feat(signature): add HTML signature support by joshua-grimmett · Pull Request #10876 · thunderbird/thunderbird-android

joshua-grimmett · 2026-04-14T19:09:24Z

Summary

Adds a per-identity "Format signature as HTML" toggle so users can write rich-text signatures and have them sent as HTML in outgoing mail. Refs #8841.

When the flag is on, the signature is embedded verbatim in outgoing HTML messages (no text-to-HTML conversion), converted via Jsoup for outgoing plain-text messages, and rendered as a live WebView preview in the compose screen so drafts and new composes show the rendered result instead of raw tags.

Scope (vs #8841)

In scope ✅

Users can input signatures as HTML tags
HTML signatures sent with outgoing email

Stretch (not in this PR)

Import HTML from file — can follow up in a separate PR if desired

Out of scope per #8841

Full visual / WYSIWYG editor
Attaching vCards as signatures

Changes

Data model: Identity.signatureIsHtml: Boolean added, persisted via LegacyAccountStorageHandler under key signatureIsHtml.$ident. IdentitySettingsDescriptions registers the new setting at version 111.
UI: "Format signature as HTML" checkbox added to both the Edit Identity screen and the Composition defaults screen, with a summary line explaining the sanitisation behaviour.
Outgoing mail: TextBodyBuilder.getSignatureHtml() short-circuits HtmlConverter.textToHtmlFragment() when the flag is set. For plain-text messages, TextBodyBuilder.getSignature() runs the HTML signature through HtmlConverter.htmlToText() to produce a plain-text fallback.
Sanitisation: HtmlSignatureSanitizer wraps Jsoup.clean() with a Safelist.relaxed() baseline that strips <script>, event handler attributes, javascript: URLs, <iframe>, <object>, and <embed> elements.
Compose preview: MessageCompose renders the HTML signature in a MessageWebView (reusing the component already used for quoted HTML) instead of showing raw tags in the plain EditText. Remote images and natural device-size rendering are enabled since the signature is the user's own content.
Draft reload: When an existing draft is reopened, account.findIdentity(email) looks up the matching account identity and inherits its signatureIsHtml value, preserving the flag across drafts for multi-identity accounts.

Tests

New HtmlSignatureSanitizerTest — 10 cases covering sanitisation (preserves basic formatting, strips scripts/event handlers / javascript: URLs / iframes, passes plain text unchanged).
New TextBodyBuilderHtmlSignatureTest — 4 cases covering the HTML short-circuit in both the HTML and plain-text body paths.
Existing TextBodyBuilderTest, MessageBuilderTest, ReplyToPresenterTest, IdentityHeaderBuilderTest updated for the new Identity field and continue to pass.
./gradlew spotlessCheck detekt pass locally.

Screenshots

Edit Identity screen — new HTML checkbox:

Compose screen — rendered HTML signature preview:

Test plan

Set HTML signature in Edit Identity → compose new message → recipient sees rendered HTML
Save message as draft → reopen draft → signature renders correctly
Multi-identity: drafts preserve per-identity HTML flag correctly
Sanitiser strips <script> / onclick / javascript: URLs
Unchecking HTML flag → compose falls back to plain-text signature EditText
Sending plain-text message with HTML signature produces a text/plain fallback via HtmlConverter.htmlToText()

github-actions · 2026-04-14T19:09:33Z

Missing report label. Set exactly one of: report: include, report: exclude OR report: highlight.

ryanleesipes · 2026-04-16T23:57:21Z

Thank you for this @joshua-grimmett - very cool stuff.

jbott-tbird · 2026-04-17T16:24:47Z

hey @joshua-grimmett, we haven't forgotten about this and appreciate you doing this (especially since it's one of our main roadmap items this year). @rafaeltonholo was put on some last minute changes for our Thundermail project, but will be back on this in the next week or so.

joshua-grimmett · 2026-04-19T01:56:15Z

No worries, @ryanleesipes glad to contribute. I love the work you guys are doing.

joshua-grimmett · 2026-04-19T01:56:54Z

Thanks @jbott-tbird, look forward to seeing how it goes!

rafaeltonholo

Hi @joshua-grimmett, thanks for this contribution and sorry for the delay in reviewing this PR.

