Improved detection of OpenGL software emulation

Adding a new method to retrieve whether the OpenGL implementation
uses any kind of software emulation and no software emulation can
provide GLSL support, even if it claims so.

Thanks to Maurel for testing again and again proposed patches.

BUG: 271166

libkwineffects/kwinglplatform.cpp

@@ -632,9 +632,14 @@ void GLPlatform::detect()
             m_driver = Driver_Nouveau;
         }
 
-        else if (m_chipset == "softpipe" || m_chipset == "llvmpipe") {
-            // Vendor: VMware, Inc.
-            // TODO
+        // softpipe
+        else if (m_vendor == "VMware, Inc." && m_chipset == "softpipe" ) {
+            m_driver = Driver_Softpipe;
+        }
+
+        // llvmpipe
+        else if (m_vendor == "VMware, Inc." && m_chipset == "llvmpipe") {
+            m_driver = Driver_Llvmpipe;
         }
     }
 
@@ -712,6 +717,11 @@ void GLPlatform::detect()
     // Loose binding is broken with Gallium drivers in Mesa 7.10
     if (isGalliumDriver() && mesaVersion() >= kVersionNumber(7, 10))
         m_looseBinding = false;
+
+    if (isSoftwareEmulation()) {
+        // Software emulation does not provide GLSL
+        m_limitedGLSL = m_supportsGLSL = false;
+    }
 }
 
 static void print(const QString &label, const QString &setting)
@@ -851,6 +861,11 @@ bool GLPlatform::isIntel() const
     return m_chipClass >= I8XX && m_chipClass <= UnknownIntel;
 }
 
+bool GLPlatform::isSoftwareEmulation() const
+{
+    return m_driver == Driver_Softpipe || m_driver == Driver_Swrast || m_driver == Driver_Llvmpipe;
+}
+
 } // namespace KWin
 
 #endif // KWIN_HAVE_OPENGL

libkwineffects/kwinglplatform.h

@@ -238,6 +238,12 @@ public:
      */
     bool isIntel() const;
 
+    /**
+     * @returns @c true if OpenGL is emulated in software.
+     * @since 4.7
+     **/
+    bool isSoftwareEmulation() const;
+
 private:
     GLPlatform();
 

scene_opengl_glx.cpp

@@ -61,7 +61,7 @@ SceneOpenGL::SceneOpenGL(Workspace* ws)
     // Initialize OpenGL
     initGL();
     GLPlatform *glPlatform = GLPlatform::instance();
-    if (glPlatform->driver() == Driver_Swrast || glPlatform->driver() == Driver_Softpipe) {
+    if (glPlatform->isSoftwareEmulation()) {
         kError(1212) << "OpenGL Software Rasterizer detected. Falling back to XRender.";
         QTimer::singleShot(0, Workspace::self(), SLOT(fallbackToXRenderCompositing()));
         return;