From 50123c6e0e10571fcd5830526a6027403dec4767 Mon Sep 17 00:00:00 2001
From: Ethan Reynolds <ereynolds@briar.systems>
Date: Thu, 1 Oct 2026 13:19:38 -0400
Subject: [PATCH] fix(#194): an unshrunk tab is exactly its natural width

tabs.width rebuilt every tab's width as least plus the rest times the
shrink factor. at a factor of one that sum can land a hair short of the
natural width in floating point, so the label box came out a fraction of a
pixel narrower than the label and fit_box cut it with an ellipsis. a tab the
bar has room for now takes its natural width directly. the test sweeps
paddings that do not land on whole pixels and fails without the fix.
---
 src/tabs.mach | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/tabs.mach b/src/tabs.mach
index 39daf3e..5316ac5 100644
--- a/src/tabs.mach
+++ b/src/tabs.mach
@@ -357,8 +357,11 @@ fun least(ctx: *context.Context, g: *Geom, t: *Tab) f32 {
     ret minf(natural(ctx, g, t), g.pad * 2.0::f32 + g.lh * 2.0::f32 + close_w(g, t));
 }
 
-# a tab's width this frame
+# a tab's width this frame. a tab the bar has room for is exactly its natural
+# width: rebuilt through the shrink, least plus the rest times one, it can come
+# out a hair short and cut a label that fits.
 fun width(ctx: *context.Context, g: *Geom, t: *Tab) f32 {
+    if (g.fit >= 1.0::f32) { ret natural(ctx, g, t); }
     val lo: f32 = least(ctx, g, t);
     ret lo + (natural(ctx, g, t) - lo) * g.fit;
 }
@@ -751,6 +754,34 @@ fun keys(a: *App) u64 {
     ret k;
 }
 
+test bar__unshrunk_tabs_are_their_natural_width {
+    var al:   allo.Allocator;
+    val made: err[allo.Error] = page.make(?al);
+    if (sel made.err) { ret 1; }
+    var a: App;
+    var d: driver.Driver;
+    if (!app(?d, ?al, ?a, 8, 2000.0::f32)) { ret 1; }
+    a.tabs[1].closable = false;
+    a.tabs[4].closable = false;
+    var g: Geom;
+    g.fit = 1.0::f32;
+    g.lh  = context.line_height(?d.ctx);
+    # paddings that do not land on whole pixels, as a scaled theme gives
+    var k: u32 = 1;
+    for (k < 400) {
+        g.pad = k::f32 * 0.037::f32;
+        var i: usize = 0;
+        for (i < a.n) {
+            if (width(?d.ctx, ?g, ?a.tabs[i]) != natural(?d.ctx, ?g, ?a.tabs[i])) { ret 2; }
+            i = i + 1;
+        }
+        k = k + 1;
+    }
+    val f: err[allo.Error] = driver.free(?d);
+    if (sel f.err) { ret 1; }
+    ret 0;
+}
+
 test bar__selects_closes_and_reorders {
     var al:   allo.Allocator;
     val made: err[allo.Error] = page.make(?al);