system/nxstore: add LVGL app-store UI

Add nxstore, an LVGL-based frontend for nxpkg (system/nxpkg): lists
packages from the local index, installs/launches the selected one,
and supervises whatever it hands the screen to.

Card-based app list (populate_app_list()): each row shows name,
version, and description/status, install/launch state reflected via
icon glyph and color (LV_SYMBOL_DOWNLOAD/PLAY, accent/success color),
and a sliding-segment progress bar during install (no real byte-level
progress is available from pkg_install(), so this reads as
'actively working' without fabricating a percentage). Explicit
LV_STATE_PRESSED styling on every tappable row/button, since no LVGL
theme is loaded and a tap would otherwise give no visual feedback at
all.

Supervisor screen (build_run_screen()/nxstore_enter_running_screen()):
a launched app (e.g. a game that owns /dev/fb0 directly, not just
another LVGL client) gets a dedicated screen with a name label and a
Close button, confined to the border region the launched app's own
scaled/centered framebuffer output never draws into, so switching
back to it doesn't fight over pixels with whatever the app already
put in the framebuffer.

Close/reap handling (close_running_app_event_cb()/
nxstore_poll_running_app()): sends SIGTERM and polls waitpid(WNOHANG)
for the launched pid, but explicitly also treats waitpid() returning
ECHILD as 'already gone' rather than 'still running' - both the
close-button handler and the passive per-loop poll independently race
to reap the same child, so whichever one loses that race must not
spin forever waiting for a wait() that can now never succeed. Requires
the target app to install its own SIGTERM handler to exit cleanly
(this is why there is no generic force-kill fallback here: an
earlier version of this code called task_delete() when SIGTERM wasn't
reaped quickly enough, which was found on real hardware to hang the
entire board - not just the one task - when it landed mid
framebuffer/heap access on this flat-memory build).

Toast notifications (nxstore_toast()) provide a transient, unmissable
confirmation for install/uninstall/launch outcomes and app-closed
events, additive to the durable per-row subtitle text rather than a
replacement for it.

nxstore's own boot-time catalog sync waits (bounded, 15s) on
g_wifi_dhcp_ret before attempting a network fetch, since Wi-Fi
association completing doesn't imply DHCP has - an HTTP fetch
attempted in that window fails with -ENETUNREACH even though the
link itself is already up, indistinguishable from being genuinely
offline without this wait.

Signed-off-by: aviralgarg05 <gargaviral99@gmail.com>

Author: aviralgarg05

system/nxstore/CMakeLists.txt

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+# ##############################################################################
+# apps/system/nxstore/CMakeLists.txt
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more contributor
+# license agreements.  See the NOTICE file distributed with this work for
+# additional information regarding copyright ownership.  The ASF licenses this
+# file to you under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+#
+# ##############################################################################
+
+if(CONFIG_SYSTEM_NXSTORE)
+  nuttx_add_application(
+    NAME
+    ${CONFIG_SYSTEM_NXSTORE_PROGNAME}
+    PRIORITY
+    ${CONFIG_SYSTEM_NXSTORE_PRIORITY}
+    STACKSIZE
+    ${CONFIG_SYSTEM_NXSTORE_STACKSIZE}
+    MODULE
+    ${CONFIG_SYSTEM_NXSTORE}
+    SRCS
+    nxstore_main.c)
+endif()

system/nxstore/Kconfig

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+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config SYSTEM_NXSTORE
+	tristate "Nxstore LVGL App Store"
+	default n
+	depends on GRAPHICS_LVGL && SYSTEM_NXPKG
+	select NETUTILS_CJSON
+	---help---
+		Enable the Nxstore LVGL graphical application store frontend.
+		Lists packages from the local nxpkg repository, installs the
+		selected one via nxpkg, and launches it.
+
+if SYSTEM_NXSTORE
+
+config SYSTEM_NXSTORE_PROGNAME
+	string "Program name"
+	default "nxstore"
+
+config SYSTEM_NXSTORE_PRIORITY
+	int "nxstore task priority"
+	default 100
+
+config SYSTEM_NXSTORE_STACKSIZE
+	int "nxstore stack size"
+	default 8192
+
+endif

system/nxstore/Make.defs

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+############################################################################
+# apps/system/nxstore/Make.defs
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifneq ($(CONFIG_SYSTEM_NXSTORE),)
+CONFIGURED_APPS += $(APPDIR)/system/nxstore
+endif

system/nxstore/Makefile

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+############################################################################
+# apps/system/nxstore/Makefile
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/Make.defs
+
+PROGNAME  = $(CONFIG_SYSTEM_NXSTORE_PROGNAME)
+PRIORITY  = $(CONFIG_SYSTEM_NXSTORE_PRIORITY)
+STACKSIZE = $(CONFIG_SYSTEM_NXSTORE_STACKSIZE)
+MODULE    = $(CONFIG_SYSTEM_NXSTORE)
+
+MAINSRC = nxstore_main.c
+
+include $(APPDIR)/Application.mk

