loader: fix the 'constrain_geometry()' function

Fixes #1014.

os/src/server/loader/child.h

@@ -86,8 +86,6 @@ namespace Loader {
 			Init::Child_policy_enforce_labeling _labeling_policy;
 			Init::Child_policy_pd_args          _pd_args_policy;
 
-			int _max_width, _max_height;
-
 			Genode::Child _child;
 
 			Rom_session_capability _rom_session(char const *name)
@@ -115,9 +113,7 @@ namespace Loader {
 			      Service                   &local_cpu_service,
 			      Service                   &local_rm_service,
 			      Service                   &local_nitpicker_service,
-			      Signal_context_capability fault_sigh,
+			      Signal_context_capability fault_sigh)
-			      int                       max_width,
-			      int                       max_height)
 			:
 				_label(label),
 				_pd_args(pd_args),
@@ -132,7 +128,6 @@ namespace Loader {
 				_binary_policy("binary", _binary_rom_session.dataspace(), &_ep),
 				_labeling_policy(_label.string),
 				_pd_args_policy(&_pd_args),
-				_max_width(max_width), _max_height(max_height),
 				_child(_binary_rom_session.dataspace(),
 				       _resources.ram.cap(), _resources.cpu.cap(),
 				       _resources.rm.cap(), &_ep, this)
@@ -155,29 +150,6 @@ namespace Loader {
 			{
 				_labeling_policy.filter_session_args(service, args, args_len);
 				_pd_args_policy. filter_session_args(service, args, args_len);
-
-				if (!strcmp(service, "Nitpicker")) {
-
-					/*
-					 * Restrict the child's framebuffer size to the maximum
-					 * size given by the client.
-					 */
-
-					if (_max_width > -1) {
-						int fb_width = Arg_string::find_arg(args, "fb_width" ).long_value(_max_width);
-						if (!Arg_string::set_arg(args, args_len, "fb_width",
-						                         min(fb_width, _max_width))) {
-							PERR("could not set fb_width argument");
-						}
-					}
-					if (_max_height > -1) {
-						int fb_height = Arg_string::find_arg(args, "fb_height" ).long_value(_max_height);
-						if (!Arg_string::set_arg(args, args_len, "fb_height",
-						                         min(fb_height, _max_height))) {
-							PERR("could not set fb_height argument");
-						}
-					}
-				}
 			}
 
 			Service *resolve_session_request(const char *name,

os/src/server/loader/main.cc

@@ -176,6 +176,9 @@ namespace Loader {
 				Rpc_entrypoint &ep;
 				Allocator      &_md_alloc;
 
+				int             _max_width;
+				int             _max_height;
+
 				Signal_context_capability view_ready_sigh;
 
 				Nitpicker::Session_component *open_session;
@@ -186,6 +189,8 @@ namespace Loader {
 					Service("virtual_nitpicker"),
 					ep(ep),
 					_md_alloc(md_alloc),
+					_max_width(-1),
+					_max_height(-1),
 					open_session(0)
 				{ }
 
@@ -198,6 +203,11 @@ namespace Loader {
 					destroy(&_md_alloc, open_session);
 				}
 
+				void constrain_geometry(int width, int height)
+				{
+					_max_width = width, _max_height = height;
+				}
+
 				Genode::Session_capability session(char     const *args,
 				                                   Affinity const &)
 				{
@@ -205,7 +215,11 @@ namespace Loader {
 						throw Unavailable();
 
 					open_session = new (&_md_alloc)
-						Nitpicker::Session_component(ep, view_ready_sigh, args);
+						Nitpicker::Session_component(ep,
+						                             _max_width,
+						                             _max_height,
+						                             view_ready_sigh,
+						                             args);
 
