Adds linear gradient support to 2D meshes in the canvas widget.

8 files changed, 429 insertions, 123 deletions

diff --git a/glow/src/backend.rs b/glow/src/backend.rs
index 78d4229e..6fc4fb38 100644
--- a/glow/src/backend.rs
+++ b/glow/src/backend.rs
@@ -1,7 +1,6 @@
-use crate::program;
+use crate::{program, triangle};
 use crate::quad;
 use crate::text;
-use crate::triangle;
 use crate::{Settings, Transformation, Viewport};
 
 use iced_graphics::backend;
@@ -100,16 +99,16 @@ impl Backend {
             );
         }
 
-        if !layer.meshes.is_empty() {
+        if !layer.meshes.0.is_empty() {
             let scaled = transformation
                 * Transformation::scale(scale_factor, scale_factor);
 
             self.triangle_pipeline.draw(
+                &layer.meshes,
                 gl,
                 target_height,
                 scaled,
                 scale_factor,
-                &layer.meshes,
             );
         }
 
diff --git a/glow/src/shader/common/gradient.frag b/glow/src/shader/common/gradient.frag
new file mode 100644
index 00000000..588f63e0
--- /dev/null
+++ b/glow/src/shader/common/gradient.frag
@@ -0,0 +1,48 @@
+// GLSL does not support dynamically sized arrays without SSBOs
+#define MAX_STOPS 64
+
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
+#endif
+
+#ifdef HIGHER_THAN_300
+layout (location = 0) out vec4 fragColor;
+#define gl_FragColor fragColor
+#endif
+
+in vec2 raw_position;
+
+uniform vec2 gradient_start;
+uniform vec2 gradient_end;
+
+uniform uint color_stops_size;
+uniform float color_stop_offsets[MAX_STOPS];
+uniform vec4 color_stop_colors[MAX_STOPS];
+
+void main() {
+    vec2 gradient_vec = vec2(gradient_end - gradient_start);
+    vec2 current_vec = vec2(raw_position.xy - gradient_start);
+    vec2 unit = normalize(gradient_vec);
+    float coord_offset = dot(unit, current_vec) / length(gradient_vec);
+
+    for (uint i = 0; i < color_stops_size - 1; i++) {
+        float stop_offset = color_stop_offsets[i];
+        float next_stop_offset = color_stop_offsets[i + 1];
+
+        if (stop_offset <= coord_offset && coord_offset <= next_stop_offset) {
+            fragColor = mix(color_stop_colors[i], color_stop_colors[i+1], smoothstep(
+                stop_offset,
+                next_stop_offset,
+                coord_offset
+            ));
+        } else if (coord_offset < color_stop_offsets[0]) {
+            fragColor = color_stop_colors[0];
+        } else if (coord_offset > color_stop_offsets[color_stops_size - 1]) {
+            fragColor = color_stop_colors[color_stops_size - 1];
+        }
+    }
+}
\ No newline at end of file
diff --git a/glow/src/shader/common/triangle.frag b/glow/src/shader/common/triangle.frag
index e8689f2e..0ee65239 100644
--- a/glow/src/shader/common/triangle.frag
+++ b/glow/src/shader/common/triangle.frag
@@ -11,8 +11,8 @@ out vec4 fragColor;
 #define gl_FragColor fragColor
 #endif
 
-in vec4 v_Color;
+uniform vec4 color;
 
 void main() {
-    gl_FragColor = v_Color;
+    fragColor = color;
 }
\ No newline at end of file
diff --git a/glow/src/shader/common/triangle.vert b/glow/src/shader/common/triangle.vert
index d0494a5f..09a4e324 100644
--- a/glow/src/shader/common/triangle.vert
+++ b/glow/src/shader/common/triangle.vert
@@ -1,11 +1,9 @@
 uniform mat4 u_Transform;
 
 in vec2 i_Position;
-in vec4 i_Color;
-
-out vec4 v_Color;
+out vec2 raw_position;
 
 void main() {
     gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
-    v_Color = i_Color;
+    raw_position = i_Position;
 }
\ No newline at end of file
diff --git a/glow/src/triangle.rs b/glow/src/triangle.rs
index ae4f83ef..7d0e14c7 100644
--- a/glow/src/triangle.rs
+++ b/glow/src/triangle.rs
@@ -1,66 +1,41 @@
-//! Draw meshes of triangles.
+//! Draw meshes of triangle.
+mod gradient;
+mod solid;
+
 use crate::program::{self, Shader};
 use crate::Transformation;
 use glow::HasContext;
-use iced_graphics::layer;
+use iced_graphics::layer::{Mesh, Meshes};
+use iced_graphics::shader;
 use std::marker::PhantomData;
 
