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Fix the rendering of PDF covers in some edge cases #64

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Merged
merged 2 commits into from
Dec 17, 2021
Merged

Fix the rendering of PDF covers in some edge cases #64

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2e3b99b
Fix the rendering of PDF covers in some edge cases
mickael-menu Dec 3, 2021
7c0ed10
Merge branch 'develop' into fix/pdf-cover
mickael-menu Dec 17, 2021
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -44,6 +44,10 @@ All notable changes to this project will be documented in this file. Take a look

* Fix building with Kotlin 1.6.

#### Streamer

* Fixed the rendering of PDF covers in some edge cases.

#### Navigator

* Fixed turning pages of an EPUB reflowable resource with an odd number of columns. A virtual blank trailing column is appended to the resource when displayed as two columns.
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12 changes: 5 additions & 7 deletions readium/streamer/src/main/java/org/readium/r2/streamer/parser/pdf/PdfiumDocument.kt
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Expand Up @@ -54,22 +54,20 @@ internal class PdfiumDocument(
}

private fun PdfiumCore.renderCover(document: _PdfiumDocument): Bitmap? {
try {
val pointer = openPage(document, 0)
if (pointer <= 0) return null
Comment on lines -58 to -59
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@mickael-menu mickael-menu Dec 3, 2021

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I'm not sure why I checked for the pointer to be above 0, but sometimes it is negative and still valid. This prevented a few PDF covers to be rendered on some devices.

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@qnga qnga Dec 6, 2021

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0 is supposed to be an invalid pointer. I'm not sure the method can return it here though.

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@mickael-menu mickael-menu Dec 6, 2021

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Yes that's weird. Maybe the openPage() fails for some reason, but that doesn't prevent the rest of the code from working as we don't use the pointer directly.

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@qnga qnga Dec 6, 2021

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I suppose in case of failure you won't get the first page though...

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@mickael-menu mickael-menu Dec 6, 2021

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In practice yes, but that's not guaranteed... I will look again on Friday to see if I can find a better way.

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@mickael-menu mickael-menu Dec 17, 2021

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@qnga I investigated more and looking at the Java and C++ code of PdfiumAndroid, I don't think the returned long is the address of a C++ pointer. I also tried giving a non-existing page index and this function throws an exception, so the error handling is properly handled inside.

So I think this PR is safe to merge as is. We also used this code in production for the past two weeks without bug reports.


return try {
openPage(document, 0)
val width = getPageWidth(document, 0)
val height = getPageHeight(document, 0)
val bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
renderPageBitmap(document, bitmap, 0, 0, 0, width, height, false)
return bitmap
bitmap

} catch (e: Exception) {
Timber.e(e)
return null
null
} catch (e: OutOfMemoryError) { // We don't want to catch any Error, only OOM.
Timber.e(e)
return null
null
}
}

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