Before merging this, we have some points we need to address first.

rafaeltonholo · 2026-05-04T12:51:18Z

+        // multi-identity accounts preserve each identity's setting. If no match, fall back
+        // to the currently-loaded default identity.
+        Identity matchedIdentity = null;
+        String draftEmail = newIdentity.getEmail();


nit: could be final

Suggested change

String draftEmail = newIdentity.getEmail();

final String draftEmail = newIdentity.getEmail();

rafaeltonholo · 2026-05-04T12:51:32Z

+                // Ignore — fall back to default identity below.
+            }
+        }
+        boolean signatureIsHtml = matchedIdentity != null


nit: could be final

Suggested change

boolean signatureIsHtml = matchedIdentity != null

final boolean signatureIsHtml = matchedIdentity != null

jbott-tbird · 2026-06-03T16:01:01Z

Hi @joshua-grimmett, thank you again for working on this. It is a feature on our roadmap for this year, and I would love to get this in. Are you able to make the change that @rafaeltonholo suggested? We would love to work with you on getting this through!

guardian-groot · 2026-07-17T20:06:36Z

@joshua-grimmett thank you for your work! Are there any ways to support this PR?

apidemy · 2026-08-14T09:49:21Z

Hi! I’m interested in helping get HTML signature support completed and merged into Thunderbird for Android.

I’d be happy to contribute code to this PR, address outstanding review comments, add or improve tests, and help with any remaining work needed to make the feature ready for merging.

Please let me know if it would be helpful for me to pick up any specific remaining tasks on this PR, or if you’re happy for me to start working through the open review feedback.

rafaeltonholo · 2026-08-17T12:57:13Z

Hi! I’m interested in helping get HTML signature support completed and merged into Thunderbird for Android.

I’d be happy to contribute code to this PR, address outstanding review comments, add or improve tests, and help with any remaining work needed to make the feature ready for merging.

Please let me know if it would be helpful for me to pick up any specific remaining tasks on this PR, or if you’re happy for me to start working through the open review feedback.

Hi @apidemy,

Unfortunately, I have already begun working on this PR to ensure we can deliver it as planned. However, we will soon have additional items related to HTML signature support, and we would be glad to have your assistance if you're still interested.

Add a per-identity "Format signature as HTML" toggle so users can set rich-text signatures and have them sent as HTML in outgoing mail, addressing issue thunderbird#8841. - Identity.signatureIsHtml persisted alongside the existing signature fields; LegacyAccountStorageHandler reads/writes/deletes the new key; IdentitySettingsDescriptions bumps to settings version 111. - Edit Identity and Account Composition defaults screens gain a "Format signature as HTML" checkbox. - TextBodyBuilder short-circuits HtmlConverter.textToHtmlFragment when the flag is set, and runs the signature through HtmlConverter.htmlToText for the plain-text message path. - HtmlSignatureSanitizer sanitizes user HTML via a Jsoup Safelist.relaxed baseline, stripping scripts, event handlers, and javascript: URLs. - MessageCompose renders the HTML signature in a MessageWebView preview instead of raw text, so drafts and new composes show the rendered result. Remote images and natural device-size rendering are enabled for the user's own signature content. - Draft reload looks up the matching identity by email via account.findIdentity() to preserve signatureIsHtml for multi-identity accounts, since the X-K9mail-Identity header does not encode the flag. - Tests: HtmlSignatureSanitizerTest (10 cases) and TextBodyBuilderHtmlSignatureTest (4 cases).

