[Interest] Qt5 on OSX --> draw exact RGB device colors

[Nils Heidorn]

Hi List !
I work on an Application that needs to draw specific device RGB colors 
to multiple monitors on OSX 10.9 using Qt 5.3.2.
If i just draw a QColor(240,120,60) to a Widget, this is measured 
exactly as 240/120/60 on the primary monitor but if i create the same 
widget on a secondary monitor is is measured e.g. 240/117/51 .

OSX tries to be smart ant to make the color on the second screen appear 
as the color on the primary screen. While this is nice its not usable 
for my Application.

In former Qt / OSX versions we had this approach (c_ containg the 
current RGB Values to be painted):

void RGBFrame::paintEvent(QPaintEvent* e)
{
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
float components[4] = { 1.0, 1.0, 1.0, 1.0 };
components[0] = ((float)c_.red() * 1000 / 255) / 1000;
components[1] = ((float)c_.green() * 1000 / 255) / 1000;
components[2] = ((float)c_.blue() * 1000 / 255) / 1000;
CGColorRef color = CGColorCreate (colorSpaceRef, components);
CGRect cgrect = CGRectMake(e->rect().x(), e->rect().y(), e->rect().x() + 
e->rect().width(), e->rect().y() + e->rect().height());
CGContextRef context = qt_mac_cg_context(this);
CGContextSetFillColorWithColor(context, color);
CGContextFillRect(context, cgrect);
CGColorRelease(color);
CGColorSpaceRelease(colorSpaceRef);
}


i tried to upgrade this to Qt5 using QMac::currentCGContext() instead of 
the no more available qt_mac_cg_context(this) but it simply does not work.

Do you guys have a working or even more elegant approach ?

Greetings & thank you,

Nils Heidorn
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20141113/fd882562/attachment.html>