Rename iced_virtual to iced_pure

`virtual` is a reserved keyword in Rust 😬

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)
+}