Add a build target and a proper export header for shared library builds.

This CL adds support for Chromium's component build feature to pdfium.

The export header stub in fpdfview.h is expanded to match Chromium's
export mechanisms and patterns (fixes pdfium:825).

A component/shared library build can be triggered by adding

is_component_build = true

as a gn argument. Please note that setting this will also affect some
of pdfiums dependencies like v8, which will be build as components
too.

Additionally, this CL provides a "pdf_source_set" template which
dynamically enables the use of "source_set" when building a complete
static library or a shared library to reduce build time.

When testing this it is recommended to only build the pdfium target as
most of pdfiums test rely on non-public functions which aren't exported
by the shared library.

Bug: pdfium:825,pdfium:826
Change-Id: Icedc538ec535e11d1e53c4d5fabc8c064b275752
Reviewed-on: https://pdfium-review.googlesource.com/8970
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/pdfium.gni b/pdfium.gni
index 530301a5d9..1842ae095b 100644
--- a/pdfium.gni
+++ b/pdfium.gni
@@ -66,3 +66,26 @@ declare_args() {
 if (pdf_use_skia && pdf_use_skia_paths) {
   assert(false, "Enable at most ONE of pdf_use_skia and pdf_use_skia_paths")
 }
+
+# Custom template used to enable building with "source_set" instead of
+# "static_library" when doing component or complete static library builds
+
+template("pdf_source_set") {
+  if (is_component_build || pdf_is_complete_lib) {
+    pdf_link_target_type = "source_set"
+  } else {
+    pdf_link_target_type = "static_library"
+  }
+  target(pdf_link_target_type, target_name) {
+    # See http://crbug.com/594610
+    forward_variables_from(invoker, [ "visibility" ])
+    forward_variables_from(invoker, "*", [ "visibility" ])
+  }
+}
+
+set_defaults("pdf_source_set") {
+  if (!defined(deps)) {
+    deps = []
+  }
+  configs = default_compiler_configs
+}