Improve shader version selection

16 files changed, 178 insertions, 66 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,
diff --git a/glow/src/program.rs b/glow/src/program.rs
index 601f9ce6..13676c70 100644
--- a/glow/src/program.rs
+++ b/glow/src/program.rs
@@ -3,6 +3,7 @@ use glow::HasContext;
 pub unsafe fn create(
     gl: &glow::Context,
     shader_sources: &[(u32, &str)],
+    attributes: &[(u32, &str)],
 ) -> <glow::Context as HasContext>::Program {
     let program = gl.create_program().expect("Cannot create program");
 
@@ -25,6 +26,10 @@ pub unsafe fn create(
         shaders.push(shader);
     }
 
+    for (i, name) in attributes {
+        gl.bind_attrib_location(program, *i, name);
+    }
+
     gl.link_program(program);
     if !gl.get_program_link_status(program) {
         panic!("{}", gl.get_program_info_log(program));
diff --git a/glow/src/quad.rs b/glow/src/quad.rs
index 75740c7e..e965f3c9 100644
--- a/glow/src/quad.rs
+++ b/glow/src/quad.rs
@@ -13,14 +13,22 @@ pub enum Pipeline {
 }
 
 impl Pipeline {
-    pub fn new(gl: &glow::Context) -> Pipeline {
+    pub fn new(
+        gl: &glow::Context,
+        shader_version: &(String, String),
+    ) -> Pipeline {
         let version = gl.version();
-        if version.is_embedded || version.major == 2 {
-            log::info!("Mode: compatibility");
-            Pipeline::Compatibility(compatibility::Pipeline::new(gl))
-        } else {
+
+        // OpenGL 3.0+ and OpenGL ES 3.0+ have instancing (which is what separates `core` from `compatibility`)
+        if version.major >= 3 {
             log::info!("Mode: core");
-            Pipeline::Core(core::Pipeline::new(gl))
+            Pipeline::Core(core::Pipeline::new(gl, shader_version))
+        } else {
+            log::info!("Mode: compatibility");
+            Pipeline::Compatibility(compatibility::Pipeline::new(
+                gl,
+                shader_version,
+            ))
         }
     }
 
diff --git a/glow/src/quad/compatibility.rs b/glow/src/quad/compatibility.rs
index e083dcf1..28ad214d 100644
--- a/glow/src/quad/compatibility.rs
+++ b/glow/src/quad/compatibility.rs
@@ -25,20 +25,39 @@ pub struct Pipeline {
 }
 
 impl Pipeline {
-    pub fn new(gl: &glow::Context) -> Pipeline {
+    pub fn new(
+        gl: &glow::Context,
+        (vertex_version, fragment_version): &(String, String),
+    ) -> Pipeline {
         let program = unsafe {
             program::create(
                 gl,
                 &[
                     (
                         glow::VERTEX_SHADER,
-                        include_str!("../shader/compatibility/quad.vert"),
+                        &format!(
+                            "{}\n{}",
+                            vertex_version,
+                            include_str!("../shader/compatibility/quad.vert")
+                        ),
                     ),
                     (
                         glow::FRAGMENT_SHADER,
-                        include_str!("../shader/compatibility/quad.frag"),
+                        &format!(
+                            "{}\n{}",
+                            fragment_version,
+                            include_str!("../shader/compatibility/quad.frag")
+                        ),
                     ),
                 ],
+                &[
+                    (0, "i_Pos"),
+                    (1, "i_Scale"),
+                    (2, "i_Color"),
+                    (3, "i_BorderColor"),
+                    (4, "i_BorderRadius"),
+                    (5, "i_BorderWidth"),
+                ],
             )
         };
 
diff --git a/glow/src/quad/core.rs b/glow/src/quad/core.rs
index c843e8c7..274ade67 100644
--- a/glow/src/quad/core.rs
+++ b/glow/src/quad/core.rs
@@ -20,20 +20,39 @@ pub struct Pipeline {
 }
 
 impl Pipeline {
-    pub fn new(gl: &glow::Context) -> Pipeline {
+    pub fn new(
+        gl: &glow::Context,
+        (vertex_version, fragment_version): &(String, String),
+    ) -> Pipeline {
         let program = unsafe {
             program::create(
                 gl,
                 &[
                     (
                         glow::VERTEX_SHADER,
-                        include_str!("../shader/core/quad.vert"),
+                        &format!(
+                            "{}\n{}",
+                            vertex_version,
+                            include_str!("../shader/core/quad.vert")
+                        ),
                     ),
                     (
                         glow::FRAGMENT_SHADER,
-                        include_str!("../shader/core/quad.frag"),
+                        &format!(
+                            "{}\n{}",
+                            fragment_version,
+                            include_str!("../shader/core/quad.frag")
+                        ),
                     ),
                 ],
+                &[
+                    (0, "i_Pos"),
+                    (1, "i_Scale"),
+                    (2, "i_Color"),
+                    (3, "i_BorderColor"),
+                    (4, "i_BorderRadius"),
+                    (5, "i_BorderWidth"),
+                ],
             )
         };
 
