forked from joejulian/gio
Elias Naur
50 lines
1.6 KiB
Go
50 lines
1.6 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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/*
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Package layout implements layouts common to GUI programs.
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Constraints and dimensions
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Constraints and dimensions form the interface between
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layouts and interface child elements. Every layout operation
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start with a set of constraints for acceptable widths and heights
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of a child. The operation ends with the child computing and returning
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its size and baseline (if any).
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For example, to add space above a widget:
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var cs layout.Constraints = ...
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// Configure a top inset.
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inset := layout.Inset{Top: ui.Dp(8), ...}
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// Use the inset to lay out a widget.
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inset.Layout(..., cs, func(cs layout.Constraints) layout.Dimensions {
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// Lay out widget and determine its size given the constraints.
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dimensions := widget.Layout(..., cs)
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return dimensions
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})
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Note that the example does not generate any garbage even though the
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Inset is transient. Layouts that don't accept user input are designed
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to escape to the heap during their use.
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Layout operations are recursive: a child in a layout operation can
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itself be another layout. That way, complex user interfaces can
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be created from a few generic layouts.
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This example both aligns and insets a child:
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inset := layout.Inset{...}
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inset.Layout(..., cs, func(cs layout.Constraints) layout.Dimensions {
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align := layout.Align{...}
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return align.Layout(..., cs, func(cs layout.Constraints) layout.Dimensions {
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return widget.Layout(..., cs)
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})
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})
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More complex layouts such as Stack and Flex lay out multiple children,
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and stateful layouts such as List accept user input.
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*/
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package layout
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