#error exactly one of IMGUI_IMPL_WEBGPU_BACKEND_DAWN or IMGUI_IMPL_WEBGPU_BACKEND_WGPU must be defined!

[tadeohepperle]

I can't get zgui to compile with zig 0.15.1. The following build error occurs:

/home/tadeo/.cache/zig/p/zgui-0.6.0-dev--L6sZL7tbQAPRLYrcQAVx0V49tPHAXNxclZ-v8IP4wLr/libs/imgui/backends/imgui_impl_wgpu.cpp:54:6: error: exactly one of IMGUI_IMPL_WEBGPU_BACKEND_DAWN or IMGUI_IMPL_WEBGPU_BACKEND_WGPU must be defined!
    #error exactly one of IMGUI_IMPL_WEBGPU_BACKEND_DAWN or IMGUI_IMPL_WEBGPU_BACKEND_WGPU must be defined!

In the dependencies of my build.zig.zon file I have the following fields:

.zgui = .{
    .url = "https://github.com/zig-gamedev/zgui/archive/7fa8081c208885b85e3fdfc043cd9d9cb9559123.tar.gz",
    .hash = "zgui-0.6.0-dev--L6sZL7tbQAPRLYrcQAVx0V49tPHAXNxclZ-v8IP4wLr",
},
.zgpu = .{
    .url = "https://github.com/zig-gamedev/zgpu/archive/96f3ce2229e4836daec714a3f0b8c3c3218a6b2c.tar.gz",
    .hash = "zgpu-0.12.0-dev-nqFT5LqgCACR_1wEhi7rveY3ocKJczfRaXQoisCmpohn",
},
.dawn_x86_64_linux_gnu = .{
    .url = "https://github.com/michal-z/webgpu_dawn-x86_64-linux-gnu/archive/7d70db023bf254546024629cbec5ee6113e12a42.tar.gz",
    .hash = "N-V-__8AAK7XUQNKNRnv1J6i189jtURJKjp3HTftoyD4Y4CB",
    .lazy = true,
},

In my build.zig file I have these lines:

@import("zgpu").addLibraryPathsTo(exe);
const zgpu = b.dependency("zgpu", .{});
exe.root_module.addImport("zgpu", zgpu.module("root"));
exe.linkLibrary(zgpu.artifact("zdawn"));
const zgui = b.dependency("zgui", .{
    .target = target,
    .backend = .glfw_wgpu,
});
exe.root_module.addImport("zgui", zgui.module("root"));
exe.linkLibrary(zgui.artifact("imgui"));
const zglfw = b.dependency("zglfw", .{
    .target = target,
});
exe.root_module.addImport("zglfw", zglfw.module("root"));
exe.linkLibrary(zglfw.artifact("glfw"));

If I add a "-IMGUI_IMPL_WEBGPU_BACKEND_DAWN" to the cflags in the build.zig file, the error disappears but it complains about not finding some structs like unknown type name 'WGPUComputeState'. I think there is either some file not included or there is a version mismatch for the dawn version built by zgpu.

[Logickin-Lambda]

I am working on a toy project with these libraries and I also faced the error, currently investigating the issue.

What zig version you have used and did you use the zgpu from my fork or from the official branch? I wanna know if this issues is caused from my ends.

Updated: I remembered I have a zig project used for testing the zgpu with my branch, and now, I just re-built and run the test project, and the zgpu works fine, so this might be narrowed down to zgui alone.

[tadeohepperle]

What zig version you have used and did you use the zgpu from my fork or from the official branch? I wanna know if this issues is caused from my ends.

I have indeed forked your branch to get 0.15.1 support, see here: https://github.com/tadeohepperle/zgpu

I had to add some code in the build.zig file to let the dawn library link against X11 on Linux correctly. Now zgpu works for me eith that fix, but the dear Imgui wrapper zgui does not. I think these are two separate issues, I am just gonna use zgpu without zgui for now, making my own UI anyway.

[Logickin-Lambda]

Found the problem! In the commit for the imgui update (in imgui_impl_wgpu.h), there was possibly a temporary fix to this problem by adding the Macro IMGUI_IMPL_WEBGPU_BACKEND_WGPU in the imgui side of the library, but since it was accidentally removed after the updating the imgui library, thus the error.

However, I am more concerned about that there are many other code in imgui of the zgui with // FIX(zig-gamedev) got removed since the update, and there are probably issues reported recently related to this reason, but since there is a pr replacing the original imgui library with cimgui, perhaps we could only fix the problems with the immediate effect like this one just to get everyone's projects work for now.

Update: Seems the issue is known, and there are some incompatibility between the latest wgpu standard and the version of dawn we used in zgui. If that is the case, I am going to test the cimgui branch to see if that solve the problem orelse let see if there are solution based on that branch.