LibGUI: Add FilteringProxyModel

This model does not support nested indices well, in that it flattens
them all out.
That's a FIXME for the future as it does its job for now.

Libraries/LibGUI/FilteringProxyModel.cpp

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibGUI/FilteringProxyModel.h>
+
+namespace GUI {
+
+ModelIndex FilteringProxyModel::index(int row, int column, const ModelIndex& parent_index) const
+{
+    int parent_row = parent_index.row();
+    if (!parent_index.is_valid())
+        parent_row = 0;
+
+    return create_index(parent_row + row, column);
+}
+
+int FilteringProxyModel::row_count(const ModelIndex&) const
+{
+    return m_matching_indices.size();
+}
+
+int FilteringProxyModel::column_count(const ModelIndex& index) const
+{
+    if (!index.is_valid())
+        return {};
+
+    if ((size_t)index.row() > m_matching_indices.size() || index.row() < 0)
+        return 0;
+
+    return m_model.column_count(m_matching_indices[index.row()]);
+}
+
+Variant FilteringProxyModel::data(const ModelIndex& index, Role role) const
+{
+    if (!index.is_valid())
+        return {};
+
+    if ((size_t)index.row() > m_matching_indices.size() || index.row() < 0)
+        return 0;
+
+    return m_model.data(m_matching_indices[index.row()], role);
+}
+
+void FilteringProxyModel::update()
+{
+    m_model.update();
+    filter();
+    did_update();
+}
+
+void FilteringProxyModel::filter()
+{
+    m_matching_indices.clear();
+
+    Function<void(ModelIndex&)> add_matching = [&](ModelIndex& parent_index) {
+        for (auto i = 0; i < m_model.row_count(parent_index); ++i) {
+            auto index = m_model.index(i, 0, parent_index);
+            if (!index.is_valid())
+                continue;
+
+            auto filter_matches = m_model.data_matches(index, m_filter_term);
+            bool matches = filter_matches == TriState::True;
+            if (filter_matches == TriState::Unknown) {
+                auto data = m_model.data(index, Role::Display);
+                if (data.is_string() && data.as_string().contains(m_filter_term))
+                    matches = true;
+            }
+            if (matches)
+                m_matching_indices.append(index);
+
+            add_matching(index);
+        }
+    };
+
+    ModelIndex parent_index;
+    add_matching(parent_index);
+}
+
+void FilteringProxyModel::set_filter_term(const StringView& term)
+{
+    if (m_filter_term == term)
+        return;
+    m_filter_term = term;
+    update();
+}
+
+ModelIndex FilteringProxyModel::map(const ModelIndex& index) const
+{
+    if (!index.is_valid())
+        return {};
+
+    auto row = index.row();
+    if (m_matching_indices.size() > (size_t)row)
+        return m_matching_indices[row];
+
+    return {};
+}
+
+}