Add support for advanced blend equations to our OpenGL QPainter

Mesa and NVidia have been supporting these extensions several years now.
It also means we can get rid of the dead unused code we had for advanced
compositions.

Change-Id: I6a2fcda13490abd977eb4cc3d8b34f186d05ca25
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 18 insertions, 5 deletions

diff --git a/src/gui/opengl/qopenglfunctions.cpp b/src/gui/opengl/qopenglfunctions.cpp
index ff044a91da..236c81ac93 100644
--- a/src/gui/opengl/qopenglfunctions.cpp
+++ b/src/gui/opengl/qopenglfunctions.cpp
@@ -294,9 +294,19 @@ QOpenGLExtensions::QOpenGLExtensions(QOpenGLContext *context)
 static int qt_gl_resolve_features()
 {
     QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    QOpenGLExtensionMatcher extensions;
+    int features = 0;
+    if ((extensions.match("GL_KHR_blend_equation_advanced")
+        || extensions.match("GL_NV_blend_equation_advanced")) &&
+        (extensions.match("GL_KHR_blend_equation_advanced_coherent")
+        || extensions.match("GL_NV_blend_equation_advanced_coherent"))) {
+        // We need both the advanced equations and the coherency for us
+        // to be able to easily use the new blend equations
+        features |= QOpenGLFunctions::BlendEquationAdvanced;
+    }
     if (ctx->isOpenGLES()) {
         // OpenGL ES
-        int features = QOpenGLFunctions::Multitexture |
+        features |= QOpenGLFunctions::Multitexture |
             QOpenGLFunctions::Shaders |
             QOpenGLFunctions::Buffers |
             QOpenGLFunctions::Framebuffers |
@@ -308,7 +318,6 @@ static int qt_gl_resolve_features()
             QOpenGLFunctions::CompressedTextures |
             QOpenGLFunctions::Multisample |
             QOpenGLFunctions::StencilSeparate;
-        QOpenGLExtensionMatcher extensions;
         if (extensions.match("GL_IMG_texture_npot"))
             features |= QOpenGLFunctions::NPOTTextures;
         if (extensions.match("GL_OES_texture_npot"))
@@ -320,14 +329,18 @@ static int qt_gl_resolve_features()
             if (!(renderer && strstr(renderer, "Mesa")))
                 features |= QOpenGLFunctions::TextureRGFormats;
         }
-        if (ctx->format().majorVersion() >= 3)
+        if (ctx->format().majorVersion() >= 3) {
             features |= QOpenGLFunctions::MultipleRenderTargets;
+            if (ctx->format().minorVersion() >= 2 && extensions.match("GL_KHR_blend_equation_advanced_coherent")) {
+                // GL_KHR_blend_equation_advanced is included in OpenGL ES/3.2
+                features |= QOpenGLFunctions::BlendEquationAdvanced;
+            }
+        }
         return features;
     } else {
         // OpenGL
-        int features = QOpenGLFunctions::TextureRGFormats;
+        features |= QOpenGLFunctions::TextureRGFormats;
         QSurfaceFormat format = QOpenGLContext::currentContext()->format();
-        QOpenGLExtensionMatcher extensions;
 
         if (format.majorVersion() >= 3)
             features |= QOpenGLFunctions::Framebuffers | QOpenGLFunctions::MultipleRenderTargets;