Use texture_from_pixmap on X11 & avoid copies

The patch tries to use texture_from_pixmap extentions on glX to properly
bind an X Pixmap to a texture in QGLContextPrivate::bindTexture(QPixmap,).
Because GL & X have different coordinate systems, the pixmap will be
inverted about the y-axis. The extension does however allow a
GLX_Y_INVERTED_EXT attribute to be set which will bind the pixmap the
correct way up. If the underlying driver doesn't support this,
texture_from_pixmap can't be used for QGLContext::bindTexture, because
that function expects the resulting texture to be the right way up.
However, it can still be used internally by the paint engine for
drawPixmap operations. For these cases, if the pixmap is inverted, the
paint engine can simply invert the texture coords to compensate. This is
why this patch also moves QGLTexture into qgl_p.h.
QGLContextPrivate::bindTexture(QPixmap,) now returns a QGLTexture which
the paint engine can inspect to see if it needs to invert the texture
coords.

Finally, it seems on some (probably all) drivers, deleting an X pixmap
which has been bound to a texture before calling glFinish/swapBuffers
renders garbage. Presumably this is because X deletes the pixmap behind
the driver's back before it's had a chance to use it. To fix this, we
reference all QPixmaps which have been bound to stop them being deleted
and only deref them after we swap the buffer, when they can be safely
deleted.

Reviewed-By: Kim

1 files changed, 133 insertions, 0 deletions

diff --git a/src/opengl/qgl_x11.cpp b/src/opengl/qgl_x11.cpp
index 631625b..0399b48 100644
--- a/src/opengl/qgl_x11.cpp
+++ b/src/opengl/qgl_x11.cpp
@@ -52,6 +52,7 @@
 #include "qdebug.h"
 #include <private/qfontengine_ft_p.h>
 #include <private/qt_x11_p.h>
+#include <private/qpixmap_x11_p.h>
 #ifdef Q_OS_HPUX
 // for GLXPBuffer
 #include <private/qglpixelbuffer_p.h>
@@ -1516,4 +1517,136 @@ void QGLExtensions::init()
     }
 }
 
