Add image/svg support to `iced_glow`

https://github.com/iced-rs/iced/issues/674

Uses image/svg support in `iced_graphics`. The is not currently using an
atlas, and uses one texture/draw per image. This should be good enough
for now; supporting images with glow is better than not supporting them,
and if something else performs better, that improvement can be made
without any change to the public API.

7 files changed, 366 insertions, 6 deletions

diff --git a/glow/Cargo.toml b/glow/Cargo.toml
index 18215e9b..476547d4 100644
--- a/glow/Cargo.toml
+++ b/glow/Cargo.toml
@@ -8,12 +8,23 @@ license = "MIT AND OFL-1.1"
 repository = "https://github.com/iced-rs/iced"
 
 [features]
+svg = ["iced_graphics/svg"]
+image = ["image_rs", "iced_graphics/image", "png", "jpeg", "jpeg_rayon", "gif", "webp", "bmp"]
+image_rs = ["iced_graphics/image_rs"]
+png = ["iced_graphics/png"]
+jpeg = ["iced_graphics/jpeg"]
+jpeg_rayon = ["iced_graphics/jpeg_rayon"]
+gif = ["iced_graphics/gif"]
+webp = ["iced_graphics/webp"]
+pnm = ["iced_graphics/pnm"]
+ico = ["iced_graphics/ico"]
+bmp = ["iced_graphics/bmp"]
+hdr = ["iced_graphics/hdr"]
+dds = ["iced_graphics/dds"]
+farbfeld = ["iced_graphics/farbfeld"]
 canvas = ["iced_graphics/canvas"]
 qr_code = ["iced_graphics/qr_code"]
 default_system_font = ["iced_graphics/font-source"]
-# Not supported yet!
-image = []
-svg = []
 
 [dependencies]
 glow = "0.11.1"
@@ -22,6 +33,8 @@ glyph_brush = "0.7"
 euclid = "0.22"
 bytemuck = "1.4"
 log = "0.4"
+kamadak-exif = "0.5"
+bitflags = "1.2"
 
 [dependencies.iced_native]
 version = "0.5"
diff --git a/glow/src/backend.rs b/glow/src/backend.rs
index 21af2ecf..1ba70a49 100644
--- a/glow/src/backend.rs
+++ b/glow/src/backend.rs
@@ -1,3 +1,5 @@
+#[cfg(any(feature = "image_rs", feature = "svg"))]
+use crate::image;
 use crate::quad;
 use crate::text;
 use crate::{program, triangle};
@@ -15,6 +17,8 @@ use iced_native::{Font, Size};
 /// [`iced`]: https://github.com/iced-rs/iced
 #[derive(Debug)]
 pub struct Backend {
+    #[cfg(any(feature = "image_rs", feature = "svg"))]
+    image_pipeline: image::Pipeline,
     quad_pipeline: quad::Pipeline,
     text_pipeline: text::Pipeline,
     triangle_pipeline: triangle::Pipeline,
@@ -32,10 +36,14 @@ impl Backend {
 
         let shader_version = program::Version::new(gl);
 
+        #[cfg(any(feature = "image_rs", feature = "svg"))]
+        let image_pipeline = image::Pipeline::new(gl, &shader_version);
         let quad_pipeline = quad::Pipeline::new(gl, &shader_version);
         let triangle_pipeline = triangle::Pipeline::new(gl, &shader_version);
 
         Self {
+            #[cfg(any(feature = "image_rs", feature = "svg"))]
+            image_pipeline,
             quad_pipeline,
             text_pipeline,
             triangle_pipeline,
@@ -70,6 +78,9 @@ impl Backend {
                 viewport_size.height,
             );
         }
+
+        #[cfg(any(feature = "image_rs", feature = "svg"))]
+        self.image_pipeline.trim_cache(gl);
     }
 
     fn flush(
@@ -112,6 +123,15 @@ impl Backend {
             );
         }
 
+        #[cfg(any(feature = "image_rs", feature = "svg"))]
+        if !layer.images.is_empty() {
+            let scaled = transformation
+                * Transformation::scale(scale_factor, scale_factor);
+
+            self.image_pipeline
+                .draw(gl, scaled, scale_factor, &layer.images);
+        }
+
         if !layer.text.is_empty() {
             for text in layer.text.iter() {
                 // Target physical coordinates directly to avoid blurry text
@@ -236,10 +256,10 @@ impl backend::Text for Backend {
     }
 }
 
