From 334dd098170d56c004d7a97bdfbbffe6f63f0ebd Mon Sep 17 00:00:00 2001
From: Clark Moody <clark@clarkmoody.com>
Date: Tue, 26 May 2020 16:11:49 -0500
Subject: [PATCH] Pane Grid spacing applied prior to rounding

On low-DPI screens, the rounding order of operations made it impossible
to produce an odd-pixel spacing. Specifying 1, for instance, produced
zero space between panes.

This approach subtracts half the spacing from the first pane prior to
rounding and uses the whole spacing for the second pane size and
coordinate.
---
 native/src/widget/pane_grid/axis.rs | 24 +++++++++++++-----------
 native/src/widget/pane_grid/node.rs | 22 ++++++++++------------
 2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/native/src/widget/pane_grid/axis.rs b/native/src/widget/pane_grid/axis.rs
index f0e3f362..7181f9bf 100644
--- a/native/src/widget/pane_grid/axis.rs
+++ b/native/src/widget/pane_grid/axis.rs
@@ -14,37 +14,39 @@ impl Axis {
         &self,
         rectangle: &Rectangle,
         ratio: f32,
-        halved_spacing: f32,
+        spacing: f32,
     ) -> (Rectangle, Rectangle) {
         match self {
             Axis::Horizontal => {
-                let height_top = (rectangle.height * ratio).round();
-                let height_bottom = rectangle.height - height_top;
+                let height_top =
+                    (rectangle.height * ratio - spacing / 2.0).round();
+                let height_bottom = rectangle.height - height_top - spacing;
 
                 (
                     Rectangle {
-                        height: height_top - halved_spacing,
+                        height: height_top,
                         ..*rectangle
                     },
                     Rectangle {
-                        y: rectangle.y + height_top + halved_spacing,
-                        height: height_bottom - halved_spacing,
+                        y: rectangle.y + height_top + spacing,
+                        height: height_bottom,
                         ..*rectangle
                     },
                 )
             }
             Axis::Vertical => {
-                let width_left = (rectangle.width * ratio).round();
-                let width_right = rectangle.width - width_left;
+                let width_left =
+                    (rectangle.width * ratio - spacing / 2.0).round();
+                let width_right = rectangle.width - width_left - spacing;
 
                 (
                     Rectangle {
-                        width: width_left - halved_spacing,
+                        width: width_left,
                         ..*rectangle
                     },
                     Rectangle {
-                        x: rectangle.x + width_left + halved_spacing,
-                        width: width_right - halved_spacing,
+                        x: rectangle.x + width_left + spacing,
+                        width: width_right,
                         ..*rectangle
                     },
                 )
diff --git a/native/src/widget/pane_grid/node.rs b/native/src/widget/pane_grid/node.rs
index 723ec393..b13c5e26 100644
--- a/native/src/widget/pane_grid/node.rs
+++ b/native/src/widget/pane_grid/node.rs
@@ -56,7 +56,7 @@ impl Node {
         let mut regions = HashMap::new();
 
         self.compute_regions(
-            spacing / 2.0,
+            spacing,
             &Rectangle {
                 x: 0.0,
                 y: 0.0,
@@ -83,7 +83,7 @@ impl Node {
         let mut splits = HashMap::new();
 
         self.compute_splits(
-            spacing / 2.0,
+            spacing,
             &Rectangle {
                 x: 0.0,
                 y: 0.0,
@@ -185,7 +185,7 @@ impl Node {
 
     fn compute_regions(
         &self,
-        halved_spacing: f32,
+        spacing: f32,
         current: &Rectangle,
         regions: &mut HashMap<Pane, Rectangle>,
     ) {
@@ -193,11 +193,10 @@ impl Node {
             Node::Split {
                 axis, ratio, a, b, ..
             } => {
-                let (region_a, region_b) =
-                    axis.split(current, *ratio, halved_spacing);
+                let (region_a, region_b) = axis.split(current, *ratio, spacing);
 
-                a.compute_regions(halved_spacing, &region_a, regions);
-                b.compute_regions(halved_spacing, &region_b, regions);
+                a.compute_regions(spacing, &region_a, regions);
+                b.compute_regions(spacing, &region_b, regions);
             }
             Node::Pane(pane) => {
                 let _ = regions.insert(*pane, *current);
@@ -207,7 +206,7 @@ impl Node {
 
     fn compute_splits(
         &self,
-        halved_spacing: f32,
+        spacing: f32,
         current: &Rectangle,
         splits: &mut HashMap<Split, (Axis, Rectangle, f32)>,
     ) {
@@ -219,13 +218,12 @@ impl Node {
                 b,
                 id,
             } => {
-                let (region_a, region_b) =
-                    axis.split(current, *ratio, halved_spacing);
+                let (region_a, region_b) = axis.split(current, *ratio, spacing);
 
                 let _ = splits.insert(*id, (*axis, *current, *ratio));
 
-                a.compute_splits(halved_spacing, &region_a, splits);
-                b.compute_splits(halved_spacing, &region_b, splits);
+                a.compute_splits(spacing, &region_a, splits);
+                b.compute_splits(spacing, &region_b, splits);
             }
             Node::Pane(_) => {}
         }