Add winedbg support behind a feature flag

I had something similar saved as a stash since I did not want to make
things more complicated by adding feature flags, but this should be
fine.

README.md

@@ -123,12 +123,16 @@ instance of Carla with gdb attached:
 env YABRIDGE_DEBUG_FILE=/tmp/yabridge.log YABRIDGE_DEBUG_LEVEL=1 carla --gdb
 ```
 
-Doing the same thing with the Wine VST host is also possible but it's a bit
-tricky. I have not had any success with attaching winedbg to running processes.
-The only thing that seems to work is to modify `host-bridge.cpp` to not launch
-`yabridge-host.exe` normally, but to instead start a new (detached) terminal
-emulator process running the Wine host through `winedbg --gdb`. I wouldn't
-recommended doing this if you can avoid it.
+Doing the same thing for the Wine VST host can be a bit trick., You'll need to
+launch winedbg in a seperate detached terminal emulator so it doesn't with the
+plugin, and winedbg can be a bit picky in the arguments it accepts. I've already
+set this up behind a feature flag for KDE Plasma. Other desktop environments and
+window managers will require some slight modifications in
+`src/plugin/host-bridge.cpp`. To enable this, simply run:
+
+```shell
+meson configure build -Duse-winedbg=true
+```
 
 ## Rationale
 

meson.build

@@ -15,6 +15,13 @@ if not meson.get_compiler('cpp').compiles(winelib_check)
   error('You need to set up a cross compiler, check the README for more information.')
 endif
 
+# This provides an easy way to start the Wine VST host using winedbg since it
+# can be quite a pain to set up
+compiler_options = []
+if get_option('use-winedbg')
+  compiler_options += '-DUSE_WINEDBG'
+endif
+
 # The application consists of a VST plugin (yabridge) that calls a winelib
 # program (yabridge-host) that can host Windows VST plugins. More information
 # about the way these two components work together can be found in the readme
@@ -39,6 +46,7 @@ shared_library(
   native : true,
   include_directories : include_dir,
   dependencies : [boost_dep, bitsery_dep, threads_dep],
+  cpp_args : compiler_options,
   link_args : ['-ldl']
 )
 
@@ -53,5 +61,6 @@ executable(
   native : false,
   include_directories : include_dir,
   dependencies : [boost_dep, bitsery_dep, wine_threads_dep],
+  cpp_args : compiler_options,
   link_args : []
 )

meson_options.txt

@@ -0,0 +1 @@
+option('use-winedbg', type : 'boolean', value : false)

src/plugin/host-bridge.cpp

@@ -25,6 +25,10 @@
 #include <iostream>
 #include <random>
 
+#ifdef USE_WINEDBG
+#include <boost/process/start_dir.hpp>
+#endif
+
 #include "../common/communication.h"
 #include "../common/events.h"
 
@@ -86,6 +90,7 @@ HostBridge::HostBridge(audioMasterCallback host_callback)
           create_logger_prefix(socket_endpoint.path()))),
       wine_stdout(io_context),
       wine_stderr(io_context),
+#ifndef USE_WINEDBG
       vst_host(vst_host_path,
                // The Wine VST host needs to know which plugin to load
                // and which Unix domain socket to connect to
@@ -93,7 +98,26 @@ HostBridge::HostBridge(audioMasterCallback host_callback)
                socket_endpoint.path(),
                bp::env = set_wineprefix(),
                bp::std_out = wine_stdout,
-               bp::std_err = wine_stderr) {
+               bp::std_err = wine_stderr)
+#else
+      // This is set up for KDE Plasma. Other desktop environments and window
+      // managers require some slight modifications to spawn a detached terminal
+      // emulator.
+      vst_host("/usr/bin/kstart5",
+               "konsole",
+               "--",
+               "-e",
+               "winedbg",
+               "--gdb",
+               vst_host_path.string() + ".so",
+               vst_plugin_path.filename(),
+               socket_endpoint.path(),
+               bp::env = set_wineprefix(),
+               // winedbg has no reliable way to escape spaces, so we'll start
+               // the process in the plugin's directory
+               bp::start_dir = vst_plugin_path.parent_path())
+#endif
+{
     logger.log("Initializing yabridge using '" + vst_host_path.string() + "'");
     logger.log("plugin:     '" + vst_plugin_path.string() + "'");
     logger.log("socket:     '" + socket_endpoint.path() + "'");