- Convert legacy tests to use AAA pattern with explicit sections - Replace inline assertions with descriptive test names using backticks - Add testSubject property for clarity - Reorder tests logically (basic → allowed → removed content) - Add language hints to HTML string literals - Add missing assertions for sanitize tests - Replace mock() with FakeGeneralSettingsManager in TextBodyBuilderHtmlSignatureTest

… implementation - Extract HtmlSignatureSanitizer to interface in feature.mail.message.composer - Move implementation from legacy.core to DefaultHtmlSignatureSanitizer - Replace jsoup with ksoup for Kotlin Multiplatform compatibility - Inject HtmlSignatureSanitizer via DI into MessageBuilder and TextBodyBuilder - Move tests to new package and convert to kotlin.test

…essageWebView - Add ThunderbirdWebViewSettings interface in webkit api module - Move WebViewConfig from legacy.ui.legacy to core.android.webkit.api - Deprecate legacy WebViewConfig with replacement directive - Make MessageWebView implement ThunderbirdWebViewSettings - Expose loadWithOverviewMode property in interface - Add KDoc to interface methods

…to reusable function - Move SignaturePreviewWebView configuration logic from MessageCompose to new SignaturePreviewWebView.kt - Add configureForSignaturePreview extension function on ThunderbirdWebViewSettings - Include KDoc explaining network data unblocking and overview mode behavior - Add comprehensive tests covering config application and signature-specific overrides

… content - Replace manual HTML document construction with displayHtml.wrapMessageContent - Remove duplicate HtmlSignatureSanitizer import - Remove fully qualified class names for MessageWebView and WebViewConfigProvider

- Add saveSignatureAsHtml to AccountSetupComposition state and OnFormatSignatureAsHtmlCheck event, persisted via LegacyAccount.signatureIsHtml. - Render a live signature preview with RichText when a signature is set. - Pass the whole state object to AccountSetupCompositionScreen instead of individual parameters. - Replace the hand-rolled checkbox row with CheckboxInput and adjust signature labels.

… header - Add SIGNATURE_IS_HTML field to IdentityField enum - Persist signatureIsHtml flag in identity blob when signature is customized - Parse and apply signature HTML setting from identity header on draft restore - Remove workaround that matched identity by email to infer HTML signature setting

…on and edit identity - Extract LegacyIdentitySignatureWebViewConfigurator to share WebView config and HTML preview logic - Add signature preview WebView to EditIdentity layout with debounced updates - Adjust AccountSetupComposition signature UI spacing and label styling - Remove unused account_setup_composition.xml layout file - Add edit_identity_screen dimension resources for consistent padding

I've applied all the required changes

rafaeltonholo · 2026-08-19T12:26:59Z

Hi all!

I've applied all the required changes and also included a few others to make this PR mergeable. Aside from the changes I've asked for in the PR comments, the new changes also include:

A preview of the signature on both "Composition defaults" and "Edit Identity" screens; see videos below

Composition defaults	Edit Identity
Screen.Recording.2026-08-19.at.9.12.11.AM.mp4	Screen.Recording.2026-08-19.at.9.14.16.AM.mp4

A button to clear the signature when editing it in the Composition defaults screen; see screenshot below
Removed new code from the legacy module to a dedicated module called :core:android:webkit
Properly saved the identity signature when saving a draft

Important

It is important to note that this isn't the final version of the signature feature. There are still some improvements to be made, such as:

Include a WYSIWYG editor for the signature, so that users can format their signature text without needing to know HTML
Migrate the Edit Identity screen to Compose, so we can have a consistent experience across the app
And other improvements that will be discussed in future with the team.

I really appreciate all your patience and feedback on this PR. We know this is a very important feature for our users, and we want to make sure we get it right.

