Android: Threading issues

[MoAlyousef]

On Android, FLTK's locking mechanisms don't work correctly (deadlock crashes), neither for enabling the global lock (via Fl::lock) or thru the Fl::awake(void *) messages (pipes). The Fl_lock.cxx file has the locking functions in an Android ifdef and remain to be implemented. I was able to get things working by subclassing the Fl_Android_System_Driver from the Fl_Posix_System_Driver instead of the Fl_System_Driver. I had to copy some implementation of the other posix systems (X11 namely for locking) since Android also uses pthreads.

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4e8d8c759..c7aa9d93c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -300,6 +300,7 @@ elseif (ANDROID)
 
   set (DRIVER_FILES
     drivers/Android/Fl_Android_Application.cxx
+    drivers/Posix/Fl_Posix_System_Driver.cxx
     drivers/Android/Fl_Android_System_Driver.cxx
     drivers/Android/Fl_Android_Screen_Driver.cxx
     drivers/Android/Fl_Android_Screen_Keyboard.cxx
@@ -311,6 +312,7 @@ elseif (ANDROID)
   )
   set (DRIVER_HEADER_FILES
     drivers/Android/Fl_Android_Application.H
+    drivers/Posix/Fl_Posix_System_Driver.H
     drivers/Android/Fl_Android_System_Driver.H
     drivers/Android/Fl_Android_Screen_Driver.H
     drivers/Android/Fl_Android_Window_Driver.H
diff --git a/src/drivers/Android/Fl_Android_System_Driver.H b/src/drivers/Android/Fl_Android_System_Driver.H
index 5e6dafb1e..a985d9324 100644
--- a/src/drivers/Android/Fl_Android_System_Driver.H
+++ b/src/drivers/Android/Fl_Android_System_Driver.H
@@ -25,6 +25,7 @@
 #include <string.h>
 #include <FL/fl_string.h>
 #include "../../Fl_System_Driver.H"
+#include "../Posix/Fl_Posix_System_Driver.H"
 #include <stdarg.h>
 
 /*
@@ -38,7 +39,7 @@
  - multithreading
  */
 
-class Fl_Android_System_Driver : public Fl_System_Driver
+class Fl_Android_System_Driver : public Fl_Posix_System_Driver
 {
 #if 0
 public:
@@ -122,9 +123,8 @@ public:
   virtual void add_fd(int fd, Fl_FD_Handler cb, void* = 0);
   virtual void remove_fd(int, int when);
   virtual void remove_fd(int);
-  virtual void gettime(time_t *sec, int *usec);
-#endif
   virtual char *strdup(const char *s) {return ::strdup(s);}
+#endif
 };
 
 #endif // FL_ANDROID_SYSTEM_DRIVER_H

The above diff works for multithreading, for Fl::awake I just use a std::queue, std::unique_lock and a mutex (in the Rust wrapper).

Edit: cleaned up patch thanks to Manolo's refactoring.

[Albrecht-S]

I believe this is something that @MatthiasWM could address. Matthias?

Note: I'm working on a new implementation of FLTK's timeout mechanism which could affect the internals used here in the Android port. But anyway, maybe the suggestion can be applied.

[MatthiasWM]

Sorry, I have not touched the Android implementation in a long while. It will take at least a week to find myself back into the code. Wrapping up Fluid and Preferences has priority right now. But, yeah, the patch doesn't look wrong at first glance.

[Albrecht-S]

Thanks, Matthias, I assigned this issue to you. Feel free to unassign...

[MatthiasWM]

The Android port has been removed from the FLTK for now. The implementation was incomplete and highly experimental.

[MatthiasWM]

Sorry for any inconvenience.

[dumblob]

Let's hope FLTK will return to Android (and maybe even iOS) sooner or later.

[MatthiasWM]

Yes, Android, iOS, and Linux frame buffer support are in the pipeline.