 					return ep.manage(open_session);
 				}
@@ -219,7 +233,6 @@ namespace Loader {
 			Ram_session_client_guard  _ram_session_client;
 			Heap                      _md_alloc;
 			size_t                    _subsystem_ram_quota_limit;
-			int                       _width, _height;
 			Rpc_entrypoint            _ep;
 			Service_registry          _parent_services;
 			Rom_module_registry       _rom_modules;
@@ -252,7 +265,6 @@ namespace Loader {
 				_ram_session_client(env()->ram_session_cap(), _ram_quota),
 				_md_alloc(&_ram_session_client, env()->rm_session()),
 				_subsystem_ram_quota_limit(0),
-				_width(-1), _height(-1),
 				_ep(&cap, STACK_SIZE, "session_ep"),
 				_rom_modules(_ram_session_client, _md_alloc),
 				_rom_service(_ep, _md_alloc, _rom_modules),
@@ -300,7 +312,7 @@ namespace Loader {
 
 			void constrain_geometry(int width, int height)
 			{
-				_width = width, _height = height;
+				_nitpicker_service.constrain_geometry(width, height);
 			}
 
 			void view_ready_sigh(Signal_context_capability sigh)
@@ -346,7 +358,7 @@ namespace Loader {
 						      pd_args, _ep, _ram_session_client,
 						      ram_quota, _parent_services, _rom_service,
 						      _cpu_service, _rm_service, _nitpicker_service,
-						      _fault_sigh, _width, _height);
+						      _fault_sigh);
 				}
 				catch (Genode::Parent::Service_denied) {
 					throw Rom_module_does_not_exist(); }

os/src/server/loader/nitpicker.h

@@ -161,6 +161,9 @@ namespace Nitpicker {
 
 			Rpc_entrypoint           &_ep;
 
+			int                       _max_width;
+			int                       _max_height;
+
 			Nitpicker::Connection     _nitpicker;
 			View_capability           _nitpicker_view;
 
@@ -181,12 +184,17 @@ namespace Nitpicker {
 			/**
 			 * Constructor
 			 */
-			Session_component(Rpc_entrypoint           &ep,
+			Session_component(Rpc_entrypoint            &ep,
-			                  Signal_context_capability view_ready_sigh,
+			                  int                        max_width,
-			                  const char               *args)
+			                  int                        max_height,
+			                  Signal_context_capability  view_ready_sigh,
+			                  const char                *args)
 			:
 				_ep(ep),
 
+				_max_width(max_width),
+				_max_height(max_height),
+
 				/* create Nitpicker view */
 				_nitpicker_view(_nitpicker.create_view()),
 
@@ -235,7 +243,16 @@ namespace Nitpicker {
 
 			Framebuffer::Mode mode()
 			{
-				return _nitpicker.mode();
+				int mode_width = (_max_width > -1) ?
+				                 _max_width :
+				                 _nitpicker.mode().width();
+
+				int mode_height = (_max_height > -1) ?
+				                  _max_height :
+				                  _nitpicker.mode().height();
+
+				return Framebuffer::Mode(mode_width, mode_height,
+				                         _nitpicker.mode().format());
 			}
 
 			void buffer(Framebuffer::Mode mode, bool use_alpha)
@@ -271,11 +288,17 @@ namespace Nitpicker {
 			 */
 			Loader::Session::View_geometry loader_view_geometry()
 			{
-				Framebuffer::Session_client framebuffer(framebuffer_session());
+				int view_width = (_max_width > -1) ?
-				Framebuffer::Mode const mode = framebuffer.mode();
+				                 min(_proxy_view.w(), _max_width) :
+				                 _proxy_view.w();
+
+				int view_height = (_max_height > -1) ?
+				                  min(_proxy_view.h(), _max_height) :
+				                  _proxy_view.h();
+
 				Loader::Session::View_geometry result(
-					min(_proxy_view.w(), mode.width()),
+					view_width,
-					min(_proxy_view.h(), mode.height()),
+					view_height,
 					_proxy_view.buf_x(),
 					_proxy_view.buf_y());