ui/screen/layout.go

package screen

import (
	"errors"
	"fmt"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/layout"
)

type Layout string

const (
	Border Layout = "Border"
	Form   Layout = "Form"
	Grid   Layout = "Grid"
	HBox   Layout = "HBox"
	Stack  Layout = "Stack"
	VBox   Layout = "VBox"
)

func (l Layout) Build(e *Element, s ScreenHandler) (c *fyne.Container, err error) {
	switch l {
	case Border:
		c, err = l.buildBorderLayout(e, s)
	case Form:
		c, err = l.buildFormLayout(e, s)
	case Grid:
		c, err = l.buildGridLayout(e, s)
	case HBox:
		c, err = l.buildHBoxLayout(e, s)
	case Stack:
		c, err = l.buildStackLayout(e, s)
	case VBox:
		c, err = l.buildVBoxLayout(e, s)
	default:
		err = errors.New("invalid layout")
	}
	if err != nil {
		return
	}

	if e.Hidden {
		c.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) 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
}