From b53326b38c85d3c64db444a978b06c65bd23fde7 Mon Sep 17 00:00:00 2001
From: Vanuan <vanuan@gmail.com>
Date: Wed, 29 Jul 2020 05:41:42 +0300
Subject: [PATCH] High DPI support: Scale Draft cursor to device pixel ratio

---
 src/Mod/Draft/draftguitools/gui_snapper.py | 53 +++++++++++++++++-----
 1 file changed, 42 insertions(+), 11 deletions(-)

diff --git a/src/Mod/Draft/draftguitools/gui_snapper.py b/src/Mod/Draft/draftguitools/gui_snapper.py
index 702e6ff19e..a480cda1f4 100644
--- a/src/Mod/Draft/draftguitools/gui_snapper.py
+++ b/src/Mod/Draft/draftguitools/gui_snapper.py
@@ -1111,6 +1111,44 @@ class Snapper:
             if self.dim2.Distance:
                 self.dim2.on()
 
+    def get_cursor_size(self):
+        # TODO Unfortunately, there's no way to get the cursor size in Qt
+        # Either provide platform-specific implementation or make it a user preference
+        # This should be in device-independent pixels
+        return 32
+
+    def device_pixel_ratio(self):
+        device_pixel_ratio = 1
+        mw = Gui.getMainWindow()
+        for w in mw.findChild(QtGui.QMdiArea).findChildren(QtGui.QWidget):
+            if w.metaObject().className() == "SIM::Coin3D::Quarter::QuarterWidget":
+                device_pixel_ratio = w.devicePixelRatio()
+        return device_pixel_ratio
+
+    def get_cursor_with_tail(self, base_icon_name, tail_icon_name=None):
+        base_icon = QtGui.QPixmap(base_icon_name)
+        device_pixel_ratio = self.device_pixel_ratio()
+        full_icon_size = self.get_cursor_size()
+        new_icon_width = full_icon_size * device_pixel_ratio
+        new_icon_height = 0.75 * full_icon_size * device_pixel_ratio
+        new_icon = QtGui.QPixmap(new_icon_width, new_icon_height)
+        new_icon.fill(QtCore.Qt.transparent)
+        qp = QtGui.QPainter()
+        qp.begin(new_icon)
+        base_icon = base_icon.scaledToWidth(0.5 * full_icon_size * device_pixel_ratio)
+        qp.drawPixmap(0, 0, base_icon)
+        if tail_icon_name:
+            tail_icon_width = 0.5 * full_icon_size * device_pixel_ratio
+            tail_icon_x = 0.5 * full_icon_size * device_pixel_ratio
+            tail_icon_y = 0.25 * full_icon_size * device_pixel_ratio
+            tail_pixmap = QtGui.QPixmap(tail_icon_name).scaledToWidth(tail_icon_width)
+            qp.drawPixmap(QtCore.QPoint(tail_icon_x, tail_icon_y), tail_pixmap)
+        qp.end()
+        cur_hot_x = 0.25 * full_icon_size * device_pixel_ratio
+        cur_hot_y = 0.25 * full_icon_size * device_pixel_ratio
+        new_icon.setDevicePixelRatio(device_pixel_ratio)
+        cur = QtGui.QCursor(new_icon, cur_hot_x, cur_hot_y)
+        return cur
 
     def setCursor(self, mode=None):
         """Set or reset the cursor to the given mode or resets."""
@@ -1128,24 +1166,17 @@ class Snapper:
             self.cursorMode = None
         else:
             if mode != self.cursorMode:
-                baseicon = QtGui.QPixmap(":/icons/Draft_Cursor.svg")
-                newicon = QtGui.QPixmap(32, 24)
-                newicon.fill(QtCore.Qt.transparent)
-                qp = QtGui.QPainter()
-                qp.begin(newicon)
-                qp.drawPixmap(0, 0, baseicon)
+                base_icon_name = ":/icons/Draft_Cursor.svg"
+                tail_icon_name = None
                 if not (mode == 'passive'):
-                    tp = QtGui.QPixmap(self.cursors[mode]).scaledToWidth(16)
-                    qp.drawPixmap(QtCore.QPoint(16, 8), tp)
-                qp.end()
-                cur = QtGui.QCursor(newicon, 8, 8)
+                    tail_icon_name = self.cursors[mode]
+                cur = self.get_cursor_with_tail(base_icon_name, tail_icon_name)
                 mw = Gui.getMainWindow()
                 for w in mw.findChild(QtGui.QMdiArea).findChildren(QtGui.QWidget):
                     if w.metaObject().className() == "SIM::Coin3D::Quarter::QuarterWidget":
                         w.setCursor(cur)
                 self.cursorMode = mode
 
-
     def restack(self):
         """Lower the grid tracker so it doesn't obscure other objects."""
         if self.grid: