Embedding Pharo

This repository demonstrates embedding Pharo inside host programs written in Free Pascal. It is inspired by Pablo Tesone's C example.

Embedding Pharo in Pascal takes advantage of Pascal's cross-platform portability.

How It Works

The application Pharo image is as per Pablo's repository, running SDL2AthensDrawingExample headlessly. This image is compiled into a Windows resource.

Free Pascal has built-in cross-platform support for programmatically accessing Windows resources. The source code in embedded-cli implements FFI to Pharo's shared library libPharoVMCore, routines to access the Pharo image Windows resource for callback from libPharoVMCore, and a driver program. When run, the compiled driver program invokes the Pharo VM with the embedded Pharo image which puts up an SDL window where it is possible to draw with the mouse.

How To Build

Pharo headless VM

First, build the Pharo headless VM, following the instructions in its README. When done, the VM files are in build/vm.

Pharo application image

Next, prepare the Pharo application image. Basically, start from a fresh Pharo 8.0 image and load the EmbeddedSupport code from Pablo's repository. The following snippet works, assuming you have cloned Pablo's repository locally; adjust the gitlocal path in the snippet, of course.

Metacello new
	baseline: 'EmbeddedSupport';
	repository: 'gitlocal:///home/pierce/src/st/pharo-vm-embedded-example/smalltalk-src';
	load.

NoChangesLog install.
NoPharoFilesOpener install.
PharoCommandLineHandler forcePreferencesOmission: true.

SmalltalkImage current snapshot: true andQuit: true

Windows resource

Then, embed the Pharo application image into a Windows resource file.

Here's a simplified version of resources.rc. This assumes you have named the image to be embedded Pharo.image.

300 RCDATA "Pharo.image"

Building a Windows resource file on Linux requires windres. On Ubuntu, this program is part of the package binutils-mingw-w64-x86-64.

Place the application Pharo.image and resources.rc in the same directory. Then,

% /usr/bin/x86_64-w64-mingw32-windres -i resources.rc -o resources.res
% ls -l
total 113488
-rw-r--r-- 2 pierce pierce 58098672 Jan 23 14:10 Pharo.image
-rw-r--r-- 2 pierce pierce       25 Jan 23 14:01 resources.rc
-rw-r--r-- 2 pierce pierce 58098736 Jan 23 14:10 resources.res

The output resources.res is the compiled resources file.

Pascal host program

Finally we are ready to build the Pascal host program. Move resources.res to this repository's embedded-cli directory. Also create a link to libPharoVMCore.so or make a copy of it. The directory's content is now as follows:

% ls -l
total 58736
-rwxr-xr-x 2 pierce pierce  3344760 Jan 23 09:26 libPharoVMCore.so*
-rw-r--r-- 2 pierce pierce 58098736 Jan 23 14:10 resources.res
-rw-r--r-- 4 pierce pierce     1945 Jan 23 12:55 runPharoEmbedded.pas
-rw-r--r-- 4 pierce pierce     3824 Jan 23 12:54 ulibEmbeddedImage.pas
-rw-r--r-- 5 pierce pierce     1045 Jan 22 15:42 ulibPharoVM.pas

At the start of runPharoEmbedded.pas, the line {$R resources.res} is the Pascal compiler directive to incorporate resources.res into the executable that is being built:

program runPharoEmbedded;

{$mode objfpc}{$H+}
{$R resources.res} { <= compiler directive to incorporate resources.res }
{$linklib m}

Build the host program - the Pascal compiler is its own make system and knows to compile the necessary source files. (The Pascal compiler also knows how to invoke windres to compile resources.rc into resources.res when so configured. I've done that part by hand since this is a HOWTO.)

% fpc runPharoEmbedded.pas
Free Pascal Compiler version 3.0.4 [2018/10/29] for x86_64
Copyright (c) 1993-2017 by Florian Klaempfl and others
Target OS: Linux for x86-64
Compiling runPharoEmbedded.pas
Compiling ulibPharoVM.pas
Compiling ulibEmbeddedImage.pas
Compiling resource runPharoEmbedded.or
Linking runPharoEmbedded
/usr/bin/ld: warning: link.res contains output sections; did you forget -T?
232 lines compiled, 0.4 sec

% ls -l runPharoEmbedded
-rwxr-xr-x 1 pierce pierce 58884328 Jan 23 14:22 runPharoEmbedded*

Much of the size of the executable is due to the embedded Pharo.image.

We'll run runPharoEmbedded in the headless VM build directory because Pharo's baked-in library lookup currently requires this. So move the program over.

% mv runPharoEmbedded ~/src/st/opensmalltalk-vm-pharo/build/vm
% cd ~/src/st/opensmalltalk-vm-pharo/build/vm
% ls -T 30
libB2DPlugin.so*             libgit2.so.0.25.1             libSDL2-2.0.so.0*      libssl.so*
libBitBltPlugin.so*          libgit2.so.25                 libSDL2-2.0.so.0.7.0*  libssl.so.1.0.0*
libcrypto.so.1.0.0*          libIA32ABI.so*                libSDL2.so*            libSurfacePlugin.so*
libDSAPrims.so*              libJPEGReaderPlugin.so*       libSecurityPlugin.so*  libTestLibrary.so*
libffi.so*                   libJPEGReadWriter2Plugin.so*  libSocketPlugin.so*    libUnixOSProcessPlugin.so*
libffi.so.7*                 libLargeIntegers.so*          libSqueakFFIPrims.so*  libUUIDPlugin.so*
libffi.so.7.1.0*             libLocalePlugin.so*           libSqueakSSL.so*       pharo*
libFileAttributesPlugin.so*  libMiscPrimitivePlugin.so*    libssh2.so*            runPharoEmbedded*
libFilePlugin.so*            libPharoVMCore.so*            libssh2.so.1*
libgit2.so                   libPThreadedPlugin.so*        libssh2.so.1.0.1*

Set up LD_LIBRARY_PATH. The first path segment is for the Pharo VM. The second is for libcairo2.so needed by the embedded Pharo.image - on Ubuntu, it lives in /usr/lib/x86_64-linux-gnu, which isn't in Pharo 8's current hardcoded lookup path. Then run the executable:

% export LD_LIBRARY_PATH=`pwd`:/usr/lib/x86_64-linux-gnu
% uname -a
Linux Otrus 4.15.0-74-generic #84-Ubuntu SMP Thu Dec 19 08:06:28 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
% ./runPharoEmbedded
lala

Ta da! "lala" is printed by Pharo.