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use view::{View, SizeRequest, DimensionRequest};
use vec::Vec2;
use printer::Printer;
use orientation::Orientation;
use event::{Event, EventResult, Key};
/// Arranges its children linearly according to its orientation.
pub struct LinearLayout {
children: Vec<Child>,
orientation: Orientation,
focus: usize,
}
struct Child {
view: Box<View>,
size: Vec2,
weight: usize,
}
impl LinearLayout {
/// Creates a new layout with the given orientation.
pub fn new(orientation: Orientation) -> Self {
LinearLayout {
children: Vec::new(),
orientation: orientation,
focus: 0,
}
}
/// Modifies the weight of the last child added.
///
/// It is an error to call this before adding a child (and it will panic).
pub fn weight(mut self, weight: usize) -> Self {
self.children.last_mut().unwrap().weight = weight;
self
}
/// Adds a child to the layout.
pub fn child<V: View + 'static>(mut self, view: V) -> Self {
self.children.push(Child {
view: Box::new(view),
size: Vec2::zero(),
weight: 0,
});
self
}
/// Creates a new vertical layout.
pub fn vertical() -> Self {
LinearLayout::new(Orientation::Vertical)
}
/// Creates a new horizontal layout.
pub fn horizontal() -> Self {
LinearLayout::new(Orientation::Horizontal)
}
}
/// Returns the index of the maximum element.
/// WTF isn't it part of standard library??
fn find_max(list: &Vec<usize>) -> usize {
let mut max_value = 0;
let mut max = 0;
for (i, &x) in list.iter().enumerate() {
if x > max_value {
max_value = x;
max = i;
}
}
max
}
/// Given a total number of points and a list of weights,
/// try to share the points according to the weight,
/// rounding properly and conserving the sum of points.
fn share(total: usize, weights: Vec<usize>) -> Vec<usize> {
// It first give a base value to everyone, which is their truncated share.
// Then, it gives the rest to the most deserving.
if weights.len() == 0 {
return Vec::new();
}
let sum_weight = weights.iter().fold(0, |a, b| a + b);
if sum_weight == 0 {
return (0..weights.len()).map(|_| 0).collect();
}
let mut base = Vec::with_capacity(weights.len());
let mut rest = Vec::with_capacity(weights.len());
let mut extra = total;
for weight in weights.iter() {
let b = total * weight / sum_weight;
extra -= b;
base.push(b);
rest.push(total * weight - b * sum_weight);
}
// TODO: better to sort (base,rest) as one array and pick the extra first.
for _ in 0..extra {
let i = find_max(&rest);
rest[i] = 0;
base[i] += 1;
}
base
}
impl View for LinearLayout {
fn draw(&mut self, printer: &Printer) {
// Use pre-computed sizes
let mut offset = Vec2::zero();
for (i, child) in self.children.iter_mut().enumerate() {
child.view.draw(&printer.sub_printer(offset, child.size, i == self.focus));
*self.orientation.get_ref(&mut offset) += self.orientation.get(&child.size);
}
}
fn layout(&mut self, size: Vec2) {
// Compute the very minimal required size
let req = SizeRequest {
w: DimensionRequest::AtMost(size.x),
h: DimensionRequest::AtMost(size.y),
};
let min_sizes: Vec<Vec2> = self.children
.iter()
.map(|child| child.view.get_min_size(req))
.collect();
let min_size = self.orientation.stack(min_sizes.iter());
// Emulate 'non-strict inequality' on integers
// (default comparison on Vec2 is strict)
if !(min_size < size + (1, 1)) {
// Error! Not enough space! Emergency procedures!
return;
}
// Now share this extra space among everyone
let extras = {
let extra = size - min_size;
let space = self.orientation.get(&extra);
share(space,
self.children.iter().map(|child| child.weight).collect())
};
for (child, (child_size, extra)) in self.children
.iter_mut()
.zip(min_sizes.iter().zip(extras.iter())) {
let mut child_size = *child_size;
*self.orientation.get_ref(&mut child_size) += *extra;
*self.orientation.swap().get_ref(&mut child_size) = self.orientation.swap().get(&size);
child.size = child_size;
child.view.layout(child_size);
}
}
fn get_min_size(&self, req: SizeRequest) -> Vec2 {
// First, make a naive scenario: everything will work fine.
let sizes: Vec<Vec2> = self.children
.iter()
.map(|view| view.view.get_min_size(req))
.collect();
self.orientation.stack(sizes.iter())
// Did it work? Champagne!
// Ok, so maybe it didn't.
// Last chance: did someone lie about his needs?
// Could we squash him a little?
// Find out who's fluid, if any.
}
fn on_event(&mut self, event: Event) -> EventResult {
match self.children[self.focus].view.on_event(event) {
EventResult::Ignored => {
match event {
Event::KeyEvent(Key::Tab) if self.focus > 0 => {
self.focus -= 1;
EventResult::Consumed(None)
}
Event::KeyEvent(Key::ShiftTab) if self.focus + 1 < self.children.len() => {
self.focus += 1;
EventResult::Consumed(None)
}
Event::KeyEvent(Key::Left) if self.orientation == Orientation::Horizontal &&
self.focus > 0 => {
self.focus -= 1;
EventResult::Consumed(None)
}
Event::KeyEvent(Key::Up) if self.orientation == Orientation::Vertical &&
self.focus > 0 => {
self.focus -= 1;
EventResult::Consumed(None)
}
Event::KeyEvent(Key::Right) if self.orientation == Orientation::Horizontal &&
self.focus + 1 < self.children.len() => {
self.focus += 1;
EventResult::Consumed(None)
}
Event::KeyEvent(Key::Down) if self.orientation == Orientation::Vertical &&
self.focus + 1 < self.children.len() => {
self.focus += 1;
EventResult::Consumed(None)
}
_ => EventResult::Ignored,
}
}
res => res,
}
}
}