Merge lp:~agateau/unity-2d/dash-fork-on-close into lp:unity-2d/3.0

[Aurélien Gâteau]

After running out of ideas to plug dash memory leaks, I came to try a workaround which can be summarized like this:

forever:
   run the dash in a subprocess
   when the user closes the view, exit the subprocess

It is definitely not a proper fix but it works well here. I believe the cost is acceptable: ld shouldn't load the libraries again so forking should remain fast, but it would need to be tested on lower-end machines.

[lp:~agateau/unity-2d/dash-fork-on-close]

519. By Aurélien Gâteau on 2011-04-07

Do not fork endlessly when X goes down

[Florian Boucault (fboucault)]

Fix was committed to Qt4. This workaround is not needed anymore.

review: Disapprove

Unmerged revisions

519. By Aurélien Gâteau on 2011-04-07

Do not fork endlessly when X goes down

518. By Aurélien Gâteau on 2011-04-07

[dash] Work around memory leaks by running the application in a subprocess

See comments in places.cpp

=== modified file 'places/app/dashdeclarativeview.cpp'
--- places/app/dashdeclarativeview.cpp	2011-03-23 11:30:21 +0000
+++ places/app/dashdeclarativeview.cpp	2011-04-07 21:46:49 +0000
@@ -147,9 +147,10 @@
     DashDeclarativeView::DashMode oldMode = m_mode;
     m_mode = mode;
     if (m_mode == HiddenMode) {
-        hide();
         m_launcherClient->endForceVisible();
         activeChanged(false);
+        // See main() for why we do this instead of calling hide();
+        QApplication::exit(12);
     } else {
         show();
         raise();
 
=== modified file 'places/app/places.cpp'
--- places/app/places.cpp	2011-03-16 16:51:20 +0000
+++ places/app/places.cpp	2011-04-07 21:46:49 +0000
@@ -37,10 +37,23 @@
 #include <unity2ddebug.h>
 #include <unity2dtr.h>
 
+// libc
+#include <sys/wait.h>
+#include <stdio.h>
+
 #include "dashdeclarativeview.h"
 #include "config.h"
 
-int main(int argc, char *argv[])
+/*
+ * unity-2d-places has memory leaks which seem to come from within Qt
+ * Declarative itself. We workaround this by forking in main() and running the
+ * whole application in a child process which stops itself after the dash
+ * closes (see DashDeclarativeView::setDashMode()). When the child process stops,
+ * the main process creates a new one. This way memory is released but we save
+ * time on startup compared to the other solution of restarting the whole
+ * application because libraries have already been loaded.
+ */
+int childMain(int argc, char *argv[])
 {
     /* gtk needs to be inited, otherwise we get an assert failure in gdk */
     gtk_init(&argc, &argv);
@@ -90,3 +103,21 @@
     application.setProperty("view", QVariant::fromValue(&view));
     return application.exec();
 }
+
+int main(int argc, char* argv[])
+{
+    bool restart = true;
+    while (restart) {
+        pid_t pid = fork();
+        if (pid == 0) {
+            return childMain(argc, argv);
+        } else {
+            int status;
+            waitpid(pid, &status, 0);
+            fprintf(stderr, "Child exited with status %d\n", status);
+            // If exit code is not the "restart" exit code, quit: we do not
+            // want to prevent the session from ending
+            restart = WEXITSTATUS(status) == 12;
+        }
+    }
+}