Metal backend: secondary viewports are not rendered

[dmirty-kuzmenko]

Version: 18916
Branch: docking
Backend: imgui_impl_metal.mm + (imgui_impl_sdlrenderer.cpp or imgui_impl_glfw.cpp or imgui_impl_osx.mm)
Operating System: macOS 12.5 (monterey)

My Issue/Question:

The following happens even with example code provided by this repo.
On the docking branch with metal backend "child" windows are not rendered if they are outside of the main window (or some part of them is outside, for example a popup or something). Depending on the implementation (sdl vs glfw vs osx) they either completely greyed out or not shown at all. In terminal I get [CAMetalLayer nextDrawable] returning nil because device is nil. every frame.

Replacing line id<MTLDevice> device = [bd->SharedMetalContext.depthStencilState device]; in the imgui_impl_metal.mm file with id<MTLDevice> device = bd->SharedMetalContext.device; fixes the issue (shown on the video), but I did not investigate this "fix" seriously.

Screenshots/Video

[ocornut]

Applied your fix, it makes sense to use device directly.

I consider this fixed, but but simultaneously I'm not sure I understand why this didn't happen before.?
ImGui_ImplMetal_NewFrame() does:

if (bd->SharedMetalContext.depthStencilState == nil)
    ImGui_ImplMetal_CreateDeviceObjects(bd->SharedMetalContext.device);

and

bool ImGui_ImplMetal_CreateDeviceObjects(id<MTLDevice> device)
{
    ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
    MTLDepthStencilDescriptor* depthStencilDescriptor = [[MTLDepthStencilDescriptor alloc] init];
    depthStencilDescriptor.depthWriteEnabled = NO;
    depthStencilDescriptor.depthCompareFunction = MTLCompareFunctionAlways;
    bd->SharedMetalContext.depthStencilState = [device newDepthStencilStateWithDescriptor:depthStencilDescriptor];
    ImGui_ImplMetal_CreateDeviceObjectsForPlatformWindows();
    ImGui_ImplMetal_CreateFontsTexture(device);

    return true;
}

I would assume depthStencilState.device would be set there?

Previous code added by @stuartcarnie, commit 6868d11 (#4821, #2778)