Imgui: example_glfw_opengl3 doesn't display imgui content on OpenGL3.0

[linaran]

Version/Branch of Dear ImGui:

1.62 release

Back-end file/Renderer/OS:

Trying to use GLFW with OpenGL3 on Linaro Linux release 16.02. Dragonboard 410c came with that OS. Supported OpenGL by the driver is "OpenGL version string: 3.0 Mesa 18.0.3" (output from glxinfo).

My Issue/Question:

In short I don't see any imgui content (no window it's just simple blue color) when I run the example_glfw_opengl3 sample. Note that I modified the main.cpp. I changed the minor version to 0 (since my driver supports OpenGL3.0) and removed the glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE) line since OpenGL3.0 doesn't support profiles.

OpenGL2 examples and it's integration with my own code works fine. I'm just not having any luck with OpenGL3.0 (can't try OpenGL3.2). I read the documentation and searched through the issues and googled this issue but didn't find anything helpful. If this is a duplicate question I'll see to removing it.

Standalone, minimal, complete and verifiable example:
I marked the changes within main.cpp with 3 excalamation marks (!!!). Everything else is vanilla.

int main(int, char**)
{
    // Setup window
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
        return 1;
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0); // Changed to 0!!!
//    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); Commented out!!!
#if __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
    GLFWwindow* window = glfwCreateWindow(1280, 720, "ImGui GLFW+OpenGL3 example", NULL, NULL);
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); // Enable vsync
    gl3wInit();

[ocornut]

Could you try changing the GLSL version to #130 and/or querying the shader compilation steps for errors?
I will/should add more error handling to this example, will try to do so now..

[ebachard]

Hello,

@linaran : can you please comment the #if __APPLE__ ... #endif in main.cpp ? Looks like you need the line
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
FYI, I got Linux (x86_64, Intel) here too. My new machine is OpenGL 4.5 capable, but I got the same issue when using 3.0. And commenting the lines above (#ifdef / #endif) makes it work as expected.

HTH

[ocornut]

I have pushed a change to report shader compile and link error (I wonder how it is reported in this situation).

We ought to fix those recurring problem, perhaps lock the version GL/GLSL version on Mac and use lower one on other platforms?

Also linking to #1900, #1513, #1466, #1116 etc.

[linaran]

@ocornut
I'm sort of still learning OpenGL but I was under the impression that OpenGL3.0 came with GLSL1.30 by default (didn't know you can change GLSL versions)? I'll build the example with your changes and report errors.

@ebachard
I tried commenting out those lines and nothing changed.

[ocornut]

You can call `ImGui_ImplOpenGL3_Init("#version 130") to build with a different version.
Try updating to latest/master so you'll also benefit from the error reporting code I have just pushed.

[ebachard]

@linaran

Let's start with at the begining. Can you post the full output of :
````
glxinfo -B

````
-B option gives a summary of the most important information returned by your graphic card driver.

This will tell us what exactly you can expect with your machine.

[linaran]

Okay I just cloned the latest commit from master.

@ebachard
Since I'm working on 2 computers and the linux one has a limited number of usb ports direct copy paste from the terminal is cumbersome (doing it over SD card).

name of display: :0
display: :0  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: freedreno (0x5143)
    Device: FD307 (0xffffffff)
    Version: 18.0.3
    Accelerated: yes
    Video memory: 10MB
    Unified memory: yes
    Preferred profile: core (0x1)
    Max core profile version: 3.1
    Max compat profile version: 3.0
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.0
OpenGL vendor string: freedreno
OpenGL renderer string: FD307
OpenGL core profile version string: 3.1 (Core Profile) Mesa 18.0.3
OpenGL core profile shading language version string: 1.40
OpenGL core profile context flags: (none)

OpenGL version string: 3.0 Mesa 18.0.3
OpenGL shading language version string: 1.30
OpenGL context flags: (none)

OpenGL ES profile version string: OpenGL ES 3.0 Mesa 18.0.3
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.00

@ocornut
I pulled the latest commit from master, implemented the changes to OpenGL3.0 and these are the errros I got.

ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to compile vertex sahder!
0:1(10): error: GLSL 1.50 is not supported. Supported versions are: 1.10, 1.20, 1.30 and 1.00 ES

The same goes for the fragment shader and the linker failed as expected. I will be changing the version to GLSL1.30 per your instructions.

[linaran]

@ocornut
Changing the GLSL to 1.30 did the trick 👍
Thanks :)

[ocornut]

Thanks for the confirmation @linaran.

I noticed that the shader works with 130 140 150 with the same context here,
If I change the Texture() call to Texture2D() is also work with 100 (with warnings) and 120.
I'll put a few changes soon.

What's unclear to me is how good GL drivers are honoring compatibility with older GLSL versions than the one desired by the context..

[ocornut]

I have pushed changes to the Examples+Bindings now. @linaran if you have a chance could you confirm that the unmodified repository now works with your configuration? Thanks!

[linaran]

@ocornut I'm confirming that the unmodified repository works. Cheers!

[ocornut]

Excellent, closing this issue then!