OpenGL: Attempt to enable multisampling on Android

modules/juce_opengl/native/juce_OpenGL_android.h

@@ -78,9 +78,9 @@ class OpenGLContext::NativeContext   : private SurfaceHolderCallback
 {
 public:
     NativeContext (Component& comp,
-                   const OpenGLPixelFormat& /*pixelFormat*/,
+                   const OpenGLPixelFormat& pixelFormat,
                    void* /*contextToShareWith*/,
-                   bool /*useMultisampling*/,
+                   bool useMultisamplingIn,
                    OpenGLVersion)
         : component (comp),
           surface (EGL_NO_SURFACE), context (EGL_NO_CONTEXT)
@@ -92,7 +92,7 @@ public:
             return;
 
         // Initialise the EGL display
-        if (! initEGLDisplay())
+        if (! initEGLDisplay (pixelFormat, useMultisamplingIn))
             return;
 
         // create a native surface view
@@ -288,27 +288,34 @@ private:
             juceContext->triggerRepaint();
     }
 
+    bool tryChooseConfig (const std::vector<EGLint>& optionalAttribs)
+    {
+        std::vector<EGLint> allAttribs
+        {
+            EGL_RENDERABLE_TYPE,    EGL_OPENGL_ES2_BIT,
+            EGL_SURFACE_TYPE,       EGL_WINDOW_BIT,
+            EGL_BLUE_SIZE,          8,
+            EGL_GREEN_SIZE,         8,
+            EGL_RED_SIZE,           8,
+            EGL_ALPHA_SIZE,         0,
+            EGL_DEPTH_SIZE,         16
+        };
+
+        allAttribs.insert (allAttribs.end(), optionalAttribs.begin(), optionalAttribs.end());
+
+        allAttribs.push_back (EGL_NONE);
+
+        EGLint numConfigs{};
+        return eglChooseConfig (display, allAttribs.data(), &config, 1, &numConfigs);
+    }
+
     //==============================================================================
-    bool initEGLDisplay()
+    bool initEGLDisplay (const OpenGLPixelFormat& pixelFormat, bool multisample)
     {
         // already initialised?
         if (display != EGL_NO_DISPLAY)
             return true;
 
-        const EGLint attribs[] =
-        {
-            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
-            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
-            EGL_BLUE_SIZE, 8,
-            EGL_GREEN_SIZE, 8,
-            EGL_RED_SIZE, 8,
-            EGL_ALPHA_SIZE, 0,
-            EGL_DEPTH_SIZE, 16,
-            EGL_NONE
-        };
-
-        EGLint numConfigs;
-
         if ((display = eglGetDisplay (EGL_DEFAULT_DISPLAY)) == EGL_NO_DISPLAY)
         {
             jassertfalse;
@@ -321,14 +328,15 @@ private:
             return false;
         }
 
-        if (! eglChooseConfig (display, attribs, &config, 1, &numConfigs))
-        {
-            eglTerminate (display);
-            jassertfalse;
-            return false;
-        }
+        if (tryChooseConfig ({ EGL_SAMPLE_BUFFERS, multisample ? 1 : 0, EGL_SAMPLES, pixelFormat.multisamplingLevel }))
+            return true;
 
-        return true;
+        if (tryChooseConfig ({}))
+            return true;
+
+        eglTerminate (display);
+        jassertfalse;
+        return false;
     }
 
     //==============================================================================