Display Scaling issue with glfw/wgpu

[echoptic]

Version/Branch of Dear ImGui:

Version 1.92.0 WIP, Branch: master

Back-ends:

imgui_impl_glfw.cpp + imgui_impl_wgpu.cpp

Compiler, OS:

Linux 6.14.5 (KDE/Wayland) + Clang

Full config/build information:

Dear ImGui 1.92.0 WIP (19194)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201703
define: __linux__
define: __GNUC__=4
define: __clang_version__=20.1.2 (https://github.com/ziglang/zig-bootstrap 2fd9c31b6156e8691f2ec87fc6e56fc68038252a)
--------------------------------
io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_webgpu_wgpu
io.ConfigFlags: 0x00000001
 NavEnableKeyboard
io.ConfigNavCaptureKeyboard
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x0000000E
 HasMouseCursors
 HasSetMousePos
 RendererHasVtxOffset
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,64
io.DisplaySize: 1280.00,720.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Details:

Whenever I would draw any widget and tried to draw it using ImGui_ImplWGPU_RenderDrawData i would get an error:

wgpu uncaptured error:
Validation Error

Caused by:
  In wgpuRenderPassEncoderEnd
    In a set_viewport command
      Viewport has invalid rect Rect { x: 0.0, y: 0.0, w: 1536.0, h: 864.00006 }; origin and/or size is less than or equal to 0, and/or is not contained in the render target (1280, 720, 1)

This problem only exists when Im using higher that 100% display scale. I was using 120%. I noticed that no matter what window size i set the rect would always be 20% larger and when I set the scale back to 100% everything worked perfectly.

Im not sure if this is an error on my part, the glfw + webgpu example is very outdated and i didnt try to follow it perfectly, but i didnt see any code handling display scale in the example.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

No response

[ocornut]

What's the value of io.DisplayFramebufferScale in the crashing state?
That's local WGPU or Emscripten WGPU ?

[ocornut]

The example code does this:

        // React to changes in screen size
        int width, height;
        glfwGetFramebufferSize((GLFWwindow*)window, &width, &height);
        if (width != wgpu_swap_chain_width || height != wgpu_swap_chain_height)
        {
            ImGui_ImplWGPU_InvalidateDeviceObjects();
            CreateSwapChain(width, height);
            ImGui_ImplWGPU_CreateDeviceObjects();
        }

To obtain the expected framebuffer size.
What's your value for this?

[echoptic]

DisplayFramebufferScale: { .x = 1.2, .y = 1.2 }
Its not Emscripten.
I have this in the main loop, the swapchain api was removed and merged into surface:

            var width: c_int = undefined;
            var height: c_int = undefined;
            c.glfwGetFramebufferSize(window, &width, &height);
            if (width != window_width or height != window_height) {
                c.cImGui_ImplWGPU_InvalidateDeviceObjects();
                config.width = @intCast(width);
                config.height = @intCast(height);
                c.wgpuSurfaceConfigure(surface, &config);
                _ = c.cImGui_ImplWGPU_CreateDeviceObjects();
            }

[echoptic]

Also I dont know if it matters, i have a print statement to print DisplayFramebufferScale after ImGui_Render and it prints 2 times before crashing:

DisplayFramebufferScale: cimport.struct_ImVec2_t{ .x = 1.2e0, .y = 1.2e0 }
DisplayFramebufferScale: cimport.struct_ImVec2_t{ .x = 1.2e0, .y = 1.2e0 }

thread '<unnamed>' panicked at src/lib.rs:417:5:
wgpu uncaptured error:
Validation Error

Caused by:
  In wgpuRenderPassEncoderEnd
    In a set_viewport command
      Viewport has invalid rect Rect { x: 0.0, y: 0.0, w: 1536.0, h: 864.00006 }; origin and/or size is less than or equal to 0, and/or is not contained in the render target (1536, 864, 1)