-#[cfg(feature = "image")]
+#[cfg(feature = "image_rs")]
 impl backend::Image for Backend {
-    fn dimensions(&self, _handle: &iced_native::image::Handle) -> (u32, u32) {
-        (50, 50)
+    fn dimensions(&self, handle: &iced_native::image::Handle) -> (u32, u32) {
+        self.image_pipeline.dimensions(handle)
     }
 }
 
diff --git a/glow/src/image.rs b/glow/src/image.rs
new file mode 100644
index 00000000..51e3016e
--- /dev/null
+++ b/glow/src/image.rs
@@ -0,0 +1,212 @@
+use crate::program::{self, Shader};
+use crate::Transformation;
+use glow::HasContext;
+use iced_graphics::layer;
+#[cfg(feature = "image_rs")]
+use std::cell::RefCell;
+
+pub use iced_graphics::triangle::{Mesh2D, Vertex2D};
+
+#[cfg(feature = "image_rs")]
+use iced_graphics::image::raster;
+
+#[cfg(feature = "svg")]
+use iced_graphics::image::vector;
+
+mod textures;
+use textures::{Entry, Textures};
+
+#[derive(Debug)]
+pub(crate) struct Pipeline {
+    program: <glow::Context as HasContext>::Program,
+    vertex_array: <glow::Context as HasContext>::VertexArray,
+    vertex_buffer: <glow::Context as HasContext>::Buffer,
+    transform_location: <glow::Context as HasContext>::UniformLocation,
+    textures: Textures,
+    #[cfg(feature = "image_rs")]
+    raster_cache: RefCell<raster::Cache<Textures>>,
+    #[cfg(feature = "svg")]
+    vector_cache: vector::Cache<Textures>,
+}
+
+impl Pipeline {
+    pub fn new(
+        gl: &glow::Context,
+        shader_version: &program::Version,
+    ) -> Pipeline {
+        let program = unsafe {
+            let vertex_shader = Shader::vertex(
+                gl,
+                shader_version,
+                include_str!("shader/common/image.vert"),
+            );
+            let fragment_shader = Shader::fragment(
+                gl,
+                shader_version,
+                include_str!("shader/common/image.frag"),
+            );
+
+            program::create(
+                gl,
+                &[vertex_shader, fragment_shader],
+                &[(0, "i_Position")],
+            )
+        };
+
+        let transform_location =
+            unsafe { gl.get_uniform_location(program, "u_Transform") }
+                .expect("Get transform location");
+
+        unsafe {
+            gl.use_program(Some(program));
+
+            let transform: [f32; 16] = Transformation::identity().into();
+            gl.uniform_matrix_4_f32_slice(
+                Some(&transform_location),
+                false,
+                &transform,
+            );
+
+            gl.use_program(None);
+        }
+
+        let vertex_buffer =
+            unsafe { gl.create_buffer().expect("Create vertex buffer") };
+        let vertex_array =
+            unsafe { gl.create_vertex_array().expect("Create vertex array") };
+
+        unsafe {
+            gl.bind_vertex_array(Some(vertex_array));
+            gl.bind_buffer(glow::ARRAY_BUFFER, Some(vertex_buffer));
+
+            let vertices = &[0u8, 0, 1, 0, 0, 1, 1, 1];
+            gl.buffer_data_size(
+                glow::ARRAY_BUFFER,
+                vertices.len() as i32,
+                glow::STATIC_DRAW,
+            );
+            gl.buffer_sub_data_u8_slice(
+                glow::ARRAY_BUFFER,
+                0,
+                bytemuck::cast_slice(vertices),
+            );
+
+            gl.enable_vertex_attrib_array(0);
+            gl.vertex_attrib_pointer_f32(
+                0,
+                2,
+                glow::UNSIGNED_BYTE,
+                false,
+                0,
+                0,
+            );
+
