Improve shader version selection

1 files changed, 55 insertions, 2 deletions

diff --git a/glow/src/backend.rs b/glow/src/backend.rs
index 5ab7f922..69d04168 100644
--- a/glow/src/backend.rs
+++ b/glow/src/backend.rs
@@ -3,6 +3,7 @@ use crate::text;
 use crate::triangle;
 use crate::{Settings, Transformation, Viewport};
 
+use glow::HasContext;
 use iced_graphics::backend;
 use iced_graphics::font;
 use iced_graphics::{Layer, Primitive};
@@ -30,8 +31,60 @@ impl Backend {
             settings.text_multithreading,
         );
 
-        let quad_pipeline = quad::Pipeline::new(gl);
-        let triangle_pipeline = triangle::Pipeline::new(gl);
+        let version = gl.version();
+        let shader_version = match (
+            version.major,
+            version.minor,
+            version.is_embedded,
+        ) {
+            // OpenGL 3.0+
+            (3, 0 | 1 | 2, false) => (
+                format!("#version 1{}0", version.minor + 3),
+                format!(
+                    "#version 1{}0\n#define HIGHER_THAN_300 1",
+                    version.minor + 3
+                ),
+            ),
+            // OpenGL 3.3+
+            (3 | 4, _, false) => (
+                format!("#version {}{}0", version.major, version.minor),
+                format!(
+                    "#version {}{}0\n#define HIGHER_THAN_300 1",
+                    version.major, version.minor
+                ),
+            ),
+            // OpenGL ES 3.0+
+            (3, _, true) => (
+                format!("#version 3{}0 es", version.minor),
+                format!(
+                    "#version 3{}0 es\n#define HIGHER_THAN_300 1",
+                    version.minor
+                ),
+            ),
+            // OpenGL ES 2.0+
+            (2, _, true) => (
+                String::from(
+                    "#version 100\n#define in attribute\n#define out varying",
+                ),
+                String::from("#version 100\n#define in varying"),
+            ),
+            // OpenGL 2.1
+            (2, _, false) => (
+                String::from(
+                    "#version 120\n#define in attribute\n#define out varying",
+                ),
+                String::from("#version 120\n#define in varying"),
+            ),
+            // OpenGL 1.1+
+            _ => panic!("Incompatible context version: {:?}", version),
+        };
+        log::info!(
+            "Shader directive: {}",
+            shader_version.0.lines().next().unwrap()
+        );
+
+        let quad_pipeline = quad::Pipeline::new(gl, &shader_version);
+        let triangle_pipeline = triangle::Pipeline::new(gl, &shader_version);
 
         Self {
             quad_pipeline,