Support RGB30 formats in OpenGL framebuffers and paint engine

This patch adds support for binding RGB30 images as textures, and as
internal format of framebuffer objects. Together with the
QOpenGLPaintDevice
this provides support for rendering to and from RGB30 in full precision.

[ChangeLog][QtGui][QOpenGLFramebufferObject] Support 10-bit per color
channels formats as the internal framebuffer format, making it possible
to render in that precision.

Change-Id: I06de2d12dfe1c1adc466d574fdffbc77f88f4f16
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

2 files changed, 63 insertions, 3 deletions

diff --git a/src/gui/opengl/qopenglframebufferobject.cpp b/src/gui/opengl/qopenglframebufferobject.cpp
index 0c05b61e76..16094804c2 100644
--- a/src/gui/opengl/qopenglframebufferobject.cpp
+++ b/src/gui/opengl/qopenglframebufferobject.cpp
@@ -104,10 +104,18 @@ QT_BEGIN_NAMESPACE
 #define GL_RGB8                           0x8051
 #endif
 
+#ifndef GL_RGB10
+#define GL_RGB10                          0x8052
+#endif
+
 #ifndef GL_RGBA8
 #define GL_RGBA8                          0x8058
 #endif
 
+#ifndef GL_RGB10_A2
+#define GL_RGB10_A2                       0x8059
+#endif
+
 #ifndef GL_BGRA
 #define GL_BGRA                           0x80E1
 #endif
@@ -116,6 +124,10 @@ QT_BEGIN_NAMESPACE
 #define GL_UNSIGNED_INT_8_8_8_8_REV       0x8367
 #endif
 
+#ifndef GL_UNSIGNED_INT_2_10_10_10_REV
+#define GL_UNSIGNED_INT_2_10_10_10_REV    0x8368
+#endif
+
 
 /*!
     \class QOpenGLFramebufferObjectFormat
@@ -539,8 +551,12 @@ void QOpenGLFramebufferObjectPrivate::initTexture(GLenum target, GLenum internal
     funcs.glTexParameteri(target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     funcs.glTexParameteri(target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
+    GLuint pixelType = GL_UNSIGNED_BYTE;
+    if (internal_format == GL_RGB10_A2 || internal_format == GL_RGB10)
+        pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+
     funcs.glTexImage2D(target, 0, internal_format, size.width(), size.height(), 0,
-                       GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+                       GL_RGBA, pixelType, NULL);
     if (mipmap) {
         int width = size.width();
         int height = size.height();
@@ -550,7 +566,7 @@ void QOpenGLFramebufferObjectPrivate::initTexture(GLenum target, GLenum internal
             height = qMax(1, height >> 1);
             ++level;
             funcs.glTexImage2D(target, level, internal_format, width, height, 0,
-                               GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+                               GL_RGBA, pixelType, NULL);
         }
     }
     funcs.glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
@@ -1142,6 +1158,14 @@ static inline QImage qt_gl_read_framebuffer_rgba8(const QSize &size, bool includ
     return rgbaImage;
 }
 
+static inline QImage qt_gl_read_framebuffer_rgb10a2(const QSize &size, bool include_alpha, QOpenGLContext *context)
+{
+    // We assume OpenGL 1.2+ or ES 3.0+ here.
+    QImage img(size, include_alpha ? QImage::Format_A2BGR30_Premultiplied : QImage::Format_BGR30);
+    context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_UNSIGNED_INT_2_10_10_10_REV, img.bits());
+    return img;
+}
+
 static QImage qt_gl_read_framebuffer(const QSize &size, GLenum internal_format, bool include_alpha, bool flip)
 {
     QOpenGLContext *ctx = QOpenGLContext::currentContext();
@@ -1152,6 +1176,10 @@ static QImage qt_gl_read_framebuffer(const QSize &size, GLenum internal_format,
     case GL_RGB:
     case GL_RGB8:
         return qt_gl_read_framebuffer_rgba8(size, false, ctx).mirrored(false, flip);
+    case GL_RGB10:
+        return qt_gl_read_framebuffer_rgb10a2(size, false, ctx).mirrored(false, flip);
+    case GL_RGB10_A2:
+        return qt_gl_read_framebuffer_rgb10a2(size, include_alpha, ctx).mirrored(false, flip);
     case GL_RGBA:
     case GL_RGBA8:
     default:
@@ -1177,7 +1205,8 @@ Q_GUI_EXPORT QImage qt_gl_read_framebuffer(const QSize &size, bool alpha_format,
     of QOpenGLPaintDevice::paintFlipped().
 
     Will try to return a premultiplied ARBG32 or RGB32 image. Since 5.2 it will fall back to
-    a premultiplied RGBA8888 or RGBx8888 image when reading to ARGB32 is not supported.
+    a premultiplied RGBA8888 or RGBx8888 image when reading to ARGB32 is not supported. Since 5.4 an
+    A2BGR30 image is returned if the internal format is RGB10_A2.
 
     For multisampled framebuffer objects the samples are resolved using the
     \c{GL_EXT_framebuffer_blit} extension. If the extension is not available, the contents
diff --git a/src/gui/opengl/qopengltexturecache.cpp b/src/gui/opengl/qopengltexturecache.cpp
index 4a4a36d7e5..055974d5a4 100644
--- a/src/gui/opengl/qopengltexturecache.cpp
+++ b/src/gui/opengl/qopengltexturecache.cpp
@@ -49,6 +49,10 @@
 
 QT_BEGIN_NAMESPACE
 
+#ifndef GL_RGB10_A2
+#define GL_RGB10_A2                       0x8059
+#endif
+
 #ifndef GL_BGR
 #define GL_BGR 0x80E0
 #endif
@@ -61,6 +65,10 @@ QT_BEGIN_NAMESPACE
 #define GL_UNSIGNED_INT_8_8_8_8_REV       0x8367
 #endif
 
+#ifndef GL_UNSIGNED_INT_2_10_10_10_REV
+#define GL_UNSIGNED_INT_2_10_10_10_REV    0x8368
+#endif
+
 class QOpenGLTextureCacheWrapper
 {
 public:
@@ -228,6 +236,29 @@ GLuint QOpenGLTextureCache::bindTexture(QOpenGLContext *context, qint64 key, con
         }
         targetFormat = image.format();
         break;
+    case QImage::Format_BGR30:
+    case QImage::Format_A2BGR30_Premultiplied:
+        if (isOpenGL12orBetter || (context->isOpenGLES() && context->format().majorVersion() >= 3)) {
+            pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+            externalFormat = GL_RGBA;
+            internalFormat = GL_RGB10_A2;
+            targetFormat =  image.format();
+        }
+        break;
+    case QImage::Format_RGB30:
+    case QImage::Format_A2RGB30_Premultiplied:
+        if (isOpenGL12orBetter) {
+            pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+            externalFormat = GL_BGRA;
+            internalFormat = GL_RGB10_A2;
+            targetFormat = image.format();
+        } else if (context->isOpenGLES() && context->format().majorVersion() >= 3) {
+            pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+            externalFormat = GL_RGBA;
+            internalFormat = GL_RGB10_A2;
+            targetFormat = QImage::Format_A2BGR30_Premultiplied;
+        }
+        break;
     case QImage::Format_RGB444:
     case QImage::Format_RGB555:
     case QImage::Format_RGB16: