[Interest] High-dpi fixing for Qt 5.5

[Eddie Sutton]

Thanks Laszlo for the nice presentation "News from the Graphics Stack: Improvements to the core OpenGL enablers in Qt 5.3 & 5.4”.  

Are related code samples available?  Do you know if there be a 2015 Fall Qt Developer Days event in U.S.?

Qt3D documentation seems to be in the form of examples only.  I am using these for clues on how to integrate Qt3D into an existing QWidget app.

The OpenGL learning resources are very much appreciated!

-Ed

> On Mar 24, 2015, at 9:46 AM, Agocs Laszlo <laszlo.agocs at theqtcompany.com> wrote:
> 
> Because Qt 3D most likely misses a few multiplications by devicePixelRatio(). Probably easy to correct.
>  
> See http://www.qtdeveloperdays.com/sites/default/files/presentation_pdf/AgocsLaszlo_opengl_enablers_news.pdf#26 <http://www.qtdeveloperdays.com/sites/default/files/presentation_pdf/AgocsLaszlo_opengl_enablers_news.pdf#26>
>  
> Best regards,
> Laszlo
>  
> From: interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org [mailto:interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org] On Behalf Of Till Oliver Knoll
> Sent: 24. mars 2015 15:06
> To: Qt Project
> Subject: Re: [Interest] High-dpi fixing for Qt 5.5
>  
>  
> 
> Am 24.03.2015 um 14:39 schrieb Eddie Sutton <edsutton at gmail.com <mailto:edsutton at gmail.com>>:
> 
> >My knowledge of available "HiDPI" APIs is currently based on your (excellent) blog post, which does not seem to mention that use case:
> 
>  >http://blog.qt.io/blog/2013/04/25/retina-display-support-for-mac-os-ios-and-x11/ <http://blog.qt.io/blog/2013/04/25/retina-display-support-for-mac-os-ios-and-x11/>
>  
> Thanks for posting the excellent link.  It may help me find a work-around for a Qt3D windows scaling issue that affects OS X and iOS as well.
>  
> This, plus the Apple Developer docs may help as well, see "Enable OpenGL for High-Resolution Drawing"
> 
>  https://developer.apple.com/library/mac/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/CapturingScreenContents/CapturingScreenContents.html#//apple_ref/doc/uid/TP40012302-CH10-SW1 <https://developer.apple.com/library/mac/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/CapturingScreenContents/CapturingScreenContents.html#//apple_ref/doc/uid/TP40012302-CH10-SW1>
> 
> "OpenGL is a pixel-based API. The NSOpenGLView class does not provide high-resolution surfaces by default. Because adding more pixels to renderbuffers has performance implications, you must explicitly opt in to support high-resolution screens.
> 
> You can opt in to high resolution by calling the method setWantsBestResolutionOpenGLSurface: when you initialize the view, and supplying YES as an argument:
> 
> [self  setWantsBestResolutionOpenGLSurface:YES];
> 
> If you don't opt in, the system magnifies the rendered results."
> 
> /quote
> 
> Basically the docs say that OpenGL is a pixel-based drawing system, so any conversions between "points" and "pixels" needs to be done explicitly by the application itself, e.g. when resizing a window. And that you have to explicitly enable the "HiDPI" mode for the OpenGL context first.
> 
> How much that helps you to fix problems with the Qt3D module I can't say, but it is generally something you have to keep in mind when developing your own OpenGL based application (under OS X - on other OSes similar rules probably apply, too).
> 
> Cheers, Oliver
> 
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