Fixed extension checks and usage of the GL 2 engine on old X11 systems.

This fixes a regression from 4.5, where exporting a GL capable display
from an old X11 HP/Sun workstation to a modern Linux machine causes
crashes and lots of X11 error output. Just relying on the client
GL version number is not enough under X11, since the server might
only support GL 1.1 with non or very few extensions.
Also, the extension checks worked a bit randomly since it checked
for sub-strings which might or might not occur within one or more
full extension names.

Task-number: QTBUG-5853
Reviewed-by: Kim

2 files changed, 36 insertions, 25 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index f8a2ea461e..d5ca218af1 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -184,8 +184,13 @@ public:
             engineType = QPaintEngine::OpenGL2;
 #else
             // We can't do this in the constructor for this object because it
-            // needs to be called *before* the QApplication constructor
+            // needs to be called *before* the QApplication constructor.
+            // Also check for the FragmentProgram extension in conjunction with
+            // the 2.0 version flag, to cover the case where we export the display
+            // from an old GL 1.1 server to a GL 2.x client. In that case we can't
+            // use GL 2.0.
             if ((QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0)
+                && (QGLExtensions::glExtensions & QGLExtensions::FragmentProgram)
                 && qgetenv("QT_GL_USE_OPENGL1ENGINE").isEmpty())
                 engineType = QPaintEngine::OpenGL2;
             else
@@ -2170,8 +2175,8 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     int tx_h = qt_next_power_of_two(image.height());
 
     QImage img = image;
-    if (( !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0) &&
-          !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_ES_Version_2_0) )
+    if (!(QGLExtensions::glExtensions & QGLExtensions::NPOTTextures)
+        && !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_ES_Version_2_0)
         && (target == GL_TEXTURE_2D && (tx_w != image.width() || tx_h != image.height())))
     {
         img = img.scaled(tx_w, tx_h);
@@ -2192,9 +2197,9 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     bool genMipmap = false;
 #endif
     if (glFormat.directRendering()
-        && QGLExtensions::glExtensions & QGLExtensions::GenerateMipmap
+        && (QGLExtensions::glExtensions & QGLExtensions::GenerateMipmap)
         && target == GL_TEXTURE_2D
-        && options & QGLContext::MipmapBindOption)
+        && (options & QGLContext::MipmapBindOption))
     {
 #ifdef QGL_BIND_TEXTURE_DEBUG
         printf(" - generating mipmaps (%d ms)\n", time.elapsed());
@@ -2220,7 +2225,7 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     bool premul = options & QGLContext::PremultipliedAlphaBindOption;
     GLenum externalFormat;
     GLuint pixel_type;
-    if (QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_1_2) {
+    if (QGLExtensions::glExtensions & QGLExtensions::BGRATextureFormat) {
         externalFormat = GL_BGRA;
         pixel_type = GL_UNSIGNED_INT_8_8_8_8_REV;
     } else {
@@ -4886,54 +4891,59 @@ QGLWidget::QGLWidget(QGLContext *context, QWidget *parent,
 
