ui/screen/layout.go

package screen

import (
	"errors"
	"fmt"

	"gitea.hevanto-it.com/hevanto/ui/uilayout"
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/layout"
)

// The constants for the Layouts
//
// Available yaml options for all layouts:
//   - id: The ID for exporting the layout to code
//   - decorators: The decorators to wrap the layout into
//   - hidden: Wether the layout is hidden or not
type Layout string

const (
	// Border Layout
	//
	// Available yaml options
	//	- top: The top pane (contains 1 widget)
	//	- bottom: The bottom pane (contains 1 widget)
	//	- left: The left pane (contains 1 widget)
	//	- right: The right pane (contains 1 widget)
	//	- center: The center pane (contains multiple widgets)
	Border Layout = "Border"

	// Form Layout
	//
	// Available yaml options
	//	- children: The children of the form
	//		- label: The label of the form element
	//		- field: The field of the form element
	Form Layout = "Form"

	// Grid Layout
	//
	// Available yaml options
	//	- columns: The number of columns (GridWithColumns)
	//	- rows: The number of rows (GridWithRows)
	//	- rowColumns: The number of rows and columns (AdaptiveGrid)
	//	- elementSize: The size of the elements (GridWrap)
	//	- children: The children of the grid
	Grid Layout = "Grid"

	// HBox Layout
	//
	// Available yaml options
	//	- children: The children of the HBox
	HBox Layout = "HBox"

	// MinSize Layout
	//
	// Available yaml options
	//	- minSize: The minimum size of the layout
	//  - children: The children of the MinSize
	MinSize Layout = "MinSize"

	// Stack Layout
	//
	// Available yaml options
	// - children: The children of the Stack
	Stack Layout = "Stack"

	// VBox Layout
	//
	// Available yaml options
	//	- children: The children of the VBox
	VBox Layout = "VBox"
)

// Build builds the layout based on the given Layout and Element
// using the provided ScreenHandler to fetch functions, data bindings, etc.
//
// Parameters:
// - e: The Element to build the Layout for
// - s: The ScreenHandler to use to fetch functions, data bindings, etc.
// Returns the CanvasObject for the Layout, the CanvasObject for the decorator
// and an error if any.
// If no decorators are specified, the widget and decorator will be the same.
func (l Layout) Build(
	e *Element,
	s ScreenHandler,
) (
	lay fyne.CanvasObject,
	decorator fyne.CanvasObject,
	err error,
) {
	switch l {
	case Border:
		lay, err = l.buildBorderLayout(e, s)
	case Form:
		lay, err = l.buildFormLayout(e, s)
	case Grid:
		lay, err = l.buildGridLayout(e, s)
	case HBox:
		lay, err = l.buildHBoxLayout(e, s)
	case MinSize:
		lay, err = l.buildMinSizeLayout(e, s)
	case Stack:
		lay, err = l.buildStackLayout(e, s)
	case VBox:
		lay, err = l.buildVBoxLayout(e, s)
	default:
		err = errors.New("invalid layout")
	}
	if err != nil {
		return
	}

	decorator = applyPadding(e, lay)
	decorator = applyDecorators(e, decorator)
	decorator = applyMargins(e, decorator)

	if e.Hidden {
		decorator.Hide()
	}
	return
}

func (l Layout) buildBorderLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	var top, left, right, bottom fyne.CanvasObject
	var center []fyne.CanvasObject

	if e.Top != nil {
		if top, err = e.Top.BuildUI(s); err != nil {
			err = fmt.Errorf("BorderLayout: failed to create top element: %w", err)
			return
		}
	}

	if e.Left != nil {
		if left, err = e.Left.BuildUI(s); err != nil {
			err = fmt.Errorf("BorderLayout: failed to create left element: %w", err)
			return
		}
	}

	if e.Center != nil {
		center = make([]fyne.CanvasObject, 0, len(e.Center))
		for _, elem := range e.Center {
			var ce fyne.CanvasObject
			if ce, err = elem.BuildUI(s); err != nil {
				err = fmt.Errorf("BorderLayout: failed to create center element: %w", err)
				return
			}
			center = append(center, ce)
		}
	}

