1 files changed, 81 insertions, 0 deletions
diff --git a/webhogg/wasm/src/context/graphics.rs b/webhogg/wasm/src/context/graphics.rs
new file mode 100644
index 0000000..6af35a2
--- /dev/null
+++ b/webhogg/wasm/src/context/graphics.rs
@@ -0,0 +1,81 @@
+use crate::error::WasmError;
+use wasm_bindgen::JsCast;
+use web_sys::WebGl2RenderingContext as GlContext;
+
+use super::webgl;
+use super::webgl::{Color4, ShaderType, WebGl2};
+use super::shader::{MAIN_VERTEX_SHADER, MAIN_FRAGMENT_SHADER};
+use super::shader::ShaderProgram;
+
+pub struct GraphicsContext {
+    gl: WebGl2,
+    frame_nr: u64,
+    shader: ShaderProgram,
+    vao: webgl::WebGlVertexArrayObject,
+    buffer: webgl::WebGlBuffer,
+}
+
+impl GraphicsContext {
+    pub fn from_canvas(canvas: web_sys::OffscreenCanvas) -> Result<Self, WasmError> {
+        let context = canvas.get_context("webgl2")
+            .map_err(|_| WasmError::WebGl2ContextCreation(
+                    format!("context cration failed: getContext returned an exception")))?
+            .ok_or_else(|| WasmError::WebGl2ContextCreation(
+                    format!("context cration failed: getContext returned nothing")))?;
+        let context = context
+            .dyn_into::<GlContext>()
+            .map_err(|_| WasmError::WebGl2ContextCreation(
+                    format!("context object is not a context")))?;
+
+        let gl = WebGl2::from_context(context);
+        let shader = ShaderProgram::from_sources(&gl, &[
+            (ShaderType::Vertex, MAIN_VERTEX_SHADER.to_string()),
+            (ShaderType::Fragment, MAIN_FRAGMENT_SHADER.to_string()),
+        ])?;
+
+        let vao = gl.create_vertex_array()
+            .map_err(|_| WasmError::WebGlBuffer(
+                    format!("glGenVertexArrays failed")))?;
+        gl.bind_vertex_array(&vao);
+
+        let buffer = gl.create_buffer()
+            .map_err(|_| WasmError::WebGlBuffer(
+                    format!("glCreateBuffer failed")))?;
+        gl.bind_array_buffer(&buffer);
+        gl.array_buffer_data_f32(&[
+            0.0, 0.0,
+            1.0, 0.0,
+            0.0, 1.0,
+            1.0, 1.0,
+            0.0, 1.0,
+            1.0, 0.0,
+        ]);
+        gl.enable_vertex_attrib_array(0);
+            
+        Ok(Self {
+            gl, frame_nr: 0,
+            shader, vao, buffer
+        })
+    }
+
+    pub fn update(&mut self) -> Result<(), WasmError> {
+        let light = 0.5;
+        let speed = 60.0;
+
+        let a = (self.frame_nr as f32) / speed;
+        let a = f32::abs(f32::sin(a));
+        let b = f32::abs(f32::cos(a));
+        let (a, b) = (a * light, b * light);
+
+        self.gl.set_viewport();
+        self.gl.clear(&Color4::new(a, light - a, b, 1.0));
+
+        self.shader.run(&self.gl);
+        self.gl.vertex_attrib_f32_pointer(0, 2);
+        self.gl.draw_triangle_arrays(6);
+
+        self.frame_nr += 1;
+
+        Ok(())
+    }
+}