Use FBOs as pixmap backend in GL graphics system.

We now use FBOs to implement render-to-pixmap for the GL pixmap backend.
A multisample FBO is used for rendering, and is then blitted onto a
non-multisample FBO dynamically bound to the relevant texture.

Reviewed-by: Tom

1 files changed, 168 insertions, 68 deletions

diff --git a/src/opengl/qpixmapdata_gl.cpp b/src/opengl/qpixmapdata_gl.cpp
index ec71fa6..0656880 100644
--- a/src/opengl/qpixmapdata_gl.cpp
+++ b/src/opengl/qpixmapdata_gl.cpp
@@ -40,6 +40,7 @@
 ****************************************************************************/
 
 #include "qpixmap.h"
+#include "qglframebufferobject.h"
 
 #include <private/qpaintengine_raster_p.h>
 
@@ -48,6 +49,12 @@
 #include <private/qgl_p.h>
 #include <private/qdrawhelper_p.h>
 
+#if 1 || defined(QT_OPENGL_ES_2)
+#include <private/qpaintengineex_opengl2_p.h>
+#else
+#include <private/qpaintengine_opengl_p.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 extern QGLWidget* qt_gl_share_widget();
@@ -89,48 +96,16 @@ private:
     QGLContext *m_ctx;
 };
 
-void qt_gl_convertFromGLImage(QImage *img)
-{
-    const int w = img->width();
-    const int h = img->height();
-
-    if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
-        uint *p = (uint*)img->bits();
-        uint *end = p + w*h;
-
-        while (p < end) {
-            uint a = *p << 24;
-            *p = (*p >> 8) | a;
-            p++;
-        }
-
-        *img = img->mirrored();
-    } else {
-        // mirror image
-        uint *data = (uint *)img->bits();
-
-        const int mid = h/2;
-
-        for (int y = 0; y < mid; ++y) {
-            uint *p = data + y * w;
-            uint *end = p + w;
-            uint *q = data + (h - y - 1) * w;
-
-            while (p < end)
-                qSwap(*p++, *q++);
-        }
-    }
-}
-
-
 static int qt_gl_pixmap_serial = 0;
 
 QGLPixmapData::QGLPixmapData(PixelType type)
     : QPixmapData(type, OpenGLClass)
     , m_width(0)
     , m_height(0)
+    , m_renderFbo(0)
+    , m_textureId(0)
+    , m_engine(0)
     , m_ctx(0)
-    , m_texture(0)
     , m_dirty(false)
 {
     setSerialNumber(++qt_gl_pixmap_serial);
@@ -138,10 +113,11 @@ QGLPixmapData::QGLPixmapData(PixelType type)
 
 QGLPixmapData::~QGLPixmapData()
 {
-    if (m_texture && qt_gl_share_widget()) {
-        QGLShareContextScope ctx(qt_gl_share_widget()->context());
-        glDeleteTextures(1, &m_texture);
-    }
+    QGLWidget *shareWidget = qt_gl_share_widget();
+    if (!shareWidget)
+        return;
+    QGLShareContextScope ctx(shareWidget->context());
+    glDeleteTextures(1, &m_textureId);
 }
 
 bool QGLPixmapData::isValid() const
@@ -166,6 +142,12 @@ void QGLPixmapData::resize(int width, int height)
     m_width = width;
     m_height = height;
 
+    if (m_textureId) {
+        QGLShareContextScope ctx(qt_gl_share_widget()->context());
+        glDeleteTextures(1, &m_textureId);
+        m_textureId = 0;
+    }
+
     m_source = QImage();
     m_dirty = isValid();
     setSerialNumber(++qt_gl_pixmap_serial);
@@ -184,24 +166,30 @@ void QGLPixmapData::ensureCreated() const
     const GLenum format = qt_gl_preferredTextureFormat();
     const GLenum target = qt_gl_preferredTextureTarget();
 
