feat(compose): a signature switch on the editor bar

A QToolButton with a checkable menu at the right end of the editor bar,
where item 142 put the controls of the editor. Not registered in KeyMap:
parented to the composer like the formatting actions, so its scope is this
window.

The signature is applied through a QTextCursor rather than setPlainText(),
which destroys the undo stack, and the seeded one is cleared from that
stack for the reason the seeded quote already is: one Ctrl+Z must not wipe
content the user never typed.

A resumed draft seeds nothing. Its body already carries the signature it
was written with, and seeding again would put a second one on a message
written once.

Part of item 152.

1 files changed, 33 insertions, 0 deletions

diff --git a/src/composewindow.h b/src/composewindow.h
index c44fcda..918d4e3 100644
--- a/src/composewindow.h
+++ b/src/composewindow.h
@@ -96,6 +96,21 @@ public:
     /// and quitting therefore loses that text.
     bool lastSaveFailed() const { return m_saveFailed; }
 
+    /// Where the signature files live. Defaults to
+    /// <config>/qtmaildir/signatures; a test points it at its own directory.
+    ///
+    /// A setter rather than a config key: nothing yet suggests the user wants
+    /// a second location, and the tests need to not read the real one.
+    void setSignatureDir(const QString &dir);
+
+    /// Seeds the signature from config and fills the switch.
+    ///
+    /// Public and called by the constructor rather than private, so a test can
+    /// drive it after pointing setSignatureDir() somewhere safe. A resumed
+    /// draft seeds nothing: its body already carries the signature it was
+    /// written with.
+    void seedSignature();
+
     /// Writes the current buffer to the drafts folder now. Returns false and
     /// leaves the banner up on failure.
     ///
@@ -176,6 +191,16 @@ private:
     /// a silently wrong send is not among the outcomes.
     void extractForwardedAttachments();
     void seedBody();
+
+    /// Applies \p name to the buffer, replacing whatever is there.
+    void applySignature(const QString &name);
+
+    /// The text of every signature on disk, for replace()'s guard.
+    QStringList knownSignatures() const;
+
+    /// The signature name this account seeds, falling through to [compose].
+    QString seededSignatureName() const;
+
     void refreshAttachmentList();
     void setInputsEnabled(bool enabled);
     void showSendFailure(const QString &stderrText);
@@ -227,6 +252,14 @@ private:
     QComboBox *m_from = nullptr;
     QPlainTextEdit *m_body = nullptr;
     QToolButton *m_sendHtml = nullptr;
+    QToolButton *m_signatureSwitch = nullptr;
+    QString m_signatureDir;
+    QString m_signatureName;  ///< The selected signature, empty for None.
+
+    /// True once the user has used the switch. From then on a From: change
+    /// stops re-seeding, so a deliberate choice is never overwritten. Matches
+    /// how send_html seeds from context and is then left alone.
+    bool m_signatureChosen = false;
     QLabel *m_banner = nullptr;
     QListWidget *m_attachmentList = nullptr;
     QWidget *m_sendLogPane = nullptr;