Add explicit OpenGL 3.2 support

Some old OS X environments refuse to work with OpenGL 3.0 even though
they support later versions.

imgui-examples/examples/support_gfx/mod.rs

@@ -36,7 +36,11 @@ pub fn run<F: FnMut(&Ui) -> bool>(title: String, clear_color: [f32; 4], mut run_
         } else if version.major >= 4 {
             Shaders::GlSl400
         } else if version.major >= 3 {
-            Shaders::GlSl130
+            if version.minor >= 2 {
+                Shaders::GlSl150
+            } else {
+                Shaders::GlSl130
+            }
         } else {
             Shaders::GlSl110
         }

imgui-gfx-renderer/src/lib.rs

@@ -97,6 +97,7 @@ extended_defines! {
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Shaders {
     GlSl400,   // OpenGL 4.0+
+    GlSl150,   // OpenGL 3.2+
     GlSl130,   // OpenGL 3.0+
     GlSl110,   // OpenGL 2.0+
     GlSlEs300, // OpenGL ES 3.0+
@@ -111,6 +112,10 @@ impl Shaders {
                 include_bytes!("shader/glsl_400.vert"),
                 include_bytes!("shader/glsl_400.frag"),
             ),
+            GlSl150 => (
+                include_bytes!("shader/glsl_150.vert"),
+                include_bytes!("shader/glsl_150.frag"),
+            ),
             GlSl130 => (
                 include_bytes!("shader/glsl_130.vert"),
                 include_bytes!("shader/glsl_130.frag"),

imgui-gfx-renderer/src/shader/glsl_150.frag

@@ -0,0 +1,12 @@
+#version 150
+
+uniform sampler2D tex;
+
+in vec2 f_uv;
+in vec4 f_color;
+
+out vec4 Target0;
+
+void main() {
+  Target0 = f_color * texture(tex, f_uv.st);
+}

imgui-gfx-renderer/src/shader/glsl_150.vert

@@ -0,0 +1,19 @@
+#version 150
+
+uniform mat4 matrix;
+
+in vec2 pos;
+in vec2 uv;
+in vec4 col;
+
+out vec2 f_uv;
+out vec4 f_color;
+
+// Built-in:
+// vec4 gl_Position
+
+void main() {
+  f_uv = uv;
+  f_color = col;
+  gl_Position = matrix * vec4(pos.xy, 0, 1);
+}

imgui-glium-renderer/src/lib.rs

@@ -197,6 +197,11 @@ fn compile_default_program<F: Facade>(
             fragment: include_str!("shader/glsl_400.frag"),
             outputs_srgb: true,
         },
+        150 => {
+            vertex: include_str!("shader/glsl_150.vert"),
+            fragment: include_str!("shader/glsl_150.frag"),
+            outputs_srgb: true,
+        },
         130 => {
             vertex: include_str!("shader/glsl_130.vert"),
             fragment: include_str!("shader/glsl_130.frag"),

imgui-glium-renderer/src/shader/glsl_150.frag

@@ -0,0 +1,12 @@
+#version 150
+
+uniform sampler2D tex;
+
+in vec2 f_uv;
+in vec4 f_color;
+
+out vec4 out_color;
+
+void main() {
+  out_color = f_color * texture(tex, f_uv.st);
+}

imgui-glium-renderer/src/shader/glsl_150.vert

@@ -0,0 +1,19 @@
+#version 150
+
+uniform mat4 matrix;
+
+in vec2 pos;
+in vec2 uv;
+in vec4 col;
+
+out vec2 f_uv;
+out vec4 f_color;
+
+// Built-in:
+// vec4 gl_Position
+
+void main() {
+  f_uv = uv;
+  f_color = col / 255.0;
+  gl_Position = matrix * vec4(pos.xy, 0, 1);
+}