-    if (!m_texture)
-        glGenTextures(1, &m_texture);
-
-    glBindTexture(target, m_texture);
+    if (!m_textureId) {
+        glGenTextures(1, &m_textureId);
+        glBindTexture(target, m_textureId);
+        glTexImage2D(target, 0, GL_RGBA, m_width, m_height, 0,
+                GL_RGBA, GL_UNSIGNED_BYTE, 0);
+    }
 
-    if (m_source.isNull()) {
-        glTexImage2D(target, 0, GL_RGBA, m_width, m_height, 0, format, GL_UNSIGNED_BYTE, 0);
-    } else {
+    if (!m_source.isNull()) {
         const QImage tx = ctx->d_func()->convertToGLFormat(m_source, true, format);
 
-        glBindTexture(target, m_texture);
-        glTexImage2D(target, 0, GL_RGBA, m_width, m_height, 0, format,
-                GL_UNSIGNED_BYTE, tx.bits());
+        glBindTexture(target, m_textureId);
+        glTexSubImage2D(target, 0, 0, 0, m_width, m_height, format,
+                        GL_UNSIGNED_BYTE, tx.bits());
 
-        m_source = QImage();
+        if (useFramebufferObjects())
+            m_source = QImage();
     }
 }
 
+QGLFramebufferObject *QGLPixmapData::fbo() const
+{
+    return m_renderFbo;
+}
+
 void QGLPixmapData::fromImage(const QImage &image,
                               Qt::ImageConversionFlags)
 {
@@ -220,6 +208,17 @@ bool QGLPixmapData::scroll(int dx, int dy, const QRect &rect)
     return false;
 }
 
+void QGLPixmapData::copy(const QPixmapData *data, const QRect &rect)
+{
+    if (data->classId() != QPixmapData::OpenGLClass) {
+        QPixmapData::copy(data, rect);
+        return;
+    }
+
+    // can be optimized to do a framebuffer blit or similar ...
+    QPixmapData::copy(data, rect);
+}
+
 void QGLPixmapData::fill(const QColor &color)
 {
     if (!isValid())
@@ -246,7 +245,9 @@ QImage QGLPixmapData::toImage() const
     if (!isValid())
         return QImage();
 
-    if (!m_source.isNull())
+    if (m_renderFbo)
+        return m_renderFbo->toImage().copy(0, m_renderFbo->height() - m_height, m_width, m_height);
+    else if (!m_source.isNull())
         return m_source;
     else if (m_dirty)
         return QImage(m_width, m_height, QImage::Format_ARGB32_Premultiplied);
@@ -254,21 +255,84 @@ QImage QGLPixmapData::toImage() const
     ensureCreated();
 
     QGLShareContextScope ctx(qt_gl_share_widget()->context());
-    QImage img(m_width, m_height, QImage::Format_ARGB32_Premultiplied);
+    extern QImage qt_gl_read_texture(const QSize &size, bool alpha_format, bool include_alpha);
+    glBindTexture(qt_gl_preferredTextureTarget(), m_textureId);
+    return qt_gl_read_texture(QSize(m_width, m_height), true, true);
+}
 
-    GLenum format = qt_gl_preferredTextureFormat();
-    GLenum target = qt_gl_preferredTextureTarget();
+struct TextureBuffer
+{
+    QGLFramebufferObject *fbo;
+    QGL2PaintEngineEx *engine;
+};
 
-    glBindTexture(target, m_texture);
-#ifndef QT_OPENGL_ES
-    glGetTexImage(target, 0, format, GL_UNSIGNED_BYTE, img.bits());
-#else
-    // XXX - cannot download textures this way on OpenGL/ES.
-#endif
+static QVector<TextureBuffer> textureBufferStack;
+static int currentTextureBuffer = 0;
 
-    qt_gl_convertFromGLImage(&img);
+void QGLPixmapData::beginPaint()
+{
+    if (!isValid())
+        return;
 
