Fix getShaderPrecisionFormat on desktop

Task-number: QTBUG-46410
Change-Id: I0f221ff495f9d7910e8c2f8f88aa639556e8cc96
Reviewed-by: Tomi Korpipää <tomi.korpipaa@theqtcompany.com>
Reviewed-by: Pasi Keränen <pasi.keranen@digia.com>

2 files changed, 61 insertions, 36 deletions

diff --git a/src/imports/qtcanvas3d/context3d.cpp b/src/imports/qtcanvas3d/context3d.cpp
index 8a3e0b2..a34d8f9 100644
--- a/src/imports/qtcanvas3d/context3d.cpp
+++ b/src/imports/qtcanvas3d/context3d.cpp
@@ -312,11 +312,40 @@ QJSValue CanvasContext::getShaderPrecisionFormat(glEnums shadertype,
     qCDebug(canvas3drendering).nospace() << "Context3D::" << str;
 
     GLint range[2];
-    range[0] = 1;
-    range[1] = 1;
-    GLint precision = 1;
+    GLint precision;
+
+    // Default values from OpenGL ES2 spec
+    switch (precisiontype) {
+    case LOW_INT:
+    case MEDIUM_INT:
+    case HIGH_INT:
+        // 32-bit twos-complement integer format
+        range[0] = 31;
+        range[1] = 30;
+        precision = 0;
+        break;
+    case LOW_FLOAT:
+    case MEDIUM_FLOAT:
+    case HIGH_FLOAT:
+        // IEEE single-precision floating-point format
+        range[0] = 127;
+        range[1] = 127;
+        precision = 23;
+        break;
+    default:
+        range[0] = 1;
+        range[1] = 1;
+        precision = 1;
+        m_error |= CANVAS_INVALID_ENUM;
+        break;
+    }
 
-    glGetShaderPrecisionFormat((GLenum)(shadertype), (GLenum)(precisiontype), range, &precision);
+    // On desktop envs glGetShaderPrecisionFormat is part of OpenGL 4.x, so it is not necessarily
+    // available. Let's just return the default values if not ES2.
+    if (m_isOpenGLES2) {
+        glGetShaderPrecisionFormat((GLenum)(shadertype), (GLenum)(precisiontype),
+                                   range, &precision);
+    }
     logAllGLErrors(str);
 
     CanvasShaderPrecisionFormat *format = new CanvasShaderPrecisionFormat();
diff --git a/tests/auto/qmltest/canvas3d/tst_program.js b/tests/auto/qmltest/canvas3d/tst_program.js
index eb7903c..7555c24 100644
--- a/tests/auto/qmltest/canvas3d/tst_program.js
+++ b/tests/auto/qmltest/canvas3d/tst_program.js
@@ -304,38 +304,34 @@ function initializeGL(canvas) {
                     canvas.width * canvas.devicePixelRatio,
                     canvas.height * canvas.devicePixelRatio);
 
-        // Skipping getShaderPrecisionFormat as on OS X these will
-        // fail as the method doesn't work, it produces INVALID_OPERATION error.
-        // TODO: Uncomment once QTBUG-46410 has been fixed
-
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.LOW_FLOAT, false))
-//            return 20;
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.MEDIUM_FLOAT, false))
-//            return 21;
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.HIGH_FLOAT, false))
-//            return 22;
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.LOW_INT, false))
-//            return 23;
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.MEDIUM_INT, false))
-//            return 24;
-//        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.HIGH_INT, false))
-//            return 25;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.LOW_FLOAT, false))
-//            return 26;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.MEDIUM_FLOAT, false))
-//            return 27;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT, false))
-//            return 28;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.LOW_INT, false))
-//            return 29;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.MEDIUM_INT, false))
-//            return 30;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_INT, false))
-//            return 31;
-//        if (!getShaderPrecisionFormat(77, gl.LOW_INT, true))
-//            return 32;
-//        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, 77, true))
-//            return 33;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.LOW_FLOAT, false))
+            return 20;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.MEDIUM_FLOAT, false))
+            return 21;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.HIGH_FLOAT, false))
+            return 22;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.LOW_INT, false))
+            return 23;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.MEDIUM_INT, false))
+            return 24;
+        if (!getShaderPrecisionFormat(gl.VERTEX_SHADER, gl.HIGH_INT, false))
+            return 25;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.LOW_FLOAT, false))
+            return 26;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.MEDIUM_FLOAT, false))
+            return 27;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT, false))
+            return 28;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.LOW_INT, false))
+            return 29;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.MEDIUM_INT, false))
+            return 30;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_INT, false))
+            return 31;
+        if (!getShaderPrecisionFormat(77, gl.LOW_INT, true))
+            return 32;
+        if (!getShaderPrecisionFormat(gl.FRAGMENT_SHADER, 77, true))
+            return 33;
 
         if (!isProgram(shaderProgram, true))
             return 40;