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https://github.com/chromium/pdfium

The PDF library used by the Chromium project
https://github.com/chromium/pdfium

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The PDF library used by the Chromium project

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README 

        
# PDFium



## Prerequisites



PDFium uses the same build tooling as Chromium. See the platform-specific

Chromium build instructions to get started, but replace Chromium's

"Get the code" instructions with [PDFium's](#get-the-code).



*   [Chromium Linux build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/linux/build_instructions.md)

*   [Chromium Mac build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/mac_build_instructions.md)

*   [Chromium Windows build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/windows_build_instructions.md)



### CPU Architectures supported



The default architecture for Windows, Linux, and Mac is "`x64`". On Windows,

"`x86`" is also supported. GN parameter "`target_cpu = "x86"`" can be used to

override the default value. If you specify Android build, the default CPU

architecture will be "`arm`".



It is expected that there are still some places lurking in the code which will

not function properly on big-endian architectures. Bugs and/or patches are

welcome, however providing this support is **not** a priority at this time.



#### Google employees



Run: `download_from_google_storage --config` and follow the

authentication instructions. **Note that you must authenticate with your

@google.com credentials**. Enter "0" if asked for a project-id.



Once you've done this, the toolchain will be installed automatically for

you in the [Generate the build files](#generate-the-build-files) step below.



The toolchain will be in `depot_tools\win_toolchain\vs_files\`, and

windbg can be found in

`depot_tools\win_toolchain\vs_files\\win_sdk\Debuggers`.



If you want the IDE for debugging and editing, you will need to install

it separately, but this is optional and not needed for building PDFium.



## Get the code



The name of the top-level directory does not matter. In the following example,

the directory name is "repo". This directory must not have been used before by

`gclient config` as each directory can only house a single gclient

configuration.



```

mkdir repo

cd repo

gclient config --unmanaged https://pdfium.googlesource.com/pdfium.git

gclient sync

cd pdfium

```



On Linux, additional build dependencies need to be installed by running the

following from the `pdfium` directory.



```

./build/install-build-deps.sh

```



## Generate the build files



PDFium uses GN to generate the build files and [Ninja](https://ninja-build.org/)

to execute the build files.  Both of these are included with the

depot\_tools checkout.



### Selecting build configuration



PDFium may be built either with or without JavaScript support, and with

or without XFA forms support.  Both of these features are enabled by

default. Also note that the XFA feature requires JavaScript.



Configuration is done by executing `gn args ` to configure the build.

This will launch an editor in which you can set the following arguments.

By convention, `` should be named `out/foo`, and some tools / test

support code only works if one follows this convention.

A typical `` name is `out/Debug`.



```

use_remoteexec = false # Approved users only.  Do necessary setup & authentication first.

is_debug = true  # Enable debugging features.



# Set true to enable experimental Skia backend.

pdf_use_skia = false



# Set true to enable experimental Fontations backend.

pdf_enable_fontations = false



pdf_enable_xfa = true  # Set false to remove XFA support (implies JS support).

pdf_enable_v8 = true  # Set false to remove Javascript support.

pdf_is_standalone = true  # Set for a non-embedded build.

is_component_build = false # Disable component build (Though it should work)

```



For test applications like `pdfium_test` to build, one must set

`pdf_is_standalone = true`.



By default, the entire project builds with C++20.



By default, PDFium expects to build with a clang compiler that provides

additional chrome plugins. To build against a vanilla one lacking these,

one must set

`clang_use_chrome_plugins = false`.



When complete the arguments will be stored in `/args.gn`, and

GN will automatically use the new arguments to generate build files.

Should your files fail to generate, please double-check that you have set

use\_sysroot as indicated above.



## Building the code



You can build the standalone test program by running:

`ninja -C  pdfium_test`

You can build the entire product (which includes a few unit tests) by running:

`ninja -C  pdfium_all`



## Running the standalone test program



The pdfium\_test program supports reading, parsing, and rasterizing the pages of

a .pdf file to .ppm or .png output image files (Windows supports two other

formats). For example: `/pdfium_test --ppm path/to/myfile.pdf`. Note

that this will write output images to `path/to/myfile.pdf..ppm`.

