From 28ec6df8f0ebf96966bee61caf5a325695314b7a Mon Sep 17 00:00:00 2001
From: Héctor Ramón Jiménez <hector@hecrj.dev>
Date: Fri, 8 Nov 2024 18:07:11 +0100
Subject: Fix cross-axis compression in `layout::flex`
---
core/src/layout/flex.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 52 insertions(+), 1 deletion(-)
diff --git a/core/src/layout/flex.rs b/core/src/layout/flex.rs
index ac80d393..2cff5bfd 100644
--- a/core/src/layout/flex.rs
+++ b/core/src/layout/flex.rs
@@ -79,6 +79,7 @@ where
let max_cross = axis.cross(limits.max());
let mut fill_main_sum = 0;
+ let mut some_fill_cross = false;
let (mut cross, cross_compress) = match axis {
Axis::Vertical if width == Length::Shrink => (0.0, true),
Axis::Horizontal if height == Length::Shrink => (0.0, true),
@@ -90,6 +91,10 @@ where
let mut nodes: Vec<Node> = Vec::with_capacity(items.len());
nodes.resize(items.len(), Node::default());
+ // FIRST PASS
+ // We lay out non-fluid elements in the main axis.
+ // If we need to compress the cross axis, then we skip any of these elements
+ // that are also fluid in the cross axis.
for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate() {
let (fill_main_factor, fill_cross_factor) = {
let size = child.as_widget().size();
@@ -121,6 +126,41 @@ where
nodes[i] = layout;
} else {
fill_main_sum += fill_main_factor;
+ some_fill_cross = some_fill_cross || fill_cross_factor != 0;
+ }
+ }
+
+ // SECOND PASS (conditional)
+ // If we must compress the cross axis and there are fluid elements in the
+ // cross axis, we lay out any of these elements that are also non-fluid in
+ // the main axis (i.e. the ones we deliberately skipped in the first pass).
+ //
+ // We use the maximum cross length obtained in the first pass as the maximum
+ // cross limit.
+ if cross_compress && some_fill_cross {
+ for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate()
+ {
+ let (fill_main_factor, fill_cross_factor) = {
+ let size = child.as_widget().size();
+
+ axis.pack(size.width.fill_factor(), size.height.fill_factor())
+ };
+
+ if fill_main_factor == 0 && fill_cross_factor != 0 {
+ let (max_width, max_height) = axis.pack(available, cross);
+
+ let child_limits =
+ Limits::new(Size::ZERO, Size::new(max_width, max_height));
+
+ let layout =
+ child.as_widget().layout(tree, renderer, &child_limits);
+ let size = layout.size();
+
+ available -= axis.main(size);
+ cross = cross.max(axis.cross(size));
+
+ nodes[i] = layout;
+ }
}
}
@@ -135,6 +175,9 @@ where
},
};
+ // THIRD PASS
+ // We only have the elements that are fluid in the main axis left.
+ // We use the remaining space to evenly allocate space based on fill factors.
for (i, (child, tree)) in items.iter().zip(trees).enumerate() {
let (fill_main_factor, fill_cross_factor) = {
let size = child.as_widget().size();
@@ -142,10 +185,16 @@ where
axis.pack(size.width.fill_factor(), size.height.fill_factor())
};
- if fill_main_factor != 0 || (cross_compress && fill_cross_factor != 0) {
+ if fill_main_factor != 0 {
let max_main =
remaining * fill_main_factor as f32 / fill_main_sum as f32;
+ let max_main = if max_main.is_nan() {
+ f32::INFINITY
+ } else {
+ max_main
+ };
+
let min_main = if max_main.is_infinite() {
0.0
} else {
@@ -178,6 +227,8 @@ where
let pad = axis.pack(padding.left, padding.top);
let mut main = pad.0;
+ // FOURTH PASS
+ // We align all the laid out nodes in the cross axis, if needed.
for (i, node) in nodes.iter_mut().enumerate() {
if i > 0 {
main += spacing;
--
cgit