Screenshots: Fn+p on every screen (#83)

Fn+p saves the screen as it is to /screenshots, as the Shell's `screenshot`
does, from anywhere: text fields, dialogs and the help panel included. The
key never reaches an App.

It refuses on Settings > Debug Console, which shows the token: a picture of
that page is a copy of the token in a file (App::showsSecret). `key shot`
presses it over the consoles.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/apps/settings_app.h

@@ -52,6 +52,7 @@ class SettingsApp : public App {
     void draw(Canvas& c) override;
     void help(std::vector<KeyHelp>& out) const override;
     const char* helpTitle() const override;
+    bool showsSecret() const override { return page_ == Page::Debug; }  // the Debug Console's token
 
    private:
     enum class Page { Menu, Text, Choice, About, Wifi, Firmware, Debug };

src/apps/shell_app.cpp

@@ -26,7 +26,7 @@ void ShellApp::onEnter() {
     scroll_ = 0;
     confirm_.reset();
     // What Tab completes besides the firmware's own commands, written as `help` writes them.
-    ownHelp_ = "help | clear | quit | exit\nkey up|down|left|right|select|back|home|del|tab|space|help\n";
+    ownHelp_ = "help | clear | quit | exit\nkey up|down|left|right|select|back|home|del|tab|space|help|shot\n";
     log_.clear();
     log_.add(open_ ? "The console's commands. `help` lists them." : "No memory for the Shell: leave an App, or stop IRC.");
 }

src/main.cpp

@@ -656,7 +656,7 @@ static const char* const kHelp =
     "gnss status | gnss restart | gnss track start|stop | gnss nmea on|off | gnss send <sentence without $ and checksum>\n"
     "crash             the last crash: firmware, reason, task, backtrace\n"
     "coredump erase    forget the core dump in flash\n"
-    "key <name|char>   press a key: up down left right select back home del tab space help, or one character; ctrl- alt- shift- before it (key ctrl-down)\n"
+    "key <name|char>   press a key: up down left right select back home del tab space help shot, or one character; ctrl- alt- shift- before it (key ctrl-down)\n"
     "wifi status | wifi add <ssid><TAB><password>\n"
     "wifi ip <ssid> dhcp | wifi ip <ssid> <address>/<prefix> [gateway]   a Saved Network's IP setting\n"
     "wifi dns <a> [b] | wifi dns always on|off | wifi ntp <a> [b]   DNS and NTP servers\n"
@@ -725,6 +725,26 @@ static void saveScreenshot() {
     });
 }
 
+// Fn+p (issue #83): the screen as it is, dialog, help panel or Toast included. Not the page that
+// shows the Debug Console's token: a picture of it is a copy of the token in a file.
+static void screenshotKey() {
+    const char* why = nullptr;
+    if (apps->foreground().showsSecret()) why = "No screenshot here: it shows the token";
+    else if (!storageService || !storageService->state().present) why = "No SD card for the screenshot";
+    if (why) {
+        bus.publish(Event::withText(EventType::Notification, why, static_cast<int32_t>(NotificationLevel::Warning)));
+        return;
+    }
+    shotFrom = Console::Origin::System;
+    saveScreenshot();
+}
+
+// Every key goes through here, from the keyboard or from a console's `key`.
+static void handleKey(const KeyEvent& e) {
+    if (e.key == Key::Screenshot) return screenshotKey();
+    apps->handleKey(e);
+}
+
 static void screenshotStep() {
     if (shotPending && static_cast<int32_t>(millis() - shotDueMs) >= 0) {
         shotPending = false;
@@ -1039,14 +1059,14 @@ static void runCommand(String line, bool fromSerial = false) {
         }
         Key key = k == "up" ? Key::Up : k == "down" ? Key::Down : k == "left" ? Key::Left
                 : k == "right" ? Key::Right : k == "back" ? Key::Back : k == "home" ? Key::Home
-                : k == "del" ? Key::Delete : k == "tab" ? Key::Tab : k == "help" ? Key::Help : Key::Select;
+                : k == "del" ? Key::Delete : k == "tab" ? Key::Tab : k == "help" ? Key::Help : k == "shot" ? Key::Screenshot : Key::Select;
         KeyEvent ev = k == "space"                       ? KeyEvent::character(' ')
                       : k.length() == 1 && k[0] > ' ' ? KeyEvent::character((unsigned char)k[0])
                                                       : KeyEvent::of(key);
         ev.ctrl = ctrl;
         ev.alt = alt;
         ev.shift = shift;
-        if (!power->onKey(millis())) apps->handleKey(ev);
+        if (!power->onKey(millis())) handleKey(ev);
     }
     if (line.startsWith("wifi add ")) {  // wifi add <ssid>\t<password>: credentials never touch the repo
         int tab = line.indexOf('\t');
@@ -1385,7 +1405,7 @@ static void loopPass() {
         keyMapper.setTextEntry(apps->foreground().textEntryActive());
         auto events = keyMapper.update(readKeys());  // always, so held keys are tracked
         if (!swallow)
-            for (auto& e : events) apps->handleKey(e);
+            for (auto& e : events) handleKey(e);
     }
 
     // Issue #20: the GNSS receiver costs the LoRa radio 8 dB while it runs. If the user chose so,