Add image render tests

Add tests that will match rendered words/paragraphs against reference
images.

Use env var `GENERATE_IMAGES` to write the initial reference images to
the repository.

tests/common/mod.rs

@@ -0,0 +1,144 @@
+use std::path::PathBuf;
+
+use cosmic_text::{
+    fontdb::Database, Attrs, AttrsOwned, Buffer, Color, Family, FontSystem, Metrics, Shaping,
+    SwashCache,
+};
+use tiny_skia::{Paint, Pixmap, Rect, Transform};
+
+/// The test configuration.
+/// The text in the test will be rendered as image using the one of the fonts found under the
+/// `fonts` directory in this repository.
+/// The image will then be compared to an image with the name `name` under the `tests/images`
+/// directory in this repository.
+/// If the images do not match the test will fail.
+/// NOTE: if an environment variable `GENERATE_IMAGES` is set, the test will create and save
+/// the images instead.
+#[derive(Debug)]
+pub struct DrawTestCfg {
+    /// The name of the test.
+    /// Will be used for the image name under the `tests/images` directory in this repository.
+    name: String,
+    /// The text to render to image
+    text: String,
+    /// The name, details of the font to be used.
+    /// Expected to be one of the fonts found under the `fonts` directory in this repository.
+    font: AttrsOwned,
+
+    font_size: f32,
+    line_height: f32,
+    canvas_width: u32,
+    canvas_height: u32,
+}
+
+impl Default for DrawTestCfg {
+    fn default() -> Self {
+        let font = Attrs::new().family(Family::Serif);
+        Self {
+            name: "default".into(),
+            font: AttrsOwned::new(font),
+            text: "".into(),
+            font_size: 16.0,
+            line_height: 20.0,
+            canvas_width: 300,
+            canvas_height: 300,
+        }
+    }
+}
+
+impl DrawTestCfg {
+    pub fn new(name: impl Into<String>) -> Self {
+        Self {
+            name: name.into(),
+            ..Default::default()
+        }
+    }
+
+    pub fn text(mut self, text: impl Into<String>) -> Self {
+        self.text = text.into();
+        self
+    }
+
+    pub fn font_attrs(mut self, attrs: Attrs) -> Self {
+        self.font = AttrsOwned::new(attrs);
+        self
+    }
+
+    pub fn font_size(mut self, font_size: f32, line_height: f32) -> Self {
+        self.font_size = font_size;
+        self.line_height = line_height;
+        self
+    }
+
+    pub fn canvas(mut self, width: u32, height: u32) -> Self {
+        self.canvas_width = width;
+        self.canvas_height = height;
+        self
+    }
+
+    pub fn validate_text_rendering(self) {
+        let repo_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+        // Create a db with just the fonts in our fonts dir to make sure we only test those
+        let fonts_path = PathBuf::from(&repo_dir).join("fonts");
+        let mut font_db = Database::new();
+        font_db.load_fonts_dir(fonts_path);
+        let mut font_system = FontSystem::new_with_locale_and_db("En-US".into(), font_db);
+        let mut swash_cache = SwashCache::new();
+        let metrics = Metrics::new(self.font_size, self.line_height);
+        let mut buffer = Buffer::new(&mut font_system, metrics);
+        let mut buffer = buffer.borrow_with(&mut font_system);
+        let margins = 5;
+        buffer.set_size(
+            (self.canvas_width - margins * 2) as f32,
+            (self.canvas_height - margins * 2) as f32,
+        );
+        buffer.set_text(&self.text, self.font.as_attrs(), Shaping::Advanced);
+        buffer.shape_until_scroll();
+
+        // Black
+        let text_color = Color::rgb(0x00, 0x00, 0x00);
+
+        let mut pixmap = Pixmap::new(self.canvas_width, self.canvas_height).unwrap();
+        pixmap.fill(tiny_skia::Color::WHITE);
+
+        buffer.draw(&mut swash_cache, text_color, |x, y, w, h, color| {
+            let mut paint = Paint {
+                anti_alias: true,
+                ..Paint::default()
+            };
+            paint.set_color_rgba8(color.r(), color.g(), color.b(), color.a());
+            let rect = Rect::from_xywh(
+                (x + margins as i32) as f32,
+                (y + margins as i32) as f32,
+                w as f32,
+                h as f32,
+            )
+            .unwrap();
+            pixmap.fill_rect(rect, &paint, Transform::identity(), None);
+        });
+
+        let image_name = format!("{}.png", self.name);
+        let reference_image_path = PathBuf::from(&repo_dir)
+            .join("tests")
+            .join("images")
+            .join(image_name);
+
+        let generate_images = std::env::var("GENERATE_IMAGES")
+            .map(|v| {
+                let val = v.trim().to_ascii_lowercase();
+                ["t", "true", "1"].iter().any(|&v| v == val)
+            })
+            .unwrap_or_default();
+
+        if generate_images {
+            pixmap.save_png(reference_image_path).unwrap();
+        } else {
+            let reference_image_data = std::fs::read(reference_image_path).unwrap();
+            let image_data = pixmap.encode_png().unwrap();
+            assert_eq!(
+                reference_image_data, image_data,
+                "rendering failed of {self:?}"
+            )
+        }
+    }
+}

