Add public and QPA APIs for adapting existing OpenGL contexts

For now only xcb on GLX is supported. Other platforms will follow later.

Add also some missing documentation for the platform OpenGL context factory
functions.

[ChangeLog] QOpenGLContext is now able to adopt existing native contexts.

Task-number: QTBUG-37552
Change-Id: I5dd959f102df178f646b2df5989203b5dc6de376
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

2 files changed, 38 insertions, 4 deletions

diff --git a/src/platformsupport/glxconvenience/qglxconvenience.cpp b/src/platformsupport/glxconvenience/qglxconvenience.cpp
index 4630b12a57..851ad37a6a 100644
--- a/src/platformsupport/glxconvenience/qglxconvenience.cpp
+++ b/src/platformsupport/glxconvenience/qglxconvenience.cpp
@@ -250,7 +250,7 @@ XVisualInfo *qglx_findVisualInfo(Display *display, int screen, QSurfaceFormat *f
     return visualInfo;
 }
 
-void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display, GLXFBConfig config, GLXContext)
+void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display, GLXFBConfig config)
 {
     int redSize     = 0;
     int greenSize   = 0;
@@ -262,8 +262,6 @@ void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display,
     int sampleCount = 0;
     int stereo      = 0;
 
-    XVisualInfo *vi = glXGetVisualFromFBConfig(display,config);
-    XFree(vi);
     glXGetFBConfigAttrib(display, config, GLX_RED_SIZE,     &redSize);
     glXGetFBConfigAttrib(display, config, GLX_GREEN_SIZE,   &greenSize);
     glXGetFBConfigAttrib(display, config, GLX_BLUE_SIZE,    &blueSize);
@@ -287,6 +285,41 @@ void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display,
     format->setStereo(stereo);
 }
 
+void qglx_surfaceFormatFromVisualInfo(QSurfaceFormat *format, Display *display, XVisualInfo *visualInfo)
+{
+    int redSize     = 0;
+    int greenSize   = 0;
+    int blueSize    = 0;
+    int alphaSize   = 0;
+    int depthSize   = 0;
+    int stencilSize = 0;
+    int sampleBuffers = 0;
+    int sampleCount = 0;
+    int stereo      = 0;
+
+    glXGetConfig(display, visualInfo, GLX_RED_SIZE,     &redSize);
+    glXGetConfig(display, visualInfo, GLX_GREEN_SIZE,   &greenSize);
+    glXGetConfig(display, visualInfo, GLX_BLUE_SIZE,    &blueSize);
+    glXGetConfig(display, visualInfo, GLX_ALPHA_SIZE,   &alphaSize);
+    glXGetConfig(display, visualInfo, GLX_DEPTH_SIZE,   &depthSize);
+    glXGetConfig(display, visualInfo, GLX_STENCIL_SIZE, &stencilSize);
+    glXGetConfig(display, visualInfo, GLX_SAMPLES_ARB,  &sampleBuffers);
+    glXGetConfig(display, visualInfo, GLX_STEREO,       &stereo);
+
+    format->setRedBufferSize(redSize);
+    format->setGreenBufferSize(greenSize);
+    format->setBlueBufferSize(blueSize);
+    format->setAlphaBufferSize(alphaSize);
+    format->setDepthBufferSize(depthSize);
+    format->setStencilBufferSize(stencilSize);
+    if (sampleBuffers) {
+        glXGetConfig(display, visualInfo, GLX_SAMPLES_ARB, &sampleCount);
+        format->setSamples(sampleCount);
+    }
+
+    format->setStereo(stereo);
+}
+
 QSurfaceFormat qglx_reduceSurfaceFormat(const QSurfaceFormat &format, bool *reduced)
 {
     QSurfaceFormat retFormat = format;
diff --git a/src/platformsupport/glxconvenience/qglxconvenience_p.h b/src/platformsupport/glxconvenience/qglxconvenience_p.h
index 66548a3479..04fa8595ef 100644
--- a/src/platformsupport/glxconvenience/qglxconvenience_p.h
+++ b/src/platformsupport/glxconvenience/qglxconvenience_p.h
@@ -50,7 +50,8 @@
 
 XVisualInfo *qglx_findVisualInfo(Display *display, int screen, QSurfaceFormat *format);
 GLXFBConfig qglx_findConfig(Display *display, int screen, const QSurfaceFormat &format, int drawableBit = GLX_WINDOW_BIT);
-void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display, GLXFBConfig config, GLXContext context = 0);
+void qglx_surfaceFormatFromGLXFBConfig(QSurfaceFormat *format, Display *display, GLXFBConfig config);
+void qglx_surfaceFormatFromVisualInfo(QSurfaceFormat *format, Display *display, XVisualInfo *visualInfo);
 QVector<int> qglx_buildSpec(const QSurfaceFormat &format, int drawableBit = GLX_WINDOW_BIT);
 QSurfaceFormat qglx_reduceSurfaceFormat(const QSurfaceFormat &format, bool *reduced);