Layouts

Layouts are technically View subclasses (well, actually, there’s a Layout class in the middle, but it’s not intended to be directly instantiated), but that’s a temporary hack and they are not generated in Objective-C code. All they do is that they make the task of calling layout-related methods easier. See Layout for more information.

class HLayout(subviews[, filler, height, margin, align])

Parameters:

• subviews – List of View
• filler – View instance
• height – Numeric
• margin – Numeric
• align – Numeric

Creates a layout representing a horizontal row managing subviews. The first element is the leftmost one and the rest is going to be placed sequetially to the right. The list of subviews can contain at most one None element. That element represents an empty space filler. Views before the None element will be aligned to the left, and views after the None element will be aligned right. If there are no None element, everything is aligned to the left.

If you specify a filler that element will be the one taking up all free space in your layout. That filler must, of course, be present in your subviews and you cannot specify one while at the same time having a None element in your subviews. In other words, at most one “thing” can eat up free space in your layout at once, either empty space or a filler.

If you don’t specify a height, the height of the highest subview will be used. In a layout, all subviews that can have their height adjusted will have their height set to the layout’s height. Instead of automatically determining the layout’s height from subviews, you can specify a height with the height argument.

You can specify a margin argument if you want to force a certain margin between your layout elements. If you don’t, standard margins will be applied.

When placing views with a height that is smaller than the layout’s height, we have to decide how to vertically align the view. Will it be sent above, below, in the middle? You decide. If you don’t middle is the default alignment. Valid values are Pack.Above, Pack.Middle, Pack.Below.

setAnchor(side)

Parameters:side – One of the Side constants. Only vertical ones.

Because the layout is not generated in Objective-C code, it doesn’t make sense to set it’s autoresizing mask (that’s what View.setAnchor() does). This method doesn’t do that. What it does is that it sets the anchor of all its subviews at once, the left subviews being anchored left, and the right subviews being anchored right.

class VLayout(subviews[, filler, width, margin, align])

Parameters:

• subviews – List of View
• filler – View instance
• width – Numeric
• margin – Numeric
• align – Numeric

The principle of VLayout is the same as HLayout, but vertically. The order in which subviews are consider is from top to bottom. The first subview is at the top, and the last is at the bottom.

Alignment for vertical layout is done horizontally. Therefore, valid values are Pack.Left, Pack.Middle, Pack.Right. Default is left.

class VHLayout(subviews[, hfillers, vfiller, width, hmargin, vmargin, halign, valign])

Parameters:

• subviews – List of lists of View
• hfillers – A collection of View
• vfiller – A View instance.
• width – Numeric
• hmargin – Numeric
• vmargin – Numeric
• halign – Numeric
• valign – Numeric

This is a shortcut to creating a VLayout with multiple HLayout inside. The subview argument must be given in a “grid” fashion like this:

VHLayout([
    [line1view1, line1view2],
    [line2view1, line2view2, line2view3],
    [line3view1, line3view2],
])

Specifying fillers in such a layout is a complex matter. There’s two types of fillers, first the horizontal fillers. They’re given as a collection of views (because there can be more than one in the grid) as the hfillers argument. You include the filler for each line (if there’s no filler for a line, you add nothing) of the layout. The order in which they’re added is not important. If you have space fillers (None fillers), you don’t have to add None to the hfillers collection. For example, if you want the second view of each line to be fillers, you’d specifiy {line1view2, line2view2, line3view2} as the hfillers argument.

Then, there’s also the vfiller argument, which is the vertical filler (there’s only one). Because the VHLayout is a vertical layout that dynamically creates horizontal layouts, it’s impossible for you to specify a filler instance beforehand because you don’t have access to the horizontal layout instances that have yet to be created. Therefore, in the case of VHLayout, you can specify an instance in the view array. For example, if, in the example above, you wanted to make the middle line the filler, you could have specified any of line2view1, line2view2 or line2view3 as the vfiller and the result would have been the same.

Margin and align arguments are the same as simple layouts. hmargin is the horizontal margin and vmargin is the vertical one. halign is the horizontal alignment (applied to the vertical layout) and valign is the vertical alignment (applied to the horizontal layout).