	if e.Right != nil {
		if right, err = e.Right.BuildUI(s); err != nil {
			err = fmt.Errorf("BorderLayout: failed to create right element: %w", err)
			return
		}
	}

	if e.Bottom != nil {
		if bottom, err = e.Bottom.BuildUI(s); err != nil {
			err = fmt.Errorf("BorderLayout: failed to create bottom element: %w", err)
			return
		}
	}

	c = container.NewBorder(top, bottom, left, right, center...)
	return
}

func (l Layout) buildFormLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children)*2)
	for _, child := range e.Children {
		if child.Label == nil {
			child.Label = &Element{
				Text: "",
			}
		}
		if child.Field == nil {
			child.Field = &Element{
				Widget: Label,
				Text:   "",
			}
		}

		child.Label.Widget = Label
		if child.Label.Options == nil {
			child.Label.Options = make(map[string]any)
		}
		if child.Label.Options["TextStyle"] == nil {
			child.Label.Options["TextStyle"] = make(map[string]any)
		}
		child.Label.Options["TextStyle"].(map[string]any)["Bold"] = true

		var label, field fyne.CanvasObject
		if label, err = child.Label.BuildUI(s); err != nil {
			err = fmt.Errorf("FormLayout: failed to create label element: %w", err)
			return
		}
		if field, err = child.Field.BuildUI(s); err != nil {
			err = fmt.Errorf("FormLayout: failed to create field element: %w", err)
			return
		}

		children = append(children, label, field)
	}

	c = container.New(layout.NewFormLayout(), children...)
	return
}

func (l Layout) buildGridLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children))
	for _, child := range e.Children {
		var obj fyne.CanvasObject
		if obj, err = child.BuildUI(s); err != nil {
			err = fmt.Errorf("GridLayout failed to create child element %w", err)
			return
		}
		children = append(children, obj)
	}
	if e.Columns != nil {
		c = container.NewGridWithColumns(*e.Columns, children...)
		return
	}
	if e.Rows != nil {
		c = container.NewGridWithRows(*e.Rows, children...)
		return
	}
	if e.RowColumns != nil {
		c = container.NewAdaptiveGrid(*e.RowColumns, children...)
		return
	}
	if e.ElementSize != nil {
		c = container.NewGridWrap(fyne.NewSize(e.ElementSize.Width, e.ElementSize.Height), children...)
		return
	}
	err = errors.New("GridLayout failed due to incomplete grid type definition")
	return
}

func (l Layout) buildHBoxLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children))
	for _, child := range e.Children {
		var obj fyne.CanvasObject
		if obj, err = child.BuildUI(s); err != nil {
			err = fmt.Errorf("HBoxLayout failed to create child element: %w", err)
			return
		}
		children = append(children, obj)
	}
	c = container.New(layout.NewHBoxLayout(), children...)
	return
}

func (l Layout) buildMinSizeLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children))
	for _, child := range e.Children {
		var obj fyne.CanvasObject
		if obj, err = child.BuildUI(s); err != nil {
			err = fmt.Errorf("MinSizeLayout failed to create child element: %w", err)
			return
		}
		children = append(children, obj)
	}
	if e.MinSize == nil {
		e.MinSize = &Size{
			Width:  0,
			Height: 0,
		}
	}
	c = container.New(
		uilayout.NewMinSizeLayout(
			fyne.NewSize(e.MinSize.Width, e.MinSize.Height)),
		children...)
	return
}

func (l Layout) buildStackLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children))
	for _, child := range e.Children {
		var obj fyne.CanvasObject
		if obj, err = child.BuildUI(s); err != nil {
			err = fmt.Errorf("StackLayout failed to create child element: %w", err)
			return
		}
		children = append(children, obj)
	}
	c = container.New(layout.NewStackLayout(), children...)
	return
}

func (l Layout) buildVBoxLayout(
	e *Element,
	s ScreenHandler,
) (c *fyne.Container, err error) {
	children := make([]fyne.CanvasObject, 0, len(e.Children))
	for _, child := range e.Children {
		var obj fyne.CanvasObject
		if obj, err = child.BuildUI(s); err != nil {
			err = fmt.Errorf("VBoxLayout failed to create child element: %w", err)
			return
		}
		children = append(children, obj)
	}
	c = container.New(layout.NewVBoxLayout(), children...)
	return
}