Show line indicator instead of rectangle while dragging in tables (#5252)

CHANGELOG.md

@@ -48,6 +48,7 @@
 - Minor: Add wrappers for Lua `io` library for experimental plugins feature. (#5231)
 - Minor: Add permissions to experimental plugins feature. (#5231)
 - Minor: Add support to send /announce[color] commands. (#5250)
+- Minor: Added drop indicator line while dragging in tables. (#5252)
 - Bugfix: Fixed an issue where certain emojis did not send to Twitch chat correctly. (#4840)
 - Bugfix: Fixed capitalized channel names in log inclusion list not being logged. (#4848)
 - Bugfix: Trimmed custom streamlink paths on all platforms making sure you don't accidentally add spaces at the beginning or end of its path. (#4834)

src/CMakeLists.txt

@@ -651,6 +651,8 @@ set(SOURCE_FILES
         widgets/helper/SettingsDialogTab.hpp
         widgets/helper/SignalLabel.cpp
         widgets/helper/SignalLabel.hpp
+        widgets/helper/TableStyles.cpp
+        widgets/helper/TableStyles.hpp
         widgets/helper/TitlebarButton.cpp
         widgets/helper/TitlebarButton.hpp
         widgets/helper/TitlebarButtons.cpp

src/widgets/helper/EditableModelView.cpp

@@ -1,6 +1,7 @@
 #include "EditableModelView.hpp"
 
 #include "widgets/helper/RegExpItemDelegate.hpp"
+#include "widgets/helper/TableStyles.hpp"
 
 #include <QAbstractItemView>
 #include <QAbstractTableModel>
@@ -28,6 +29,8 @@ EditableModelView::EditableModelView(QAbstractTableModel *model, bool movable)
     this->tableView_->verticalHeader()->setVisible(false);
     this->tableView_->horizontalHeader()->setSectionsClickable(false);
 
+    TableRowDragStyle::applyTo(this->tableView_);
+
     // create layout
     QVBoxLayout *vbox = new QVBoxLayout(this);
     vbox->setContentsMargins(0, 0, 0, 0);

src/widgets/helper/TableStyles.cpp

@@ -0,0 +1,66 @@
+#include "widgets/helper/TableStyles.hpp"
+
+#include <QAbstractItemView>
+#include <QPainter>
+#include <QStyleOption>
+#include <QTableView>
+#include <QWidget>
+
+namespace chatterino {
+
+TableRowDragStyle::TableRowDragStyle(QStyle *target)
+    : QProxyStyle(target)
+{
+}
+
+void TableRowDragStyle::applyTo(QTableView *view)
+{
+    auto *proxyStyle = new TableRowDragStyle(view->style());
+    proxyStyle->setParent(view);
+    view->setStyle(proxyStyle);
+}
+
+void TableRowDragStyle::drawPrimitive(QStyle::PrimitiveElement element,
+                                      const QStyleOption *option,
+                                      QPainter *painter,
+                                      const QWidget *widget) const
+{
+    if (element != QStyle::PE_IndicatorItemViewItemDrop)
+    {
+        QProxyStyle::drawPrimitive(element, option, painter, widget);
+        return;
+    }
+
+    const auto *view = dynamic_cast<const QAbstractItemView *>(widget);
+    if (!view)
+    {
+        assert(false && "TableStyle must be used on a QAbstractItemView");
+        return;
+    }
+
+    if (option->rect.isNull())
+    {
+        return;
+    }
+
+    // Get the direction a row is dragged in
+    auto selected = view->currentIndex();
+    auto hovered = view->indexAt(option->rect.center());
+    if (!selected.isValid() || !hovered.isValid())
+    {
+        // This shouldn't happen as we're in a drag operation
+        assert(false && "Got bad indices");
+        return;
+    }
+
+    int y = option->rect.top();  // move up
+    if (hovered.row() >= selected.row())
+    {
+        y = option->rect.bottom();  // move down
+    }
+
+    painter->setPen({Qt::white, 2});
+    painter->drawLine(0, y, widget->width(), y);
+}
+
+}  // namespace chatterino

src/widgets/helper/TableStyles.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <QProxyStyle>
+
+class QTableView;
+
+namespace chatterino {
+
+/// @brief A custom style for drag operations of rows on tables
+///
+/// This style overwrites how `PE_IndicatorItemViewItemDrop`, the drop
+/// indicator of item-views, is drawn. It's intended to be used on QTableViews
+/// where entire rows are moved (not individual cells). The indicator is shown
+/// as a line at the position where the dragged item should be inserted. If no
+/// such position exists, a red border is drawn around the viewport.
+class TableRowDragStyle : public QProxyStyle
+{
+public:
+    /// Applies the style to @a view
+    static void applyTo(QTableView *view);
+
+    void drawPrimitive(QStyle::PrimitiveElement element,
+                       const QStyleOption *option, QPainter *painter,
+                       const QWidget *widget = nullptr) const override;
+
+private:
+    /// @param target The style to wrap. This is **not** the parent of this
+    ///               object. This object will become the parent of @a target.
+    TableRowDragStyle(QStyle *target);
+};
+
+}  // namespace chatterino