Check for focus before reading input.

The udev and sdl joypad drivers were reading input in all cases.
Now state is not changed if window has no focus, connect / disconnect
events are still processed.

input/drivers_joypad/sdl_joypad.c

@@ -24,6 +24,7 @@
 
 #include "../input_driver.h"
 
+#include "../../gfx/video_driver.h"
 #include "../../tasks/tasks_internal.h"
 #include "../../verbosity.h"
 
@@ -422,7 +423,7 @@ static int16_t sdl_joypad_state(
    uint16_t port_idx                    = joypad_info->joy_idx;
    sdl_joypad_t *pad                    = (sdl_joypad_t*)&sdl_pads[port_idx];
 
-   if (!pad || !pad->joypad)
+   if (!pad || !pad->joypad || !video_driver_has_focus())
       return 0;
    if (port_idx >= MAX_USERS)
       return 0;

input/drivers_joypad/udev_joypad.c

@@ -38,6 +38,8 @@
 #include "../../configuration.h"
 #include "../../config.def.h"
 
+#include "../../gfx/video_driver.h"
+
 #include "../../tasks/tasks_internal.h"
 
 #include "../../verbosity.h"
@@ -518,7 +520,7 @@ static void udev_joypad_poll(void)
       }
    }
 
-   for (p = 0; p < MAX_USERS; p++)
+   for (p = 0; p < MAX_USERS && video_driver_has_focus(); p++)
    {
       int i, len;
       struct input_event events[32];