Bug 4070 - Intellisense popup - focus first item in list so I can press TAB and use it
Summary: Intellisense popup - focus first item in list so I can press TAB and use it
Alias: None
Product: Xamarin Studio
Classification: Desktop
Component: C# Binding ()
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: ---
Assignee: Mike Krüger
Depends on:
Reported: 2012-03-23 09:41 UTC by Neal
Modified: 2012-03-26 17:33 UTC (History)
1 user (show)

Is this bug a regression?: ---
Last known good build:

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Description Neal 2012-03-23 09:41:56 UTC

Take for example I'm creating a new instance of a class that has an ENUM as a parameter.  When I press the comma key MD knows it's an enum and shows Intellisense and puts that enum definition at the top of the list.  However, the top item is NOT selected so I can't just press TAB and then period to select the ENUM.  Instead I have to do some mouse work or keyboard work to select that top item.  It really makes coding a little less efficient.  If you could select the enum item in the intellisense list it would really help us accept the default selection and then just choose the enum from the list of enum items.

Thank you.
Comment 1 Mikayla Hutchinson [MSFT] 2012-03-23 13:56:30 UTC
If the list doesn't select something by default, that means it's not able to provide a list of all valid values for that position. In such cases it goes into "suggestion mode" - for an explanation and some tips, http://mjhutchinson.com/journal/2011/02/monodevelop_tips_suggestion_mode for info.

In this particular case, it's because the completion list has been triggered by the fact that you're in the position of an argument that takes an enum value. It's particularly eager - it doesn't even wait for you to type a letter. It can take a good guess, but it can't know everything you might want to type for sure.

For example, what if you want to type a left parent for a  (Cast) of some other value to that enum types? I suppose we could add that cast into the list too, so we could fix that case. But others aren't so easy. What about whitespace for alignment? Space commits in completion mode, so this would be annoying. In fact, this makes me wonder whether we should stop Enter from committing in suggestion mode, and limit it to Tab.

The biggest issue is other overloads of the method. MD can't know for sure which one you're using until you actually provided the arguments. Sure, if they take other enums, we could put those enums in the list too. But what if they take lambdas or numbers?
Comment 2 Neal 2012-03-23 14:22:37 UTC
I think the problem would be solved if the top item in the popup list (intellisense) were selected.  In all cases of an enum param it would choose the right one that I've seen.  It's like a focus problem, not anything else.  If only the list were focused and top item selected the issue would be solved.
Comment 3 Mikayla Hutchinson [MSFT] 2012-03-23 15:47:03 UTC
Perhaps my explanation wasn't clear. The use of completion mode is a tradeoff between saving keystrokes and interfering with normal typing.

Completion mode allows accepting the completion values by typing space or punctuation, which is also inserted. This saves keystrokes. In suggestion mode, you must explicitly accept the value using the tab or enter key, or by using the up/down arrow keys to select an item before typing space or punctuation.

The problem with completion mode is that it only works perfectly if the list contains all the values that the user might want to type. If not, then when you type some other value out in full then press space, the completion list will overwrite what you typed with something in its list. This is *extremely* annoying when it happens. The only workaround is to watch out for it and press "escape" to dismiss the list when this happens. For fast typists, this pretty breaks the usefulness of code completion.

Obviously it's impossible for completion to know all valid values everywhere. For example, when typing a class name or a number, it doesn't know any (non-infinite set of) valid values, so it doesn't trigger at all.

There are some places where it knows *some values*, but not *all*. It's useful to it to be able to provide some assistance in these cases.  Our solution - which is the same as Visual Studio - is for the completion list to be in suggestion mode in such places, so it will provide assistance, but not interfere with typing the other possible values.

In summary: the completion engine has a policy to never "overwrite" valid typing, as long as the code up to the caret position is valid. Fixing this bug would violate that in many cases.
Comment 4 Mikayla Hutchinson [MSFT] 2012-03-23 16:03:33 UTC
Actually, having re-read your original report, I'm confused. You say that you can't press tab then period to complete the top item - but this works perfectly for me. This is exactly what you have to do in suggestion mode. In completion mode (if the item had a solid selection) you would only have to press period.

You can see it here: I press tab immediate after I press type "(".

Now, there is one slight oddity - it should be in completion mode after I type the ".", since does know the set of enum members. Is this what you meant?
Comment 5 Neal 2012-03-23 16:16:29 UTC
In MD prefs I have ALL checkboxes checked in Text Editor / General.

When I am creating a new instance such as:

var myButton = new CustomButton(new RectangleF(0,0,0,0), <myenumhere>

When I press the comma after the RectangleF I get an Intellisense popup, however, the top item in the list, which is the enum and is correct, is NOT selected so that I can tab and press period.

Maybe next week, if needed, I can do a quick camtasia for you to see it.
Comment 6 Neal 2012-03-26 09:50:25 UTC
In coding this weekend I see that if I just press tab when intellisense shows the list it does accept the top value.  What is confusing me is that it's not "selected" (blue highlight) in the list as if you were to arrow up or down.  It's "outlined" so the position in the list is correct, it's just not selecting the top item visually, i.e. highlighted in blue background white text.
Comment 7 Mikayla Hutchinson [MSFT] 2012-03-26 14:22:24 UTC
Please take a look at the page I linked on suggestion mode. The outline indicates it's in suggestion mode, so you know it won't be committed by space/punctuation. This is exactly the same as Visual Studio.
Comment 8 Mikayla Hutchinson [MSFT] 2012-03-26 14:27:26 UTC
Ah, I appear to have omitted the link from comment 4, sorry about that: http://www.screencast.com/t/zysnC6MSjiif
Comment 9 Neal 2012-03-26 15:21:42 UTC
Okay, if you feel this is by design that's fine, just wanted to bring it to your attention as I didn't think I could tab with nothing selected in the intellisense list.

Comment 10 Mikayla Hutchinson [MSFT] 2012-03-26 17:28:04 UTC
If you have suggestions for making it easier to understand that would be wonderful. I'm not trying to discount your input, just explaining the reasons that it behaves the way it does.

I did notice a bug when I was trying to repro the issue, as you can see in my screencast - after typing the ".", it should be in suggestion mode. I filed a bug for that - bug 4100.
Comment 11 Neal 2012-03-26 17:33:09 UTC
You're just smarter than me on this issue as I'm not aware of the "suggestion" mode vs. just having an item selected (highlighted in blue) in the list.  I would assume the top item would be "focused" i.e. not just outlined but actually selected so it's obvious to me that I could press TAB and it's going to use the highlighted item.  I'll have to pay attention to VS.NET in the future to notice the behavior of the intellisense popup list in the future.  If after that point I see a problem I'll certainly bring it to your attention.

Thanks Michael.