Add mode_sigh and release to framebuffer::Session

The 'mode_sigh' function allows the client to receive notifications
about server-side display-mode changes. To respond to such a signal, the
client can use the new 'release' function, which acknowledges the mode
change at the server and frees the original framebuffer dataspace. Via a
subsequent call of 'dataspace', a framebuffer dataspace corresponding to
the new mode can be obtained. Related to issue #11.

demo/src/server/liquid_framebuffer/services.cc

@@ -196,7 +196,10 @@ namespace Framebuffer
 	{
 		public:
 
-			Genode::Dataspace_capability dataspace() { return _window_content->fb_ds_cap(); }
+			Genode::Dataspace_capability dataspace() {
+				return _window_content->fb_ds_cap(); }
+
+			void release() { }
 
 			Mode mode()
 			{
@@ -204,6 +207,8 @@ namespace Framebuffer
 				            Mode::RGB565);
 			}
 
+			void mode_sigh(Genode::Signal_context_capability) { }
+
 			void refresh(int x, int y, int w, int h) {
 				window_content()->redraw_area(x, y, w, h); }
 	};

os/include/framebuffer_session/client.h

@@ -27,8 +27,12 @@ namespace Framebuffer {
 		Genode::Dataspace_capability dataspace() {
 			return call<Rpc_dataspace>(); }
 
-		Mode mode() {
+		void release() { call<Rpc_release>(); }
-			return call<Rpc_mode>(); }
+
+		Mode mode() { return call<Rpc_mode>(); }
+
+		void mode_sigh(Genode::Signal_context_capability sigh) {
+			call<Rpc_mode_sigh>(sigh); }
 
 		void refresh(int x, int y, int w, int h) {
 			call<Rpc_refresh>(x, y, w, h); }

os/include/framebuffer_session/framebuffer_session.h

@@ -14,11 +14,15 @@
 #ifndef _INCLUDE__FRAMEBUFFER_SESSION__FRAMEBUFFER_SESSION_H_
 #define _INCLUDE__FRAMEBUFFER_SESSION__FRAMEBUFFER_SESSION_H_
 
+#include <base/signal.h>
 #include <dataspace/capability.h>
 #include <session/session.h>
 
 namespace Framebuffer {
 
+	/**
+	 * Framebuffer mode info as returned by 'Framebuffer::Session::mode()'
+	 */
 	struct Mode
 	{
 		public:
@@ -57,6 +61,7 @@ namespace Framebuffer {
 				return bytes_per_pixel(_format); }
 	};
 
+
 	struct Session : Genode::Session
 	{
 		static const char *service_name() { return "Framebuffer"; }
@@ -69,10 +74,35 @@ namespace Framebuffer {
 		virtual Genode::Dataspace_capability dataspace() = 0;
 
 		/**
-		 * Request current screen mode properties
+		 * Release framebuffer, free dataspace
+		 *
+		 * By calling this function, the framebuffer client enables the server
+		 * to reallocate the framebuffer dataspace on mode changes. Prior
+		 * calling this function, the client should have detached the dataspace
+		 * from its local address space.
+		 */
+		virtual void release() = 0;
+
+		/**
+		 * Request current display-mode properties
 		 */
 		virtual Mode mode() = 0;
 
+		/**
+		 * Register signal handler to be notified on mode changes
+		 *
+		 * The framebuffer server may support changing the display mode on the
+		 * fly. For example, a virtual framebuffer presented in a window may
+		 * get resized according to the window dimensions. By installing a
+		 * signal handler for mode changes, the framebuffer client can respond
+		 * to such changes. From the client's perspective, the original mode
+		 * stays in effect until the client calls 'release()'. After having
+		 * released the framebuffer, the new mode can be obtained using the
+		 * 'mode()' function and a new framebuffer dataspace can be requested
+		 * by calling 'dataspace()'.
+		 */
+		virtual void mode_sigh(Genode::Signal_context_capability sigh) = 0;
+
 		/**
 		 * Flush specified pixel region
 		 *
@@ -86,10 +116,13 @@ namespace Framebuffer {
 		 *********************/
 
