Fl_Gl_Window glViewport(0,0,pixel_w(),pixel_h()) and child widget size?

[duncan gibson]

Hi everyone, I'm back for my annual foray with an FLTK OpengGL3 project.

I'm on a MacBook Pro running MacOS 14.0 (Sonoma) with a 3024x1964 Retina XDR display

Can I first just say the CMake support for FetchContent(FLTK) makes life so much easier :-)

My project basically has half of the main window dedicated to user interface widgets.

and the other half is derived from Fl_Gl_Window, and a lot of the setup logic is based

on the OpenGL3test example and previous help in this forum with Apple specifics.

In a previous incarnation, I had an Fl_Box child of the main window, declared after the

derived Fl_Gl_Window, and positioned over it, to be used for status messages, etc.

That mostly worked, but introduced a dependency on the main window that I thought

could be encapsulated as a true child of the derived Fl_GL_Window instead, especially

when I noticed the Fl_Gl_Window docs describing the additional explicit call to begin().

But, there's no example code to base this on, and when I implemented it, I found that

the size of the Fl_Gl_Window Fl_Box child is half what I think it should be, and if I double

the width, the box appears to be clipped half-way across the Fl_Gl_Window.

Is this me not understanding something [as usual] or possibly a bug?

I've simplified the code down as much as possible, so there's no real OpenGL3 code

with shaders,  there's basically just the OpenGL3 checks, initialization and glViewport().

Any insights gratefully received.

[Manolo]

I didn't look at the attached code yet but can already put here some probably relevant information:

An example of adding child FLTK widgets to an Fl_Gl_Window is available with test/cube.cxx.
Another one uses OpenGL3 and is at examples/OpenGL3test.cxx.

Both create child widgets with the desired size and work equally well under macOS with and

without a retina display.
They also show how it's possible to otain a partially transparent color in such widgets.