[Development] QOpenGLContext::currentContext()->functions()->glCreateShader(GL_VERTEX_SHADER) returns 0

[Dov Grobgeld]

Shouldn't the 3rd step of the fallback kick in if my Direct3D is *not*
functional over RDP and I should be left with a software only 3D rendering?
Why doesn't that happen? Or did I misunderstand something in your blog post?

Thanks for the explanation about DebugView. I'll check it out.

Thanks!
Dov


On Sat, Jan 24, 2015 at 11:18 PM, Agocs Laszlo <
laszlo.agocs at theqtcompany.com> wrote:

>  Do "set QT_LOGGING_RULES=qt.qpa.gl=true" in the command prompt before
> launching the app. Then check the debug output with DebugView. During
> application startup a bunch of lines starting with qt.qpa.gl: ... will be
> printed. This will tell you which OpenGL implementation is in use.
> Alternatively, if using Creator, set the environment variable under the Run
> settings. The logs will then show up in the Application Output tab.
>
>
>  Real OpenGL is not an option since you will be left with OpenGL 1.1.
> ANGLE should work, as long as Direct3D is functional over RDP in your
> setup. You might want to try with some Qt examples first. For example
> try the Qt Quick examples under qtdeclarative/examples/quick. These all
> require OpenGL 2.0.
>
>
>  BR,
>
> Laszlo
>
>
>
>  ------------------------------
> *From:* development-bounces+laszlo.agocs=theqtcompany.com at qt-project.org
> <development-bounces+laszlo.agocs=theqtcompany.com at qt-project.org> on
> behalf of Dov Grobgeld <dov.grobgeld at gmail.com>
> *Sent:* Saturday, January 24, 2015 5:34 PM
> *To:* development at qt-project.org
> *Subject:* [Development]
> QOpenGLContext::currentContext()->functions()->glCreateShader(GL_VERTEX_SHADER)
> returns 0
>
>   I'm trying to write a cross platform OpenGL application. It is
> currently working both on Linux and on Windows when I'm working at the
> actual computer, but it fails when trying to run the application under the
> remote desktop rdp protocol from Windows to Linux. I traced down the
> failure to the fact that:
>
> QOpenGLContext::currentContext()->functions()
>   ->glCreateShader(GL_VERTEX_SHADER)
>
> returns 0, which indicates that the current context was not able to create
> a shader. But according to the blog entry at:
>
>
> http://blog.qt.digia.com/blog/2014/11/27/qt-weekly-21-dynamic-opengl-implementation-loading-in-qt-5-4/
>
>  the following fallback chain should fallback all the way to a software
> renderer if no OpenGL or DirectX (through ANGLE) is supported:
>
>
>    1. Try opengl32 and check if OpenGL 2.0 functions are available.
>    2. If this fails, try ANGLE.
>    3. If initialization fails either due to missing ANGLE libraries or
>    some other reason, try opengl32sw.dll. In practice this will be a software
>    rasterizer based implementation. To make it easy to get started, a
>    pre-built version of Mesa llvmpipe
>    <http://www.mesa3d.org/llvmpipe.html> is bundled with the binary
>    packages of Qt 5.4.
>
> I tried the above program with both the OpenGL and the non-open gl
> prebuild Qt-5.4 binary packages, but returned 0 under the remote desktop.
>
> Am I mistaken to assume that an OpenGL program will work (albeit slow!)
> under remote desktop? If not how can I trace down the failure?
>
> The above blog entry also discusses logging for tracing failures. But
> there is no explanation for where this logging is collected, how it is
> read, and interpreted.
>
> Thankful for any help, as it will save me the need to physically access a
> windows machine for my Qt OpenGL development!
>
> Regards,
>
> Dov
>
>
>
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