note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread '<unnamed>' panicked at library/core/src/panicking.rs:218:5:
panic in a function that cannot unwind
stack backtrace:
   0:          0x18516ca - std::backtrace_rs::backtrace::libunwind::trace::h2740d05102fd9881
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:          0x18516ca - std::backtrace_rs::backtrace::trace_unsynchronized::h93ae2edf130065c8
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:          0x18516ca - std::sys::backtrace::_print_fmt::h7660a544e6110dd9
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/sys/backtrace.rs:66:9
   3:          0x18516ca - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hfc616348d9ad0abc
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/sys/backtrace.rs:39:26
   4:          0x17ffd03 - core::fmt::rt::Argument::fmt::h3a92517f8117fcd5
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/fmt/rt.rs:177:76
   5:          0x17ffd03 - core::fmt::write::h7ca648217bc79799
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/fmt/mod.rs:1440:21
   6:          0x1844fd3 - std::io::Write::write_fmt::h7960c58bfa5ccbcb
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/io/mod.rs:1887:15
   7:          0x1851512 - std::sys::backtrace::BacktraceLock::print::h3fb349e80cbe0423
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/sys/backtrace.rs:42:9
   8:          0x1853bf0 - std::panicking::default_hook::{{closure}}::h3366e5842cba645d
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:295:22
   9:          0x18539d0 - std::panicking::default_hook::hd7573a5d4879884b
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:322:9
  10:          0x1854442 - std::panicking::rust_panic_with_hook::h66e909d048c263a9
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:828:13
  11:          0x1854196 - std::panicking::begin_panic_handler::{{closure}}::h8d9aa8be7e8634cf
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:694:13
  12:          0x1851bd9 - std::sys::backtrace::__rust_end_short_backtrace::h7d7e47ef99abf6aa
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/sys/backtrace.rs:168:18
  13:          0x1853e5d - rust_begin_unwind
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/std/src/panicking.rs:692:5
  14:          0x17fbe0d - core::panicking::panic_nounwind_fmt::runtime::h19438eeae7eaf031
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/panicking.rs:117:22
  15:          0x17fbe0d - core::panicking::panic_nounwind_fmt::h57347130f21a7343
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/intrinsics/mod.rs:3869:9
  16:          0x17fbea2 - core::panicking::panic_nounwind::h2f7749cb358aa979
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/panicking.rs:218:5
  17:          0x17fc066 - core::panicking::panic_cannot_unwind::hf517234e476fc7c7
                               at /rustc/4eb161250e340c8f48f66e2b929ef4a5bed7c181/library/core/src/panicking.rs:307:5
  18:          0x17d8042 - wgpu_native::default_uncaptured_error_handler::h7da5c1449171eff8
  19:          0x17d8411 - wgpu_native::ErrorSinkRaw::handle_error::hb8ae9c14271dc633
  20:          0x17d9db2 - wgpu_native::handle_error::h26da8dc4d06d00ce
  21:          0x17eee85 - wgpuRenderPassEncoderEnd
  22:          0x1e8ba74 - main.main
                               at /home/echoptic/src/voxel/src/main.zig:354:35
  23:          0x1e8c41d - start.callMain
                               at /home/echoptic/zig/0.15.0-dev.471+369177f0b/files/lib/std/start.zig:671:37
  24:          0x1e8c41d - start.callMainWithArgs
                               at /home/echoptic/zig/0.15.0-dev.471+369177f0b/files/lib/std/start.zig:631:20
  25:          0x1e8c41d - start.main
                               at /home/echoptic/zig/0.15.0-dev.471+369177f0b/files/lib/std/start.zig:646:28
  26:     0x7fef649cabfc - __libc_start_call_main
                               at ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
  27:     0x7fef649cacb5 - __libc_start_main_impl
                               at ./csu/../csu/libc-start.c:360:3
  28:          0x131e751 - _start
                               at /builddir/glibc-2.41/csu/../sysdeps/x86_64/start.S:115
thread caused non-unwinding panic. aborting.

[ocornut]

can you print for each frame:

• the value returned by glfwGetFramebufferSize()
• the value of io.DisplaySize
• the value of io.DisplayFramebufferScale

[echoptic]

width: 1536, height: 864
DisplaySize: cimport.struct_ImVec2_t{ .x = -1e0, .y = -1e0 }
DisplayFramebufferScale: cimport.struct_ImVec2_t{ .x = 1e0, .y = 1e0 }
width: 1536, height: 864
DisplaySize: cimport.struct_ImVec2_t{ .x = 1.28e3, .y = 7.2e2 }
DisplayFramebufferScale: cimport.struct_ImVec2_t{ .x = 1.2e0, .y = 1.2e0 }

thread '<unnamed>' panicked at src/lib.rs:417:5:
wgpu uncaptured error:
Validation Error

Caused by:
  In wgpuRenderPassEncoderEnd
    In a set_viewport command
      Viewport has invalid rect Rect { x: 0.0, y: 0.0, w: 1536.0, h: 864.00006 }; origin and/or size is less than or equal to 0, and/or is not contained in the render target (1536, 864, 1)