+use crate::triangle::gradient::GradientProgram;
+use crate::triangle::solid::SolidProgram;
 pub use iced_graphics::triangle::{Mesh2D, Vertex2D};
 
-const VERTEX_BUFFER_SIZE: usize = 10_000;
-const INDEX_BUFFER_SIZE: usize = 10_000;
-
 #[derive(Debug)]
 pub(crate) struct Pipeline {
-    program: <glow::Context as HasContext>::Program,
     vertex_array: <glow::Context as HasContext>::VertexArray,
     vertices: Buffer<Vertex2D>,
     indices: Buffer<u32>,
-    transform_location: <glow::Context as HasContext>::UniformLocation,
     current_transform: Transformation,
+    programs: TrianglePrograms,
 }
 
-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/triangle.vert"),
-            );
-            let fragment_shader = Shader::fragment(
-                gl,
-                shader_version,
-                include_str!("shader/common/triangle.frag"),
-            );
-
-            program::create(
-                gl,
-                &[vertex_shader, fragment_shader],
-                &[(0, "i_Position"), (1, "i_Color")],
-            )
-        };
-
-        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,
-            );
+#[derive(Debug)]
+struct TrianglePrograms {
+    solid: TriangleProgram,
+    gradient: TriangleProgram,
+}
 
-            gl.use_program(None);
-        }
+#[derive(Debug)]
+enum TriangleProgram {
+    Solid(SolidProgram),
+    Gradient(GradientProgram),
+}
 
+impl Pipeline {
+    pub fn new(gl: &glow::Context, shader_version: &program::Version) -> Self {
         let vertex_array =
             unsafe { gl.create_vertex_array().expect("Create vertex array") };
 
@@ -73,7 +48,7 @@ impl Pipeline {
                 gl,
                 glow::ARRAY_BUFFER,
                 glow::DYNAMIC_DRAW,
-                VERTEX_BUFFER_SIZE,
+                std::mem::size_of::<Vertex2D>() as usize,
             )
         };
 
@@ -82,7 +57,7 @@ impl Pipeline {
                 gl,
                 glow::ELEMENT_ARRAY_BUFFER,
                 glow::DYNAMIC_DRAW,
-                INDEX_BUFFER_SIZE,
+                std::mem::size_of::<u32>() as usize,
             )
         };
 
@@ -92,58 +67,45 @@ impl Pipeline {
             gl.enable_vertex_attrib_array(0);
             gl.vertex_attrib_pointer_f32(0, 2, glow::FLOAT, false, stride, 0);
 
-            gl.enable_vertex_attrib_array(1);
-            gl.vertex_attrib_pointer_f32(
-                1,
-                4,
-                glow::FLOAT,
-                false,
-                stride,
-                4 * 2,
-            );
-
             gl.bind_vertex_array(None);
-        }
+        };
 
-        Pipeline {
-            program,
+        Self {
             vertex_array,
             vertices,
             indices,
-            transform_location,
             current_transform: Transformation::identity(),
+            programs: TrianglePrograms {
+                solid: TriangleProgram::Solid(SolidProgram::new(
+                    gl,
+                    shader_version,
+                )),
+                gradient: TriangleProgram::Gradient(GradientProgram::new(
+                    gl,
+                    shader_version,
+                )),
+            },
         }
     }
 
     pub fn draw(
         &mut self,
+        meshes: &Meshes<'_>,
         gl: &glow::Context,
         target_height: u32,
         transformation: Transformation,
         scale_factor: f32,
-        meshes: &[layer::Mesh<'_>],
     ) {
         unsafe {
             gl.enable(glow::MULTISAMPLE);
             gl.enable(glow::SCISSOR_TEST);
-            gl.use_program(Some(self.program));
-            gl.bind_vertex_array(Some(self.vertex_array));
+            gl.bind_vertex_array(Some(self.vertex_array))
         }
 