Please let me know if you have any questions or concerns regarding the changes made.

cc: @jbott-tbird, @Alecaddd, @ryanleesipes, @dani-zilla

…ries

dani-zilla

Looks good! Tested locally and sent some beautiful HTML signatures to test it out. Great work!

dani-zilla · 2026-08-19T20:06:51Z

+
+    @Test
+    fun `sanitize should return empty string when input is empty`() {
+        // Arrange


Is there a reason for the arrange/act/assert labels and language as well? Feels like something AI may have done, but I don't know if it has value to analog intelligence 😆

I've always used the comments Arrange/Act/Assert to organize the test cases by blocks, so it is easier to understand:

Where I'm preparing the test case (Arrange)

Where I'm actually triggering the test subject action (Act), and

Where I'm verifying the test subject output (Assert).

This is a well-known test pattern that predates AI; see more: "Arrange-Act-Assert" and Arrange-Act-Assert: A Pattern for Writing Good Tests

Regarding the language feature, it is just my OCD of seeing code inside a string and not having it show in the syntax colour. The language comment makes AS understand that this is code and show the syntax colour.

thunderbird-botmobile · 2026-08-20T12:31:40Z

Thanks for your contribution! Your pull request has been merged and will be part of Thunderbird 24. We appreciate the time and effort you put into improving Thunderbird. If you haven’t already, you’re welcome to join our Matrix chat for contributors. It’s where we discuss development and help each other out. https://matrix.to/#/#tb-android-dev:mozilla.org
Hope to see you there! 🚀📱🐦

joshua-grimmett requested a review from a team as a code owner April 14, 2026 19:09

joshua-grimmett requested a review from rafaeltonholo April 14, 2026 19:09

joshua-grimmett temporarily deployed to botmobile April 14, 2026 19:09 — with GitHub Actions Inactive

joshua-grimmett temporarily deployed to review April 14, 2026 19:09 — with GitHub Actions Inactive

thunderbird-botmobile Bot assigned rafaeltonholo Apr 14, 2026

joshua-grimmett mentioned this pull request Apr 14, 2026

Signature editor #8841

Open

Alecaddd added the report: highlight Highlight changes (major feature, breaking, or noticeable to users) in user-facing reports. label Apr 16, 2026

rafaeltonholo previously requested changes May 4, 2026

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jbott-tbird mentioned this pull request Aug 13, 2026

Shepherd Signature PR #11405

Closed

rafaeltonholo force-pushed the feat/8841/html-signature branch from de45233 to fdc3210 Compare August 19, 2026 11:57

rafaeltonholo requested a review from dani-zilla August 19, 2026 11:58

rafaeltonholo temporarily deployed to botmobile August 19, 2026 11:58 — with GitHub Actions Inactive

rafaeltonholo assigned dani-zilla Aug 19, 2026

rafaeltonholo added 6 commits August 19, 2026 09:02

feat(webkit): add webkit api and internal modules

d4ea8df

rafaeltonholo added 3 commits August 19, 2026 09:02

rafaeltonholo force-pushed the feat/8841/html-signature branch from fdc3210 to fc71357 Compare August 19, 2026 12:02

refactor(account-setup): extract SignatureContent to separate file

dcc3b5a

chore: update dependency lists after adding ksoup and fleeksoft libra…

3b44122

…ries

dani-zilla approved these changes Aug 19, 2026

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rafaeltonholo merged commit 88212e4 into thunderbird:main Aug 20, 2026
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rafaeltonholo temporarily deployed to botmobile August 20, 2026 12:31 — with GitHub Actions Inactive

thunderbird-botmobile Bot added this to the Thunderbird 24 milestone Aug 20, 2026

wmontwe mentioned this pull request Sep 11, 2026

uplift(beta): fix(settings): prevent HTML signature preview reloads on rotation (#11538) #11541

Open

11 tasks

	String draftEmail = newIdentity.getEmail();
	final String draftEmail = newIdentity.getEmail();

	boolean signatureIsHtml = matchedIdentity != null
	final boolean signatureIsHtml = matchedIdentity != null

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Summary

Scope (vs #8841)

Changes

Tests

Screenshots

Test plan

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joshua-grimmett commented Apr 14, 2026 •

edited by rafaeltonholo

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