Enable opening of downloaded fonts only in ForKit in Online

(This is the second attempt at this, I had to revert the first one as
it broke desktop Collabora Office.)

We want that only the ForKit process needs to have access to new font
files added to a Collabora Online instance dynamically by downloading
from a server. There are however many locations in the Kit process, in
core and in external libraries like harfbuzz, where the code wants to
open a font file.

Handle this so that the ForKit process opens such a downloaded font
file and doesn't close it. The file descriptor is thus inherited by
Kit processes.  The font file pathname passed on to other code is a
fake on in the format "/:FD:/%d" where the %d is the file descriptor
of the opened font file. Add checks in all places where font files are
opened, look for this special pathname format, and modify the code to
just dup() the already open file descriptor in that case.

All this is relevant for Linux only, as Collabora Online runs on
Linux.

Do the above for harfbuzz, cairo, fontconfig, and freetype.

In addition make sure that these libraries (except harfbuzz which
needs to be a static library) when bundled, on Linux, are built as
shared libraries, and won't be confused with the corresponding system
libraries by making sure their sonames are different.

Change-Id: Ib059cb27e1637d07bb709249abd0d984f948caa9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/140714
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tor Lillqvist <tml@collabora.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/desktop/source/lib/init.cxx b/desktop/source/lib/init.cxx
index 559c8fe9cd1b..8b93b9815a8f 100644
--- a/desktop/source/lib/init.cxx
+++ b/desktop/source/lib/init.cxx
@@ -25,6 +25,10 @@
 #include <postmac.h>
 #endif
 
+#ifdef LINUX
+#include <fcntl.h>
+#endif
+
 #ifdef ANDROID
 #include <osl/detail/android-bootstrap.h>
 #endif
@@ -4331,13 +4335,27 @@ static void lo_setOption(LibreOfficeKit* /*pThis*/, const char *pOption, const c
         else
             sal_detail_set_log_selector(pCurrentSalLogOverride);
     }
+#ifdef LINUX
     else if (strcmp(pOption, "addfont") == 0)
     {
+        if (memcmp(pValue, "file://", 7) == 0)
+            pValue += 7;
+
+        int fd = open(pValue, O_RDONLY);
+        if (fd == -1)
+        {
+            std::cerr << "Could not open font file '" << pValue << "': " << strerror(errno) << std::endl;
+            return;
+        }
+
+        OUString sMagicFileName = "file:///:FD:/" + OUString::number(fd);
+
         OutputDevice *pDevice = Application::GetDefaultDevice();
         OutputDevice::ImplClearAllFontData(false);
-        pDevice->AddTempDevFont(OUString::fromUtf8(pValue), "");
+        pDevice->AddTempDevFont(sMagicFileName, "");
         OutputDevice::ImplRefreshAllFontData(false);
     }
+#endif
 }
 
 static void lo_dumpState (LibreOfficeKit* pThis, const char* /* pOptions */, char** pState)