i agree, but the solution is worse. having a checkbox affect choices made previously in the form is a surefire way to confuse users.
the larger problem here is the select box. not only does it only have two options (generally best avoid select boxes of 3 or fewer options), but it obscures the drag option which makes the inactive checkbox ambiguous. i'd recommend considering an alternate input type.
Yep, agreed, the select box is problematic here. The relationship between option 2 and the disabled checkbox is obscured by the select box. If Option 1 and 2 were radio buttons and the checkbox was positioned underneath option 2, it's status (enabled/disabled) would be obviously tied to Option 2. So when Option 2 is selected, the checkbox is enabled.
I don't like the idea of hiding the dependent options because it makes finding it difficult. If my task is, in this case, "I want to see the window near my mouse when I start dragging," it's hard for me to complete that when it's hidden in a select box.
love the write up! Even when I'm not a fan of the end result, I love hearing the thoughts and decision process from other designers.
That being said, I would suggest one tweak to this solution:
Show options based on availability.
If the "show window near mouse pointer" feature isn't available under the "mouse pointer is at edge of screen", then simply don't show that option until the "drag starts" option is selected.
In certain instances, I feel inactive checkboxes (or radio buttons) can in fact be useful...
At the moment I am working on a project where users can purchase tickets to an event.
On the 'Select date and time' screen we've decided to show the option where the time/s that an event might not be available i.e. '8.30pm session - sold out'
We feel it's important to show this option as it alerts the user that the 8.30pm session might in fact be available on another date.
A slightly different scenario than the example given by the OP but nevertheless an example where displaying unavailable option could in fact be helpful to the user.
I was about to say pretty much the same thing. When the user expects a pre-defined set of options then a disabled item can be helpful to show that ordinarily that option would be available but a specific condition prevents it being selected.
My example is that we have an web app that allows a user to apply to live in a number of different accommodation sites. There's a good chance that they know what sites exist - but some of them will be unavailable because they are ineligible. In that case we show a disabled checkbox with a tooltip to explain why it's unavailable.
I think the better thing to do here would be giving some visual cue as to why the checkbox is disabled, or hide the checkbox entirely until it's a valid option.
I agree with Jim that changing a form value, specifically one in a dropdown that the user might not notice will lead to confusion and likely frustration.
I did just purchase your app Yoink though, and it really is great. Finding little usability apps like that make my day.