Run `pdfium_test --help` to see all the options.



## Testing



There are currently several test suites that can be run:



 * pdfium\_unittests

 * pdfium\_embeddertests

 * testing/tools/run\_corpus\_tests.py

 * testing/tools/run\_javascript\_tests.py

 * testing/tools/run\_pixel\_tests.py



It is possible the tests in the `testing` directory can fail due to font

differences on the various platforms. These tests are reliable on the bots. If

you see failures, it can be a good idea to run the tests on the tip-of-tree

checkout to see if the same failures appear.



### Pixel Tests



If your change affects rendering, a pixel test should be added. Simply add a

`.in` or `.pdf` file in `testing/resources/pixel` and the pixel runner will

pick it up at the next run.



Make sure that your test case doesn't have any copyright issues. It should also

be a minimal test case focusing on the bug that renders the same way in many

PDF viewers. Try to avoid binary data in streams by using the `ASCIIHexDecode`

simply because it makes the PDF more readable in a text editor.



To try out your new test, you can call the `run_pixel_tests.py` script:



```bash

$ ./testing/tools/run_pixel_tests.py your_new_file.in

```



To generate the expected image, you can use the `make_expected.sh` script:



```bash

$ ./testing/tools/make_expected.sh your_new_file.pdf

```



Please make sure to have `optipng` installed which optimized the file size of

the resulting png.



### `.in` files



`.in` files are PDF template files. PDF files contain many byte offsets that

have to be kept correct or the file won't be valid. The template makes this

easier by replacing the byte offsets with certain keywords.



This saves space and also allows an easy way to reduce the test case to the

essentials as you can simply remove everything that is not necessary.



A simple example can be found [here](https://pdfium.googlesource.com/pdfium/+/refs/heads/main/testing/resources/rectangles.in).



To transform this into a PDF, you can use the `fixup_pdf_template.py` tool:



```bash

$ ./testing/tools/fixup_pdf_template.py your_file.in

```



This will create a `your_file.pdf` in the same directory as `your_file.in`.



There is no official style guide for the .in file, but a consistent style is

preferred simply to help with readability. If possible, object numbers should

be consecutive and `/Type` and `/SubType` should be on top of a dictionary to

make object identification easier.



## Embedding PDFium in your own projects



The public/ directory contains header files for the APIs available for use by

embedders of PDFium. The PDFium project endeavors to keep these as stable as

possible.



Outside of the public/ directory, code may change at any time, and embedders

should not directly call these routines.



## Code Coverage



Code coverage reports for PDFium can be generated in Linux development

environments. Details can be found [here](/docs/code-coverage.md).



Chromium provides code coverage reports for PDFium

[here](https://chromium-coverage.appspot.com/). PDFium is located in

`third_party/pdfium` in Chromium's source code.

This includes code coverage from PDFium's fuzzers.



## Waterfall



The current health of the source tree can be found

[here](https://ci.chromium.org/p/pdfium/g/main/console).



## Community



There are several mailing lists that are setup:



 * [PDFium](https://groups.google.com/forum/#!forum/pdfium)

 * [PDFium Reviews](https://groups.google.com/forum/#!forum/pdfium-reviews)

 * [PDFium Bugs](https://groups.google.com/forum/#!forum/pdfium-bugs)



Note, the Reviews and Bugs lists are typically read-only.



## Bugs



PDFium uses this [bug tracker](https://bugs.chromium.org/p/pdfium/issues/list),

but for security bugs, please use

[Chromium's security bug template](https://bugs.chromium.org/p/chromium/issues/entry?template=Security%20Bug)

and add the "Cr-Internals-Plugins-PDF" label.



## Contributing code



See the [CONTRIBUTING](CONTRIBUTING.md) document for more information on

contributing to the PDFium project.