diff options
Diffstat (limited to 'pure/src/flex.rs')
| -rw-r--r-- | pure/src/flex.rs | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/pure/src/flex.rs b/pure/src/flex.rs new file mode 100644 index 00000000..8d473f08 --- /dev/null +++ b/pure/src/flex.rs @@ -0,0 +1,232 @@ +//! Distribute elements using a flex-based layout. +// This code is heavily inspired by the [`druid`] codebase. +// +// [`druid`]: https://github.com/xi-editor/druid +// +// Copyright 2018 The xi-editor Authors, Héctor Ramón +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +use crate::Element; + +use iced_native::layout::{Limits, Node}; +use iced_native::{Alignment, Padding, Point, Size}; + +/// The main axis of a flex layout. +#[derive(Debug)] +pub enum Axis { + /// The horizontal axis + Horizontal, + + /// The vertical axis + Vertical, +} + +impl Axis { + fn main(&self, size: Size) -> f32 { + match self { + Axis::Horizontal => size.width, + Axis::Vertical => size.height, + } + } + + fn cross(&self, size: Size) -> f32 { + match self { + Axis::Horizontal => size.height, + Axis::Vertical => size.width, + } + } + + fn pack(&self, main: f32, cross: f32) -> (f32, f32) { + match self { + Axis::Horizontal => (main, cross), + Axis::Vertical => (cross, main), + } + } +} + +/// Computes the flex layout with the given axis and limits, applying spacing, +/// padding and alignment to the items as needed. +/// +/// It returns a new layout [`Node`]. +pub fn resolve<Message, Renderer>( + axis: Axis, + renderer: &Renderer, + limits: &Limits, + padding: Padding, + spacing: f32, + align_items: Alignment, + items: &[Element<Message, Renderer>], +) -> Node +where + Renderer: iced_native::Renderer, +{ + let limits = limits.pad(padding); + let total_spacing = spacing * items.len().saturating_sub(1) as f32; + let max_cross = axis.cross(limits.max()); + + let mut fill_sum = 0; + let mut cross = axis.cross(limits.min()).max(axis.cross(limits.fill())); + let mut available = axis.main(limits.max()) - total_spacing; + + let mut nodes: Vec<Node> = Vec::with_capacity(items.len()); + nodes.resize(items.len(), Node::default()); + + if align_items == Alignment::Fill { + let mut fill_cross = axis.cross(limits.min()); + + items.iter().for_each(|child| { + let cross_fill_factor = match axis { + Axis::Horizontal => child.as_widget().height(), + Axis::Vertical => child.as_widget().width(), + } + .fill_factor(); + + if cross_fill_factor == 0 { + let (max_width, max_height) = axis.pack(available, max_cross); + + let child_limits = + Limits::new(Size::ZERO, Size::new(max_width, max_height)); + + let layout = child.as_widget().layout(renderer, &child_limits); + let size = layout.size(); + + fill_cross = fill_cross.max(axis.cross(size)); + } + }); + + cross = fill_cross; + } + + for (i, child) in items.iter().enumerate() { + let fill_factor = match axis { + Axis::Horizontal => child.as_widget().width(), + Axis::Vertical => child.as_widget().height(), + } + .fill_factor(); + + if fill_factor == 0 { + let (min_width, min_height) = if align_items == Alignment::Fill { + axis.pack(0.0, cross) + } else { + axis.pack(0.0, 0.0) + }; + + let (max_width, max_height) = if align_items == Alignment::Fill { + axis.pack(available, cross) + } else { + axis.pack(available, max_cross) + }; + + let child_limits = Limits::new( + Size::new(min_width, min_height), + Size::new(max_width, max_height), + ); + + let layout = child.as_widget().layout(renderer, &child_limits); + let size = layout.size(); + + available -= axis.main(size); + + if align_items != Alignment::Fill { + cross = cross.max(axis.cross(size)); + } + + nodes[i] = layout; + } else { + fill_sum += fill_factor; + } + } + + let remaining = available.max(0.0); + + for (i, child) in items.iter().enumerate() { + let fill_factor = match axis { + Axis::Horizontal => child.as_widget().width(), + Axis::Vertical => child.as_widget().height(), + } + .fill_factor(); + + if fill_factor != 0 { + let max_main = remaining * fill_factor as f32 / fill_sum as f32; + let min_main = if max_main.is_infinite() { + 0.0 + } else { + max_main + }; + + let (min_width, min_height) = if align_items == Alignment::Fill { + axis.pack(min_main, cross) + } else { + axis.pack(min_main, axis.cross(limits.min())) + }; + + let (max_width, max_height) = if align_items == Alignment::Fill { + axis.pack(max_main, cross) + } else { + axis.pack(max_main, max_cross) + }; + + let child_limits = Limits::new( + Size::new(min_width, min_height), + Size::new(max_width, max_height), + ); + + let layout = child.as_widget().layout(renderer, &child_limits); + + if align_items != Alignment::Fill { + cross = cross.max(axis.cross(layout.size())); + } + + nodes[i] = layout; + } + } + + let pad = axis.pack(padding.left as f32, padding.top as f32); + let mut main = pad.0; + + for (i, node) in nodes.iter_mut().enumerate() { + if i > 0 { + main += spacing; + } + + let (x, y) = axis.pack(main, pad.1); + + node.move_to(Point::new(x, y)); + + match axis { + Axis::Horizontal => { + node.align( + Alignment::Start, + align_items, + Size::new(0.0, cross), + ); + } + Axis::Vertical => { + node.align( + align_items, + Alignment::Start, + Size::new(cross, 0.0), + ); + } + } + + let size = node.size(); + + main += axis.main(size); + } + + let (width, height) = axis.pack(main - pad.0, cross); + let size = limits.resolve(Size::new(width, height)); + + Node::with_children(size.pad(padding), nodes) +} |