From 34f24c3c6c1d0876785616cb64df80f33b928259 Mon Sep 17 00:00:00 2001
From: Damien Seguin <dmnsgn@gmail.com>
Date: Sun, 13 Jan 2019 22:08:42 +0000
Subject: [PATCH] Add shader precision

---
 index.js | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 04f13ef2..6c63e3ea 100644
--- a/index.js
+++ b/index.js
@@ -28,7 +28,8 @@ function createContext (opts) {
   let gl = null
 
   const defaultOpts = {
-    pixelRatio: 1
+    pixelRatio: 1,
+    precision: 'highp'
   }
 
   opts = Object.assign({}, defaultOpts, opts)
@@ -269,6 +270,28 @@ function createContext (opts) {
     capabilities.maxColorAttachments = gl.getParameter('MAX_COLOR_ATTACHMENTS')
   }
 
+  function getMaxPrecision(precision = 'highp') {
+    if (precision === "highp") {
+      if (
+        gl.getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.HIGH_FLOAT).precision > 0 &&
+        gl.getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT).precision > 0
+      ) {
+        return "highp";
+      }
+      precision = "mediump";
+    }
+    if (precision === "mediump") {
+      if (
+        gl.getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.MEDIUM_FLOAT).precision > 0 &&
+        gl.getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.MEDIUM_FLOAT).precision > 0
+      ) {
+        return "mediump";
+      }
+    }
+    return "lowp";
+  }
+  capabilities.maxPrecision = getMaxPrecision(opts.precision)
+
   log('capabilities', capabilities)
 
   Object.assign(ctx, {
@@ -300,6 +323,7 @@ function createContext (opts) {
       }
       return str
     },
+    getMaxPrecision,
     set: function (opts) {
       assert(isBrowser, 'changing resolution is not supported in Plask')
       if (opts.pixelRatio) {