Added QGLPixelBuffer implementation using framebuffer objects.

Instead of having QGLPixelBuffer be a unusable stub implementation we
deprecate it and implement it in terms of QOpenGLFramebufferObject.
Framebuffer objects are anyway the recommended replacement for
pixelbuffers in modern OpenGL, as the context switching overhead is
avoided.

Change-Id: Ia220c358ee92813e87981d297c51d84525010322
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 106 insertions, 11 deletions

diff --git a/src/opengl/qglpixelbuffer.cpp b/src/opengl/qglpixelbuffer.cpp
index d9480c4994..135f2edd01 100644
--- a/src/opengl/qglpixelbuffer.cpp
+++ b/src/opengl/qglpixelbuffer.cpp
@@ -92,7 +92,10 @@
     \sa {opengl/pbuffers}{Pbuffers Example}
 */
 
+#include <private/qopenglextensions_p.h>
+
 #include <QtCore/qglobal.h>
+#include <QtGui/qopenglframebufferobject.h>
 
 #include "gl2paintengineex/qpaintengineex_opengl2_p.h"
 
@@ -129,16 +132,7 @@ void QGLPixelBufferPrivate::common_init(const QSize &size, const QGLFormat &form
         req_format = format;
         req_shareWidget = shareWidget;
         invalid = false;
-        qctx = new QGLContext(format);
-        qctx->d_func()->sharing = (shareWidget != 0);
-        if (shareWidget != 0 && shareWidget->d_func()->glcx) {
-            QGLContextGroup::addShare(qctx, shareWidget->d_func()->glcx);
-            shareWidget->d_func()->glcx->d_func()->sharing = true;
-        }
-
         glDevice.setPBuffer(q);
-        qctx->d_func()->paintDevice = q;
-        qctx->d_func()->valid = true;
     }
 }
 
@@ -198,7 +192,6 @@ QGLPixelBuffer::~QGLPixelBuffer()
     if (current != d->qctx)
         makeCurrent();
     d->cleanup();
-    delete d->qctx;
     if (current && current != d->qctx)
         current->makeCurrent();
 }
@@ -217,6 +210,17 @@ bool QGLPixelBuffer::makeCurrent()
     if (d->invalid)
         return false;
     d->qctx->makeCurrent();
+    if (!d->fbo) {
+        QOpenGLFramebufferObjectFormat format;
+        if (d->req_format.stencil())
+            format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
+        else if (d->req_format.depth())
+            format.setAttachment(QOpenGLFramebufferObject::Depth);
+        if (d->req_format.sampleBuffers())
+            format.setSamples(d->req_format.samples());
+        d->fbo = new QOpenGLFramebufferObject(d->req_size, format);
+        d->fbo->bind();
+    }
     return true;
 }
 
@@ -306,14 +310,39 @@ bool QGLPixelBuffer::doneCurrent()
 void QGLPixelBuffer::updateDynamicTexture(GLuint texture_id) const
 {
     Q_D(const QGLPixelBuffer);
-    if (d->invalid)
+    if (d->invalid || !d->fbo)
+        return;
+
+    QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    if (!ctx)
         return;
+
+#undef glBindFramebuffer
+
+#ifndef GL_READ_FRAMEBUFFER
+#define GL_READ_FRAMEBUFFER 0x8CA8
+#endif
+
+#ifndef GL_DRAW_FRAMEBUFFER
+#define GL_DRAW_FRAMEBUFFER 0x8CA9
+#endif
+
+    QOpenGLExtensions extensions(ctx);
+
+    if (d->blit_fbo) {
+        QOpenGLFramebufferObject::blitFramebuffer(d->blit_fbo, d->fbo);
+        extensions.glBindFramebuffer(GL_READ_FRAMEBUFFER, d->blit_fbo->handle());
+    }
+
     glBindTexture(GL_TEXTURE_2D, texture_id);
 #ifndef QT_OPENGL_ES
     glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 0, 0, d->req_size.width(), d->req_size.height(), 0);
 #else
     glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, d->req_size.width(), d->req_size.height(), 0);
 #endif
+
+    if (d->blit_fbo)
+        extensions.glBindFramebuffer(GL_READ_FRAMEBUFFER, ctx->d_func()->current_fbo);
 }
 
 /*!
@@ -521,4 +550,70 @@ QGLFormat QGLPixelBuffer::format() const
     \internal
 */
 
+bool QGLPixelBufferPrivate::init(const QSize &, const QGLFormat &f, QGLWidget *shareWidget)
+{
+    widget = new QGLWidget(f, 0, shareWidget);
+    widget->resize(1, 1);
+    qctx = const_cast<QGLContext *>(widget->context());
+    return widget->isValid();
+}
+
+bool QGLPixelBufferPrivate::cleanup()
+{
+    delete fbo;
+    fbo = 0;
+    delete blit_fbo;
+    blit_fbo = 0;
+    delete widget;
+    widget = 0;
+    return true;
+}
+
+bool QGLPixelBuffer::bindToDynamicTexture(GLuint texture_id)
+{
+    Q_UNUSED(texture_id);
+    return false;
+}
+
+void QGLPixelBuffer::releaseFromDynamicTexture()
+{
+}
+
+GLuint QGLPixelBuffer::generateDynamicTexture() const
+{
+    Q_D(const QGLPixelBuffer);
+    if (!d->fbo)
+        return 0;
+
+    if (d->fbo->format().samples() > 0
+        && QOpenGLExtensions(QOpenGLContext::currentContext())
+           .hasOpenGLExtension(QOpenGLExtensions::FramebufferBlit))
+    {
+        if (!d->blit_fbo)
+            const_cast<QOpenGLFramebufferObject *&>(d->blit_fbo) = new QOpenGLFramebufferObject(d->req_size);
+    } else {
+        return d->fbo->texture();
+    }
+
+    GLuint texture;
+
+    glGenTextures(1, &texture);
+    glBindTexture(GL_TEXTURE_2D, texture);
+
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, d->req_size.width(), d->req_size.height(), 0,
+            GL_RGBA, GL_UNSIGNED_BYTE, 0);
+
+    return texture;
+}
+
+bool QGLPixelBuffer::hasOpenGLPbuffers()
+{
+    return QOpenGLFramebufferObject::hasOpenGLFramebufferObjects();
+}
+
 QT_END_NAMESPACE