Get the Chromium depot_tools via the instructions. This provides the gclient utility needed below and many other tools needed for PDFium development.
Also install Python, Subversion, and Git and make sure they're in your path.
PDFium uses the same build tool as Chromium:
Please refer to Chromium's Visual Studio set up for requirements and instructions on build environment configuration.
set DEPOT_TOOLS_WIN_TOOLCHAIN=0, or set that variable in your global environment.
Compilation is done through Ninja, not Visual Studio.
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 “
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.
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 step below.
The toolchain will be in
depot_tools\win_toolchain\vs_files\<hash>, and windbg can be found in
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.
The name of the top-level directory does not matter. In our examples, we use “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
Additional build dependencies need to be installed by running the following from the
We use GN to generate the build files and Ninja to execute the build files. Both of these are included with the depot_tools checkout.
Configuration is done by executing
gn args <directory> to configure the build. This will launch an editor in which you can set the following arguments. By convention,
<directory> should be named
out/foo, and some tools / test support code only works if one follows this convention. A typical
<directory> name is
For sample applications like
pdfium_test to build, one must set
pdf_is_standalone = true.
By default, the entire project builds with C++14, because features like V8 support, XFA support, and the Skia backend all have dependencies on libraries that require C++14. If one does not need any of those features, and need to fall back to building in C++11 mode, then set
use_cxx11 = true. This fallback is temporary and will go away in the future when PDFium fully transitions to C++14. See this bug for details.
When building with the experimental Skia backend, Skia itself it built with C++17. There is no configuration for this. One just has to use a build toolchain that supports C++17.
When complete the arguments will be stored in
<directory>/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.
You can build the sample program by running:
ninja -C <directory> pdfium_test You can build the entire product (which includes a few unit tests) by running:
ninja -C <directory> pdfium_all.
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:
<directory>/pdfium_test --ppm path/to/myfile.pdf. Note that this will write output images to
pdfium_test --help to see all the options.
There are currently several test suites that can be run:
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.
If your change affects rendering, a pixel test should be added. Simply add a
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
$ ./testing/tools/run_pixel_tests.py your_new_file.in
To generate the expected image, you can use the
$ ./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 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.
To transform this into a PDF, you can use the
$ ./testing/tools/fixup_pdf_template.py your_file.in
This will create a
your_file.pdf in the same directory as
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
/SubType should be on top of a dictionary to make object identification easier.
The public/ directory contains header files for the APIs available for use by embedders of PDFium. We endeavor 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 reports for PDFium can be generated in Linux development environments. Details can be found here.
Chromium provides code coverage reports for PDFium here. PDFium is located in
third_party/pdfium in Chromium‘s source code. This includes code coverage from PDFium’s fuzzers.
Valgrind and other profiling tools do not work correctly with the standard build setup that PDFium uses. You will need to add
args.gn to get symbols to correctly appear.
The current health of the source tree can be found here.
There are several mailing lists that are setup:
Note, the Reviews and Bugs lists are typically read-only.
For contributing code, we will follow Chromium's process as much as possible. The main exceptions are:
Before submitting a fix for a bug, it can help if you create an issue in the bug tracker. This allows easier discussion about the problem and also helps with statistics tracking.