-        // This looks a bit crazy, but we are just counting how many vertices
-        // and indices we will need to handle.
-        // TODO: Improve readability
-        let (total_vertices, total_indices) = meshes
-            .iter()
-            .map(|layer::Mesh { buffers, .. }| {
-                (buffers.vertices.len(), buffers.indices.len())
-            })
-            .fold((0, 0), |(total_v, total_i), (v, i)| {
-                (total_v + v, total_i + i)
-            });
-
-        // Then we ensure the current buffers are big enough, resizing if
-        // necessary
+        //count the total number of vertices & indices we need to handle for all meshes
+        let (total_vertices, total_indices) = meshes.attribute_count();
+
+        // Then we ensure the current attribute buffers are big enough, resizing if necessary
         unsafe {
             self.vertices.bind(gl, total_vertices);
             self.indices.bind(gl, total_indices);
@@ -153,7 +115,7 @@ impl Pipeline {
         let mut last_vertex = 0;
         let mut last_index = 0;
 
-        for layer::Mesh { buffers, .. } in meshes {
+        for Mesh { buffers, .. } in meshes.0.iter() {
             unsafe {
                 gl.buffer_sub_data_u8_slice(
                     glow::ARRAY_BUFFER,
@@ -176,11 +138,12 @@ impl Pipeline {
         let mut last_vertex = 0;
         let mut last_index = 0;
 
-        for layer::Mesh {
+        for Mesh {
             buffers,
             origin,
             clip_bounds,
-        } in meshes
+            shader,
+        } in meshes.0.iter()
         {
             let transform =
                 transformation * Transformation::translate(origin.x, origin.y);
@@ -188,17 +151,6 @@ impl Pipeline {
             let clip_bounds = (*clip_bounds * scale_factor).snap();
 
             unsafe {
-                if self.current_transform != transform {
-                    let matrix: [f32; 16] = transform.into();
-                    gl.uniform_matrix_4_f32_slice(
-                        Some(&self.transform_location),
-                        false,
-                        &matrix,
-                    );
-
-                    self.current_transform = transform;
-                }
-
                 gl.scissor(
                     clip_bounds.x as i32,
                     (target_height - (clip_bounds.y + clip_bounds.height))
@@ -207,6 +159,15 @@ impl Pipeline {
                     clip_bounds.height as i32,
                 );
 
+                let t = if self.current_transform != transform {
+                    self.current_transform = transform;
+                    Some(transform)
+                } else {
+                    None
+                };
+
+                self.use_with_shader(gl, shader, t);
+
                 gl.draw_elements_base_vertex(
                     glow::TRIANGLES,
                     buffers.indices.len() as i32,
@@ -222,34 +183,79 @@ impl Pipeline {
 
         unsafe {
             gl.bind_vertex_array(None);
-            gl.use_program(None);
             gl.disable(glow::SCISSOR_TEST);
             gl.disable(glow::MULTISAMPLE);
         }
     }
-}
 
-#[repr(C)]
-#[derive(Debug, Clone, Copy)]
-struct Uniforms {
-    transform: [f32; 16],
+    fn use_with_shader(
+        &mut self,
+        gl: &glow::Context,
+        shader: &shader::Shader,
+        transform: Option<Transformation>,
+    ) {
+        match shader {
+            shader::Shader::Solid(color) => {
+                if let TriangleProgram::Solid(solid_program) =
+                    &mut self.programs.solid
+                {
+                    unsafe { gl.use_program(Some(solid_program.program)) }
+                    solid_program.set_uniforms(gl, color, transform);
+                }
+            }
+            shader::Shader::Gradient(gradient) => {
+                if let TriangleProgram::Gradient(gradient_program) =
+                    &mut self.programs.gradient
+                {
+                    unsafe { gl.use_program(Some(gradient_program.program)) }
+                    gradient_program.set_uniforms(gl, gradient, transform);
+                }
+            }
+        }
+    }
 }
 
-unsafe impl bytemuck::Zeroable for Uniforms {}
-unsafe impl bytemuck::Pod for Uniforms {}
-
-impl Default for Uniforms {
-    fn default() -> Self {
-        Self {
-            transform: *Transformation::identity().as_ref(),
-        }
+/// A simple shader program. Uses [`triangle.vert`] for its vertex shader and only binds position
+/// attribute location.
+pub(super) fn simple_triangle_program(
+    gl: &glow::Context,
+    shader_version: &program::Version,
+    fragment_shader: &'static str,
+) -> <glow::Context as HasContext>::Program {
+    unsafe {
+        let vertex_shader = Shader::vertex(
+            gl,
+            shader_version,
+            include_str!("shader/common/triangle.vert"),
+        );
+
+        let fragment_shader =
+            Shader::fragment(gl, shader_version, fragment_shader);
+
+        program::create(
+            gl,
+            &[vertex_shader, fragment_shader],
+            &[(0, "i_Position")],
+        )
     }
 }
 
