> On Jul 20, 2015, at 1:30 PM, Thomas Wetmore <t...@verizon.net> wrote: > > I really try to figure this stuff out. No kidding. I am trying this simple > experiment: > > I define an NSView that has nothing more than a resize handle, defined as a > rectangular NSBezierPath in its lower right corner. There are no subviews and > no superviews involved here. I resize the NSView by implementing a mouse > event loop in the NSView code. I also drag the NSView within its window > within the same mouse event loop if the mouse down was not in the resize > Bezier path. > > In the view’s initializer I create two NSLayoutConstraints, to set a minimum > height and minimum width on the NSView, and add them to the view. I also set > the NSView’s translatesAutoresizingMaskIntoConstraints property to false, so > that these are the only two constraints defined on the the view. > > This is all done programmatically. There is no NIB for this NSView. For > reference here is the code that creates and adds the constraints, found > inside the view’s initializer: > > widthConstraint = NSLayoutConstraint(item: self, attribute: > NSLayoutAttribute.Width, > relatedBy: NSLayoutRelation.GreaterThanOrEqual, toItem: nil, > attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant: > 100.0) > heightConstraint = NSLayoutConstraint(item: self, attribute: > NSLayoutAttribute.Height, > relatedBy: NSLayoutRelation.GreaterThanOrEqual, toItem: nil, > attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant: > 100.0) > addConstraint(widthConstraint) > addConstraint(heightConstraint)
Nit: instead of using addConstraint(), you can use .active = true on the constraints themselves and the constraints will find the most appropriate view to add themselves to. > > [Peeve, before I move on. I have to include the names of the two enum types > (NSLayoutAttribute and NSLayoutRelation) in this code in order for the > compiler to be happy — why? — I thought the compiler knows what the parameter > types are so only the enum constants should be needed. End peeve.] > > When I instantiate one of these views and place it in an NSWindow, I can drag > it around and I can resize it, as expected. Notably, however, I can resize it > down to zero size (and even smaller!), even though the two constraints exist. > I kind of expected the program to crash when the constraints were violated, > but things keep on running. I can drag and resize the view at will with no > repercussions. Since you’ve only given height & width constraints, you have an ambiguous position for this view and no actual relation to the superview. Likely when you get into this case the view is still respecting the size you gave it, but since there is no relation to its parent, the parent will simply size smaller and clip it. If you add constraints to match this view to its superview’s top/leading/bottom/trailing you will likely see the behavior you expect. > > I would really like to be able to do resizing using a mouse event loop, but > have the layout constraints somehow involved. Reading through references for > NSView I don’t see how to do this. I guess I am looking for a way from within > the event loop to be able to check whether a proposed new frame rectangle for > the view obeys the view’s size constraints. > > Anyone have advice of what I should be reading to figure out what to do? All > the examples I can find seem so simple. Whenever I get into one these, what > seems to me to be a simple, real world situations (how unusual is a resizable > view with constraints, after all?), I seem to get lost reading a plethora of > confusing documents. It’s either me or the documentation, or maybe a lack of > documentation. I can easily believe it’s me. But that doesn’t help me get > this experiment to work. > > Clearly what I need is a better mental model of how the auto constraint > system operates at run time. Maybe someone can point me in the direction of a > good tutorial. > > Thanks, > > Tom Wetmore > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/david.duncan%40apple.com > > This email sent to david.dun...@apple.com -- David Duncan _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