 		GENODE_RPC(Rpc_dataspace, Genode::Dataspace_capability, dataspace);
+		GENODE_RPC(Rpc_release, void, release);
 		GENODE_RPC(Rpc_mode, Mode, mode);
 		GENODE_RPC(Rpc_refresh, void, refresh, int, int, int, int);
+		GENODE_RPC(Rpc_mode_sigh, void, mode_sigh, Genode::Signal_context_capability);
 
-		GENODE_RPC_INTERFACE(Rpc_dataspace, Rpc_mode, Rpc_refresh);
+		GENODE_RPC_INTERFACE(Rpc_dataspace, Rpc_release, Rpc_mode,
+		                     Rpc_mode_sigh, Rpc_refresh);
 	};
 }
 

os/src/drivers/framebuffer/fiasco_ux/main.cc

@@ -45,17 +45,18 @@ namespace Framebuffer {
 
 			Dataspace_capability dataspace() { return Framebuffer_drv::hw_framebuffer(); }
 
-			void info(int *out_w, int *out_h, Mode *out_mode)
+			void release() { }
-			{
-				*out_w = scr_width;
-				*out_h = scr_height;
 
-				switch (scr_mode) {
+			Mode mode()
-				case 16: *out_mode = RGB565; break;
+			{
-				default: *out_mode = INVALID;
+				if (scr_mode != 16)
-				}
+					return Mode(); /* invalid mode */
+
+				return Mode(scr_width, scr_height, Mode::RGB565);
 			}
 
+			void mode_sigh(Genode::Signal_context_capability sigh) { }
+
 			void refresh(int x, int y, int w, int h)
 			{
 #if 0

os/src/drivers/framebuffer/pl11x/main.cc

@@ -165,8 +165,12 @@ namespace Framebuffer
 
 			Genode::Dataspace_capability dataspace() { return _fb_ds_cap; }
 
+			void release() { }
+
 			Mode mode() { return Mode(SCR_WIDTH, SCR_HEIGHT, Mode::RGB565); }
 
+			void mode_sigh(Genode::Signal_context_capability) { }
+
 			void refresh(int x, int y, int w, int h) { }
 	};
 

os/src/drivers/framebuffer/sdl/fb_sdl.cc

@@ -61,8 +61,12 @@ namespace Framebuffer {
 
 			Genode::Dataspace_capability dataspace() { return fb_ds_cap; }
 
+			void release() { }
+
 			Mode mode() { return _mode; }
 
+			void mode_sigh(Genode::Signal_context_capability) { }
+
 			void refresh(int x, int y, int w, int h)
 			{
 				/* clip refresh area to screen boundaries */

os/src/drivers/framebuffer/vesa/main.cc

@@ -150,12 +150,16 @@ namespace Framebuffer {
 				return _buffered ? Dataspace_capability(_bb_ds)
 				                 : Dataspace_capability(_fb_ds); }
 
+			void release() { }
+
 			Mode mode()
 			{
 				return Mode(_scr_width, _scr_height,
 				            _scr_mode == 16 ? Mode::RGB565 : Mode::INVALID);
 			}
 
+			void mode_sigh(Genode::Signal_context_capability) { }
+
 			/* not implemented */
 			void refresh(int x, int y, int w, int h)
 			{

os/src/server/nitpicker/genode/main.cc

@@ -341,12 +341,16 @@ namespace Framebuffer {
 
 			Genode::Dataspace_capability dataspace() { return _buffer->ds_cap(); }
 
+			void release() { }
+
 			Mode mode()
 			{
 				return Mode(_buffer->size().w(), _buffer->size().h(),
 				            _buffer->format());
 			}
 
+			void mode_sigh(Genode::Signal_context_capability) { }
+
 			void refresh(int x, int y, int w, int h)
 			{
 				_view_stack->update_session_views(_session,