diff --git a/glow/src/shader/common/triangle.frag b/glow/src/shader/common/triangle.frag
new file mode 100644
index 00000000..e8689f2e
--- /dev/null
+++ b/glow/src/shader/common/triangle.frag
@@ -0,0 +1,18 @@
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
+#endif
+
+#ifdef HIGHER_THAN_300
+out vec4 fragColor;
+#define gl_FragColor fragColor
+#endif
+
+in vec4 v_Color;
+
+void main() {
+    gl_FragColor = v_Color;
+}
\ No newline at end of file
diff --git a/glow/src/shader/core/triangle.vert b/glow/src/shader/common/triangle.vert
index 895652ea..d0494a5f 100644
--- a/glow/src/shader/core/triangle.vert
+++ b/glow/src/shader/common/triangle.vert
@@ -1,5 +1,3 @@
-#version 130
-
 uniform mat4 u_Transform;
 
 in vec2 i_Position;
@@ -10,4 +8,4 @@ out vec4 v_Color;
 void main() {
     gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
     v_Color = i_Color;
-}
+}
\ No newline at end of file
diff --git a/glow/src/shader/compatibility/quad.frag b/glow/src/shader/compatibility/quad.frag
index c2634c65..8ea5693d 100644
--- a/glow/src/shader/compatibility/quad.frag
+++ b/glow/src/shader/compatibility/quad.frag
@@ -1,5 +1,10 @@
-#version 100
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
 precision mediump float;
+#endif
+#endif
 
 uniform float u_ScreenHeight;
 
@@ -10,7 +15,7 @@ varying vec2 v_Scale;
 varying float v_BorderRadius;
 varying float v_BorderWidth;
 
-float _distance(in vec2 frag_coord, in vec2 position, in vec2 size, float radius)
+float _distance(vec2 frag_coord, vec2 position, vec2 size, float radius)
 {
     // TODO: Try SDF approach: https://www.shadertoy.com/view/wd3XRN
     vec2 inner_size = size - vec2(radius, radius) * 2.0;
diff --git a/glow/src/shader/compatibility/quad.vert b/glow/src/shader/compatibility/quad.vert
index 0d02e9d0..abe70c0e 100644
--- a/glow/src/shader/compatibility/quad.vert
+++ b/glow/src/shader/compatibility/quad.vert
@@ -1,5 +1,3 @@
-#version 100
-
 uniform mat4 u_Transform;
 uniform float u_Scale;
 
diff --git a/glow/src/shader/compatibility/triangle.frag b/glow/src/shader/compatibility/triangle.frag
deleted file mode 100644
index 58fca553..00000000
--- a/glow/src/shader/compatibility/triangle.frag
+++ /dev/null
@@ -1,8 +0,0 @@
-#version 100
-precision mediump float;
-
-varying vec4 v_Color;
-
-void main() {
-    gl_FragColor = v_Color;
-}
diff --git a/glow/src/shader/compatibility/triangle.vert b/glow/src/shader/compatibility/triangle.vert
deleted file mode 100644
index 975c9781..00000000
--- a/glow/src/shader/compatibility/triangle.vert
+++ /dev/null
@@ -1,13 +0,0 @@
-#version 100
-
-uniform mat4 u_Transform;
-
-attribute vec2 i_Position;
-attribute vec4 i_Color;
-
-varying vec4 v_Color;
-
-void main() {
-    v_Color = i_Color;
-    gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
-}
diff --git a/glow/src/shader/core/quad.frag b/glow/src/shader/core/quad.frag
index 18fd5baa..57e2e8e7 100644
--- a/glow/src/shader/core/quad.frag
+++ b/glow/src/shader/core/quad.frag
@@ -1,4 +1,15 @@
-#version 130
+#ifdef GL_ES
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
+#endif
+
+#ifdef HIGHER_THAN_300
+out vec4 fragColor;
+#define gl_FragColor fragColor
+#endif
 
 uniform float u_ScreenHeight;
 
@@ -9,9 +20,7 @@ in vec2 v_Scale;
 in float v_BorderRadius;
 in float v_BorderWidth;
 
