feat(tags): add an Edit tags dialog on Ctrl+T

Five hardcoded tags were the only ones reachable from the UI: archive,
delete, spam, flag and toggle_unread. For an application whose purpose is
organising mail by tag, applying any other one meant leaving for a
terminal. Item 26 of the usability backlog, raised by the user asking how
to add a tag and finding they could not.

One dialog rather than separate add and remove actions, at the user's
choice: filing something under a new tag while dropping inbox is one
thought, not two. Type tags to add or remove, comma separated, or clear a
checkbox to drop a tag already on the selection without retyping its
name.

Both fields complete against the tag list MainWindow already holds for
the query completer. Completion is a guard against typing shoppping
beside shopping, never a whitelist: inventing a tag is the entire point,
so any valid name goes through whether or not it exists yet.

Tri-state checkboxes carry the multi-thread case, and are where the risk
is. A tag on some selected threads shows partially checked, and leaving
it alone changes nothing; the opposite reading would silently tag threads
the user never looked at. A tag already on every thread and left checked
is likewise not a change and is not sent as one.

Tag names are validated before anything is applied, through a free
function so the rules are testable on their own. Empty, a leading dash
(notmuch's CLI reads it as removal, making such a tag a trap), whitespace
and control characters are refused by name and reason. Nothing is applied
until the whole set passes, since the user cannot tell which half of a
partial change landed.

TagDialog is pure UI: handed the vocabulary and the current state,
returning two lists, contacting no worker. That is what lets its fifteen
tests run without a notmuch database. Integration is a single call to the
existing tagSelected(), so undo, the optimistic model update, the
combined multi-row query and the completer refresh for a brand-new tag
all come for free.

One test assumption was wrong and the code was right: a case asserted
that QStringLiteral("null\0byte") truncates at the null and reads as
empty. It does not, so the null is caught as a control character. The
test was corrected rather than the validator.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index d8fba3e..000be85 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -52,6 +52,7 @@
 #include "notmuchworker.h"
 #include "querycompleter.h"
 #include "tagchip.h"
+#include "tagdialog.h"
 #include "threadlistmodel.h"
 #include "version.h"
 
@@ -548,6 +549,10 @@ void MainWindow::registerActions()
         else
             tagSelected({ QStringLiteral("unread") }, {}, tr("Mark unread"));
     });
+    addAction(QStringLiteral("edit_tags"), tr("Edit &tags..."),
+              tr("Add or remove any tag on the selected threads"), [this]() {
+        editTagsOnSelection();
+    });
     addAction(QStringLiteral("toggle_html"), tr("Toggle &HTML"),
               tr("Switch the thread between HTML and plain text"), [this]() {
         m_messageView->toggleHtml();
@@ -634,6 +639,7 @@ void MainWindow::buildMenus()
     messageMenu->addAction(m_actions.value(QStringLiteral("spam")));
     messageMenu->addSeparator();
     messageMenu->addAction(m_actions.value(QStringLiteral("toggle_unread")));
+    messageMenu->addAction(m_actions.value(QStringLiteral("edit_tags")));
     messageMenu->addAction(m_actions.value(QStringLiteral("flag")));
 
     auto *viewMenu = menuBar()->addMenu(tr("&View"));
@@ -1152,6 +1158,41 @@ void MainWindow::markCurrentThreadRead()
                         tr("Mark read"));
 }
 
+void MainWindow::editTagsOnSelection()
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty()) {
+        m_statusLabel->setText(tr("Select a thread first"));
+        return;
+    }
+
+    // How many of the selected threads carry each tag, which is what tells a
+    // tag that is on all of them from one that is on some.
+    QHash<QString, int> counts;
+    for (const QModelIndex &index : rows) {
+        const ThreadSummary thread = m_model->threadAt(index.row());
+        for (const QString &tag : thread.tags)
+            counts[tag] += 1;
+    }
+
+    // m_knownTags is the same list the query completer uses, so the dialog
+    // offers every tag in the database without a round trip.
+    TagDialog dialog(m_knownTags, counts, rows.size(), this);
+    if (dialog.exec() != QDialog::Accepted)
+        return;
+
+    const QStringList add = dialog.tagsToAdd();
+    const QStringList remove = dialog.tagsToRemove();
+    if (add.isEmpty() && remove.isEmpty())
+        return;   // Applied with nothing changed.
+
+    // Straight through tagSelected(), so this inherits undo, the optimistic
+    // model update, the one-query multi-row resolution, and the completer
+    // refresh for a tag that did not exist before.
+    tagSelected(add, remove, tr("Edit tags"));
+}
+
 void MainWindow::tagSelected(const QStringList &add, const QStringList &remove,
                              const QString &description)
 {