feat(filters): put the four built-in filters on the query row

Item 93, the UI half. Unread, Inbox, Flagged and Sent are buttons the
application ships, sitting first on the row, ahead of the user's pinned saved
queries.

runFilter() is runSavedQuery()'s opposite in the one way that matters: it READS
the account box and never writes it. That is item 90's defect. A filter narrows
what the user is already looking at, so the dropdown is its input rather than
something it resets on the way past. A saved query keeps setting the account
from what it stored, because it is a destination and states its own scope.

runQuery() gains an AccountScope parameter. A filter's text arrives already
resolved in the selected account's scope, and scoping it again would put
path:"work/Sent/**" inside path:"work/**".

Two migration changes, both of which unpin rather than delete:

- Sent is no longer migrated from the INI into queries.json. The built-in
  filter covers it, and migrating one too would put two Sent buttons on the
  row, one editable and one not.
- A stored entry naming a known generator is unpinned on load, which is what
  every install upgraded through 0.19.0 carries. It keeps its name and its
  generator and moves to the menu. Deleting it would be data loss on a file
  whose readers are supposed to preserve what they do not own.

The test suite needed the same distinction the design makes.
savedQueryButtonLabels() now skips the filters, and savedQueryButton(window,
label) replaces five positional row->findChild<QPushButton *>() lookups that
were silently returning Unread.

One rendering probe had to be fixed rather than adapted.
replyRowsKeepTheirTextUnderTheThreadLine resized the window to 300px, and four
more buttons pushed the reply row below the viewport: the pixel loop then ran
zero times and reported "0 pixels, the row was painted over", which is a
different defect from the one it exists to catch. It gets 600px and a guard
asserting the row is really inside the viewport, so the next person to shrink
it gets told the truth. Verified by putting 300 back: the guard names the row
at 83..165 in an 82px viewport.

1 files changed, 50 insertions, 12 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index c6df95c..6bd91d9 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -1717,12 +1717,31 @@ void MainWindow::buildSavedQueryRow(QWidget *parent, QVBoxLayout *layout)
     auto *box = new QHBoxLayout(row);
     box->setContentsMargins(0, 0, 0, 0);
 
-    // Sent is an ordinary row here, not a hardcoded button beside the others.
-    // It is still GENERATED, so its query is composed from the accounts' `sent`
-    // keys at click time and correcting a folder name stays a config edit and
-    // nothing else; what changed is that the entry can now be reordered,
-    // renamed, unpinned or removed like every other, instead of being the one
-    // control on the row the user did not own.
+    // The built-in filters come first, in their own fixed order, and they are
+    // not saved queries: they are shipped, they are not in queries.json, and
+    // the user cannot edit or delete them (item 93). They are what the row is
+    // FOR; the pinned saved queries below them are the transitional half that
+    // item 94 removes.
+    for (const SavedQuery &filter : Config::builtinFilters()) {
+        // Sent with no account configuring a sent folder finds nothing by
+        // construction. Hidden rather than present and empty, which is what the
+        // hardcoded Sent button did and is worth keeping: a control that always
+        // returns nothing reads as broken rather than as absent.
+        if (m_config.resolvedQuery(filter, QString())
+            == Config::matchNothingQuery())
+            continue;
+
+        auto *button = new QPushButton(filter.name, row);
+        // A stable object name per filter, so a test finds the button without
+        // depending on the label, which is translated.
+        button->setObjectName(filter.generated + QStringLiteral("Button"));
+        connect(button, &QPushButton::clicked, this,
+                [this, filter]() { runFilter(filter); });
+        box->addWidget(button);
+    }
+
+    // The user's own saved queries. A pinned one is still a button, beside the
+    // filters, until item 94 makes the menu their only home.
     QList<SavedQuery> unpinned;
     for (const SavedQuery &saved : m_config.savedQueries()) {
         // A generator whose accounts configure nothing produces a button that
@@ -1736,10 +1755,9 @@ void MainWindow::buildSavedQueryRow(QWidget *parent, QVBoxLayout *layout)
             continue;
         }
         auto *button = new QPushButton(saved.name, row);
-        // The generated entries keep a stable object name so a test can find
-        // the sent button without depending on what the user renamed it to.
-        if (saved.generated == QStringLiteral("sent"))
-            button->setObjectName(QStringLiteral("sentButton"));
+        // No object name here any more. "sentButton" now belongs to the BUILT-IN
+        // Sent filter, and a migrated Sent entry claiming it too would give two
+        // buttons one name, so findChild() would return whichever came first.
         connect(button, &QPushButton::clicked, this,
                 [this, saved]() { runSavedQuery(saved); });
         addSavedQueryActions(button, saved);
@@ -1928,6 +1946,22 @@ void MainWindow::runSavedQuery(const SavedQuery &saved)
     runQuery(saved.flat ? FlatResult::Yes : FlatResult::No);
 }
 
+void MainWindow::runFilter(const SavedQuery &filter)
+{
+    // The account box is READ and never written. That is the whole difference
+    // from runSavedQuery(), and it is item 90's defect: a filter narrows what
+    // the user is already looking at, so the dropdown is its input rather than
+    // something it resets on the way past.
+    const QString accountKey = m_accountBox->currentData().toString();
+
+    // Resolved here, in the account's scope, and put in the bar so what ran is
+    // visible and editable. runQuery() is told not to scope it again.
+    m_queryEdit->setText(m_config.resolvedQuery(filter, accountKey));
+
+    runQuery(filter.flat ? FlatResult::Yes : FlatResult::No,
+             AccountScope::AlreadyScoped);
+}
+
 void MainWindow::saveCurrentQuery()
 {
     const QString query = m_queryEdit->text().trimmed();
@@ -2007,7 +2041,7 @@ void MainWindow::rebuildSavedQueryRow()
     }
 }
 
-void MainWindow::runQuery(FlatResult flat)
+void MainWindow::runQuery(FlatResult flat, AccountScope scope)
 {
     // Set on EVERY run, not only when Yes. This is the line that stops flat
     // mode leaking: any query that is not the Sent button restores the tree,
@@ -2017,8 +2051,12 @@ void MainWindow::runQuery(FlatResult flat)
 
     QString query = m_queryEdit->text().trimmed();
 
+    // A built-in filter arrives already resolved in the selected account's
+    // scope, because a generator has to be asked for the account's own query
+    // rather than have its all-accounts query wrapped. Scoping again here would
+    // put path:"work/Sent/**" inside path:"work/**".
     const QString accountKey = m_accountBox->currentData().toString();
-    if (!accountKey.isEmpty())
+    if (scope == AccountScope::Apply && !accountKey.isEmpty())
         query = m_config.account(accountKey).scopedQuery(query);
 
     if (query.isEmpty())