GLES2: Check for GPU capabilities to display an error

[akien-mga]

The engine will still segfault, but the error message should be displayed by the
OS in a blocking manner, so that it will only crash once users have acknowledged
the error dialog.

Please test, especially if you have hardware that does not support GL 2.1 / GLES 2.0. I only tested on Linux X11, and by tweaking the if to make it fail when GL 2.1 was actually supported. @SuperUserNameMan's test in #1162 (comment) seems to indicate that it would be working on Windows for his hardware.

Closes #1162.

[akien-mga]

I pushed a test build of this commit on our CI-based deployment system: https://github.com/GodotBuilder/godot-builds/releases/tag/test_20160725
There should be binaries to test for all platforms in a couple of hours.

[SuperUserNameMan]

to test under linux without changing the code and recompiling, i think you can set the environment variable MESA_GL_VERSION_OVERRIDE to 2.0 : http://www.mesa3d.org/envvars.html

IIRC, that's also how to proceeded to force MESA to allow black listed GPU to work with Godot.

[akien-mga]

to test under linux without changing the code and recompiling, i think you can set the environment variable MESA_GL_VERSION_OVERRIDE to 2.0

Nice trick, that works for me :)

[akien-mga]

Note that only desktop platforms use GLEW, so this error should not show on Android and iOS devices.

[SuperUserNameMan]

So I tested on my Acer eMachine Netbook with Intel Atom N450 and integrated Intel GMA 3150 :

under LinuxMint18, MATE, 32bits (MESA Opengl 1.4) :

• the warning dialog box is displayed correctly.
• through the console, it complains that it could not load libXrandr.so.
• If I override opengl version to 2.1 or 3.0 using the env var, Godot runs despite the missing libXrandr, But the 3D viewport is all messed up.
• also, as side note, 1024x768 is too small to display Godot interface correctly. The project manager interface is not displayed correctly unless you expand the window, and into the editor I can't even access the "Quit" menu item.

same netbook, under Windows 10, 32bits (Opengl 1.4 default Microsoft Opengl 1.1 ) :

• it crashed without displaying the dialog box.
• however into the console, the ERROR: RasterizerGLES2::init: message is written.

I also tested on my regular laptop with radeon R4 and Windows 8.1 and it worked correctly.

[SuperUserNameMan]

Okay, i've found why the dialog box was not displayed into Windows 10 before crashing.

Into godot/platform/windows/os_windows.cpp, at line 1346, into OS_Windows::alert(), MessageBoxW() requires MB_TASKMODAL as extra flag :

        MessageBoxW(NULL,p_alert.c_str(),p_title.c_str(),MB_OK|MB_ICONEXCLAMATION|MB_TASKMODAL);

[akien-mga]

Nice catch @SuperUserNameMan. Here's the corresponding API reference: https://msdn.microsoft.com/en-us/library/windows/desktop/ms645505(v=vs.85).aspx

Does the message box then appear in the foreground, or in the background? I see that there is a MB_SETFOREGROUND flag we could use too.

[SuperUserNameMan]

It appears on foreground.
The Godot ongoing process is paused till OKAY is pressed. Then it crashes and display system dialog box "Godot Engine Editor (rc1) has stopped to work" .
I don't think more MB_ flags are required.

[akien-mga]

Pushed a new commit adding this flag, thanks again :)