Starting to add some documentation.

docs/getting-started.md

+# Getting Started with PDFium
+
+This guide walks through some examples of using the PDFium library. For an
+example of using PDFium see the [Chromium PDF Plugin][chrome-plugin].
+
+## Prerequisites
+
+You will need the PDFium library on your computer. You can see the
+[README](/README.md) for instructions on getting and installing PDFium.
+
+*** note
+You must compile PDFium without V8 or XFA support for the examples here to work.

[Tom Sepez, 2016/03/28 20:28:18]

nit: without both V8 and XFA support

[dsinclair, 2016/03/29 01:05:19]

Done.

+See the [V8 Getting Started][pdfium-v8] guide for how to initialize PDFium when
+V8 is compiled into the binary.
+
+V8 can be compiled out by providing `pdf_enable_v8=0 pdf_enable_xfa=0` to

[Tom Sepez, 2016/03/28 20:28:18]

nit:  move this up to line 13
GYP_DEFINES="pdf_enable_v8=0 pdf_enable_xfa=0" build/gyp_pdfium

[dsinclair, 2016/03/29 01:05:18]

Done.

+`build/gyp_pdfium`.
+***
+
+## PDFium Headers
+
+PDFium has been broken over several headers. You only need to include the

[Tom Sepez, 2016/03/28 20:28:18]

PDFium's API has been broken up over

[dsinclair, 2016/03/29 01:05:18]

Done.

+headers for functionality you need in your application. The full set of

[Tom Sepez, 2016/03/28 20:28:18]

functionality you use in your application.

[dsinclair, 2016/03/29 01:05:18]

Done.

+headers can be found in the [public/ folder of the repository][pdfium-public].
+
+In all cases you'll need to include `fpdfview.h` as it defines the needed
+methods for initialization and destruction of the library.
+
+## Initializing PDFium
+
+The first step to using PDFium is to initialize the library. As well, you'll

[Tom Sepez, 2016/03/28 20:28:18]

Having done so, you'll then need to 

[dsinclair, 2016/03/29 01:05:19]

Done.

+need to destroy the library when you're finished. When initializing the
+library you provide the `FPDF_LIBRARY_CONFIG` parameters to
+`FPDF_InitLibraryWithConfig`.
+
+```c
+#include <fpdfview.h>
+
+int main() {
+  FPDF_LIBRARY_CONFIG config;
+  config.version = 2;
+  config.m_pUserFontPaths = NULL;
+  config.m_pIsolate = NULL;
+  config.m_v8EmbedderSlot = 0;
+
+  FPDF_InitLibraryWithConfig(&config);
+
+  FPDF_DestroyLibrary();
+  return 0;
+}
+```
+
+Currently the `config.version` must be set to `2`. `m_pUserFontPaths` can be
+used to override the font paths searched by PDFium. If you wish to use your
+own font paths pass a `NULL` terminated list of `const char*` paths to use.
+
+`m_pIsolate` and `m_v8EmbedderSlot` are both used to configure the V8
+javascript engine. In the first case, you can provide an isolate through
+`m_pIsolate` for PDFium to use to store per-isolate data. Passing `NULL` will
+case PDFium to allocate a new isolate. `m_v8EmbedderSlot` is the embedder data
+slot to use in the v8::Isolate to store PDFium data. The value must be between
+0 and v8::Internals::kNumIsolateDataSlots. Typically, 0 is a good choice.
+
+For more information on using Javascript see the [V8 Getting Started][pdfium-v8]
+guide.
+
+*** aside
+PDFium is built as a set of static libraries. You'll need to specify them all on
+the link line in order to compile. My build line was:
+
+```
+PDF_LIBS="-lpdfium -lfpdfapi -lfxge -lfpdfdoc -lfxcrt -lfx_agg \

[Tom Sepez, 2016/03/28 20:28:18]

we really should consolidate our build down into fpdfcore, fpdfsdk, and xfa. 
Someday

[dsinclair, 2016/03/29 01:05:19]

I think we could just do pdfium and pdfium_xfa as you can't use core without
sdk, and both parts of those just make pdfium.
pdfium:451  

+-lfxcodec -lfx_lpng -lfx_libopenjpeg -lfx_lcms2 -lfx_freetype -ljpeg \
+-lfx_zlib -lfdrm -lpdfwindow -lbigint -lformfiller -ljavascript \
+-lfxedit"
+PDF_DIR=<path/to/pdfium>
+
+clang -I $PDF_DIR/public -o init init.c -L $PDF_DIR/out/Debug -lstdc++ -framework AppKit $PDF_LIBS
+```
+
+The `-framework AppKit` as needed as I'm building on a Mac. Internally PDFium
+uses C++, which is why `-lstdc++` is required on the link line.
+***
+
+
+[chrome-plugin]: https://chromium.googlesource.com/chromium/src/+/master/pdf/
+[pdfium-public]: https://pdfium.googlesource.com/pdfium/+/master/public/
+[pdfium-v8]: /docs/v8-getting-started.md