+
+typedef void (*qt_glXBindTexImageEXT)(Display*, GLXDrawable, int, const int*);
+typedef void (*qt_glXReleaseTexImageEXT)(Display*, GLXDrawable, int);
+static qt_glXBindTexImageEXT glXBindTexImageEXT = 0;
+static qt_glXReleaseTexImageEXT glXReleaseTexImageEXT = 0;
+static bool qt_resolved_texture_from_pixmap = false;
+
+QGLTexture *QGLContextPrivate::bindTextureFromNativePixmap(QPixmap *pm, const qint64 key, bool canInvert)
+{
+    Q_Q(QGLContext);
+
+    if (pm->data_ptr()->classId() != QPixmapData::X11Class)
+        return 0;
+    QX11PixmapData *pixmapData = static_cast<QX11PixmapData*>(pm->data_ptr());
+    const QX11Info *x11Info = qt_x11Info(pm);
+
+
+    // Check to see if we have NPOT texture support
+    // TODO: Use GLX_TEXTURE_RECTANGLE_EXT texture target on systems without npot textures
+    if ( !(QGLExtensions::glExtensions & QGLExtensions::NPOTTextures) &&
+         !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0))
+        return 0;
+
+    if (!qt_resolved_texture_from_pixmap) {
+        qt_resolved_texture_from_pixmap = true;
+
+        QString glxExt = QLatin1String(glXGetClientString(QX11Info::display(), GLX_EXTENSIONS));
+        if (glxExt.contains(QLatin1String("GLX_EXT_texture_from_pixmap"))) {
+#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
+            void *handle = dlopen(NULL, RTLD_LAZY);
+            if (handle) {
+                glXBindTexImageEXT = (qt_glXBindTexImageEXT) dlsym(handle, "glXBindTexImageEXT");
+                glXReleaseTexImageEXT = (qt_glXReleaseTexImageEXT) dlsym(handle, "glXReleaseTexImageEXT");
+                dlclose(handle);
+            }
+            if (!glXBindTexImageEXT)
+#endif
+            {
+                extern const QString qt_gl_library_name();
+                QLibrary lib(qt_gl_library_name());
+                glXBindTexImageEXT = (qt_glXBindTexImageEXT) lib.resolve("glXBindTexImageEXT");
+                glXReleaseTexImageEXT = (qt_glXReleaseTexImageEXT) lib.resolve("glXReleaseTexImageEXT");
+            }
+        }
+    }
+
+    if (!glXBindTexImageEXT)
+        return 0;
+
+#if !defined(GLX_VERSION_1_3) || defined(Q_OS_HPUX)
+    return 0;
+#else
+    GLXFBConfig    *configList = 0;
+    GLXFBConfig     glxPixmapConfig;
+    int             configCount = 0;
+    bool            hasAlpha = pixmapData->hasAlphaChannel();
+
+    int configAttribs[] = {
+        hasAlpha ? GLX_BIND_TO_TEXTURE_RGBA_EXT : GLX_BIND_TO_TEXTURE_RGB_EXT, True,
+        GLX_DRAWABLE_TYPE, GLX_PIXMAP_BIT,
+        GLX_BIND_TO_TEXTURE_TARGETS_EXT, GLX_TEXTURE_2D_BIT_EXT,
+        // QGLContext::bindTexture() can't return an inverted texture, but QPainter::drawPixmap() can:
+        GLX_Y_INVERTED_EXT, canInvert ? GLX_DONT_CARE : False,
+        XNone
+//        GLX_BIND_TO_MIPMAP_TEXTURE_EXT, False,
+//        GLX_BIND_TO_TEXTURE_TARGETS_EXT, GLX_TEXTURE_1D_BIT_EXT or GLX_TEXTURE_2D_BIT_EXT or GLX_TEXTURE_RECTANGLE_BIT_EXT
+    };
+    configList = glXChooseFBConfig(x11Info->display(), x11Info->screen(), configAttribs, &configCount);
+    if (!configList)
+        return 0;
+    glxPixmapConfig = configList[0];
+    XFree(configList);
+
+    GLXPixmap glxPixmap;
+    int pixmapAttribs[] = {
+        GLX_TEXTURE_FORMAT_EXT, hasAlpha ? GLX_TEXTURE_FORMAT_RGBA_EXT : GLX_TEXTURE_FORMAT_RGB_EXT,
+        GLX_TEXTURE_TARGET_EXT, GLX_TEXTURE_2D_EXT,
+        GLX_MIPMAP_TEXTURE_EXT, False,
+        XNone
+//        GLX_TEXTURE_FORMAT_EXT, GLX_TEXTURE_FORMAT_RGBA_EXT or GLX_TEXTURE_FORMAT_RGB_EXT or GLX_TEXTURE_FORMAT_NONE_EXT,
+//        GLX_TEXTURE_TARGET_EXT, GLX_TEXTURE_2D_EXT or GLX_TEXTURE_RECTANGLE_EXT,
+//        GLX_MIPMAP_TEXTURE_EXT, True or False,
+    };
+
+    // Wrap the X Pixmap into a GLXPixmap:
+    glxPixmap = glXCreatePixmap(x11Info->display(), glxPixmapConfig, pixmapData->handle(), pixmapAttribs);
+
+    if (!glxPixmap)
+        return 0;
+
+    int yInverted;
+    glXGetFBConfigAttrib(x11Info->display(), glxPixmapConfig, GLX_Y_INVERTED_EXT, &yInverted);
+
+    GLuint textureId;
+    glGenTextures(1, &textureId);
+    glBindTexture(GL_TEXTURE_2D, textureId);
+    glXBindTexImageEXT(x11Info->display(), glxPixmap, GLX_FRONT_LEFT_EXT, 0);
+
+    glBindTexture(GL_TEXTURE_2D, textureId);
+
+    QGLTexture *texture = new QGLTexture(q, textureId, GL_TEXTURE_2D, canInvert, yInverted);
+    texture->boundPixmap = glxPixmap;
+
+    // We assume the cost of bound pixmaps is zero
+    QGLTextureCache::instance()->insert(q, key, texture, 0);
+
+    return texture;
+#endif //!defined(GLX_VERSION_1_3) || defined(Q_OS_HPUX)
+}
+
+void QGLTexture::deleteBoundPixmap()
+{
+    if (boundPixmap) {
+        // Although glXReleaseTexImage is a glX call, it must be called while there
+        // is a current context - the context the pixmap was bound to a texture in.
+        // Otherwise the relese doesn't do anything and you get BadDrawable errors
+        // when you come to delete the context.
+
+        QGLContext *oldContext = const_cast<QGLContext*>(QGLContext::currentContext());
+        if (oldContext != context)
+            context->makeCurrent();
+        glXReleaseTexImageEXT(QX11Info::display(), boundPixmap, GLX_FRONT_LEFT_EXT);
+        if (oldContext && oldContext != context)
+            oldContext->makeCurrent();
+
+        glXDestroyPixmap(QX11Info::display(), boundPixmap);
+    }
+
+    boundPixmap = 0;
+}
+
+
 QT_END_NAMESPACE