Use LD_PRELOAD to better map DSSI plugin UIs; Don't auto-center for now

source/backend/plugin/CarlaPluginDSSI.cpp

@@ -148,19 +148,53 @@ public:
 #ifdef CARLA_OS_LINUX
             const ScopedEngineEnvironmentLocker _seel(kEngine);
 
+            // get current LD_PRELOAD, will restore it later
             const char* const oldPreload(std::getenv("LD_PRELOAD"));
 
+# ifdef HAVE_X11
+            // if the frontend uses winId parent, set LD_PRELOAD to auto-map the DSSI UI
+            const uintptr_t winId = kEngine->getOptions().frontendWinId;
+
+            if (winId != 0)
+            {
+                char strBuf[STR_MAX+1];
+                strBuf[STR_MAX] = '\0';
+                std::snprintf(strBuf, STR_MAX, P_UINTPTR, kEngine->getOptions().frontendWinId);
+                ::setenv("CARLA_ENGINE_OPTION_FRONTEND_WIN_ID", strBuf, 1);
+
+                CarlaString interposerPath(CarlaString(kEngine->getOptions().binaryDir) +
+                                           CARLA_OS_SEP_STR "libcarla_interposer-x11.so");
+                ::setenv("LD_PRELOAD", interposerPath.buffer(), 1);
+            }
+            else
+# else
+            // if no X11 or winId set, simply unset LD_PRELOAD
+            // (it might be set to libcarla_interposer-safe)
             if (oldPreload != nullptr)
                 ::unsetenv("LD_PRELOAD");
-#endif
+# endif
+#endif // CARLA_OS_LINUX
 
+            // start the DSSI UI application
             carla_stdout("starting DSSI UI...");
             started = fProcess->start(arguments);
 
 #ifdef CARLA_OS_LINUX
+            // restore initial state
             if (oldPreload != nullptr)
+            {
                 ::setenv("LD_PRELOAD", oldPreload, 1);
-#endif
+            }
+# ifdef HAVE_X11
+            if (winId != 0)
+            {
+                ::unsetenv("CARLA_ENGINE_OPTION_FRONTEND_WIN_ID");
+
+                if (oldPreload == nullptr)
+                    ::unsetenv("LD_PRELOAD");
+            }
+# endif
+#endif // CARLA_OS_LINUX
         }
 
         if (! started)

source/interposer/Makefile

@@ -22,6 +22,7 @@ endif
 # ----------------------------------------------------------------------------------------------------------------------------
 
 BUILD_CXX_FLAGS += -I$(CWD)/includes -I$(CWD)/utils
+LINK_FLAGS      += -ldl
 
 # ----------------------------------------------------------------------------------------------------------------------------
 

source/interposer/interposer-x11.cpp

@@ -17,11 +17,72 @@
 
 #include "CarlaUtils.hpp"
 
+#include <dlfcn.h>
 #include <X11/Xlib.h>
 
+// -----------------------------------------------------------------------
+// Function typedefs
+
+typedef int (*XMapWindowFunc)(Display*, Window);
+typedef int (*XUnmapWindowFunc)(Display*, Window);
+
+// -----------------------------------------------------------------------
+// Global counter so we only map the first (hopefully main) window
+
+static int sMapWindowCounter = 0;
+
+// -----------------------------------------------------------------------
+// Calling the real functions
+
+static int real_XMapWindow(Display* display, Window w)
+{
+    static XMapWindowFunc func = (XMapWindowFunc)::dlsym(RTLD_NEXT, "XMapWindow");
+    CARLA_SAFE_ASSERT_RETURN(func != nullptr, 0);
+
+    return func(display, w);
+}
+
+static int real_XUnmapWindow(Display* display, Window w)
+{
+    static XUnmapWindowFunc func = (XUnmapWindowFunc)::dlsym(RTLD_NEXT, "XUnmapWindow");
+    CARLA_SAFE_ASSERT_RETURN(func != nullptr, 0);
+
+    return func(display, w);
+}
+
+// -----------------------------------------------------------------------
+// Our custom functions
+
 CARLA_EXPORT
-int XMapWindow(Display* /*display*/, Window /*w*/)
+int XMapWindow(Display* display, Window w)
 {
     carla_stdout("------------------------------- XMapWindow called");
-    return 0;
+
+    if (++sMapWindowCounter != 1)
+        return real_XMapWindow(display, w);
+
+    if (const char* const winIdStr = std::getenv("CARLA_ENGINE_OPTION_FRONTEND_WIN_ID"))
+    {
+        CARLA_SAFE_ASSERT_RETURN(winIdStr[0] != '\0', real_XMapWindow(display, w));
+
+        const long long winId(std::strtoll(winIdStr, nullptr, 16));
+        CARLA_SAFE_ASSERT_RETURN(winId >= 0, real_XMapWindow(display, w));
+
+        carla_stdout("Transient hint correctly applied before mapping window");
+        XSetTransientForHint(display, w, static_cast<Window>(winId));
+    }
+
+    return real_XMapWindow(display, w);
 }
+
+CARLA_EXPORT
+int XUnmapWindow(Display* display, Window w)
+{
+    carla_stdout("------------------------------- XUnmapWindow called");
+
+    --sMapWindowCounter;
+
+    return real_XUnmapWindow(display, w);
+}
+
+// -----------------------------------------------------------------------

source/utils/CarlaPluginUI.cpp

@@ -716,7 +716,7 @@ bool CarlaPluginUI::tryTransientWinIdMatch(const uintptr_t pid, const char* cons
 
     XSetTransientForHint(sd.display, lastGoodWindow, hostWinId);
 
-    if (centerUI)
+    if (centerUI && false /* moving the window after being shown isn't pretty... */)
     {
         int hostX, hostY, pluginX, pluginY;
         uint hostWidth, hostHeight, pluginWidth, pluginHeight, border, depth;