filterbar: Add support to match case and glob patterns for the filter bar

Currently, Dolphin's filter bar defaults to plain text, but it actually has a hidden regex functionality too: it tries to auto-detect and switch to a regular expression if characters like '*', '?', or '[' are present in the search string.
This approach has a couple of issues. First, the regex/wildcard functionality is completely hidden from the user. Second, the auto-detection is flawed because those are perfectly valid characters in Linux filenames. If a user tries to filter for a file literally named [draft].txt, the auto-switching kicks in and causes unexpected behavior.

This MR fixes this by making the filtering modes explicit through a ComboBox at the side of the filter bar, with the options 'Plain Text', 'Glob' and 'Regular Expression'. It also adds a button to toggle the case sensitive matching. A visual feedback for when the user is inputting an invalid expression has also been implemented by turning the bar background red and making appear an error symbol.

2 files changed, 118 insertions, 4 deletions

diff --git a/src/filterbar/filterbar.cpp b/src/filterbar/filterbar.cpp
index 6cb8d5e2a..08bff24fc 100644
--- a/src/filterbar/filterbar.cpp
+++ b/src/filterbar/filterbar.cpp
@@ -2,18 +2,25 @@
  * SPDX-FileCopyrightText: 2006-2010 Peter Penz <[email protected]>
  * SPDX-FileCopyrightText: 2006 Gregor Kališnik <[email protected]>
  * SPDX-FileCopyrightText: 2012 Stuart Citrin <[email protected]>
+ * SPDX-FileCopyrightText: 2026 Alessio Bonfiglio <[email protected]>
  *
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 #include "filterbar.h"
 
+#include <KConfigGroup>
 #include <KLocalizedString>
+#include <KSharedConfig>
 
+#include <KColorScheme>
+#include <QAction>
 #include <QApplication>
+#include <QComboBox>
 #include <QHBoxLayout>
 #include <QKeyEvent>
 #include <QLineEdit>
+#include <QPalette>
 #include <QToolButton>
 
 FilterBar::FilterBar(QWidget *parent)
@@ -35,8 +42,35 @@ FilterBar::FilterBar(QWidget *parent)
     m_filterInput->setClearButtonEnabled(true);
     m_filterInput->setPlaceholderText(i18n("Filter…"));
     connect(m_filterInput, &QLineEdit::textChanged, this, &FilterBar::filterChanged);
+    connect(m_filterInput, &QLineEdit::textChanged, this, &FilterBar::updateInvalidPatternView);
     setFocusProxy(m_filterInput);
 
+    m_invalidPatternAction = new QAction(m_filterInput);
+    m_invalidPatternAction->setCheckable(false);
+    m_invalidPatternAction->setIcon(QIcon::fromTheme(QStringLiteral("error-symbolic")));
+    m_invalidPatternAction->setToolTip(i18n("Invalid expression"));
+    m_filterInput->addAction(m_invalidPatternAction, QLineEdit::TrailingPosition);
+    m_invalidPatternAction->setVisible(false);
+
+    // Create case sensitive button
+    m_caseSensitiveButton = new QToolButton(contentsContainer);
+    m_caseSensitiveButton->setAutoRaise(true);
+    m_caseSensitiveButton->setCheckable(true);
+    m_caseSensitiveButton->setIcon(QIcon::fromTheme(QStringLiteral("format-text-superscript"), QIcon::fromTheme(QStringLiteral("format-text-bold"))));
+    m_caseSensitiveButton->setToolTip(i18nc("@info:tooltip", "Match case"));
+    connect(m_caseSensitiveButton, &QToolButton::toggled, this, &FilterBar::caseSensitiveChanged);
+    connect(m_caseSensitiveButton, &QToolButton::toggled, this, &FilterBar::updateInvalidPatternView);
+
+    // Create filter mode combobox
+    m_filterModeComboBox = new QComboBox(contentsContainer);
+    m_filterModeComboBox->addItem(i18nc("@item:inlistbox", "Plain Text"), KFileItemModelFilter::FilterMode::PlainText);
+    m_filterModeComboBox->addItem(i18nc("@item:inlistbox", "Glob Pattern"), KFileItemModelFilter::FilterMode::Glob);
+    m_filterModeComboBox->addItem(i18nc("@item:inlistbox", "Regular Expression"), KFileItemModelFilter::FilterMode::Regex);
+    connect(m_filterModeComboBox, &QComboBox::currentIndexChanged, this, [this](int index) {
+        Q_EMIT filterModeChanged(m_filterModeComboBox->itemData(index).value<KFileItemModelFilter::FilterMode>());
+    });
+    connect(m_filterModeComboBox, &QComboBox::currentIndexChanged, this, &FilterBar::updateInvalidPatternView);
+
     // Create close button
     QToolButton *closeButton = new QToolButton(contentsContainer);
     closeButton->setAutoRaise(true);
@@ -49,13 +83,25 @@ FilterBar::FilterBar(QWidget *parent)
     hLayout->setContentsMargins(0, 0, 0, 0);
     hLayout->addWidget(m_lockButton);
     hLayout->addWidget(m_filterInput);
+    hLayout->addWidget(m_caseSensitiveButton);
+    hLayout->addWidget(m_filterModeComboBox);
     hLayout->addWidget(closeButton);
 
