This patch makes a clear separation between the way to draw and the editing stuff.
It adds a class DrawEditor which should be extended in order to create new drawing tools.
As an example, the ink tool has been rewritten in order to use it.
The problem with the referenced PDF document has nothing to do with invalid dates, as the issue seems to suggest, but rather with the fact that it has neither an XRef table nor a trailer dictionary.
Given that crucial parts of the internal document structure is missing, you might argue that it's not really a PDF document.
In an attempt to support this kind of corruption, we'll simply iterate through all (previously found) XRef entries and pick one that *might* be a valid /Root dictionary.
There's obviously no guarantee that this works, and it might not be fast in larger PDF documents, but at least it cannot be any worse than *immediately* throwing `InvalidPDFException` as we previously did here.
*Please note:* I'm totally fine with this patch being rejected, since it's somewhat questionable if we should actually attempt to support "PDF documents" with this level of corruption.
This extends PR 13796 to also handle the case where sub-streams contain invalid data, i.e. anything that isn't a Stream, however please note that in these cases there's no guarantee that we'll render the page "correctly".
Note that Adobe Reader, i.e. the PDF reference implementation, cannot render the last page of the referenced PDF document.
It fixes#18956.
In the patch #18029, for performance reasons and because I thought it was useless, I deliberately chose to not fill the mask
with the backdrop color when it's full black: it was a bad idea.
So in this patch we always add the backdrop color to the mask.
The PDF document is clearly corrupt, since it has /FontFile2 entries that are Dictionaries which obviously isn't correct.
While there's obviously no guarantee that things will look perfect this way, actually rendering the text at all should be an improvement in general.
The code parses the /RBGroups entry in the OC configuration dict and adds the property `rbGroups' to instances of the OptionalContentGroup class. rbGroups takes an array of Sets, where each Set instance represents an RB group the OptionalContentGroup instance is a member of. Such a Set instance contains all OCG ids within the corresponding RB group. RB groups an OCG is associated with are processed when its visibility is set to true, as required by the PDF spec.
Given that the sub-title of that document is "Public domain texts for young people." and that the images have clear sources at the end of the document, it should (hopefully) be OK to add it to the repository rather than relying on a linked test-case.
Given the following excerpt from the [Wikipedia article](https://en.wikipedia.org/wiki/Gill_Sans), mapping this to Helvetica should hopefully be fine:
> It has been described as "the British Helvetica" because of its lasting popularity in British design.
Given that we handle non-embedded Calibri fonts as "mapped to standard font", we really ought to be able to use the same glyph mapping as for an actual standard font.
Note that this actually improves consistency in the code, given how we already handle such fonts if they happen to be of the `CIDFontType2` type; see b47c7eca83/src/core/fonts.js (L1186-L1190)
This functionality is purposely limited to development mode and GENERIC builds, since it's unnecessary in e.g. the *built-in* Firefox PDF Viewer, and will only be used when a `<base>`-element is actually present.
*Please note:* We also have tests in mozilla-central that will *indirectly* ensure that relative filter-URLs work as intended in the Firefox PDF Viewer, see https://searchfox.org/mozilla-central/source/toolkit/components/pdfjs/test/browser_pdfjs_filters.js
---
To test that the issue is fixed, the following code can be used:
```html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<base href=".">
<title>base href (issue 18406)</title>
</head>
<body>
<ul>
<li>Place this code in a file, named `base_href.html`, in the root of the PDF.js repository</li>
<li>Run <pre>npx gulp dist-install</pre></li>
<li>Run <pre>npx gulp server</pre></li>
<li>Open <a href="http://localhost:8888/base_href.html">http://localhost:8888/base_href.html</a> in a browser</li>
<li>Compare rendering with <a href="http://localhost:8888/web/viewer.html?file=/test/pdfs/issue16287.pdf">http://localhost:8888/web/viewer.html?file=/test/pdfs/issue16287.pdf</a></li>
</ul>
<canvas id="the-canvas" style="border: 1px solid black; direction: ltr;"></canvas>
<script src="/node_modules/pdfjs-dist/build/pdf.mjs" type="module"></script>
<script id="script" type="module">
//
// If absolute URL from the remote server is provided, configure the CORS
// header on that server.
//
const url = '/test/pdfs/issue16287.pdf';
//
// The workerSrc property shall be specified.
//
pdfjsLib.GlobalWorkerOptions.workerSrc =
'/node_modules/pdfjs-dist/build/pdf.worker.mjs';
//
// Asynchronous download PDF
//
const loadingTask = pdfjsLib.getDocument(url);
const pdf = await loadingTask.promise;
//
// Fetch the first page
//
const page = await pdf.getPage(1);
const scale = 1.5;
const viewport = page.getViewport({ scale });
// Support HiDPI-screens.
const outputScale = window.devicePixelRatio || 1;
//
// Prepare canvas using PDF page dimensions
//
const canvas = document.getElementById("the-canvas");
const context = canvas.getContext("2d");
canvas.width = Math.floor(viewport.width * outputScale);
canvas.height = Math.floor(viewport.height * outputScale);
canvas.style.width = Math.floor(viewport.width) + "px";
canvas.style.height = Math.floor(viewport.height) + "px";
const transform = outputScale !== 1
? [outputScale, 0, 0, outputScale, 0, 0]
: null;
//
// Render PDF page into canvas context
//
const renderContext = {
canvasContext: context,
transform,
viewport,
};
page.render(renderContext);
</script>
</body>
</html>
```
There's no specification for that (even if it's possible to have an idea from
the xfa specs) so we just want to hide them in order to avoid to display something
wrong.
When an image has a non-zero SMaskInData it means that the image
has an alpha channel.
With JPX images, the colorspace isn't required (by spec) so when we
don't have it, the JPX decoder will handle the conversion in RGBA
format.
Note that the referenced file is trivially corrupt, since it contains *two* PDF documents placed in the same file which doesn't make sense (and isn't how a PDF document should be updated).
However it's still a good idea to ensure that `loadFont` is able to handle errors when resolving References, since that allows us to invoke the existing fallback font handling.
Fixes issue #16843.
In certain cases, the text layer was misaligned
due to a difference between the `lang` attribute
of the viewer and the canvas. This commit addresses
the problem by adding the `lang` attribute to the canvas.
The issue was caused because PDF.js uses serif/sans-serif
fonts to generate the text layer and relies on system fonts.
The difference in the `lang` attribute led to different fonts
being picked, causing the misalignment.
This also required changing the initial `charCodeToGlyphId`-data to an Object, which seems generally correct since it's consistent with existing code in the `src\core\{cff_font, type1_font}.js` files.
