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listbox.go
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listbox.go
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package tinygl
import (
"tinygo.org/x/drivers/pixel"
font "tinygo.org/x/tinygl-font"
)
// A scrollable list of strings, of which one is currently selected.
type ListBox[T pixel.Color] struct {
Rect[T]
children []Text[T]
handler func(Event, int) // event handler
selected int16
width int16
foreground T
tint T
numCols uint8 // number of columns, to make it a grid
}
// Create a new listbox with the given elements. The elements (and number of
// elements) cannot be changed after creation.
func NewListBox[T pixel.Color](font font.Font, foreground, background, tint T, elements []string) *ListBox[T] {
// Avoid some heap allocations by allocating all children at once.
children := make([]Text[T], len(elements))
box := &ListBox[T]{
Rect: MakeRect(background),
children: children,
selected: -1,
foreground: foreground,
tint: tint,
numCols: 1,
}
for i, text := range elements {
child := &children[i]
*child = MakeText(font, foreground, background, text)
child.SetParent(box)
child.SetAlign(AlignLeft)
}
return box
}
// MinSize returns the height of all the list items combined.
// The minimal width is always zero (it is expected to set to expand).
func (box *ListBox[T]) MinSize() (width, height int) {
if len(box.children) == 0 {
return 0, 0
}
firstChild := &box.children[0]
_, childHeight := firstChild.MinSize()
numRows := (len(box.children) + int(box.numCols) - 1) / int(box.numCols)
return 0, childHeight * numRows
}
// Len returns the number of elements in the listbox.
func (box *ListBox[T]) Len() int {
return len(box.children)
}
// SetColumns splits the view into multiple columns, so that elements can also
// display horizontally.
func (box *ListBox[T]) SetColumns(columns int) {
if columns < 1 {
columns = 1
}
box.numCols = uint8(columns)
}
// SetAlign sets the alignment of all text children.
func (box *ListBox[T]) SetAlign(align TextAlign) {
for i := range box.children {
box.children[i].SetAlign(align)
}
}
// Set padding for each text child.
func (box *ListBox[T]) SetPadding(horizontal, vertical int) {
for i := range box.children {
box.children[i].SetPadding(horizontal, vertical)
}
box.Rect.RequestUpdate()
}
// RequestUpdate will request an update for this object and all of its children.
func (box *ListBox[T]) RequestUpdate() {
box.Rect.RequestUpdate()
for i := range box.children {
box.children[i].RequestUpdate()
}
}
// Layout implements tinygl.Object.
func (box *ListBox[T]) Layout(width, height int) {
if !box.NeedsLayout() {
return
}
box.width = int16(width)
commonChildHeight := 0
if len(box.children) != 0 {
firstChild := &box.children[0]
_, commonChildHeight = firstChild.MinSize()
}
colIndex := 0
rowIndex := 0
remainingWidth := width
for i := range box.children {
child := &box.children[i]
childWidth := remainingWidth / (int(box.numCols) - colIndex)
child.Layout(childWidth, commonChildHeight)
remainingWidth -= childWidth
colIndex++
if colIndex >= int(box.numCols) {
// Wrap again back to start.
colIndex = 0
rowIndex++
remainingWidth = width
}
}
}
// Update implements tinygl.Object.
func (box *ListBox[T]) Update(screen *Screen[T], displayX, displayY, displayWidth, displayHeight, x, y int) {
needsUpdate, childNeedsUpdate := box.NeedsUpdate()
if !needsUpdate && !childNeedsUpdate {
return
}
commonChildHeight := 0
if len(box.children) != 0 {
firstChild := &box.children[0]
_, commonChildHeight = firstChild.MinSize()
}
remainingWidth := int(box.width)
if childNeedsUpdate {
colIndex := 0
rowIndex := 0
for i := range box.children {
child := &box.children[i]
// Calculate child offset from the (0, 0) coordinate of the ListBox.
childOffsetX := int(box.width) - int(remainingWidth)
childOffsetY := commonChildHeight * rowIndex
// Calculate idealized x/y/width/height for the child, ignoring the
// draw boundaries.
childDisplayX := displayX - x + childOffsetX
childDisplayY := displayY - y + childOffsetY
childDisplayWidth := remainingWidth / (int(box.numCols) - colIndex)
childDisplayHeight := commonChildHeight
remainingWidth -= childDisplayWidth
// Limit the x/y/width/height of the child to the draw area.
