macOS: Prepare adding PsychPlugins folder to linker path.

So libraries in the Psychtoolbox/PsychBasic/PsychPlugins/ folder can
always be found and linked by the linker on macOS.

We add the folder to the -rpath. Extend osxsetoctaverpath.m for this.
Add new helper script macossetmatlabrpath.m for the same purpose
wrt. Matlab.

PsychSourceGL/Source/macossetmatlabrpath.m

@@ -0,0 +1,59 @@
+function macossetmatlabrpath(mexfname, mexpath)
+% macossetmatlabrpath(mexfname [, mexpath])
+%
+% Change the @rpath library search path for some helper libraries inside the
+% given Matlab mex file, so they can be found by the dynamic linker inside the
+% Psychtoolbox/PsychBasic/PsychPlugins. We change from absolute path to @rpath.
+%
+% E.g.,
+%
+% macossetmatlabrpath('Screen'); would rewrite Screen.mexmaci64 on Intel Matlab
+% to use the @rpath settings stored in this function. We define one candidate
+% rpath as @loader_path/PsychPlugins, so the helper dylibs are expected there,
+% e.g., a system library path, or the PsychPlugins folder.
+
+    if ~IsOSX(1) || IsOctave
+        error('macossetmatlabrpath only works with 64-Bit Matlab for macOS!');
+    end
+
+    % If no mex filename given, iterate over 'mexpath' - or the default install
+    % location of mex files - and apply the rpath editing to each mex file there:
+    if nargin < 1 || isempty(mexfname)
+        if nargin < 2 || isempty(mexpath)
+            mexpath = [PsychtoolboxRoot 'PsychBasic/'];
+        end
+
+        d = dir (mexpath);
+        for j = 1:length(d)
+            if ~d(j).isdir
+                [~, mexfname, extension] = fileparts(d(j).name);
+                if ~isempty(strfind(extension, mexext)) %#ok<STREMP>
+                    macossetmatlabrpath(mexfname, mexpath);
+                end
+            end
+        end
+
+        return;
+    end
+
+    % Set default path for finding the mex file to process, if omitted:
+    if nargin < 2 || isempty(mexpath)
+        mexpath = '../Projects/MacOSX/build/';
+    end
+
+    % Build full path to file:
+    mexfname = [mexpath mexfname '.' mexext];
+
+    % We add the @loader_path/PsychPlugins path to our PsychBasic/PsychPlugins
+    % folder, so our mex files can find additional helper dylibs there, which
+    % are needed by some of them:
+    lpaths = { '@loader_path/PsychPlugins' };
+
+    % Add all paths in lpaths as potential search paths for @rpath:
+    for i = 1:length(lpaths)
+        system(['install_name_tool -add_rpath ' lpaths{i} ' ' mexfname]);
+        fprintf('Added Matlab @rpath %s to mex file %s ...\n', lpaths{i}, mexfname);
+    end
+
+return;
+

PsychSourceGL/Source/osxsetoctaverpath.m

@@ -1,8 +1,8 @@
 function osxsetoctaverpath(mexfname, mexpath)
 % osxsetoctaverpath(mexfname [, mexpath])
 %
-% Change the @rpath library search path for the octave
-% runtime libraries inside the given mex file.
+% Change the @rpath library search path for the octave runtime libraries
+% and other helper libraries inside the given mex file.
 %
 % We change from absolute path to @rpath.
 %
@@ -16,6 +16,7 @@ function osxsetoctaverpath(mexfname, mexpath)
 % PsychtoolboxPostInstallRoutine copies or symlinks the Octave
 % runtime libraries into the mex file folder of PTB, so the mex
 % files should always find a dylib for the currently running Octave.
+% We also add Psychtoolbox/PsychBasic/PsychPlugins to the dylib search path.
 
     if ~IsOSX(1) || ~IsOctave || ~compare_versions(version, '9.2.0', '==')
         error('osxsetoctaverpath only works with a 64-Bit version of HomeBrew Octave-9.2.0 for macOS!');
@@ -70,11 +71,13 @@ function osxsetoctaverpath(mexfname, mexpath)
     % Replace absolute path to liboctave.11.dylib with @rpath:
     system(['install_name_tool -change ' libdir '/liboctave.11.dylib @rpath/liboctave.dylib ' mexfname]);
 
-    % Add one single rpath: @loader_path. This is the path to our folder where our
+    % Add @loader_path to the @rpath. This is the path to our folder where our
     % mex file is stored. If we place symlinks to liboctave.dylib and liboctinterp.dylib
     % there, then the linker will find them. In absence, the linker will also search the
-    % users $HOME/lib/ directory as a possible fallback:
-    lpaths = { '@loader_path' };
+    % users $HOME/lib/ directory as a possible fallback. Additionally we add the path to
+    % our Psychtoolbox/PsychBasic/PsychPlugins folder, so our mex files can find additional
+    % helper dylibs there which are needed by some of them:
+    lpaths = { '@loader_path', '@loader_path/../PsychPlugins' };
 
     % Add all paths in lpaths as potential search paths for the octave
     % library directories, ie., as settings for @rpath: