Cocoa main loop updating
Many events, such as mouse clicks or movement have as parameters additional information like the current position of the mouse.These percent substitutions let you capture them so they can be used in your script.Of course, all these parameters are specific to grid; other geometry managers would use different ones. because the toplevel window was resized), the natural size of a slave changes (e.g. In our example, we had a content frame inside the toplevel window, and then a number of other controls in the content frame.The geometry manager takes all the information about the slaves, as well as the information about how large the master is, and uses its internal algorithms to determine the area each slave will be allocated (if any! because we've changed the text in a label), or any of the geometry manager parameters change (e.g. We therefore had a geometry manager working on two different masters.While each master can have only one geometry manager (e.g.grid), it's entirely possible for different masters to have different geometry managers; while grid is generally used, others may make sense for a particular layout used in one part of your user interface.Beyond the low-level operating system events like mouse clicks and window resizes, many widgets generate higher level events called virtual event anytime the selection changes, regardless of whether that was because the user clicked on an item, moved to it with the arrow keys, or whatever.
Buy now for your Kindle Kindle apps are also available for most smartphones, tablets, and desktops.You can think of a geometry manager as taking control of the master widget, and deciding what will be displayed within.The geometry manager will ask each slave widget for its natural size, or how large it would ideally like to be displayed.While it can be as complex as you want to make it, most times though you'll just want your callback to call some other procedure.For events that don't have a command callback associated with them, you can use Tk's to capture any event, and then (like with callbacks) execute an arbitrary piece of code.