains(pdf, "/Producer (${metadata.producer})")
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assertContains(pdf, "/CreationDate (D:20230726133742+00'00')")
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assertContains(pdf, "/ModDate (D:20240512102030+02'30')")
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assertContains(pdf, "/Lang (${metadata.lang})")
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}
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@Test
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fun draw() {
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val metadata = PDFMetadata(compressionLevel = PDFCompressionLevel.NONE)
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val baos = ByteArrayOutputStream()
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PDFDocument.make(OutputWStream(baos), metadata).use { doc ->
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val canvas = assertNotNull(doc.beginPage(100f, 250f), "Canvas is null.")
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canvas.drawRect(Rect(10f, 20f, 35f, 50f), Paint().apply { color = Color.RED })
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doc.endPage()
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}
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val pdf = baos.toString(Charsets.UTF_8)
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assertContains(pdf, "/MediaBox [0 0 100 250]")
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// Assert that the PDF contains some operations we would expect for our red rect drawing operation.
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assertContains(pdf, "1 0 0 rg")
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assertContains(pdf, "10 20 25 30 re")
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}
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@Test
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fun drawWithContentRect() {
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val metadata = PDFMetadata(compressionLevel = PDFCompressionLevel.NONE)
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val baos = ByteArrayOutputStream()
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PDFDocument.make(OutputWStream(baos), metadata).use { doc ->
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val canvas = assertNotNull(doc.beginPage(100f, 250f, Rect(60f, 40f, 90f, 220f)), "Canvas is null.")
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canvas.drawRect(Rect(10f, 20f, 35f, 50f), Paint().apply { color = Color.RED })
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doc.endPage()
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}
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val pdf = baos.toString(Charsets.UTF_8)
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// Assert that the PDF contains the content rect somewhere.
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assertContains(pdf, "60 40 30 180 re")
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}
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@Test
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fun beginInvalidPage() {
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val doc = PDFDocument.make(OutputWStream(ByteArrayOutputStream()))
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assertFailsWith<IllegalArgumentException> {
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doc.beginPage(-10f, -20f)
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}
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}
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private fun assertDoesNotContain(charSequence: CharSequence, other: CharSequence) {
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assertTrue(
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other !in charSequence,
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"Expected the char sequence to not contain the substring.\n" +
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"CharSequence <$charSequence>, substring <$other>."
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)
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}
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}

‎skiko/src/jvmMain/cpp/common/Document.cc‎

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#include <jni.h>
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#include "SkDocument.h"
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#include "interop.hh"
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extern "C" JNIEXPORT jlong JNICALL Java_org_jetbrains_skia_DocumentKt__1nBeginPage
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(JNIEnv* env, jclass jclass, jlong ptr, jfloat width, jfloat height, jfloatArray jcontentArr) {
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SkDocument* instance = reinterpret_cast<SkDocument*>(static_cast<uintptr_t>(ptr));
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jfloat* contentArr;
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SkRect content;
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SkRect* contentPtr = nullptr;
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if (jcontentArr != nullptr) {
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contentArr = env->GetFloatArrayElements(jcontentArr, 0);
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content = { contentArr[0], contentArr[1], contentArr[2], contentArr[3] };
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contentPtr = &content;
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}
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SkCanvas* canvas = instance->beginPage(width, height, contentPtr);
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if (jcontentArr != nullptr)
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env->ReleaseFloatArrayElements(jcontentArr, contentArr, 0);
19+
return reinterpret_cast<jlong>(canvas);
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}
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extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skia_DocumentKt__1nEndPage
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(JNIEnv* env, jclass jclass, jlong ptr) {
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SkDocument* instance = reinterpret_cast<SkDocument*>(static_cast<uintptr_t>(ptr));
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instance->endPage();
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}

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