Improve shader version selection

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;
+}

glow/src/shader/common/triangle.vert

@@ -0,0 +1,11 @@
+uniform mat4 u_Transform;
+
+in vec2 i_Position;
+in vec4 i_Color;
+
+out vec4 v_Color;
+
+void main() {
+    gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
+    v_Color = i_Color;
+}