The mouse is where?
The mouse is where?
- Subject: The mouse is where?
- From: email@hidden
- Date: Fri, 25 Jan 2008 14:51:09 -0800
Sorry for a longish post, but I'm bundling 3 related questions together.
Here's my scenario:
I'm working on an application that involves what you might think of as
"rollover highlighting" in a custom NSView subclass. The application
has nothing to do with web browsing, but (like a web browser) when the
mouse moves over certain objects, it wants to change the color of
those objects and change the cursor.
Here's my problem:
*Correctly* knowing where the mouse is at any time is ... sometimes
unknowable.
I thought I could use an approach based on NSTrackingArea, and the
various mouseXxx: messages.
This turned out to be a little trickier than I had anticipated, but I
seem to have most of the bases covered now, and am left with 3
specific problems/defects:
(A) Testing seems to indicate that *if the mouse button is pressed*
and I drag out of the view, I get a mouseExited: message when the
mouse actually goes outside the view (between two mouseDragged:
events), but if in the same drag I come back into the view, I do not
get a mouseEntered: event until the mouse button is released.
Clearly, this means that I can't rely on mouseEntered:/mouseExited: to
know whether the mouse is inside the view. If I have to write code to
determine the inside/outside status manually for some cases, then why
would I not just use that code all the time and forget about tracking
areas that are convenient only some of the time?
I can easily do that, but I wonder: Surely it's wrong that one of the
two messages works synchronously, and the other asynchronously, when
dragging?
(B) When I turn on mouseEntered:/mouseExited: tracking for my view's
NSTrackingArea, the mouse might obviously be inside the view or
outside the view. Surely there should be a more-or-less immediate
message (either mouseEntered: or mouseExited:) to tell me where the
frameworks thinks the mouse is?
If there's not, then I must calculate the current inside/outside state
of the mouse location as part of installing the tracking area, so that
I don't start off with a wrong assumption. That would be fine, except
that (as in part A) I wonder why I'm bothering with tracking areas at
all, AND that I'm not quite sure what test to use to match the
tracking area's test (NSView mouse:inRect:? NSPointInRect?), AND --
the $64 question -- where the mouse actually is. Which bring us to:
(C) How do I know where the mouse is, in the absence of (prior to
receiving) a mouse-related event?
-- There is not, afaik, any Cocoa frameworks function or method that
gets the mouse location other than from a NSEvent. (It may exist and I
just haven't found it.)
-- Getting the current mouse location using Carbon (if there is a
function for that) isn't the answer, because that's going to tell me
where the mouse is *right now in real time*, while the information I
need is where the mouse is *synchronized with the event stream*. (If
I'm about to receive a flood of mouseMoved: or mouseDragged: messages,
I want to know where the mouse is before them, not after. Unreceived
messages represent the future, I'm still in the present.)
Anyone have any thoughts on this?
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