[GraphWriter] Attempt to open .dot files with xdg-open/open first

[MatzeB]

Summary

Most desktop environments let the users specify his preferred application per
file type. On mac/linux we can use open/xdg-open for that and should try this
first before starting a heuristic search for various programs.

I hope this is not going to be too much of a bikesched discussion, but I really
prefer it when I can configure the applications myself instead of having a
hardcoded default list, though after seeing r210148 which tries 'gv' before
'xdg-open' I wonder if there is a problem with that approach for some people?
Can you explain why you did this alp? Couldn't people just set their system to open all postscript files gv?

[chandlerc]

I don't see how this could be worse than our previous, completely arbitrary behavior.

[• dberlin]

Just to note:
If you have word/libreoffice installed on a mac, this will now open
the .dot files in that instead of say, preview (which supports it) or
graphviz :(

(Yeah, i know, i can reset the defaults for .dot files, but it
arbitrarily worked before)

[anemet]

In D6534#152294, @dberlin wrote:

Just to note:
If you have word/libreoffice installed on a mac, this will now open
the .dot files in that instead of say, preview (which supports it) or
graphviz :(

(Yeah, i know, i can reset the defaults for .dot files, but it
arbitrarily worked before)

I just ran into this too. Danny, what did you have to do make this work?

[• dberlin]

I gave up, and set the default opener to graphviz

[MatzeB]

On OS/X you right click the file->"get information" and change the "open with:" for all files of that type.

Anyway I don't feel strongly about the patch, feel free to revert it if this causes more trouble than it helps.

[anemet]

What do you set the viewer to? dotty? I think that before the patch this was using dot to generate the PS and then open to view. Which is probably better than using an X11 program.

[MatzeB]

I have it set to /Applications/GraphViz.app (from a macos "development snapshot" from graphviz.org http://graphviz.org/ download area). The generated .ps files tended to look very strange for me (lots of whitespace so I had to zoom in before I could really see the graph).

[anemet]

OK, works now, thanks. I didn't know about the separate GUI package for graphviz.

lib/Support/GraphWriter.cpp

 bool llvm::DisplayGraph(StringRef FilenameRef, bool wait,
                         GraphProgram::Name program) {
   std::string Filename = FilenameRef;
   wait &= !ViewBackground;
   std::string ErrMsg;
   std::string ViewerPath;
   GraphSession S;
 
+#ifdef __APPLE__
+  if (S.TryFindProgram("open", ViewerPath)) {
+    std::vector<const char *> args;
+    args.push_back(ViewerPath.c_str());
+    if (wait)
+      args.push_back("-W");
+    args.push_back(Filename.c_str());
+    args.push_back(nullptr);
+    errs() << "Trying 'open' program... ";
+    if (!ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg))
+      return false;
+  }
+#endif
+  if (S.TryFindProgram("xdg-open", ViewerPath)) {
+    std::vector<const char *> args;
+    args.push_back(ViewerPath.c_str());
+    args.push_back(Filename.c_str());
+    args.push_back(nullptr);
+    errs() << "Trying 'xdg-open' program... ";
+    if (!ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg))
+      return false;
+  }
+
   // Graphviz
   if (S.TryFindProgram("Graphviz", ViewerPath)) {
     std::vector<const char *> args;
     args.push_back(ViewerPath.c_str());
     args.push_back(Filename.c_str());
     args.push_back(nullptr);
 
     errs() << "Running 'Graphviz' program... ";