+            gl.bind_buffer(glow::ARRAY_BUFFER, None);
+            gl.bind_vertex_array(None);
+        }
+
+        Pipeline {
+            program,
+            vertex_array,
+            vertex_buffer,
+            transform_location,
+            textures: Textures::new(),
+            #[cfg(feature = "image_rs")]
+            raster_cache: RefCell::new(raster::Cache::default()),
+            #[cfg(feature = "svg")]
+            vector_cache: vector::Cache::default(),
+        }
+    }
+
+    #[cfg(feature = "image_rs")]
+    pub fn dimensions(
+        &self,
+        handle: &iced_native::image::Handle,
+    ) -> (u32, u32) {
+        self.raster_cache.borrow_mut().load(handle).dimensions()
+    }
+
+    pub fn draw(
+        &mut self,
+        mut gl: &glow::Context,
+        transformation: Transformation,
+        _scale_factor: f32,
+        images: &[layer::Image],
+    ) {
+        unsafe {
+            gl.use_program(Some(self.program));
+            gl.bind_vertex_array(Some(self.vertex_array));
+            gl.bind_buffer(glow::ARRAY_BUFFER, Some(self.vertex_buffer));
+        }
+
+        #[cfg(feature = "image_rs")]
+        let mut raster_cache = self.raster_cache.borrow_mut();
+        for image in images {
+            let (entry, bounds) = match &image {
+                #[cfg(feature = "image_rs")]
+                layer::Image::Raster { handle, bounds } => (
+                    raster_cache.upload(handle, &mut gl, &mut self.textures),
+                    bounds,
+                ),
+                #[cfg(not(feature = "image_rs"))]
+                layer::Image::Raster { handle: _, bounds } => (None, bounds),
+
+                #[cfg(feature = "svg")]
+                layer::Image::Vector { handle, bounds } => {
+                    let size = [bounds.width, bounds.height];
+                    (
+                        self.vector_cache.upload(
+                            handle,
+                            size,
+                            _scale_factor,
+                            &mut gl,
+                            &mut self.textures,
+                        ),
+                        bounds,
+                    )
+                }
+
+                #[cfg(not(feature = "svg"))]
+                layer::Image::Vector { handle: _, bounds } => (None, bounds),
+            };
+
+            unsafe {
+                if let Some(Entry { texture, .. }) = entry {
+                    gl.bind_texture(glow::TEXTURE_2D, Some(*texture))
+                } else {
+                    continue;
+                }
+
+                let translate = Transformation::translate(bounds.x, bounds.y);
+                let scale = Transformation::scale(bounds.width, bounds.height);
+                let transformation = transformation * translate * scale;
+                let matrix: [f32; 16] = transformation.into();
+                gl.uniform_matrix_4_f32_slice(
+                    Some(&self.transform_location),
+                    false,
+                    &matrix,
+                );
+
+                gl.draw_arrays(glow::TRIANGLE_STRIP, 0, 4);
+
+                gl.bind_texture(glow::TEXTURE_2D, None);
+            }
+        }
+
+        unsafe {
+            gl.bind_buffer(glow::ARRAY_BUFFER, None);
+            gl.bind_vertex_array(None);
+            gl.use_program(None);
+        }
+    }
+
+    pub fn trim_cache(&mut self, mut gl: &glow::Context) {
+        #[cfg(feature = "image_rs")]
+        self.raster_cache
+            .borrow_mut()
+            .trim(&mut self.textures, &mut gl);
