Added workarounds for two MBX/SGX specific GL ES bugs/problems.

The workaround flags are put into the platform independent section
for now, since there might be a general need for these as we expand
our GL and GL ES usage. The workaround_needsFullClearOnEveryFrame flag
covers the case where you get a performance penalty on PowerVR hw
if all rendering buffers are not cleared. The
workaround_brokenFBOReadBack flag covers the case where copying pixels
from a texture (e.g. via glCopyTexSubImage2d()) bound in an FBO doesn't
work.

Task-number: QTBUG-10670
Reviewed-by: Gunnar

1 files changed, 19 insertions, 1 deletions

diff --git a/src/opengl/qgl_egl.cpp b/src/opengl/qgl_egl.cpp
index 0fbbbf9..44e8ae9 100644
--- a/src/opengl/qgl_egl.cpp
+++ b/src/opengl/qgl_egl.cpp
@@ -185,8 +185,26 @@ void QGLContext::makeCurrent()
         return;
     }
 
-    if (d->eglContext->makeCurrent(d->eglSurfaceForDevice()))
+    if (d->eglContext->makeCurrent(d->eglSurfaceForDevice())) {
         QGLContextPrivate::setCurrentContext(this);
+        if (!d->workaroundsCached) {
+            d->workaroundsCached = true;
+            const char *renderer = reinterpret_cast<const char *>(glGetString(GL_RENDERER));
+            if (strstr(renderer, "SGX") || strstr(renderer, "MBX")) {
+                // PowerVR MBX/SGX chips needs to clear all buffers when starting to render
+                // a new frame, otherwise there will be a performance penalty to pay for
+                // each frame.
+                d->workaround_needsFullClearOnEveryFrame = true;
+
+                // Older PowerVR SGX drivers (like the one in the N900) have a
+                // bug which prevents glCopyTexSubImage2D() to work with a POT
+                // or GL_ALPHA texture bound to an FBO. The only way to
+                // identify that driver is to check the EGL version number for it.
+                if (strstr(eglQueryString(d->eglContext->display(), EGL_VERSION), "1.3"))
+                    d->workaround_brokenFBOReadBack = true;
+            }
+        }
+    }
 }
 
 void QGLContext::doneCurrent()