-out vec4 o_Color;
-
-float distance(in vec2 frag_coord, in vec2 position, in vec2 size, float radius)
+float fDistance(vec2 frag_coord, vec2 position, vec2 size, float radius)
 {
     // TODO: Try SDF approach: https://www.shadertoy.com/view/wd3XRN
     vec2 inner_size = size - vec2(radius, radius) * 2.0;
@@ -35,10 +44,10 @@ void main() {
     vec2 fragCoord = vec2(gl_FragCoord.x, u_ScreenHeight - gl_FragCoord.y);
 
     // TODO: Remove branching (?)
-    if(v_BorderWidth > 0) {
+    if(v_BorderWidth > 0.0) {
         float internal_border = max(v_BorderRadius - v_BorderWidth, 0.0);
 
-        float internal_distance = distance(
+        float internal_distance = fDistance(
             fragCoord,
             v_Pos + vec2(v_BorderWidth),
             v_Scale - vec2(v_BorderWidth * 2.0),
@@ -56,7 +65,7 @@ void main() {
         mixed_color = v_Color;
     }
 
-    float d = distance(
+    float d = fDistance(
         fragCoord,
         v_Pos,
         v_Scale,
@@ -66,5 +75,5 @@ void main() {
     float radius_alpha =
         1.0 - smoothstep(max(v_BorderRadius - 0.5, 0.0), v_BorderRadius + 0.5, d);
 
-    o_Color = vec4(mixed_color.xyz, mixed_color.w * radius_alpha);
+    gl_FragColor = vec4(mixed_color.xyz, mixed_color.w * radius_alpha);
 }
diff --git a/glow/src/shader/core/quad.vert b/glow/src/shader/core/quad.vert
index 30f28d52..b1fb2365 100644
--- a/glow/src/shader/core/quad.vert
+++ b/glow/src/shader/core/quad.vert
@@ -1,5 +1,3 @@
-#version 130
-
 uniform mat4 u_Transform;
 uniform float u_Scale;
 
@@ -17,7 +15,7 @@ out vec2 v_Scale;
 out float v_BorderRadius;
 out float v_BorderWidth;
 
-const vec2 positions[4] = vec2[](
+vec2 positions[4] = vec2[](
     vec2(0.0, 0.0),
     vec2(0.0, 1.0),
     vec2(1.0, 0.0),
diff --git a/glow/src/shader/core/triangle.frag b/glow/src/shader/core/triangle.frag
deleted file mode 100644
index 39c2ff6f..00000000
--- a/glow/src/shader/core/triangle.frag
+++ /dev/null
@@ -1,9 +0,0 @@
-#version 130
-
-in vec4 v_Color;
-
-out vec4 o_Color;
-
-void main() {
-    o_Color = v_Color;
-}
diff --git a/glow/src/triangle.rs b/glow/src/triangle.rs
index d0a05be6..91bb96ba 100644
--- a/glow/src/triangle.rs
+++ b/glow/src/triangle.rs
@@ -21,20 +21,32 @@ pub(crate) struct Pipeline {
 }
 
 impl Pipeline {
-    pub fn new(gl: &glow::Context) -> Pipeline {
+    pub fn new(
+        gl: &glow::Context,
+        (vertex_version, fragment_version): &(String, String),
+    ) -> Pipeline {
         let program = unsafe {
             program::create(
                 gl,
                 &[
                     (
                         glow::VERTEX_SHADER,
-                        include_str!("shader/compatibility/triangle.vert"),
+                        &format!(
+                            "{}\n{}",
+                            vertex_version,
+                            include_str!("shader/common/triangle.vert")
+                        ),
                     ),
                     (
                         glow::FRAGMENT_SHADER,
-                        include_str!("shader/compatibility/triangle.frag"),
+                        &format!(
+                            "{}\n{}",
+                            fragment_version,
+                            include_str!("shader/common/triangle.frag")
+                        ),
                     ),
                 ],
+                &[(0, "i_Position"), (1, "i_Color")],
             )
         };
 
diff --git a/glow/src/window/compositor.rs b/glow/src/window/compositor.rs
index 8d7d21d3..44019fb2 100644
--- a/glow/src/window/compositor.rs
+++ b/glow/src/window/compositor.rs
@@ -23,7 +23,7 @@ impl iced_graphics::window::GLCompositor for Compositor {
         let version = gl.version();
         log::info!("Version: {:?}", version);
         log::info!("Embedded: {}", version.is_embedded);
-        
+
         let renderer = gl.get_parameter_string(glow::RENDERER);
         log::info!("Renderer: {}", renderer);