+
+        #[cfg(feature = "svg")]
+        self.vector_cache.trim(&mut self.textures, &mut gl);
+    }
+}
diff --git a/glow/src/image/textures.rs b/glow/src/image/textures.rs
new file mode 100644
index 00000000..f43cae1c
--- /dev/null
+++ b/glow/src/image/textures.rs
@@ -0,0 +1,82 @@
+use glow::HasContext;
+use iced_graphics::image::{TextureStore, TextureStoreEntry};
+
+#[derive(Debug)]
+pub struct Textures;
+
+impl Textures {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl TextureStore for Textures {
+    type Entry = Entry;
+    type State<'a> = &'a glow::Context;
+
+    fn upload(
+        &mut self,
+        width: u32,
+        height: u32,
+        data: &[u8],
+        gl: &mut &glow::Context,
+    ) -> Option<Self::Entry> {
+        unsafe {
+            let texture = gl.create_texture().expect("create texture");
+            gl.bind_texture(glow::TEXTURE_2D, Some(texture));
+            gl.tex_image_2d(
+                glow::TEXTURE_2D,
+                0,
+                glow::SRGB8_ALPHA8 as i32,
+                width as i32,
+                height as i32,
+                0,
+                glow::BGRA,
+                glow::UNSIGNED_BYTE,
+                Some(data),
+            );
+            gl.tex_parameter_i32(
+                glow::TEXTURE_2D,
+                glow::TEXTURE_WRAP_S,
+                glow::CLAMP_TO_EDGE as _,
+            );
+            gl.tex_parameter_i32(
+                glow::TEXTURE_2D,
+                glow::TEXTURE_WRAP_T,
+                glow::CLAMP_TO_EDGE as _,
+            );
+            gl.tex_parameter_i32(
+                glow::TEXTURE_2D,
+                glow::TEXTURE_MIN_FILTER,
+                glow::LINEAR as _,
+            );
+            gl.tex_parameter_i32(
+                glow::TEXTURE_2D,
+                glow::TEXTURE_MAG_FILTER,
+                glow::LINEAR as _,
+            );
+            gl.bind_texture(glow::TEXTURE_2D, None);
+
+            Some(Entry {
+                size: (width, height),
+                texture,
+            })
+        }
+    }
+
+    fn remove(&mut self, entry: &Entry, gl: &mut &glow::Context) {
+        unsafe { gl.delete_texture(entry.texture) }
+    }
+}
+
+#[derive(Debug)]
+pub struct Entry {
+    size: (u32, u32),
+    pub texture: glow::NativeTexture,
+}
+
+impl TextureStoreEntry for Entry {
+    fn size(&self) -> (u32, u32) {
+        self.size
+    }
+}
diff --git a/glow/src/lib.rs b/glow/src/lib.rs
index de9c0002..daeb3e32 100644
--- a/glow/src/lib.rs
+++ b/glow/src/lib.rs
@@ -24,6 +24,8 @@
 pub use glow;
 
 mod backend;
+#[cfg(any(feature = "image_rs", feature = "svg"))]
+mod image;
 mod program;
 mod quad;
 mod text;
diff --git a/glow/src/shader/common/image.frag b/glow/src/shader/common/image.frag
new file mode 100644
index 00000000..5e05abdf
--- /dev/null
+++ b/glow/src/shader/common/image.frag
@@ -0,0 +1,22 @@
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
+#endif
+
+uniform sampler2D tex;
+in vec2 tex_pos;
+
+#ifdef HIGHER_THAN_300
+out vec4 fragColor;
+#define gl_FragColor fragColor
+#endif
+#ifdef GL_ES
+#define texture texture2D
+#endif
+
+void main() {
+    gl_FragColor = texture(tex, tex_pos);
+}
diff --git a/glow/src/shader/common/image.vert b/glow/src/shader/common/image.vert
new file mode 100644
index 00000000..93e541f2
--- /dev/null
+++ b/glow/src/shader/common/image.vert
@@ -0,0 +1,9 @@
+uniform mat4 u_Transform;
+
+in vec2 i_Position;
+out vec2 tex_pos;
+
+void main() {
+    gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
+    tex_pos = i_Position;
+}