Place Scale Marker: lay out the label in points, not pixels (#5754) (#5755)

fontSize is in points and type.create renders it at resolution/72 px
per point, but the bar height, label height and baseline treated it as
pixels. At 300 ppi a 12 pt label (50 px) overlapped the bar. Lay out in
font_size * dpi / 72 px; type.create still gets points. 72 ppi is
unchanged.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/engine/src/analysis_cmds.rs

@@ -1121,8 +1121,12 @@ fn place_scale_marker(s: &mut Session, p: &Value) -> Result<Value> {
     };
     // Bottom-left with a margin; the text sits under (or over) the bar.
     let margin = (w.min(h) * 0.03).round().max(2.0);
-    let bar_h = (font_size / 4.0).round().clamp(2.0, h / 4.0);
-    let text_h = if show_text { font_size * 1.25 } else { 0.0 };
+    // `fontSize` is in points; `type.create` renders it at resolution/72 px per point, so lay out
+    // the bar and label in those pixels (at 300 ppi, 12 pt is 50 px) (#5754).
+    let dpi = f64::from(d.resolution_dpi);
+    let font_px = font_size * if dpi.is_finite() && dpi > 0.0 { dpi / 72.0 } else { 1.0 };
+    let bar_h = (font_px / 4.0).round().clamp(2.0, h / 4.0);
+    let text_h = if show_text { font_px * 1.25 } else { 0.0 };
     // Keep the bar on the canvas when the text under it doesn't fit; the label is clipped instead (#932).
     let bar_y = if text_top { h - margin - bar_h } else { h - margin - bar_h - text_h }.max(0.0);
     // Likewise pull a bar nearly as wide as the image in from the right edge (#932).
@@ -1143,7 +1147,7 @@ fn place_scale_marker(s: &mut Session, p: &Value) -> Result<Value> {
         })?;
         let mut text_layer = Value::Null;
         if show_text {
-            let baseline = if text_top { f64::from(bar.y0) - font_size * 0.3 } else { f64::from(bar.y1) + font_size };
+            let baseline = if text_top { f64::from(bar.y0) - font_px * 0.3 } else { f64::from(bar.y1) + font_px };
             let mut tp = json!({"x": bar.x0, "y": baseline, "text": label, "size": font_size, "color": [rgb[0], rgb[1], rgb[2], 1.0], "name": label});
             if let Some(f) = &font {
                 tp["font"] = json!(f);

crates/engine/src/analysis_cmds/tests.rs

@@ -1,5 +1,5 @@
 use super::*;
-use photocraft_doc::ColorMode;
+use photocraft_doc::{ColorMode, LayerContent, LayerId};
 
 fn session(w: u32, h: u32, depth: u32) -> Session {
     let mut s = Session::new();
@@ -355,6 +355,27 @@ fn place_scale_marker_builds_one_group_in_one_step() {
     assert!(d(&s).layers.iter().all(|l| l.name != "Measurement Scale Marker"));
 }
 
+#[test]
+fn place_scale_marker_lays_out_its_label_in_points_at_high_resolution() {
+    // `fontSize` is in points and `type.create` renders it at resolution/72 px per point, but the
+    // layout treated it as pixels: at 300 ppi a 12 pt label (50 px) overlapped the bar.
+    for res in [72.0, 300.0] {
+        let mut s = Session::new();
+        s.execute("file.new", json!({"width": 1200, "height": 900, "resolution": res, "background": "white"})).unwrap();
+        let r = s.execute("image.analysis.placeScaleMarker", json!({"fontSize": 12, "textPosition": "bottom"})).unwrap();
+        let bar_bottom = r["barRect"][3].as_f64().unwrap();
+        let doc = d(&s);
+        let Some(LayerContent::Text(t)) = doc.layer(LayerId(r["text"].as_u64().unwrap())).map(|l| &l.content) else { panic!("a type layer: {r}") };
+        assert_eq!(t.size_pt, 12.0, "{res} ppi: type.create still gets points");
+        let layout = photocraft_text::shared().lock().unwrap().layout(t, doc.resolution_dpi);
+        let b = layout.bounds().expect("the label has a line");
+        let ty = t.transform.m[5];
+        let (top, bottom) = (f64::from(b[1]) + ty, f64::from(b[3]) + ty);
+        assert!(top >= bar_bottom - 0.5, "{res} ppi: label top {top} overlaps the bar ending at {bar_bottom}: {r}");
+        assert!(bottom <= 900.5, "{res} ppi: label bottom {bottom} stays on the canvas: {r}");
+    }
+}
+
 #[test]
 fn place_scale_marker_on_a_short_document_errors_without_panicking() {
     // A document under 8 px tall inverted the bar-height clamp and panicked (#932). Call `run`