Implement partial screen capture for x11. Feel free to add similar code for the other platforms.

modules/access/screen/screen.c

@@ -51,6 +51,24 @@
     "of predefined height (16 might be a good value, and 0 means disabled)." )
 #endif
 
+#ifdef SCREEN_SUBSCREEN
+#define TOP_TEXT N_( "Subscreen top left corner" )
+#define TOP_LONGTEXT N_( \
+    "Top coordinate of the subscreen top left corner." )
+
+#define LEFT_TEXT N_( "Subscreen top left corner" )
+#define LEFT_LONGTEXT N_( \
+    "Left coordinate of the subscreen top left corner." )
+
+#define WIDTH_TEXT N_( "Subscreen width" )
+#define WIDTH_LONGTEXT N_( \
+    "Subscreen width." )
+
+#define HEIGHT_TEXT N_( "Subscreen height" )
+#define HEIGHT_LONGTEXT N_( \
+    "Subscreen height."  )
+#endif
+
 static int  Open ( vlc_object_t * );
 static void Close( vlc_object_t * );
 
@@ -70,6 +88,13 @@ vlc_module_begin();
         CACHING_TEXT, CACHING_LONGTEXT, true );
     add_float( "screen-fps", SCREEN_FPS, 0, FPS_TEXT, FPS_LONGTEXT, true );
 
+#ifdef SCREEN_SUBSCREEN
+    add_integer( "screen-top", 0, NULL, TOP_TEXT, TOP_LONGTEXT, true );
+    add_integer( "screen-left", 0, NULL, LEFT_TEXT, LEFT_LONGTEXT, true );
+    add_integer( "screen-width", 0, NULL, WIDTH_TEXT, WIDTH_LONGTEXT, true );
+    add_integer( "screen-height", 0, NULL, HEIGHT_TEXT, HEIGHT_LONGTEXT, true );
+#endif
+
 #ifdef WIN32
     add_integer( "screen-fragment-size", 0, NULL, FRAGS_TEXT,
         FRAGS_LONGTEXT, true );
@@ -110,6 +135,20 @@ static int Open( vlc_object_t *p_this )
     p_sys->i_incr = 1000000 / val.f_float;
     p_sys->i_next_date = 0;
 
+#ifdef SCREEN_SUBSCREEN
+    p_sys->i_top = var_CreateGetInteger( p_demux, "screen-top" );
+    p_sys->i_left = var_CreateGetInteger( p_demux, "screen-left" );
+    p_sys->i_width = var_CreateGetInteger( p_demux, "screen-width" );
+    p_sys->i_height = var_CreateGetInteger( p_demux, "screen-height" );
+    if( p_sys->i_width > 0 && p_sys->i_height > 0 )
+        msg_Dbg( p_demux, "capturing subscreen top: %d, left: %d, "
+                          "width: %d, height: %d",
+                          p_sys->i_top,
+                          p_sys->i_left,
+                          p_sys->i_width,
+                          p_sys->i_height );
+#endif
+
     if( screen_InitCapture( p_demux ) != VLC_SUCCESS )
     {
         free( p_sys );
@@ -120,6 +159,24 @@ static int Open( vlc_object_t *p_this )
              p_sys->fmt.video.i_width, p_sys->fmt.video.i_height,
              p_sys->fmt.video.i_bits_per_pixel );
 
+#ifdef SCREEN_SUBSCREEN
+    if( p_sys->i_width > 0 && p_sys->i_height > 0 )
+    {
+        if( p_sys->i_left + p_sys->i_width > p_sys->fmt.video.i_width ||
+            p_sys->i_top + p_sys->i_height > p_sys->fmt.video.i_height )
+        {
+            msg_Err( p_demux, "subscreen region overflows the screen" );
+            free( p_sys );
+            return VLC_EGENERIC;
+        }
+        else
+        {
+            p_sys->fmt.video.i_width = p_sys->i_width;
+            p_sys->fmt.video.i_height = p_sys->i_height;
+        }
+    }
+#endif
+
     p_sys->es = es_out_Add( p_demux->out, &p_sys->fmt );
 
     return VLC_SUCCESS;

modules/access/screen/screen.h

@@ -25,6 +25,10 @@
 #include <vlc_access.h>
 #include <vlc_demux.h>
 
+#if !defined( HAVE_WIN32 ) && !defined( HAVE_BEOS ) && !defined( HAVE_DARWIN )
+#   define SCREEN_SUBSCREEN
+#endif
+
 typedef struct screen_data_t screen_data_t;
 
 struct demux_sys_t
@@ -36,6 +40,13 @@ struct demux_sys_t
     mtime_t i_next_date;
     int i_incr;
 
+#ifdef SCREEN_SUBSCREEN
+    unsigned int i_top;
+    unsigned int i_left;
+    unsigned int i_width;
+    unsigned int i_height;
+#endif
+
     screen_data_t *p_data;
 };
 

modules/access/screen/x11.c

@@ -114,7 +114,7 @@ block_t *screen_Capture( demux_t *p_demux )
     int i_size;
 
     image = XGetImage( p_display, DefaultRootWindow( p_display ),
-                       0, 0, p_sys->fmt.video.i_width,
+                       p_sys->i_left, p_sys->i_top, p_sys->fmt.video.i_width,
                        p_sys->fmt.video.i_height, AllPlanes, ZPixmap );
 
     if( !image )
@@ -132,7 +132,7 @@ block_t *screen_Capture( demux_t *p_demux )
         return 0;
     }
 
-    memcpy( p_block->p_buffer, image->data, i_size );
+    vlc_memcpy( p_block->p_buffer, image->data, i_size );
 
     XDestroyImage( image );