add minimal_zgui_glfw_gl sample

[hazeycode]

zig build minimal_zgui_glfw_gl-run

Currently not working. I think zopengl's C exports are broken

lldb output

(lldb) target create "./zig-out/bin/minimal_zgui_glfw_gl"
Current executable set to '/Users/chris/Desktop/zig-gamedev/zig-out/bin/minimal_zgui_glfw_gl' (x86_64).
(lldb) run
Process 13338 launched: '/Users/chris/Desktop/zig-gamedev/zig-out/bin/minimal_zgui_glfw_gl' (x86_64)
2023-10-03 23:27:56.698007+0100 minimal_zgui_glfw_gl[13338:421632] SecTaskLoadEntitlements failed error=22 cs_flags=20, pid=13338
2023-10-03 23:27:56.698110+0100 minimal_zgui_glfw_gl[13338:421632] SecTaskCopyDebugDescription: minimal_zgui_glf[13338]/0#-1 LF=0
2023-10-03 23:27:57.477379+0100 minimal_zgui_glfw_gl[13338:421632] [Window] Warning: Window GLFWWindow 0x100f07ae0 ordered front from a non-active application and may order beneath the active application's windows.
2023-10-03 23:27:57.482626+0100 minimal_zgui_glfw_gl[13338:421632] [Window] Warning: Window GLFWWindow 0x100f07ae0 ordered front from a non-active application and may order beneath the active application's windows.
Process 13338 stopped
* thread zig-gamedev/zig-gamedev#1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2, address=0x10079b298)
    frame #0: 0x000000010079b298 minimal_zgui_glfw_gl`glGetIntegerv
minimal_zgui_glfw_gl`glGetIntegerv:
->  0x10079b298 <+0>: rep    jns	0x10079b2e3           ; glViewport + 3
    0x10079b29b <+3>: subl   $0x7ffa, %eax             ; imm = 0x7FFA 

[kanewallmann]

Oh I see what's going on. zopengl is exporting function pointers and GL_GLEXT_PROTOTYPES doesn't declare the symbols as function pointers.

Also you need to call zgui.backend.newFrame() before zgui.begin() and zgui.backend.draw() before window.swapBuffers().

Rebase your PR with my latest commit, fix those two things and I think it should work.

Not sure if this is the best way to fix it but it is working.

[kanewallmann]

Your sample is working for me with those changes. At least on Linux.

[hazeycode]

Thanks. Working for me now (except mouse input is incorrectly scaled).

I tried scaling using the method mentioned in this issue: https://github.com/michal-z/zig-gamedev/issues/258 but it did not work for me. The display, font size, etc. looks ok but the mouse position is incorrectly scaled.

[kanewallmann]

The wgpu backend has a function that accepts a framebuffer width and height which the sample uses.

https://github.com/michal-z/zig-gamedev/blob/b70608b6d8e79192dfbb4ab60e3c5b05eb9b7f6d/libs/zgui/src/backend_glfw_wgpu.zig#L40

When you say you tried the scaling method used in that issue, did it include implementing the same in the gl backend?

I don't have a high DPI display to test it on myself.

[hazeycode]

I probably missed something. I'll have another go at it. The backend interface should probably be changed to match that of the wgpu backend anyway.

[hazeycode]

DPI scaling is working now