Add shortcuts to swap the contents of brush slots

To allow for a sort of toggling behavior using a single shortcut.

ChangeLog

@@ -37,6 +37,7 @@ Unreleased Version 2.2.0-pre
  * Fix: Make reloading the last brush preset slot-specific, since it's nonsense to clobber your current slot with the last preset you set in another one.
  * Feature: Allow increasing and decreasing key frame exposure. Thanks Tabuley for suggesting.
  * Fix: Properly update the view when the canvas size changes, rather than leaving stale areas outside of the canvas.
+ * Feature: Add shortcuts to swap the contents of brush slots to allow for a kind of toggling behavior using a single shortcut. Thanks xxxx for suggesting.
 
 2023-07-31 Version 2.2.0-beta.6
  * Fix: Don't forget account password when entering a wrong session password.

src/desktop/mainwindow.cpp

@@ -3773,6 +3773,18 @@ void MainWindow::setupActions()
 		CustomShortcutModel::registerCustomizableAction(q->objectName(), q->text(), q->shortcut());
 		m_brushSlots->addAction(q);
 		addAction(q);
+		// Swapping with the eraser slot doesn't make sense.
+		if(i != 5) {
+			QAction *s = new QAction{tr("Swap With Brush Slot #%1").arg(i +1 ), this};
+			s->setAutoRepeat(false);
+			s->setObjectName(QStringLiteral("swapslot%1").arg(i));
+			CustomShortcutModel::registerCustomizableAction(
+				s->objectName(), s->text(), QKeySequence());
+			addAction(s);
+			connect(s, &QAction::triggered, this, [this, i] {
+				m_dockToolSettings->brushSettings()->swapWithSlot(i);
+			});
+		}
 	}
 	connect(m_brushSlots, &QActionGroup::triggered, this, [this](QAction *a) {
 		m_dockToolSettings->setToolSlot(a->property("toolslotidx").toInt());

src/desktop/toolwidgets/brushsettings.cpp

@@ -418,6 +418,17 @@ void BrushSettings::selectEraserSlot(bool eraser)
 	}
 }
 
+void BrushSettings::swapWithSlot(int i)
+{
+	Q_ASSERT(i >= 0);
+	Q_ASSERT(i < ERASER_SLOT);
+	if(i != d->current && !isCurrentEraserSlot()) {
+		std::swap(d->brushSlots[d->current], d->brushSlots[i]);
+		std::swap(d->lastPresets[d->current], d->lastPresets[i]);
+		updateUi();
+	}
+}
+
 void BrushSettings::setGlobalSmoothing(int smoothing)
 {
 	QSignalBlocker blocker{d->ui.smoothingBox};

src/desktop/toolwidgets/brushsettings.h

@@ -59,6 +59,7 @@ class BrushSettings final : public ToolSettings {
 public slots:
 	void selectBrushSlot(int i);
 	void selectEraserSlot(bool eraser);
+	void swapWithSlot(int i);
 	void setGlobalSmoothing(int smoothing);
 	void toggleEraserMode() override;
 	void toggleRecolorMode() override;