diff options
Diffstat (limited to 'src/platformsupport/eglconvenience/qeglconvenience.cpp')
| -rw-r--r-- | src/platformsupport/eglconvenience/qeglconvenience.cpp | 54 |
1 files changed, 34 insertions, 20 deletions
diff --git a/src/platformsupport/eglconvenience/qeglconvenience.cpp b/src/platformsupport/eglconvenience/qeglconvenience.cpp index e6624fb9ff..5eed47050f 100644 --- a/src/platformsupport/eglconvenience/qeglconvenience.cpp +++ b/src/platformsupport/eglconvenience/qeglconvenience.cpp @@ -66,26 +66,30 @@ QVector<EGLint> q_createConfigAttributesFromFormat(const QSurfaceFormat &format) int stencilSize = format.stencilBufferSize(); int sampleCount = format.samples(); - // We want to make sure 16-bit configs are chosen over 32-bit configs as they will provide - // the best performance. The EGL config selection algorithm is a bit stange in this regard: - // The selection criteria for EGL_BUFFER_SIZE is "AtLeast", so we can't use it to discard - // 32-bit configs completely from the selection. So it then comes to the sorting algorithm. - // The red/green/blue sizes have a sort priority of 3, so they are sorted by first. The sort - // order is special and described as "by larger _total_ number of color bits.". So EGL will - // put 32-bit configs in the list before the 16-bit configs. However, the spec also goes on - // to say "If the requested number of bits in attrib_list for a particular component is 0, - // then the number of bits for that component is not considered". This part of the spec also - // seems to imply that setting the red/green/blue bits to zero means none of the components - // are considered and EGL disregards the entire sorting rule. It then looks to the next - // highest priority rule, which is EGL_BUFFER_SIZE. Despite the selection criteria being - // "AtLeast" for EGL_BUFFER_SIZE, it's sort order is "smaller" meaning 16-bit configs are - // put in the list before 32-bit configs. So, to make sure 16-bit is preffered over 32-bit, - // we must set the red/green/blue sizes to zero. This has an unfortunate consequence that - // if the application sets the red/green/blue size to 5/6/5 on the QSurfaceFormat, - // they might still get a 32-bit config, even when there's an RGB565 config available. - QVector<EGLint> configAttributes; + // Map default, unspecified values (-1) to 0. This is important due to sorting rule #3 + // in section 3.4.1 of the spec and allows picking a potentially faster 16-bit config + // over 32-bit ones when there is no explicit request for the color channel sizes: + // + // The red/green/blue sizes have a sort priority of 3, so they are sorted by + // first. (unless a caveat like SLOW or NON_CONFORMANT is present) The sort order is + // Special and described as "by larger _total_ number of color bits.". So EGL will put + // 32-bit configs in the list before the 16-bit configs. However, the spec also goes + // on to say "If the requested number of bits in attrib_list for a particular + // component is 0, then the number of bits for that component is not considered". This + // part of the spec also seems to imply that setting the red/green/blue bits to zero + // means none of the components are considered and EGL disregards the entire sorting + // rule. It then looks to the next highest priority rule, which is + // EGL_BUFFER_SIZE. Despite the selection criteria being "AtLeast" for + // EGL_BUFFER_SIZE, it's sort order is "smaller" meaning 16-bit configs are put in the + // list before 32-bit configs. + // + // This also means that explicitly specifying a size like 565 will still result in + // having larger (888) configs first in the returned list. We need to handle this + // ourselves later by manually filtering the list, instead of just blindly taking the + // first config from it. + configAttributes.append(EGL_RED_SIZE); configAttributes.append(redSize > 0 ? redSize : 0); @@ -242,7 +246,7 @@ EGLConfig QEglConfigChooser::chooseConfig() #ifdef EGL_VERSION_1_4 case QSurfaceFormat::DefaultRenderableType: #ifndef QT_NO_OPENGL - if (QOpenGLContext::openGLModuleType() == QOpenGLContext::DesktopGL) + if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) configureAttributes.append(EGL_OPENGL_BIT); else #endif // QT_NO_OPENGL @@ -293,6 +297,13 @@ EGLConfig QEglConfigChooser::chooseConfig() if (!cfg && matching > 0) cfg = configs.first(); + // Filter the list. Due to the EGL sorting rules configs with higher depth are + // placed first when the minimum color channel sizes have been specified (i.e. the + // QSurfaceFormat contains color sizes > 0). To prevent returning a 888 config + // when the QSurfaceFormat explicitly asked for 565, go through the returned + // configs and look for one that exactly matches the requested sizes. When no + // sizes have been given, take the first, which will be a config with the smaller + // (e.g. 16-bit) depth. for (int i = 0; i < configs.size(); ++i) { if (filterConfig(configs[i])) return configs.at(i); @@ -306,6 +317,8 @@ EGLConfig QEglConfigChooser::chooseConfig() bool QEglConfigChooser::filterConfig(EGLConfig config) const { + // If we are fine with the highest depth (e.g. RGB888 configs) even when something + // smaller (565) was explicitly requested, do nothing. if (m_ignore) return true; @@ -314,6 +327,7 @@ bool QEglConfigChooser::filterConfig(EGLConfig config) const EGLint blue = 0; EGLint alpha = 0; + // Compare only if a size was given. Otherwise just accept. if (m_confAttrRed) eglGetConfigAttrib(display(), config, EGL_RED_SIZE, &red); if (m_confAttrGreen) @@ -366,7 +380,7 @@ QSurfaceFormat q_glFormatFromConfig(EGLDisplay display, const EGLConfig config, format.setRenderableType(QSurfaceFormat::OpenGL); else if (referenceFormat.renderableType() == QSurfaceFormat::DefaultRenderableType #ifndef QT_NO_OPENGL - && QOpenGLContext::openGLModuleType() == QOpenGLContext::DesktopGL + && QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL #endif && (renderableType & EGL_OPENGL_BIT)) format.setRenderableType(QSurfaceFormat::OpenGL); |