plugin: add help text to revealer plugin

there is no available documentation on what this plugin does or how it
works, also the concept isn't well known. By adding some information in
the form of a help box the user can understand the concept of what this
plugin does and how it is used.

electrum/plugins/revealer/qt.py

@@ -3,6 +3,7 @@
 Revealer
 Do you have something to hide?
 Secret backup plug-in for the electrum wallet.
+https://web.archive.org/web/20181204193709/https://revealer.cc/how-it-works/
 
 Copyright:
     2017 Tiago Romagnani Silveira
@@ -15,10 +16,8 @@ file LICENCE or http://www.opensource.org/licenses/mit-license.php
 
 import os
 import random
-import traceback
 from decimal import Decimal
 from functools import partial
-import sys
 from typing import TYPE_CHECKING
 
 from PyQt6.QtPrintSupport import QPrinter
@@ -31,8 +30,9 @@ from PyQt6.QtWidgets import (QGridLayout, QVBoxLayout, QHBoxLayout, QLabel,
 from electrum.plugin import hook
 from electrum.i18n import _
 from electrum.util import make_dir, InvalidPassword, UserCancelled
-from electrum.gui.qt.util import (read_QIcon, EnterButton, WWLabel, icon_path, internal_plugin_icon_path,
-                                  WindowModalDialog, Buttons, CloseButton, OkButton)
+from electrum.gui.qt.util import (read_QIcon, EnterButton, WWLabel, icon_path,
+                                  internal_plugin_icon_path, WindowModalDialog, Buttons,
+                                  CloseButton, OkButton, HelpButton)
 from electrum.gui.qt.qrtextedit import ScanQRTextEdit
 from electrum.gui.qt.main_window import StatusBarButton
 from electrum.gui.qt.util import read_QIcon_from_bytes, read_QPixmap_from_bytes
@@ -48,6 +48,22 @@ if TYPE_CHECKING:
 class Plugin(RevealerPlugin):
 
     MAX_PLAINTEXT_LEN = 189  # chars
+    HELP_TEXT = "\n".join([
+        _("Revealer is a tool to encrypt your secrets visually."),
+        _("Revealer is based on the scheme 'Visual Cryptography' by Moni Naor and Adi Shamir."),
+        "",
+        _("Each Revealer has a unique code. It starts with a version number, "
+          "then 128 bits of entropy encoded in hex format, and the last three "
+          "digits as a checksum."),
+        _("This code is visible in the bottom right corner of the Revealer."),
+        _("With the 128bits of entropy as a random seed, the software generates a noise image."),
+        _("In the following step your secret is encrypted into a second image."),
+        _("Then you can print those two images on transparent film."),
+        _("To decrypt the secret, you need to overlay the two films, "
+          "then your secret will become visible."),
+        "",
+        _("You can calibrate your printer in the plugin settings to achieve better print quality."),
+    ])
 
     def __init__(self, parent, config, name):
         RevealerPlugin.__init__(self, parent, config, name)
@@ -134,9 +150,15 @@ class Plugin(RevealerPlugin):
         # Align the logo label to the top left.
         logo_label.setAlignment(Qt.AlignmentFlag.AlignLeft)
 
+        # help text button
+        help_button = HelpButton(self.HELP_TEXT)
+
         # Create a VBox layout for the main contents of the dialog.
         vbox_layout = QVBoxLayout()
 
+        # create a HBox for the first line to show help button and label side by side
+        first_line_hbox = QHBoxLayout()
+
         # Populate the HBox layout with spacing between the two columns.
         hbox_layout.addWidget(logo_label)
         hbox_layout.addSpacing(16)
@@ -146,6 +168,9 @@ class Plugin(RevealerPlugin):
         create_or_load_noise_file_label = QLabel(_("To encrypt a secret, you must first create or load a noise file."))
         instructions_label = QLabel(_("Click the button above or type an existing revealer code in the box below."))
 
+        first_line_hbox.addWidget(create_or_load_noise_file_label)
+        first_line_hbox.addWidget(help_button)
+
         # Allow users to select text in the labels.
         create_or_load_noise_file_label.setTextInteractionFlags(Qt.TextInteractionFlag.TextSelectableByMouse)
         instructions_label.setTextInteractionFlags(Qt.TextInteractionFlag.TextSelectableByMouse)
@@ -190,7 +215,7 @@ class Plugin(RevealerPlugin):
         self.noise_scan_qr_textedit.textChanged.connect(self.on_edit)
 
         # Populate the VBox layout.
-        vbox_layout.addWidget(create_or_load_noise_file_label)
+        vbox_layout.addLayout(first_line_hbox)
         vbox_layout.addWidget(create_button, alignment=Qt.AlignmentFlag.AlignCenter)
         vbox_layout.addWidget(instructions_label)
         vbox_layout.addWidget(self.noise_scan_qr_textedit)