From 7687a6ef13359dbac63eaae0b40cb6875873ea71 Mon Sep 17 00:00:00 2001
From: John Scipione <jscipione@gmail.com>
Date: Mon, 29 Aug 2016 10:50:35 -0700
Subject: [PATCH] ListView: Don't change selection while dragging

This allows you to drag and drop list items more easily, but,
removes the ability to drag and drop color squares in Appearance from
one list item to another. Changing selected list items while dragging
was more of a helpful side-effect for Appearance but isless reasonable
default behavior.

Fixes #12990
Partially regression on #8618
---
 src/kits/interface/ListView.cpp | 48 ++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 22 deletions(-)

diff --git a/src/kits/interface/ListView.cpp b/src/kits/interface/ListView.cpp
index f26e2e7484..5cd11ac8a9 100644
--- a/src/kits/interface/ListView.cpp
+++ b/src/kits/interface/ListView.cpp
@@ -33,6 +33,7 @@ struct track_data {
 	int32		item_index;
 	bool		was_selected;
 	bool		try_drag;
+	bool		is_dragging;
 	bigtime_t	last_click_time;
 };
 
@@ -290,6 +291,11 @@ void
 BListView::MessageReceived(BMessage* message)
 {
 	switch (message->what) {
+		case B_MOUSE_WHEEL_CHANGED:
+			if (!fTrack->is_dragging)
+				BView::MessageReceived(message);
+			break;
+
 		case B_COUNT_PROPERTIES:
 		case B_EXECUTE_PROPERTY:
 		case B_GET_PROPERTY:
@@ -1453,6 +1459,7 @@ BListView::_InitObject(list_view_type type)
 	fTrack->item_index = -1;
 	fTrack->was_selected = false;
 	fTrack->try_drag = false;
+	fTrack->is_dragging = false;
 	fTrack->last_click_time = 0;
 
 	SetViewUIColor(B_LIST_BACKGROUND_COLOR);
@@ -1944,35 +1951,32 @@ void
 BListView::_DoneTracking(BPoint where)
 {
 	fTrack->try_drag = false;
+	fTrack->is_dragging = false;
 }
 
 
 void
 BListView::_Track(BPoint where, uint32)
 {
-	int32 index = IndexOf(where);
-	BListItem* item = ItemAt(index);
-
-	if (item != NULL && !item->IsSelected() && item->IsEnabled()) {
-		Select(index, fListType == B_MULTIPLE_SELECTION_LIST
-			&& (modifiers() & B_SHIFT_KEY) != 0);
-		ScrollToSelection();
-		fTrack->try_drag = false;
-			// don't try to initiate a drag once selection changes
+	if (fTrack->item_index > 0 && fTrack->try_drag) {
+		// initiate a drag if the mouse was moved far enough
+		BPoint offset = where - fTrack->drag_start;
+		float dragDistance = sqrtf(offset.x * offset.x + offset.y * offset.y);
+		if (dragDistance >= 5.0f) {
+			fTrack->try_drag = false;
+			fTrack->is_dragging = InitiateDrag(fTrack->drag_start,
+				fTrack->item_index, fTrack->was_selected);
+		}
 	}
 
-	if (fTrack->item_index < 0 || !fTrack->try_drag) {
-		// mouse was not clicked above any item
-		// or no mouse button pressed
-		return;
-	}
-
-	// Initiate a drag if the mouse was moved far enough
-	BPoint offset = where - fTrack->drag_start;
-	float dragDistance = sqrtf(offset.x * offset.x + offset.y * offset.y);
-	if (dragDistance >= 5.0f) {
-		fTrack->try_drag = false;
-		InitiateDrag(fTrack->drag_start, fTrack->item_index,
-			fTrack->was_selected);
+	if (!fTrack->is_dragging) {
+		// do selection only if a drag was not initiated
+		int32 index = IndexOf(where);
+		BListItem* item = ItemAt(index);
+		if (item != NULL && !item->IsSelected() && item->IsEnabled()) {
+			Select(index, fListType == B_MULTIPLE_SELECTION_LIST
+				&& (modifiers() & B_SHIFT_KEY) != 0);
+			ScrollToSelection();
+		}
 	}
 }