tests/src/geometries.rs: Start a test module for element geometries

This will load the SVG template files from Horizon EDA and check them
against known-good descriptions of their elements' geometries.

Horizon EDA: https://github.com/horizon-eda/horizon

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/697>

3 files changed, 54 insertions, 0 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index cbc6a599..47baec23 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -6,6 +6,7 @@ test_sources =				\
 	src/compare_surfaces.rs		\
 	src/errors.rs			\
 	src/filters.rs			\
+	src/geometries.rs		\
 	src/intrinsic_dimensions.rs	\
 	src/legacy_sizing.rs		\
 	src/loading_crash.rs		\
diff --git a/tests/src/geometries.rs b/tests/src/geometries.rs
new file mode 100644
index 00000000..409e2527
--- /dev/null
+++ b/tests/src/geometries.rs
@@ -0,0 +1,50 @@
+//! Tests for the data files from https://github.com/horizon-eda/horizon/
+//!
+//! Horizon is an app Electronic Design Automation.  It has SVG templates with specially
+//! named elements; the app extracts their geometries and renders GUI widgets instead of
+//! those elements.  So, it is critical that the geometries get computed accurately.
+//!
+//! Horizon's build system pre-computes the geometries of the SVG templates' elements, and
+//! stores them in JSON files.  You can see the SVGs and the .subs JSON files in the
+//! tests/fixtures/horizon in the librsvg source tree.
+//!
+//! This test file has machinery to load the SVG templates, and the JSON files with the
+//! expected geometries.  The tests check that librsvg computes the same geometries every
+//! time.
+
+use anyhow::{Context, Result};
+use serde::Deserialize;
+use std::{collections::BTreeMap};
+use std::fs;
+use std::path::Path;
+
+// Copy of cairo::Rectangle
+//
+// Somehow I can't make serde's "remote" work here, in combination with the BTreeMap below...
+#[derive(Deserialize, Debug, PartialEq)]
+struct Rectangle {
+    x: f64,
+    y: f64,
+    width: f64,
+    height: f64,
+}
+
+impl From<cairo::Rectangle> for Rectangle {
+    fn from(r: cairo::Rectangle) -> Rectangle {
+        Rectangle {
+            x: r.x,
+            y: r.y,
+            width: r.width,
+            height: r.height,
+        }
+    }
+}
+
+#[derive(Deserialize)]
+struct Geometries(BTreeMap<String, Rectangle>);
+
+fn read_geometries(path: &Path) -> Result<Geometries> {
+    let contents = fs::read_to_string(path).context(format!("could not read {:?}", path))?;
+    Ok(serde_json::from_str(&contents).context(format!("could not parse JSON from {:?}", path))?)
+}
+
diff --git a/tests/src/main.rs b/tests/src/main.rs
index 71bc4a09..467cbb47 100644
--- a/tests/src/main.rs
+++ b/tests/src/main.rs
@@ -17,6 +17,9 @@ mod errors;
 mod filters;
 
 #[cfg(test)]
+mod geometries;
+
+#[cfg(test)]
 mod intrinsic_dimensions;
 
 #[cfg(test)]