Transparency issues when using GLFW on Wayland

[savchenko]

Version/Branch of Dear ImGui:

Version: v1.81
Branch: master (4df5713)

Back-end/Renderer/Compiler/OS

Back-ends: GLFW/OpenGL2 and GLFW/OpenGL3
Compiler: g++ v10.2.1
Operating System: Debian Bullseye (5.10.13 kernel, AMDGPU, Renoir firmware 20.45)
WM: Sway v1.5 (implies Wayland instead of X-Server)

My Issue/Question:

Some UI elements are rendered transparent when this is not expected. The issue can be reproduced with GLFW, but not SDL:

• GLFW/OpenGL2:
  

• GLFW/OpenGL2:
  

• SDL/OpenGL3:
  

• imgui-rs (ping @thomcc) is affected as well:
  

Searching via existing bugs reveals #2764, however its author was using Windows.

Standalone, minimal, complete and verifiable example:

N/A, examples are compiled without any changes to the source code.

[ocornut]

In imgui_impl_opengl3.cpp, would changing this line:

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

into

glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

fix it for you?

cc #2766 #3447

[savchenko]

Unfortunately no, make fails with the following:

g++ -I../.. -I../../backends -g -Wall -Wformat -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W `pkg-config --cflags glfw3` -c -o imgui_impl_opengl3.o ../../backends/imgui_impl_opengl3.cpp
../../backends/imgui_impl_opengl3.cpp: In function ‘void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData*, int, int, GLuint)’:
../../backends/imgui_impl_opengl3.cpp:250:85: error: too many arguments to function
  250 |     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
      |                                                                                     ^
make: *** [Makefile:101: imgui_impl_opengl3.o] Error 1

I have opportunistically tried to build from #2766 that you have CC'd above, but it refuses to start on Wayland:

./example_glfw_opengl3 
Glfw Error 65544: Wayland: Focusing a window requires user interaction
Glfw Error 65544: Wayland: Window position retrieval not supported
Glfw Error 65544: Wayland: Window position retrieval not supported
Glfw Error 65544: Wayland: Window position retrieval not supported
Glfw Error 65544: Wayland: Window position setting not supported
Glfw Error 65544: Wayland: Window position setting not supported
xdg_wm_base@9: error 3: xdg_surface must not have a buffer at creation
Glfw Error 65544: Wayland: Window position retrieval not supported
Glfw Error 65544: Wayland: Window position retrieval not supported

[ocornut]

Unfortunately no, make fails with the following:

You didn't use the right code mentioned above.

[savchenko]

You didn't use the right code mentioned above.

Note to self: do not try to patch things late at night...

@ocornut , you are correct. With the glBlendFuncSeparate() it works perfectly:

Created pull request: #3816

[ocornut]

Hello @savchenko

We've now merged fixes and applied similar changes to multiple backends and examples, see bda12e5 and 6a161b8. Some remaining related work will be discussed in #2766

As for other Wayland errors if any:

• if not related to multi-viewports please post a separate issue and try to narrow down the GLFW calls leading to those printouts.
• if related to multi-viewports please post to Linux/Mac compatibility of multi-viewports #2117

Thank you!