| Re: Lack of KeyMods parameter in the ::MouseUp function call -> Feature request [message #92535 is a reply to message #92531] |
Wed, 06 January 2016 08:31  |
chris_torrence@NOSPAM
Messages: 528
Registered: March 2007
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Senior Member |
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On Tuesday, January 5, 2016 at 2:20:35 PM UTC-7, Helder wrote:
> On Tuesday, January 5, 2016 at 9:16:07 PM UTC, Chris Torrence wrote:
>> On Wednesday, December 30, 2015 at 4:25:08 PM UTC-7, Helder wrote:
>>> Hi,
>>> I'm intensively using the FG event handler class. In doing so, I've come to a problem where I would like the ::MouseUp function to include information about the current keyMods. Currently, the functions ::MouseDown, ::MouseMotion and ::MouseWheel have it...
>>>
>>> Let me explain why I think this is useful.
>>> I have a polygon on an image. I would like to add a point to the polygon. To distinguish from the translation case, I use the "alt" key to identify modifications (or alt-erations) to the polygon. Therefore, pressing the alt-key and the left mouse button results in an added point. Since I'm not always good with my hand, I would like to be able to:
>>>
>>> 1) press down alt-key
>>> 2) press down left mouse button (a point is added)
>>> 3) move mouse (and see the added point moving with the mouse)
>>> 4) release the left mouse button
>>> 5) release the alt-key
>>>
>>> Besides being useful, it is also "cool".
>>>
>>> However, if I would like to "cancel" the add point operation if the alt-key is released *before* the release of the left mouse button. In other words, the following sequence should delete the point after step 4):
>>>
>>> 1) press down alt-key
>>> 2) press down left mouse button (a point is added)
>>> 3) move mouse (and see the added point moving with the mouse)
>>> 4) release the alt-key (the previously added point is deleted)
>>> 5) release the left mouse button
>>>
>>> Since I cannot detect if alt is pressed when releasing the button, I cannot do this.
>>>
>>> Can this please be added? I don't think that it is that much of an effort...
>>>
>>> Cheers,
>>> Helder
>>
>> Hi Helder,
>>
>> It probably isn't too hard to add, but the problem is backwards compatibility. If we just add another argument then it will break existing event handlers. We can't add a keyword for the same reason. There might be a way to check the number of accepted arguments and make the appropriate call, but then the documentation becomes ugly.
>>
>> So, I'll add it to the list of possible enhancements, but I wouldn't count on it making the cut.
>>
>> But keep making suggestions!
>>
>> -Chris
>
> Hi Chris,
> thanks for the answer. Just out of curiosity, what would be the problem of using a keyword? I thought that that would be the way to go to avoid backwards compatibility?
>
> Cheers,
> Helder
Hi Helder,
Well, if your routine doesn't currently accept keywords, and it's called with a keyword, then IDL will throw an error...
Cheers,
Chris
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