childX := 0
childY := 0
if childDisplayX < displayX {
childX = displayX - childDisplayX
childDisplayX = displayX
childDisplayWidth -= childX
}
if childDisplayY < displayY {
childY = displayY - childDisplayY
childDisplayY = displayY
childDisplayHeight -= childY
}
maxChildDisplayWidth := displayX + displayWidth - childDisplayX
if childDisplayWidth > maxChildDisplayWidth {
childDisplayWidth = maxChildDisplayWidth
}
maxChildDisplayHeight := displayY + displayHeight - childDisplayY
if childDisplayHeight > maxChildDisplayHeight {
childDisplayHeight = maxChildDisplayHeight
}
if childDisplayWidth > 0 && childDisplayHeight > 0 {
child.Update(screen, childDisplayX, childDisplayY, childDisplayWidth, childDisplayHeight, childX, childY)
}
colIndex++
if colIndex >= int(box.numCols) {
// Wrap again back to start.
colIndex = 0
rowIndex++
remainingWidth = int(box.width)
}
}
}
// Draw the area below the children.
if needsUpdate {
if len(box.children) == 0 {
PaintSolidColor(screen, box.Background(), displayX, displayY, displayWidth, displayHeight)
} else {
if len(box.children)%int(box.numCols) != 0 {
// The grid may not fill every row entirely, like the area
// indicated with "*" here:
//
// # # #
// # # #
// # * *
// - - -
//
// Calculate the idealized paint area to draw the background
// color.
paintX := displayX - x + (int(box.width) - remainingWidth)
paintY := displayY - y + len(box.children)/int(box.numCols)*commonChildHeight
paintWidth := int(box.width) - remainingWidth
paintHeight := commonChildHeight
// Limit the paint area to the allowed display area.
if paintX < displayX {
paintWidth -= displayX - paintX
paintX = displayX
}
if paintY < displayY {
paintHeight -= displayY - paintY
paintY = displayY
}
if paintWidth > displayWidth {
paintWidth = displayWidth
}
if paintHeight > displayHeight {
paintHeight = displayHeight
}
// Draw this area.
if paintWidth > 0 && paintHeight > 0 {
PaintSolidColor(screen, box.Background(), paintX, paintY, paintWidth, paintHeight)
}
}
// Now do the same for the area below the children.
// Like the area indicated with "-":
//
// # # #
// # # #
// # * *
// - - -
paintX := displayX - x
paintY := displayY - y + (len(box.children)+int(box.numCols)-1)/int(box.numCols)*commonChildHeight
// Limit the paint area.
if paintX < displayX {
paintX = displayX
}
if paintY < displayY {
paintY = displayY
}
paintWidth := displayX + displayWidth - paintX
paintHeight := displayY + displayHeight - paintY
// Now draw this area, if there is something to draw.
if paintWidth > 0 && paintHeight > 0 {
PaintSolidColor(screen, box.Background(), paintX, paintY, paintWidth, paintHeight)
}
}
}
}
func (box *ListBox[T]) MarkUpdated() {
if _, anyChild := box.NeedsUpdate(); anyChild {
for i := range box.children {
box.children[i].MarkUpdated()
}
}
box.Rect.MarkUpdated()
}
// Selected returns the index of the currently selected element, or -1 if no
// element is selected.
func (box *ListBox[T]) Selected() int {
return int(box.selected)
}
// Select selects the given index. The index -1 means "no child selected".
func (box *ListBox[T]) Select(index int) {
if box.selected != -1 {
child := &box.children[box.selected]
child.SetBackground(box.Background())
child.SetColor(box.foreground)
}
if index >= len(box.children) {
panic("ListBox.Select: out of range")
}
box.selected = int16(index)
if index >= 0 {
child := &box.children[box.selected]
child.SetBackground(box.tint)
child.SetColor(box.Background())
firstChild := &box.children[0]
_, commonChildHeight := firstChild.MinSize()
childY := (index / int(box.numCols)) * commonChildHeight
if box.Parent() != nil {
box.Parent().ScrollIntoViewVertical(childY, childY+int(commonChildHeight), box)
}
}
}
// SetEventHandler sets the callback when one of the elements in the list gets
// selected.
func (box *ListBox[T]) SetEventHandler(eventHandler func(event Event, index int)) {
box.handler = eventHandler
}
// HandleEvent handles events such as touch events and calls the event handler
// with the given child as a parameter.
func (box *ListBox[T]) HandleEvent(event Event, x, y int) {
if box.handler == nil {
return
}
if len(box.children) == 0 {
return
}
childHeight := 0
if len(box.children) != 0 {
firstChild := &box.children[0]
_, childHeight = firstChild.MinSize()
}
row := y / childHeight
remainingWidth := int(box.width)
childX := 0
for col := 0; col < int(box.numCols); col++ {
childWidth := remainingWidth / (int(box.numCols) - col)
if x >= childX && x < childX+childWidth {
index := row*int(box.numCols) + col
if index < len(box.children) {
box.handler(event, index)
}
}
childX += childWidth
remainingWidth -= childWidth
}
}