Docking: Fix generalizing the transition from loose windows to dock node so we can switch to single window dock node while transferring viewports (vs creating two viewports and dropping one). + Extracted DockContextGenNodeID out of DockContextAddNode().

Comments, tweak

Viewport: Minor tweaks, better struct layout.

Viewport: Fixed a viewport bug which led some popups to merge in underlying host viewport when they should be z-over their parent viewport.

Version 1.67 WIP (again, this time IMGUI_VERSION_NUM has leeway for another hot-fix).

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt

Merge branch 'master' into viewport ...

# Conflicts:
#	docs/CHANGELOG.txt
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_vulkan.cpp
#	examples/imgui_impl_win32.cpp
#	imgui.h
#	imgui_demo.cpp

Version 1.66b (will revisit how to change IMGUI_VERSION_NUM across versions, this commit reduces the numerical IMGUI_VERSION_NUM compared to the commit on Nov 22).

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

Added ShowAboutWindow(), About Window now showing various config/build information.

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_win32.cpp
#	imgui.h

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

Added ShowAboutWindow(), About Window now showing various config/build information.

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Merge misc/shallow changes from Docking branch to minimize drift: moved some blocks, added comments.

Viewport: Fixed a bug where tooltips on their first frame didn't find a monitor leading to the "recovery" code to revert it to the main viewport for a frame. (#1542)

When the focused window become inactive don't restore focus to a window with the ImGuiWindowFlags_NoInputs flag. (#2213)

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui_internal.h

Viewport: Avoid calling platform functions when window is not created (apart from Platform_GetWindowDpiScale, documented as such). Main viewport situation is still ambiguous. (#1542)

Viewport: Misc renaming.

Docking: Added io.ConfigDockingTransparentPayload option (to use with ImGuiConfigFlags_ViewportsNoMerge)

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Merge branch 'master' into viewport

Viewport: Better support for toggling ImGuiConfigFlags_ViewportsEnable. (#2196)

Added ImGuiConfigFlags_None, ImGuiBackendFlags_None for good measure.

Docking: Fixed debug Rebuild operation.

Docking: Maintain CentralNode. When SetNextWindowDockID() on a now split node id, we dig to find the central node or the last focused node. (#2109)

Docking: Comments + maiintain LastFrameFocused per node + using bitfiield for docking bools.

Docking: Added internal DockBuilderGetCentralNode(). Fixed being unable to undock whole node from dock button in DockSpace with a central node. (#2109)