From 096664c1ba8c28873aa71d75d7953fc92472839c Mon Sep 17 00:00:00 2001
From: Simon Renblad <srenblad@m-labs.hk>
Date: Wed, 22 Nov 2023 17:31:30 +0800
Subject: [PATCH] dndwidgets: add drag drop helper widgets

---
 artiq/gui/dndwidgets.py | 98 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 artiq/gui/dndwidgets.py

diff --git a/artiq/gui/dndwidgets.py b/artiq/gui/dndwidgets.py
new file mode 100644
index 000000000..b93f4d330
--- /dev/null
+++ b/artiq/gui/dndwidgets.py
@@ -0,0 +1,98 @@
+from PyQt5 import QtCore, QtWidgets
+
+
+class VDragDropSplitter(QtWidgets.QSplitter):
+    def __init__(self, parent):
+        QtWidgets.QSplitter.__init__(self, parent=parent)
+        self.setAcceptDrops(True)
+        self.setContentsMargins(0, 0, 0, 0)
+        self.setOrientation(QtCore.Qt.Vertical)
+        self.setChildrenCollapsible(False)
+
+    def resetSizes(self):
+        self.setSizes(self.count() * [1])
+
+    def dragEnterEvent(self, e):
+        e.accept()
+
+    def dragLeaveEvent(self, e):
+        self.setRubberBand(-1)
+        e.accept()
+
+    def dragMoveEvent(self, e):
+        pos = e.pos()
+        src = e.source()
+        src_i = self.indexOf(src)
+        self.setRubberBand(self.height())
+        # case 0: smaller than source widget
+        if pos.y() < src.y():
+            for n in range(src_i):
+                w = self.widget(n)
+                if pos.y() < w.y() + w.size().height():
+                    self.setRubberBand(w.y())
+                    break
+        # case 2: greater than source widget
+        elif pos.y() > src.y() + src.size().height():
+            for n in range(src_i + 1, self.count()):
+                w = self.widget(n)
+                if pos.y() < w.y():
+                    self.setRubberBand(w.y())
+                    break
+        else:
+            self.setRubberBand(-1)
+        e.accept()
+
+    def dropEvent(self, e):
+        self.setRubberBand(-1)
+        pos = e.pos()
+        src = e.source()
+        src_i = self.indexOf(src)
+        for n in range(self.count()):
+            w = self.widget(n)
+            if pos.y() < w.y() + w.size().height():
+                self.insertWidget(n, src)
+                break
+        e.accept()
+
+
+# Scroll area with auto-scroll on vertical drag
+class VDragScrollArea(QtWidgets.QScrollArea):
+    def __init__(self, parent):
+        QtWidgets.QScrollArea.__init__(self, parent)
+        self.installEventFilter(self)
+        self._margin = 40
+        self._timer = QtCore.QTimer(self)
+        self._timer.setInterval(20)
+        self._timer.timeout.connect(self._on_auto_scroll)
+        self._direction = 0
+        self._speed = 10
+
+    def setAutoScrollMargin(self, margin):
+        self._margin = margin
+
+    def setAutoScrollSpeed(self, speed):
+        self._speed = speed
+
+    def eventFilter(self, obj, e):
+        if e.type() == QtCore.QEvent.DragMove:
+            val = self.verticalScrollBar().value()
+            height = self.viewport().height()
+            y = e.pos().y()
+            self._direction = 0
+            if y < val + self._margin:
+                self._direction = -1
+            elif y > height + val - self._margin:
+                self._direction = 1
+            if not self._timer.isActive():
+                self._timer.start()
+        elif e.type() in (QtCore.QEvent.Drop, QtCore.QEvent.DragLeave):
+            self._timer.stop()
+        return False
+
+    def _on_auto_scroll(self):
+        val = self.verticalScrollBar().value()
+        min_ = self.verticalScrollBar().minimum()
+        max_ = self.verticalScrollBar().maximum()
+        dy = self._direction * self._speed
+        new_val = min(max_, max(min_, val + dy))
+        self.verticalScrollBar().setValue(new_val)