-impl From<Transformation> for Uniforms {
-    fn from(transformation: Transformation) -> Uniforms {
-        Self {
-            transform: transformation.into(),
+pub(super) fn update_transform(
+    gl: &glow::Context,
+    program: <glow::Context as HasContext>::Program,
+    transform: Option<Transformation>
+) {
+    if let Some(t) = transform {
+        let transform_location =
+            unsafe { gl.get_uniform_location(program, "u_Transform") }
+                .expect("Get transform location.");
+
+        unsafe {
+            gl.uniform_matrix_4_f32_slice(
+                Some(&transform_location),
+                false,
+                t.as_ref(),
+            );
         }
     }
 }
diff --git a/glow/src/triangle/gradient.rs b/glow/src/triangle/gradient.rs
new file mode 100644
index 00000000..d1b10d77
--- /dev/null
+++ b/glow/src/triangle/gradient.rs
@@ -0,0 +1,189 @@
+use crate::program::Version;
+use crate::triangle::{simple_triangle_program, update_transform};
+use glow::{Context, HasContext, NativeProgram};
+use iced_graphics::gradient::Gradient;
+use iced_graphics::widget::canvas::gradient::Linear;
+use iced_graphics::Transformation;
+
+#[derive(Debug)]
+pub(super) struct GradientProgram {
+    pub(super) program: <Context as HasContext>::Program,
+    pub(super) uniform_data: GradientUniformData,
+}
+
+impl GradientProgram {
+    pub(super) fn new(gl: &Context, shader_version: &Version) -> Self {
+        let program = simple_triangle_program(
+            gl,
+            shader_version,
+            include_str!("../shader/common/gradient.frag"),
+        );
+
+        Self {
+            program,
+            uniform_data: GradientUniformData::new(gl, program),
+        }
+    }
+
+    pub(super) fn set_uniforms<'a>(
+        &mut self,
+        gl: &Context,
+        gradient: &Gradient,
+        transform: Option<Transformation>,
+    ) {
+        update_transform(gl, self.program, transform);
+
+        if &self.uniform_data.current_gradient != gradient {
+            match gradient {
+                Gradient::Linear(linear) => {
+                    let gradient_start: [f32; 2] = (linear.start).into();
+                    let gradient_end: [f32; 2] = (linear.end).into();
+
+                    unsafe {
+                        gl.uniform_2_f32(
+                            Some(
+                                &self
+                                    .uniform_data
+                                    .uniform_locations
+                                    .gradient_start_location,
+                            ),
+                            gradient_start[0],
+                            gradient_start[1],
+                        );
+
+                        gl.uniform_2_f32(
+                            Some(
+                                &self
+                                    .uniform_data
+                                    .uniform_locations
+                                    .gradient_end_location,
+                            ),
+                            gradient_end[0],
+                            gradient_end[1],
+                        );
+
+                        gl.uniform_1_u32(
+                            Some(
+                                &self
+                                    .uniform_data
+                                    .uniform_locations
+                                    .color_stops_size_location,
+                            ),
+                            linear.color_stops.len() as u32,
+                        );
+
+                        for (index, stop) in
+                            linear.color_stops.iter().enumerate()
+                        {
+                            gl.uniform_1_f32(
+                                Some(
+                                    &self
+                                        .uniform_data
+                                        .uniform_locations
+                                        .color_stops_locations[index]
+                                        .offset,
+                                ),
+                                stop.offset,
+                            );
+
+                            gl.uniform_4_f32(
+                                Some(
+                                    &self
+                                        .uniform_data
+                                        .uniform_locations
+                                        .color_stops_locations[index]
+                                        .color,
+                                ),
+                                stop.color.r,
+                                stop.color.g,
+                                stop.color.b,
+                                stop.color.a,
+                            );
+                        }
+                    }
+                }
+            }
+
+            self.uniform_data.current_gradient = gradient.clone();
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(super) struct GradientUniformData {
+    current_gradient: Gradient,
+    uniform_locations: GradientUniformLocations,
+}
+
+#[derive(Debug)]
+struct GradientUniformLocations {
+    gradient_start_location: <Context as HasContext>::UniformLocation,