-    setTabOrder(m_lockButton, closeButton);
-    setTabOrder(closeButton, m_filterInput);
+    setTabOrder({m_lockButton, m_caseSensitiveButton, m_filterModeComboBox, closeButton, m_filterInput});
+
+    KConfigGroup filterBarConfig(KSharedConfig::openStateConfig(), QStringLiteral("FilterBar"));
+    bool caseSensitiveEnabled = filterBarConfig.readEntry("caseSensitive", false);
+    int filterModeComboBoxIndex = filterBarConfig.readEntry("filterMode", m_filterModeComboBox->findData(KFileItemModelFilter::FilterMode::Glob));
+    m_caseSensitiveButton->setChecked(caseSensitiveEnabled);
+    m_filterModeComboBox->setCurrentIndex(filterModeComboBoxIndex);
 }
 
-FilterBar::~FilterBar() = default;
+FilterBar::~FilterBar()
+{
+    KConfigGroup filterBarConfig(KSharedConfig::openStateConfig(), QStringLiteral("FilterBar"));
+    filterBarConfig.writeEntry("caseSensitive", this->m_caseSensitiveButton->isChecked());
+    filterBarConfig.writeEntry("filterMode", this->m_filterModeComboBox->currentIndex());
+}
 
 void FilterBar::closeFilterBar()
 {
@@ -71,6 +117,16 @@ void FilterBar::selectAll()
     m_filterInput->selectAll();
 }
 
+KFileItemModelFilter::FilterMode FilterBar::filterMode() const
+{
+    return m_filterModeComboBox->itemData(m_filterModeComboBox->currentIndex()).value<KFileItemModelFilter::FilterMode>();
+}
+
+bool FilterBar::isCaseSensitive() const
+{
+    return m_caseSensitiveButton->isChecked();
+}
+
 void FilterBar::clear()
 {
     m_filterInput->clear();
@@ -93,6 +149,39 @@ void FilterBar::slotToggleLockButton(bool checked)
     }
 }
 
+void FilterBar::updateInvalidPatternView()
+{
+    bool valid = true;
+
+    KFileItemModelFilter::FilterMode current_filter_mode = filterMode();
+    if (current_filter_mode != KFileItemModelFilter::FilterMode::PlainText) {
+        QRegularExpression regExp = QRegularExpression();
+        QString pattern = m_filterInput->text();
+
+        QRegularExpression::PatternOptions options =
+            m_caseSensitiveButton->isChecked() ? QRegularExpression::NoPatternOption : QRegularExpression::CaseInsensitiveOption;
+        if (current_filter_mode == KFileItemModelFilter::FilterMode::Regex) {
+            regExp.setPattern(pattern);
+            regExp.setPatternOptions(options);
+        } else if (current_filter_mode == KFileItemModelFilter::FilterMode::Glob) {
+            regExp.setPattern(QRegularExpression::wildcardToRegularExpression(pattern, QRegularExpression::UnanchoredWildcardConversion));
+            regExp.setPatternOptions(options);
+        }
+
+        valid = regExp.isValid();
+    }
+
+    if (valid) {
+        m_filterInput->setPalette(QPalette());
+        m_invalidPatternAction->setVisible(false);
+    } else {
+        auto pal = m_filterInput->palette();
+        KColorScheme::adjustBackground(pal, KColorScheme::NegativeBackground);
+        m_filterInput->setPalette(pal);
+        m_invalidPatternAction->setVisible(true);
+    }
+}
+
 void FilterBar::showEvent(QShowEvent *event)
 {
     if (!event->spontaneous()) {
@@ -137,7 +226,10 @@ void FilterBar::keyPressEvent(QKeyEvent *event)
 
 int FilterBar::preferredHeight() const
 {
-    return std::max(m_filterInput->sizeHint().height(), m_lockButton->sizeHint().height());
+    return std::max({m_filterInput->sizeHint().height(),
+                     m_lockButton->sizeHint().height(),
+                     m_caseSensitiveButton->sizeHint().height(),
+                     m_filterModeComboBox->sizeHint().height()});
 }
 
 #include "moc_filterbar.cpp"
diff --git a/src/filterbar/filterbar.h b/src/filterbar/filterbar.h
index 1424f4cb8..924c6dba3 100644
--- a/src/filterbar/filterbar.h
+++ b/src/filterbar/filterbar.h
@@ -10,9 +10,12 @@
 #define FILTERBAR_H
 
 #include "animatedheightwidget.h"
+#include "kitemviews/private/kfileitemmodelfilter.h"
 
 class QLineEdit;
 class QToolButton;
+class QComboBox;
+class QAction;
 
 /**
  * @brief Provides an input field for filtering the currently shown items.
@@ -35,6 +38,9 @@ public:
      */
     void selectAll();
 
+    KFileItemModelFilter::FilterMode filterMode() const;
+    bool isCaseSensitive() const;
+
 public Q_SLOTS:
     /** Clears the input field. */
     void clear();
@@ -51,6 +57,16 @@ Q_SIGNALS:
     void filterChanged(const QString &nameFilter);
 
     /**
+     * Emitted when the case sensitive mode has been changed
+     */
+    void caseSensitiveChanged(bool caseSensitive);
+
+    /**
+     * Emitted when the filter mode has been changed
+     */
+    void filterModeChanged(KFileItemModelFilter::FilterMode mode);
+
+    /**
      * Emitted as soon as the filterbar should get closed.
      */
     void closeRequest();
@@ -70,6 +86,12 @@ protected:
 private:
     QLineEdit *m_filterInput;
     QToolButton *m_lockButton;
+    QToolButton *m_caseSensitiveButton;
+    QComboBox *m_filterModeComboBox;
+    QAction *m_invalidPatternAction;
+
+    /** Enable or disable the alterative view for when a pattern is invalid */
+    void updateInvalidPatternView();
 };
 
 #endif