Depth
In uiZ, when you have multiple objects, there is always an order in which objects overlay each other. For example, you may have two windows overlapping each other. One window is placed in front of the other window. In uiZ, objects can have depth. However, all depth is hierarchical. This means that depth behaves more like a tree in stead of a single list. A button which is inside the window in the background will never be able to draw in front of a window in the foreground. Consider this tree for example:
In the image you can see that by using a tree, any objects may never overlap another object if the current object's parent is not also overlapping the other object's parent. (unless the two objects have the same parent of course).
If the explanation is a bit confusing to you, just remember that when changing the depth of objects, you only have to worry about objects within the same window, frame or other object.
Now, how does uiZ determine which objects should be drawn over another object? For that there is a depth variable. This works just like the old depth system in GameMaker Studio 1.x. Each object has it's own depth variable. Objects with a lower depth value are placed at the front, while objects with a higher depth value are placed at the back.
To change the depth, you can use these functions:
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uiz_depth_set(instanceid, depth):
- instanceid: The instanceid of the uiZ object that you want to modify
- depth: The depth value of this object. With lower values the object is placed further to the front, while higher values make it go further to the back.
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depth = uiz_depth_get(instanceid):
- depth: The depth value of this object. With lower values the object is placed further to the front, while higher values make it go further to the back.
- instanceid: The instanceid of the uiZ object that you want to read the depth value from.
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uiz_depth_foreground(instanceid): Makes the depth of the given object the lowest among it's siblings (other objects in the same parent). Sets the depth of the given instance to the depth of the previous most-front object minus one.
- instanceid: The instanceid of the uiZ object that you want to read the depth value from.
Depth sorting in uiZ is really quick, because it's not recalculated every step but only when you call any of the depth functions. Also, only objects in the same parent have to be reconsidered when changing the depth of an object, releasing some burden on the internal sorting algorithm.