-    return img;
+    m_renderFbo->bind();
+}
+
+void QGLPixmapData::endPaint()
+{
+    if (!isValid())
+        return;
+
+    const QGLContext *share_ctx = qt_gl_share_widget()->context();
+    QGLShareContextScope ctx(share_ctx);
+
+    ensureCreated();
+
+    if (!ctx->d_ptr->fbo)
+        glGenFramebuffersEXT(1, &ctx->d_ptr->fbo);
+
+    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, ctx->d_ptr->fbo);
+    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+        qt_gl_preferredTextureTarget(), m_textureId, 0);
+
+    const int x0 = 0;
+    const int x1 = m_width;
+    const int y0 = 0;
+    const int y1 = m_height;
+
+    glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, m_renderFbo->handle());
+
+    glDisable(GL_SCISSOR_TEST);
+
+    glBlitFramebufferEXT(x0, y0, x1, y1,
+            x0, y0, x1, y1,
+            GL_COLOR_BUFFER_BIT,
+            GL_NEAREST);
+
+    m_renderFbo->release();
+
+    --currentTextureBuffer;
+
+    m_renderFbo = 0;
+    m_engine = 0;
+}
+
+static TextureBuffer createTextureBuffer(const QSize &size, QGL2PaintEngineEx *engine = 0)
+{
+    TextureBuffer buffer;
+    QGLFramebufferObjectFormat fmt;
+    fmt.setAttachment(QGLFramebufferObject::CombinedDepthStencil);
+    fmt.setSamples(4);
+
+    buffer.fbo = new QGLFramebufferObject(size, fmt);
+    buffer.engine = engine ? engine : new QGL2PaintEngineEx;
+
+    return buffer;
+}
+
+bool QGLPixmapData::useFramebufferObjects()
+{
+    return QGLFramebufferObject::hasOpenGLFramebufferObjects()
+           && QGLFramebufferObject::hasOpenGLFramebufferBlit();
 }
 
 QPaintEngine* QGLPixmapData::paintEngine() const
@@ -276,23 +340,59 @@ QPaintEngine* QGLPixmapData::paintEngine() const
     if (!isValid())
         return 0;
 
-    m_source = toImage();
-    m_dirty = true;
+    if (m_engine)
+        return m_engine;
+    else if (!useFramebufferObjects()) {
+        m_dirty = true;
+
+        if (m_source.size() != size())
+            m_source = QImage(size(), QImage::Format_ARGB32_Premultiplied);
+        return m_source.paintEngine();
+    }
 
-    return m_source.paintEngine();
+    extern QGLWidget* qt_gl_share_widget();
+
+    if (!QGLContext::currentContext())
+        qt_gl_share_widget()->makeCurrent();
+    QGLShareContextScope ctx(qt_gl_share_widget()->context());
+
+    if (textureBufferStack.size() <= currentTextureBuffer) {
+        textureBufferStack << createTextureBuffer(size());
+    } else {
+        QSize sz = textureBufferStack.at(currentTextureBuffer).fbo->size();
+        if (sz.width() < m_width || sz.height() < m_height) {
+            if (sz.width() < m_width)
+                sz.setWidth(qMax(m_width, qRound(sz.width() * 1.5)));
+            if (sz.height() < m_height)
+                sz.setHeight(qMax(m_height, qRound(sz.height() * 1.5)));
+            delete textureBufferStack.at(currentTextureBuffer).fbo;
+            textureBufferStack[currentTextureBuffer] =
+                createTextureBuffer(sz, textureBufferStack.at(currentTextureBuffer).engine);
+            qDebug() << "Creating new pixmap texture buffer:" << sz;
+        }
+    }
+
+    m_renderFbo = textureBufferStack.at(currentTextureBuffer).fbo;
+    m_engine = textureBufferStack.at(currentTextureBuffer).engine;
+
+    ++currentTextureBuffer;
+
+    return m_engine;
 }
 
 GLuint QGLPixmapData::bind() const
 {
     ensureCreated();
-    glBindTexture(qt_gl_preferredTextureTarget(), m_texture);
-    return m_texture;
+
+    GLuint id = m_textureId;
+    glBindTexture(qt_gl_preferredTextureTarget(), id);
+    return id;
 }
 
 GLuint QGLPixmapData::textureId() const
 {
     ensureCreated();
-    return m_texture;
+    return m_textureId;
 }
 
 extern int qt_defaultDpiX();