 void QGLExtensions::init_extensions()
 {
-    QString extensions = QLatin1String(reinterpret_cast<const char *>(glGetString(GL_EXTENSIONS)));
-    if (extensions.contains(QLatin1String("texture_rectangle")))
+    QList<QByteArray> extensions = QByteArray(reinterpret_cast<const char *>(glGetString(GL_EXTENSIONS))).split(' ');
+    if (extensions.contains("GL_ARB_texture_rectangle"))
         glExtensions |= TextureRectangle;
-    if (extensions.contains(QLatin1String("multisample")))
+    if (extensions.contains("GL_ARB_multisample"))
         glExtensions |= SampleBuffers;
-    if (extensions.contains(QLatin1String("generate_mipmap")))
+    if (extensions.contains("GL_SGIS_generate_mipmap"))
         glExtensions |= GenerateMipmap;
-    if (extensions.contains(QLatin1String("texture_compression_s3tc")))
+    if (extensions.contains("GL_EXT_texture_compression_s3tc"))
         glExtensions |= TextureCompression;
-    if (extensions.contains(QLatin1String("ARB_fragment_program")))
+    if (extensions.contains("GL_ARB_fragment_program"))
         glExtensions |= FragmentProgram;
-    if (extensions.contains(QLatin1String("mirrored_repeat")))
+    if (extensions.contains("GL_ARB_texture_mirrored_repeat"))
         glExtensions |= MirroredRepeat;
-    if (extensions.contains(QLatin1String("EXT_framebuffer_object")))
+    if (extensions.contains("GL_EXT_framebuffer_object"))
         glExtensions |= FramebufferObject;
-    if (extensions.contains(QLatin1String("EXT_stencil_two_side")))
+    if (extensions.contains("GL_EXT_stencil_two_side"))
         glExtensions |= StencilTwoSide;
-    if (extensions.contains(QLatin1String("EXT_stencil_wrap")))
+    if (extensions.contains("GL_EXT_stencil_wrap"))
         glExtensions |= StencilWrap;
-    if (extensions.contains(QLatin1String("EXT_packed_depth_stencil")))
+    if (extensions.contains("GL_EXT_packed_depth_stencil"))
         glExtensions |= PackedDepthStencil;
-    if (extensions.contains(QLatin1String("GL_NV_float_buffer")))
+    if (extensions.contains("GL_NV_float_buffer"))
         glExtensions |= NVFloatBuffer;
-    if (extensions.contains(QLatin1String("ARB_pixel_buffer_object")))
+    if (extensions.contains("GL_ARB_pixel_buffer_object"))
         glExtensions |= PixelBufferObject;
 #if defined(QT_OPENGL_ES_2)
     glExtensions |= FramebufferObject;
     glExtensions |= GenerateMipmap;
 #endif
 #if defined(QT_OPENGL_ES_1) || defined(QT_OPENGL_ES_1_CL)
-    if (extensions.contains(QLatin1String("OES_framebuffer_object")))
+    if (extensions.contains("GL_OES_framebuffer_object"))
         glExtensions |= FramebufferObject;
 #endif
 #if defined(QT_OPENGL_ES)
-    if (extensions.contains(QLatin1String("OES_packed_depth_stencil")))
+    if (extensions.contains("GL_OES_packed_depth_stencil"))
         glExtensions |= PackedDepthStencil;
 #endif
-    if (extensions.contains(QLatin1String("ARB_framebuffer_object"))) {
+    if (extensions.contains("GL_ARB_framebuffer_object")) {
         // ARB_framebuffer_object also includes EXT_framebuffer_blit.
         glExtensions |= FramebufferObject;
         glExtensions |= FramebufferBlit;
     }
-    if (extensions.contains(QLatin1String("EXT_framebuffer_blit")))
+
+    if (extensions.contains("GL_EXT_framebuffer_blit"))
         glExtensions |= FramebufferBlit;
 
-    if (extensions.contains(QLatin1String("GL_ARB_texture_non_power_of_two")))
+    if (extensions.contains("GL_ARB_texture_non_power_of_two"))
         glExtensions |= NPOTTextures;
 
+    if (extensions.contains("GL_EXT_bgra"))
+        glExtensions |= BGRATextureFormat;
+
+
     QGLContext cx(QGLFormat::defaultFormat());
     if (glExtensions & TextureCompression) {
         qt_glCompressedTexImage2DARB = (pfn_glCompressedTexImage2DARB) cx.getProcAddress(QLatin1String("glCompressedTexImage2DARB"));
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 45b29420c5..8e472e5cc2 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -375,7 +375,8 @@ public:
         NVFloatBuffer           = 0x00000400,
         PixelBufferObject       = 0x00000800,
         FramebufferBlit         = 0x00001000,
-        NPOTTextures            = 0x00002000
+        NPOTTextures            = 0x00002000,
+        BGRATextureFormat       = 0x00004000
     };
     Q_DECLARE_FLAGS(Extensions, Extension)