[trojita] Patch: show default cursor if no modifiers are pressed during DnD

[Thomas Gahr]

This is a follow-up to merger-request #10
It shows the default cursor if no modifier is pressed, since in this case the 
user will have to pick what action to take upon dropEvent - i.e. during drag 
the action is undefined.
It seems a little strange to me, though. It changes the "override cursor" and I 
would've expected sth like this:

void MailBoxTreeView::dragMoveEvent(QDragMoveEvent *event)
{
    QTreeView::dragMoveEvent(event);

    if (!event->isAccepted()) {
        return;
    }
    if (event->keyboardModifiers() == Qt::ShiftModifier) {
        event->setDropAction(Qt::MoveAction);
    } else if (event->keyboardModifiers() == Qt::ControlModifier) {
        event->setDropAction(Qt::CopyAction);
    } else {
        // Qt's default is to show a cursor indicating copy-action but we don't 
want that
        // because the action is undefined until the user has chosen
        if(qApp->overrideCursor())
            qApp->overrideCursor()->setShape(Qt::ArrowCursor);
    }
}

to work. But instead this variant changes the cursor back ot ArrowCursor for 
good. Meaning: even if the user moves the mouse over a region that changes 
state - i.e. from "drop allowed here" to "no drop allowed here" - the cursor 
stays Qt::ArrowCursor. Expected (based on noob judgement) would be a change to 
Qt::ForbiddenCursor...
So the solution seems to be to check and change overrideCursor in every 
if-branch (even the !isAccepted one) and manually set the cursor shape if 
needed.
Oh if only someone who's probably read all QWidget sources was on this mailing 
list... *cough* ;)

Cheers,
Thomas

PS: if you are reading this then the lates changes in mail-composition did not 
break anything ;)
From 7683f6da50a9f38068067ff7cd006d056e1c10ba Mon Sep 17 00:00:00 2001
From: Thomas Gahr <thomas.g...@physik.uni-muenchen.de>
Date: Fri, 20 Jul 2012 23:43:41 +0200
Subject: [PATCH] DnD: show default cursor if no modifiers are pressed

---
 src/Gui/MailBoxTreeView.cpp |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/Gui/MailBoxTreeView.cpp b/src/Gui/MailBoxTreeView.cpp
index 5fec8e3..4170927 100644
--- a/src/Gui/MailBoxTreeView.cpp
+++ b/src/Gui/MailBoxTreeView.cpp
@@ -21,6 +21,7 @@
 
 #include "MailBoxTreeView.h"
 
+#include <QApplication>
 #include <QDragMoveEvent>
 #include <QDropEvent>
 #include <QMenu>
@@ -53,12 +54,25 @@ MailBoxTreeView::MailBoxTreeView()
 void MailBoxTreeView::dragMoveEvent(QDragMoveEvent *event)
 {
     QTreeView::dragMoveEvent(event);
-    if (!event->isAccepted())
+
+    if (!event->isAccepted()) {
+        if (!qApp->overrideCursor())
+            qApp->setOverrideCursor(Qt::ForbiddenCursor);
         return;
-    if (event->keyboardModifiers() == Qt::ShiftModifier)
+    }
+    if (event->keyboardModifiers() == Qt::ShiftModifier) {
         event->setDropAction(Qt::MoveAction);
-    else
+        if (!qApp->overrideCursor())
+            qApp->setOverrideCursor(Qt::DragMoveCursor);
+    } else if (event->keyboardModifiers() == Qt::ControlModifier) {
         event->setDropAction(Qt::CopyAction);
+        if (!qApp->overrideCursor())
+            qApp->setOverrideCursor(Qt::DragCopyCursor);
+    } else {
+        // Qt's default is to show a cursor indicating copy-action but we don't want that
+        // because the action is undefined until the user has chosen
+        qApp->restoreOverrideCursor();
+    }
 }
 
 /** @short Reimplemented to present the user with a menu to choose between copy or move.
-- 
1.7.8.6