system/nxstore/README.txt

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+nxstore - an LVGL touchscreen app store for NuttX
+=================================================
+
+  nxstore is a graphical front-end for system/nxpkg.  It lists the
+  packages available in a nxpkg repository, installs the one you tap via
+  nxpkg, launches it, and supervises it with an on-screen "Close"
+  control.  It is the touchscreen equivalent of driving the nxpkg CLI by
+  hand; both consume the same repository, so the repository/server setup
+  (layout, how to serve it, populating it with tools/export_pkg_repo.py,
+  pointing the board at it) is documented once, in system/nxpkg's
+  README.txt, and is not repeated here.
+
+
+Dependencies
+============
+
+  Kconfig: SYSTEM_NXSTORE depends on GRAPHICS_LVGL and SYSTEM_NXPKG and
+  selects NETUTILS_CJSON.  It needs a working framebuffer (/dev/fb0) and
+  a touch input device (/dev/input0) - the same graphics/input stack
+  examples/lvgldemo uses.  NETUTILS_CJSON is used to parse the
+  repository index and package manifests.
+
+
+On-device lifecycle
+===================
+
+  1. Browse   - the app list is built from the repository index nxpkg
+                fetched.  Installed packages show a launch action;
+                not-yet-installed ones show an install action.
+  2. Install  - tapping an uninstalled package runs the nxpkg install
+                flow (download -> sha256 verify -> transactional
+                install) on a background worker thread, with progress
+                shown as a toast.
+  3. Launch   - tapping an installed package spawns its payload
+                (posix_spawn) and switches to the "running" screen: a
+                thin bar across the top NXSTORE_BAR_HEIGHT pixels (see
+                include/system/nxstore_chrome.h) carrying the app name
+                and a Close button, with the rest of the framebuffer
+                left to the running app.
+  4. Close    - see "Closing a running app" below.
+
+  Launched apps are given NXSTORE_LAUNCH_STACKSIZE (32 KiB) of stack -
+  posix_spawn's default (CONFIG_POSIX_SPAWN_DEFAULT_STACKSIZE, 2 KiB) is
+  far too small for a real LVGL/framebuffer app, and overflowing it does
+  not fail loudly (it corrupts adjacent heap, surfacing later as a crash
+  nowhere near the real cause).
+
+
+Closing a running app: the cooperative-SIGTERM contract
+=======================================================
+
+  This is the one thing an app author MUST get right to be launchable
+  from nxstore.
+
+  The Close button sends the running app SIGTERM and waits for it to
+  reap itself.  It does NOT (and cannot safely) force-kill the task:
+
+    - On a build with CONFIG_SIG_DEFAULT disabled (the default), NuttX
+      has no default action for SIGTERM at all.  Delivery does nothing
+      unless the app installs its own handler with sigaction().
+    - An earlier nxstore fell back to task_delete() when SIGTERM went
+      unreaped.  On real hardware that force-kill landed while the app
+      was mid framebuffer/heap access and hung the *entire board* (not
+      just the task), requiring a physical power cycle.  That fallback
+      was removed: there is no safe way to force-terminate an arbitrary
+      task from the outside here.
+
+  So an nxstore-launchable app must cooperate:
+
+    - Install an async-signal-safe SIGTERM handler that only sets a
+      volatile sig_atomic_t flag.
+    - Poll that flag from its own main loop and exit cleanly (freeing
+      the framebuffer, restoring input state, etc.) when it is set.
+
+  Apps whose main loop can never block indefinitely (they run to
+  completion on their own, or fail fast at startup) do not strictly need
+  a handler, but any app that renders in a long-lived loop does.  See
+  these in-tree examples for the exact pattern:
+
+    - games/NXDoom      (i_install_quit_signal / i_poll_quit_signal)
+    - examples/calculator
+    - games/cgol, games/brickmatch
+
+  If SIGTERM is not reaped within the timeout, nxstore keeps the running
+  screen up rather than returning to the app list - switching back while
+  the app might still be alive and drawing into the framebuffer would
+  just reproduce the original hang, hidden.
+
+
+Configuration
+=============
+
+  SYSTEM_NXSTORE_PROGNAME    program/registration name  (default nxstore)
+  SYSTEM_NXSTORE_PRIORITY    task priority              (default 100)
+  SYSTEM_NXSTORE_STACKSIZE   nxstore's own stack        (default 8192)
+
+  NXSTORE_LAUNCH_STACKSIZE (the stack given to launched apps) and
+  NXSTORE_BAR_HEIGHT (the reserved top bar) are compile-time constants in
+  the source / include/system/nxstore_chrome.h rather than Kconfig
+  options.