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flex.go
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package tview
import (
"github.com/gdamore/tcell/v2"
)
// Flex directions.
const (
// One item per row.
FlexRow = 0
// One item per column.
FlexColumn = 1
// As defined in CSS, items distributed along a row.
FlexRowCSS = 1
// As defined in CSS, items distributed within a column.
FlexColumnCSS = 0
)
// flexItem holds layout options for one item.
type flexItem struct {
Item Primitive // The item to be positioned. May be nil for an empty item.
FixedSize int // The item's fixed size which may not be changed, 0 if it has no fixed size.
Proportion int // The item's proportion.
Focus bool // Whether or not this item attracts the layout's focus.
}
// Flex is a basic implementation of the Flexbox layout. The contained
// primitives are arranged horizontally or vertically. The way they are
// distributed along that dimension depends on their layout settings, which is
// either a fixed length or a proportional length. See AddItem() for details.
//
// See https://github.com/rivo/tview/wiki/Flex for an example.
type Flex struct {
*Box
// The items to be positioned.
items []*flexItem
// FlexRow or FlexColumn.
direction int
// If set to true, Flex will use the entire screen as its available space
// instead its box dimensions.
fullScreen bool
}
// NewFlex returns a new flexbox layout container with no primitives and its
// direction set to FlexColumn. To add primitives to this layout, see AddItem().
// To change the direction, see SetDirection().
//
// Note that Box, the superclass of Flex, will not clear its contents so that
// any nil flex items will leave their background unchanged. To clear a Flex's
// background before any items are drawn, set it to a box with the desired
// color:
//
// flex.Box = NewBox()
func NewFlex() *Flex {
f := &Flex{
direction: FlexColumn,
}
f.Box = NewBox()
f.Box.dontClear = true
return f
}
// SetDirection sets the direction in which the contained primitives are
// distributed. This can be either FlexColumn (default) or FlexRow. Note that
// these are the opposite of what you would expect coming from CSS. You may also
// use FlexColumnCSS or FlexRowCSS, to remain in line with the CSS definition.
func (f *Flex) SetDirection(direction int) *Flex {
f.direction = direction
return f
}
// SetFullScreen sets the flag which, when true, causes the flex layout to use
// the entire screen space instead of whatever size it is currently assigned to.
func (f *Flex) SetFullScreen(fullScreen bool) *Flex {
f.fullScreen = fullScreen
return f
}
// AddItem adds a new item to the container. The "fixedSize" argument is a width
// or height that may not be changed by the layout algorithm. A value of 0 means
// that its size is flexible and may be changed. The "proportion" argument
// defines the relative size of the item compared to other flexible-size items.
// For example, items with a proportion of 2 will be twice as large as items
// with a proportion of 1. The proportion must be at least 1 if fixedSize == 0
// (ignored otherwise).
//
// If "focus" is set to true, the item will receive focus when the Flex
// primitive receives focus. If multiple items have the "focus" flag set to
// true, the first one will receive focus.
//
// You can provide a nil value for the primitive. This will still consume screen
// space but nothing will be drawn.
func (f *Flex) AddItem(item Primitive, fixedSize, proportion int, focus bool) *Flex {
f.items = append(f.items, &flexItem{Item: item, FixedSize: fixedSize, Proportion: proportion, Focus: focus})
return f
}
// RemoveItem removes all items for the given primitive from the container,
// keeping the order of the remaining items intact.
func (f *Flex) RemoveItem(p Primitive) *Flex {
for index := len(f.items) - 1; index >= 0; index-- {
if f.items[index].Item == p {
f.items = append(f.items[:index], f.items[index+1:]...)
}
}
return f
}
// GetItemCount returns the number of items in this container.
func (f *Flex) GetItemCount() int {
return len(f.items)
}
// GetItem returns the primitive at the given index, starting with 0 for the
// first primitive in this container.
//
// This function will panic for out of range indices.
func (f *Flex) GetItem(index int) Primitive {
return f.items[index].Item
}
// Clear removes all items from the container.
func (f *Flex) Clear() *Flex {
f.items = nil
return f
}
// ResizeItem sets a new size for the item(s) with the given primitive. If there
// are multiple Flex items with the same primitive, they will all receive the
// same size. For details regarding the size parameters, see AddItem().
func (f *Flex) ResizeItem(p Primitive, fixedSize, proportion int) *Flex {
for _, item := range f.items {
if item.Item == p {
item.FixedSize = fixedSize
item.Proportion = proportion
}
}
return f
}
// Draw draws this primitive onto the screen.
func (f *Flex) Draw(screen tcell.Screen) {
f.Box.DrawForSubclass(screen, f)
// Calculate size and position of the items.
// Do we use the entire screen?
if f.fullScreen {
width, height := screen.Size()
f.SetRect(0, 0, width, height)
}
// How much space can we distribute?
x, y, width, height := f.GetInnerRect()
var proportionSum int
distSize := width
if f.direction == FlexRow {
distSize = height
}
for _, item := range f.items {
if item.FixedSize > 0 {
distSize -= item.FixedSize
} else {
proportionSum += item.Proportion
}
}
// Calculate positions and draw items.
pos := x
if f.direction == FlexRow {
pos = y
}
for _, item := range f.items {
size := item.FixedSize
if size <= 0 {
if proportionSum > 0 {
size = distSize * item.Proportion / proportionSum
distSize -= size
proportionSum -= item.Proportion
} else {
size = 0
}
}
if item.Item != nil {
if f.direction == FlexColumn {
item.Item.SetRect(pos, y, size, height)
} else {
item.Item.SetRect(x, pos, width, size)
}
}
pos += size
if item.Item != nil {
if item.Item.HasFocus() {
defer item.Item.Draw(screen)
} else {
item.Item.Draw(screen)
}
}
}
}
// Focus is called when this primitive receives focus.
func (f *Flex) Focus(delegate func(p Primitive)) {
for _, item := range f.items {
if item.Item != nil && item.Focus {
delegate(item.Item)
return
}
}
f.Box.Focus(delegate)
}
// HasFocus returns whether or not this primitive has focus.
func (f *Flex) HasFocus() bool {
for _, item := range f.items {
if item.Item != nil && item.Item.HasFocus() {
return true
}
}
return f.Box.HasFocus()
}
// MouseHandler returns the mouse handler for this primitive.
func (f *Flex) MouseHandler() func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
return f.WrapMouseHandler(func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
if !f.InRect(event.Position()) {
return false, nil
}
// Pass mouse events along to the first child item that takes it.
for _, item := range f.items {
if item.Item == nil {
continue
}
consumed, capture = item.Item.MouseHandler()(action, event, setFocus)
if consumed {
return
}
}
return
})
}
// InputHandler returns the handler for this primitive.
func (f *Flex) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
return f.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
for _, item := range f.items {
if item.Item != nil && item.Item.HasFocus() {
if handler := item.Item.InputHandler(); handler != nil {
handler(event, setFocus)
return
}
}
}
})
}