[ui] Utils: add SelectionBox and DelegateSelectionBox

- SelectionBox: generic Selection box component.
- DelegateSelectionBox: specialized SelectionBox to select model delegates
  from an instantiator (Repeater, ListView).

Also Introduce a Geom2D helper class to provide missing features for
intersection testing in QML.

meshroom/ui/components/__init__.py

@@ -1,11 +1,12 @@
 
 def registerTypes():
-    from PySide6.QtQml import qmlRegisterType
+    from PySide6.QtQml import qmlRegisterType, qmlRegisterSingletonType
     from meshroom.ui.components.clipboard import ClipboardHelper
     from meshroom.ui.components.edge import EdgeMouseArea
     from meshroom.ui.components.filepath import FilepathHelper
     from meshroom.ui.components.scene3D import Scene3DHelper, TrackballController, Transformations3DHelper
     from meshroom.ui.components.csvData import CsvData
+    from meshroom.ui.components.geom2D import Geom2D
 
     qmlRegisterType(EdgeMouseArea, "GraphEditor", 1, 0, "EdgeMouseArea")
     qmlRegisterType(ClipboardHelper, "Meshroom.Helpers", 1, 0, "ClipboardHelper")  # TODO: uncreatable
@@ -14,3 +15,5 @@ def registerTypes():
     qmlRegisterType(Transformations3DHelper, "Meshroom.Helpers", 1, 0, "Transformations3DHelper")  # TODO: uncreatable
     qmlRegisterType(TrackballController, "Meshroom.Helpers", 1, 0, "TrackballController")
     qmlRegisterType(CsvData, "DataObjects", 1, 0, "CsvData")
+
+    qmlRegisterSingletonType(Geom2D, "Meshroom.Helpers", 1, 0, "Geom2D")

meshroom/ui/components/geom2D.py

@@ -0,0 +1,8 @@
+from PySide6.QtCore import QObject, Slot, QRectF
+
+
+class Geom2D(QObject):
+    @Slot(QRectF, QRectF, result=bool)
+    def rectRectIntersect(self, rect1: QRectF, rect2: QRectF) -> bool:
+        """Check if two rectangles intersect."""
+        return rect1.intersects(rect2)

meshroom/ui/qml/Controls/DelegateSelectionBox.qml

@@ -0,0 +1,32 @@
+import QtQuick
+import Meshroom.Helpers
+
+/*
+A SelectionBox that can be used to select delegates in a model instantiator (Repeater, ListView...).
+Interesection test is done in the coordinate system of the container Item, using delegate's bounding boxes.
+The list of selected indices is emitted when the selection ends.
+*/
+
+SelectionBox {
+    id: root
+
+    // The Item instantiating the delegates.
+    property Item modelInstantiator
+    // The Item containing the delegates (used for coordinate mapping).
+    property Item container
+    // Emitted when the selection has ended, with the list of selected indices and modifiers.
+    signal delegateSelectionEnded(list<int> indices, int modifiers)
+
+    onSelectionEnded: function(selectionRect, modifiers) {
+        let selectedIndices = [];
+        const mappedSelectionRect = mapToItem(container, selectionRect);
+        for (var i = 0; i < modelInstantiator.count; ++i) {
+            const delegate = modelInstantiator.itemAt(i);
+            const delegateRect = Qt.rect(delegate.x, delegate.y, delegate.width, delegate.height);
+            if (Geom2D.rectRectIntersect(mappedSelectionRect, delegateRect)) {
+                selectedIndices.push(i);
+            }
+        }
+        delegateSelectionEnded(selectedIndices, modifiers);
+    }
+}

meshroom/ui/qml/Controls/SelectionBox.qml

@@ -0,0 +1,60 @@
+import QtQuick
+
+/*
+Simple selection box that can be used by a MouseArea.
+
+Usage:
+1. Create a MouseArea and a SelectionBox.
+2. Bind the SelectionBox to the MouseArea by setting the `mouseArea` property.
+3. Call startSelection() with coordinates when the selection starts.
+4. Call endSelection() when the selection ends.
+5. Listen to the selectionEnded signal to get the selection rectangle.
+*/
+
+Item {
+    id: root
+
+    property MouseArea mouseArea
+    property alias color: selectionBox.color
+    property alias border: selectionBox.border
+
+    readonly property bool active: mouseArea.drag.target == dragTarget
+
+    signal selectionEnded(rect selectionRect, int modifiers)
+
+    function startSelection(mouse) {
+        dragTarget.startPos.x = dragTarget.x = mouse.x;
+        dragTarget.startPos.y = dragTarget.y = mouse.y;
+        dragTarget.modifiers = mouse.modifiers;
+        mouseArea.drag.target = dragTarget;
+    }
+
+    function endSelection() {
+        if (!active) {
+            return;
+        }
+        mouseArea.drag.target = null;
+        const rect = Qt.rect(selectionBox.x, selectionBox.y, selectionBox.width, selectionBox.height)
+        selectionEnded(rect, dragTarget.modifiers);
+    }
+
+    visible: active
+
+    Rectangle {
+        id: selectionBox
+        color: "#109b9b9b"
+        border.width: 1
+        border.color: "#b4b4b4"
+
+        x: Math.min(dragTarget.startPos.x, dragTarget.x)
+        y: Math.min(dragTarget.startPos.y, dragTarget.y)
+        width: Math.abs(dragTarget.x - dragTarget.startPos.x)
+        height: Math.abs(dragTarget.y - dragTarget.startPos.y)
+    }
+
+    Item {
+        id: dragTarget
+        property point startPos
+        property var modifiers
+    }
+}

meshroom/ui/qml/Controls/qmldir

@@ -17,3 +17,5 @@ IntSelector 1.0 IntSelector.qml
 MScrollBar 1.0 MScrollBar.qml
 MSplitView 1.0 MSplitView.qml
 DirectionalLightPane 1.0 DirectionalLightPane.qml
+SelectionBox 1.0 SelectionBox.qml
+DelegateSelectionBox 1.0 DelegateSelectionBox.qml