+    gradient_end_location: <Context as HasContext>::UniformLocation,
+    color_stops_size_location: <Context as HasContext>::UniformLocation,
+    //currently the maximum number of stops is 64 due to needing to allocate the
+    //memory for the array of stops with a const value in GLSL
+    color_stops_locations: [ColorStopLocation; 64],
+}
+
+#[derive(Copy, Debug, Clone)]
+struct ColorStopLocation {
+    color: <Context as HasContext>::UniformLocation,
+    offset: <Context as HasContext>::UniformLocation,
+}
+
+impl GradientUniformData {
+    fn new(gl: &Context, program: NativeProgram) -> Self {
+        let gradient_start_location =
+            unsafe { gl.get_uniform_location(program, "gradient_start") }
+                .expect("Gradient - Get gradient_start.");
+
+        let gradient_end_location =
+            unsafe { gl.get_uniform_location(program, "gradient_end") }
+                .expect("Gradient - Get gradient_end.");
+
+        let color_stops_size_location =
+            unsafe { gl.get_uniform_location(program, "color_stops_size") }
+                .expect("Gradient - Get color_stops_size.");
+
+        let color_stops_locations: [ColorStopLocation; 64] =
+            core::array::from_fn(|index| {
+                let offset = unsafe {
+                    gl.get_uniform_location(
+                        program,
+                        &format!("color_stop_offsets[{}]", index),
+                    )
+                }
+                .expect(&format!(
+                    "Gradient - Color stop offset with index {}",
+                    index
+                ));
+
+                let color = unsafe {
+                    gl.get_uniform_location(
+                        program,
+                        &format!("color_stop_colors[{}]", index),
+                    )
+                }
+                .expect(&format!(
+                    "Gradient - Color stop colors with index {}",
+                    index
+                ));
+
+                ColorStopLocation { color, offset }
+            });
+
+        GradientUniformData {
+            current_gradient: Gradient::Linear(Linear {
+                start: Default::default(),
+                end: Default::default(),
+                color_stops: vec![],
+            }),
+            uniform_locations: GradientUniformLocations {
+                gradient_start_location,
+                gradient_end_location,
+                color_stops_size_location,
+                color_stops_locations,
+            },
+        }
+    }
+}
diff --git a/glow/src/triangle/solid.rs b/glow/src/triangle/solid.rs
new file mode 100644
index 00000000..3a33cea8
--- /dev/null
+++ b/glow/src/triangle/solid.rs
@@ -0,0 +1,67 @@
+use crate::program::Version;
+use crate::triangle::{simple_triangle_program, update_transform};
+use crate::Color;
+use glow::{Context, HasContext, NativeProgram};
+use iced_graphics::Transformation;
+
+#[derive(Debug)]
+pub struct SolidProgram {
+    pub(crate) program: <Context as HasContext>::Program,
+    pub(crate) uniform_data: SolidUniformData,
+}
+
+impl SolidProgram {
+    pub fn new(gl: &Context, shader_version: &Version) -> Self {
+        let program = simple_triangle_program(
+            gl,
+            shader_version,
+            include_str!("../shader/common/triangle.frag"),
+        );
+
+        Self {
+            program,
+            uniform_data: SolidUniformData::new(gl, program),
+        }
+    }
+
+    pub fn set_uniforms<'a>(
+        &mut self,
+        gl: &Context,
+        color: &Color,
+        transform: Option<Transformation>,
+    ) {
+        update_transform(gl, self.program, transform);
+
+        if &self.uniform_data.color != color {
+            unsafe {
+                gl.uniform_4_f32(
+                    Some(&self.uniform_data.color_location),
+                    color.r,
+                    color.g,
+                    color.b,
+                    color.a,
+                );
+            }
+
+            self.uniform_data.color = *color;
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct SolidUniformData {
+    pub color: Color,
+    pub color_location: <Context as HasContext>::UniformLocation,
+}
+
+impl SolidUniformData {
+    fn new(gl: &Context, program: NativeProgram) -> Self {
+        Self {
+            color: Color::TRANSPARENT,
+            color_location: unsafe {
+                gl.get_uniform_location(program, "color")
+            }
+            .expect("Solid - Color uniform location."),
+        }
+    }
+}
diff --git a/glow/src/window/compositor.rs b/glow/src/window/compositor.rs
index f6afaa68..e9cf6015 100644
--- a/glow/src/window/compositor.rs
+++ b/glow/src/window/compositor.rs
@@ -26,8 +26,7 @@ impl<Theme> iced_graphics::window::GLCompositor for Compositor<Theme> {
         log::info!("{:#?}", settings);
 
         let version = gl.version();
-        log::info!("Version: {:?}", version);
-        log::info!("Embedded: {}", version.is_embedded);
+        log::info!("OpenGL version: {:?} (Embedded: {}", version, version.is_embedded);
 
         let renderer = gl.get_parameter_string(glow::RENDERER);
         log::info!("Renderer: {}", renderer);