Surge UserInteractions stubbed with Zenity (surge-synthesizer#918)

Surge UserInteractions on Linux should really use
the vst event loop and vstgui and be hand written because
otherwise you have to popen zenity which can cause audio
pauses and pops.

But audio pauses and pops on anciliary actions are better than
nothing, so stick in a crudy zenity implementation which is
a start, and someone inspired to remove it at least has a spec
in the future.

Addresses surge-synthesizer#562
Closes surge-synthesizer#637 and surge-synthesizer#917

doc/Developer Guide.md

@@ -210,8 +210,8 @@ sudo apt-get install ajmidid
 The run jac and ajmidid in separate terminals
 
 ```
-jack -d alsa -X alsa_midi
-ajmidid -e
+jackd -d alsa -X alsa_midi
+a2jmidid -e
 ```
 
 Now start surge with carla-single

src/common/gui/PopupEditorDialog.cpp

@@ -147,11 +147,27 @@ void spawn_miniedit_text(char* c, int maxchars)
 #elif LINUX
 
 #include "UserInteractions.h"
+#include <string.h>
 
 void spawn_miniedit_text(char* c, int maxchars)
 {
    // FIXME: Implement text edit popup on Linux.
-   Surge::UserInteractions::promptError( "miniedit_text is not implemented on linux", "Unimplemented Feature" );
+   char cmd[1024];
+   snprintf(cmd, 1024, "zenity --entry --entry-text \"%s\"", c );
+   FILE *z = popen( cmd, "r" );
+   if( ! z )
+   {
+      return;
+   }
+   char buffer[ 1024 ];
+   if (!fscanf(z, "%1024s", buffer))
+   {
+      return;
+   }
+   pclose(z);
+
+   strncpy( c, buffer, maxchars);
+
 }
 
 #endif

src/linux/UserInteractionsLinux.cpp

@@ -3,7 +3,18 @@
 #include <iomanip>
 #include <sys/types.h>
 #include <unistd.h>
+#include <thread>
 
+/*
+** In June 2019, @baconpaul chose to implement these with an attempt
+** to fork/exec a zenity. (He also did this for mini edit). This is not
+** ideal. Properly you would somehow asynchronously interact with 
+** vstgui and so on, which @jjs started. But we kinda gotta do something.
+**
+** If you want to come along and rip out these zenity calls and replace them
+** with vstgui, please do so! This is purely tactical stuff to get us
+** not silently failing.
+*/
 namespace Surge
 {
 
@@ -13,6 +24,17 @@ namespace UserInteractions
 void promptError(const std::string &message, const std::string &title,
                  SurgeGUIEditor *guiEditor)
 {
+   if (vfork()==0)
+   {
+      if (execlp("zenity", "zenity",
+                 "--error",
+                 "--text", message.c_str(),
+                 "--title", title.c_str(),
+                 (char*)nullptr) < 0)
+      {
+         exit(0);
+      }
+   }
     std::cerr << "Surge Error\n"
               << title << "\n"
               << message << "\n" << std::flush;
@@ -55,8 +77,22 @@ void promptFileOpenDialog(const std::string& initialDirectory,
                           std::function<void(std::string)> callbackOnOpen,
                           SurgeGUIEditor* guiEditor)
 {
-   UserInteractions::promptError("OpenFileDialog is unimplemented in this version of Surge. Sorry!",
-                                 "Unimplemented Function", guiEditor);
+   /*
+   ** This is a blocking model which will cause us problems I am sure
+   */
+   FILE *z = popen( "zenity --file-selection", "r" );
+   if( ! z )
+   {
+      return;
+   }
+   char buffer[ 1024 ];
+   if (!fscanf(z, "%1024s", buffer))
+   {
+      return;
+   }
+   pclose(z);
+
+   callbackOnOpen(buffer);
 }
 };