From 603dba29e610542187179342f8effe536e6189d7 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Date: Tue, 16 Sep 2025 13:30:28 +0200
Subject: [PATCH] Add snapshot test for text spacing/kerning (#7545)

---
 crates/egui_demo_lib/tests/misc.rs            | 26 +++++++++++++++++++
 .../image_blending/image_dark_x1.png          |  3 +++
 .../image_blending/image_dark_x2.png          |  3 +++
 .../image_blending/image_light_x1.png         |  3 +++
 .../image_blending/image_light_x2.png         |  3 +++
 crates/epaint/src/text/font.rs                |  2 +-
 6 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 crates/egui_demo_lib/tests/misc.rs
 create mode 100644 crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x1.png
 create mode 100644 crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x2.png
 create mode 100644 crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x1.png
 create mode 100644 crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x2.png

diff --git a/crates/egui_demo_lib/tests/misc.rs b/crates/egui_demo_lib/tests/misc.rs
new file mode 100644
index 00000000..5a8ae2c2
--- /dev/null
+++ b/crates/egui_demo_lib/tests/misc.rs
@@ -0,0 +1,26 @@
+use egui_kittest::Harness;
+
+#[test]
+fn test_kerning() {
+    for pixels_per_point in [1.0, 2.0] {
+        for theme in [egui::Theme::Dark, egui::Theme::Light] {
+            let mut harness = Harness::builder()
+                .with_pixels_per_point(pixels_per_point)
+                .with_theme(theme)
+                .build_ui(|ui| {
+                    ui.label("Thin spaces: −123 456 789");
+                    ui.label("Ligature: fi :)");
+                    ui.label("\ttabbed");
+                });
+            harness.run();
+            harness.fit_contents();
+            harness.snapshot(format!(
+                "image_blending/image_{theme}_x{pixels_per_point}",
+                theme = match theme {
+                    egui::Theme::Dark => "dark",
+                    egui::Theme::Light => "light",
+                }
+            ));
+        }
+    }
+}
diff --git a/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x1.png b/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x1.png
new file mode 100644
index 00000000..069d4819
--- /dev/null
+++ b/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x1.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:0b619e8dbedbfc017513111dc26144d795ce97352631ae561c1c336c3e9e0fd4
+size 5557
diff --git a/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x2.png b/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x2.png
new file mode 100644
index 00000000..020f9e37
--- /dev/null
+++ b/crates/egui_demo_lib/tests/snapshots/image_blending/image_dark_x2.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3827cbd75a015ab9d03d9f47ba40fcadb71a2ba3a312d0892ae22a8e379103bc
+size 12539
diff --git a/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x1.png b/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x1.png
new file mode 100644
index 00000000..f248a753
--- /dev/null
+++ b/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x1.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:afd019fc23aa4b8a899e2df92138b2b3e69b7cb1d20e038a5e841c84e9095fe1
+size 5740
diff --git a/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x2.png b/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x2.png
new file mode 100644
index 00000000..f5024f7a
--- /dev/null
+++ b/crates/egui_demo_lib/tests/snapshots/image_blending/image_light_x2.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:6129567eaf7d77c6656d9fe6984f1667b0817099492a24f6622da0f1d636e0e8
+size 13646
diff --git a/crates/epaint/src/text/font.rs b/crates/epaint/src/text/font.rs
index 37238918..c452eb4b 100644
--- a/crates/epaint/src/text/font.rs
+++ b/crates/epaint/src/text/font.rs
@@ -259,7 +259,7 @@ impl FontImpl {
 
             if let Some(space) = self.glyph_info(' ') {
                 let em = self.ab_glyph_font.units_per_em().unwrap_or(1.0);
-                let advance_width = f32::min(em / 6.0, space.advance_width_unscaled.0 * 0.5);
+                let advance_width = f32::min(em / 6.0, space.advance_width_unscaled.0 * 0.5); // TODO(emilk): make configurable
                 let glyph_info = GlyphInfo {
                     advance_width_unscaled: advance_width.into(),
                     ..space