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

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."),
+        }
+    }
+}