tests/images/a_hebrew_paragraph.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:e0350ffaa09ac5b9976b0441cfb0fab0db0b13e3a2d33260592e113c347bedfe
+size 23202

tests/images/a_hebrew_word.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:95bbe8f4db74914f6a124547f024463a3e434b3c7be3f86c1464af71ed39bba0
+size 3512

tests/images/an_arabic_paragraph.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:eb6966eec660c39584f11d353940f6a274eb90125c8b58fabf3c3e5066a5e1e4
+size 24322

tests/images/an_arabic_word.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ba0219c8e226f4bd79e0681a3189013ed035459fd3ed90405ec53d595e70ab81
+size 3851

tests/images/some_english_mixed_with_arabic.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ffbac330d91e73d8e28a2a83010e7f231bff6abfc9d9eda8720cb339c587084e
+size 23093

tests/images/some_english_mixed_with_hebrew.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:29fa23360829f2c11b960343b716eda01a069f6256a09b4eeb30d010abf7977f
+size 57340

tests/shaping_and_rendering.rs

@@ -0,0 +1,75 @@
+use common::DrawTestCfg;
+use cosmic_text::Attrs;
+use fontdb::Family;
+
+mod common;
+
+#[test]
+fn test_hebrew_word_rendering() {
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("a_hebrew_word")
+        .font_size(36., 40.)
+        .font_attrs(attrs)
+        .text("בדיקה")
+        .canvas(100, 60)
+        .validate_text_rendering();
+}
+
+#[test]
+fn test_hebrew_paragraph_rendering() {
+    let paragraph = "השועל החום המהיר קופץ מעל הכלב העצלן";
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("a_hebrew_paragraph")
+        .font_size(36., 40.)
+        .font_attrs(attrs)
+        .text(paragraph)
+        .canvas(400, 110)
+        .validate_text_rendering();
+}
+
+#[test]
+fn test_english_mixed_with_hebrew_paragraph_rendering() {
+    let paragraph = "Many computer programs fail to display bidirectional text correctly. For example, this page is mostly LTR English script, and here is the RTL Hebrew name Sarah: שרה, spelled sin (ש) on the right, resh (ר) in the middle, and heh (ה) on the left.";
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("some_english_mixed_with_hebrew")
+        .font_size(16., 20.)
+        .font_attrs(attrs)
+        .text(paragraph)
+        .canvas(400, 120)
+        .validate_text_rendering();
+}
+
+#[test]
+fn test_arabic_word_rendering() {
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("an_arabic_word")
+        .font_size(36., 40.)
+        .font_attrs(attrs)
+        .text("خالصة")
+        .canvas(100, 60)
+        .validate_text_rendering();
+}
+
+#[test]
+fn test_arabic_paragraph_rendering() {
+    let paragraph = "الثعلب البني السريع يقفز فوق الكلب الكسول";
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("an_arabic_paragraph")
+        .font_size(36., 40.)
+        .font_attrs(attrs)
+        .text(paragraph)
+        .canvas(400, 110)
+        .validate_text_rendering();
+}
+
+#[test]
+fn test_english_mixed_with_arabic_paragraph_rendering() {
+    let paragraph = "I like to render اللغة العربية in Rust!";
+    let attrs = Attrs::new().family(Family::Name("Noto Sans"));
+    DrawTestCfg::new("some_english_mixed_with_arabic")
+        .font_size(36., 40.)
+        .font_attrs(attrs)
+        .text(paragraph)
+        .canvas(400, 110)
+        .validate_text_rendering();
+}