Add workaround for GL on Android emulator

On the Android Emulator, the shaders will be compiled by a desktop
GL driver, since the GL driver in the emulator is just a thin
wrapper. The GL driver does not necessarily support the precision
qualifiers, which can cause applications to break. We detect this
at runtime in the platform plugin and set a workaround flag to

Task-number: QTBUG-32557
Change-Id: Ied00cfe8e804d1f7862697dd379a14f3bed3d980
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

src/gui/kernel/qopenglcontext_p.h

@@ -203,6 +203,7 @@ public:
         , max_texture_size(-1)
         , workaround_brokenFBOReadBack(false)
         , workaround_brokenTexSubImage(false)
+        , workaround_missingPrecisionQualifiers(false)
         , active_engine(0)
     {
     }
@@ -233,6 +234,7 @@ public:
 
     bool workaround_brokenFBOReadBack;
     bool workaround_brokenTexSubImage;
+    bool workaround_missingPrecisionQualifiers;
 
     QPaintEngineEx *active_engine;
 
@@ -240,6 +242,11 @@ public:
 
     int maxTextureSize();
 
+    static QOpenGLContextPrivate *get(QOpenGLContext *context)
+    {
+        return context->d_func();
+    }
+
 #if !defined(QT_NO_DEBUG)
     static bool toggleMakeCurrentTracker(QOpenGLContext *context, bool value)
     {

src/gui/opengl/qopenglshaderprogram.cpp

@@ -429,7 +429,9 @@ bool QOpenGLShader::compileSourceCode(const char *source)
         // The precision qualifiers are useful on OpenGL/ES systems,
         // but usually not present on desktop systems.
         const QSurfaceFormat currentSurfaceFormat = QOpenGLContext::currentContext()->format();
+        QOpenGLContextPrivate *ctx_d = QOpenGLContextPrivate::get(QOpenGLContext::currentContext());
         if (currentSurfaceFormat.renderableType() == QSurfaceFormat::OpenGL
+                || ctx_d->workaround_missingPrecisionQualifiers
 #ifdef QT_OPENGL_FORCE_SHADER_DEFINES
                 || true
 #endif
@@ -439,7 +441,7 @@ bool QOpenGLShader::compileSourceCode(const char *source)
         }
 
 #ifdef QOpenGL_REDEFINE_HIGHP
-        if (d->shaderType == Fragment) {
+        if (d->shaderType == Fragment && !ctx_d->workaround_missingPrecisionQualifiers) {
             src.append(redefineHighp);
             srclen.append(GLint(sizeof(redefineHighp) - 1));
         }

src/plugins/platforms/android/src/opengl/qandroidopenglcontext.cpp

@@ -46,6 +46,8 @@
 #include <QtCore/qdebug.h>
 #include <qpa/qwindowsysteminterface.h>
 
+#include <QtGui/private/qopenglcontext_p.h>
+
 QT_BEGIN_NAMESPACE
 
 QAndroidOpenGLContext::QAndroidOpenGLContext(const QAndroidPlatformIntegration *integration,
@@ -75,4 +77,17 @@ void QAndroidOpenGLContext::swapBuffers(QPlatformSurface *surface)
     }
 }
 
+bool QAndroidOpenGLContext::makeCurrent(QPlatformSurface *surface)
+{
+    bool ret = QEglFSContext::makeCurrent(surface);
+
+    const char *rendererString = reinterpret_cast<const char *>(glGetString(GL_RENDERER));
+    if (rendererString != 0 && qstrncmp(rendererString, "Android Emulator", 16) == 0) {
+        QOpenGLContextPrivate *ctx_d = QOpenGLContextPrivate::get(context());
+        ctx_d->workaround_missingPrecisionQualifiers = true;
+    }
+
+    return ret;
+}
+
 QT_END_NAMESPACE

src/plugins/platforms/android/src/opengl/qandroidopenglcontext.h

@@ -58,6 +58,7 @@ public:
                           EGLenum eglApi = EGL_OPENGL_ES_API);
 
     void swapBuffers(QPlatformSurface *surface);
+    bool makeCurrent(QPlatformSurface *surface);
 
 private:
     const QAndroidPlatformIntegration *m_platformIntegration;