From 424669eb590b2152982ece816a67286ff6a2dfb7 Mon Sep 17 00:00:00 2001
From: Taylor Bockman <tbockman@xchg.sh>
Date: Thu, 22 Aug 2019 19:44:02 -0700
Subject: [PATCH] Implement mouse drag properly

---
 clusterview/mode_handlers.py | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/clusterview/mode_handlers.py b/clusterview/mode_handlers.py
index 1b52720..3a98b28 100644
--- a/clusterview/mode_handlers.py
+++ b/clusterview/mode_handlers.py
@@ -48,6 +48,9 @@ __left_click_flag = __ClickFlag.NONE
 # Variable to track the mouse state during selection movement
 __last_mouse_pos = None
 
+# Used to implement mouse dragging when clicked
+__left_click_down = False
+
 
 def refresh_point_list(ctx):
     """
@@ -173,6 +176,7 @@ def __handle_move_points(ctx, event):
     """
 
     global __left_click_flag
+    global __left_mouse_down
     global __last_mouse_pos
 
     set_drawing_event(event)
@@ -182,28 +186,40 @@ def __handle_move_points(ctx, event):
     # Necessary to capture keyboard events
     ctx.opengl_widget.setFocusPolicy(Qt.StrongFocus)
 
+    # If we release the mouse, we want to quickly alert drag mode.
+    if (event.button() == Qt.LeftButton and
+        event.type() == QEvent.MouseButtonRelease):
+
+        __left_mouse_down = False
+
     # This if statement block is used to set the bounding box for
     # drawing and call the selection procedure.
     if (event.button() == Qt.LeftButton and
         event.type() == QEvent.MouseButtonPress):
 
+        __left_mouse_down = True
+
         if __left_click_flag is __ClickFlag.NONE:
             __left_click_flag = __ClickFlag.SELECTION_BOX
             set_move_bb_top_left(event.x(), event.y())
 
-        elif __left_click_flag is __ClickFlag.SELECTION_BOX:
+
+        elif (__left_click_flag is __ClickFlag.SELECTION_BOX
+              and __left_mouse_down):
             # We are now in the click-and-hold to signal move
             # tracking and translation
             __left_click_flag = __ClickFlag.SELECTION_MOVE
             __last_mouse_pos = (event.x(), event.y())
 
-    elif (__left_click_flag is __ClickFlag.SELECTION_BOX
+    # Post-selection handlers
+    if (__left_click_flag is __ClickFlag.SELECTION_BOX
           and event.type() == QEvent.MouseMove):
 
         set_move_bb_bottom_right(event.x(), event.y())
-
+        
     elif (__left_click_flag is __ClickFlag.SELECTION_MOVE
           and __last_mouse_pos is not None
+          and __left_mouse_down
           and event.type() == QEvent.MouseMove):
 
         dx = abs(__last_mouse_pos[0] - event.x())