Multiple Viewports without crashing?

[11Spades]

As I understand it, using multiple viewports is kind-of shaky in imgui, especially in linux, but I'd really like to do it anyway. Unfortunately, it isn't very clear to me how I can actually achieve this. I've been trying to glue something together via imgui's examples, and then praying they translate well, but this causes crashes right now.

Currently, my approach is as follows:
Before the main loop, invoke:

imgui.IO.SetConfigFlags(*imgui.CurrentIO(), imgui.ConfigFlagsViewportsEnable)

Then, at the end of the main loop, do this:

imgui.UpdatePlatformWindows()
imgui.RenderPlatformWindowsDefault()

I believe that the crucial parts missing here, at least according to the GLFW-backend examples of how to do this in imgui's examples, are as such:
GLFWwindow* backup_current_context = glfwGetCurrentContext(); -- I can't seem to figure out how to do this in GIU or it's imgui component, nor its GLFW backend component.
glfwMakeContextCurrent(backup_current_context); -- I also can't find the corresponding call for this.

I'm also unsure whether the backend is platform-dependent; while I am on Linux, the tools I am building are for people who run Windows and MacOS, so perhaps I will need to call different functions depending on the platform?

Guidance would be appreciated!

[gucio321]

Generally you shouldn't need all of that as ViewportsEnable is set by default in glfw backend

[11Spades]

Ah. I feel a bit stupid :P

Thank you for the help.

Somewhat offtopic, but is there a way to ensure that any new viewports are transparent if the master window is transparent?

[gucio321]

Idk to be honest, could you show an example when where it isn't

[11Spades]

As of right now, I'm achieving transparency by doing this outside of the main loop:

	mainPane := g.NewMasterWindow("Map", 800, 600, g.MasterWindowFlagsFloating|g.MasterWindowFlagsFrameless|g.MasterWindowFlagsTransparent) // No resize is recommended, but doesn't actually seem to be necessary, nor does it solve the problem.
	mainPane.SetBgColor(color.Transparent)

and then, in the main loop, I'm doing this:

	// Set up transparency
	imgui.PushStyleVarFloat(imgui.StyleVarWindowBorderSize, 0)
	g.PushColorWindowBg(color.RGBA{0, 0, 0, 150})
	g.PushColorFrameBg(color.RGBA{0, 0, 0, 0})
...
	// This is transparent only when docked in the main viewport
	for i, windowData := range subWindows {
		window := g.Window(windowData.From + " -> " + windowData.To)
		window.Size(vX/5, vY/3)
		window.Layout(...)
	}

	// This is transparent unconditionally, because it is always in the main window
	mainWindow := g.Window("Lodestar")
	mainWindow.Flags(g.WindowFlagsNoDecoration | g.WindowFlagsNoMove | g.WindowFlagsNoBringToFrontOnFocus)
	mainWindow.Size(vX, vY)
	mainWindow.Layout(roomGraph)
...
	// Pop our styles so we don't crash
	g.PopStyleColor()
	g.PopStyleColor()
	g.PopStyle()

In this case, my suspicion is that the g.MasterWindowFlagsTransparent flag exclusively applies to the main viewport, and there doesn't seem to be a way to contact GLFW regarding child windows to set the transparent flag on them.