Viewport: Added ConfigViewportsNoParent to parent viewport default to NULL and not main viewport. Fix eg.. popups appearing erroneously focusing parent window.

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

Viewport: Added ImGuiWindowClass / SetNextWindowClass() (concept imported from Docking ImGuiDockFamily), which currently allows to overwrite viewport flags on a per-window basis. Exposed FindViewportByID(). Win32: Support for ParentViewportId. (#1542)

Docking: Renamed SetNextWindowId() -> SetNextWindowID() for consistency. (function vs member are still horribly inconsistent atm)

Viewport: Added Platform_UpdateWindow hook for general purpose: Rework Win32 code to reflect viewport flags changes into Win32 while the window is active.

Viewport: Reorder flags. Set owned viewport common decoration flags in Begin(). Moved code in UpdateViewportsEndFrame() before we introduce family/class based overrides.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Renamed ImGuiDockFamily to ImGuiWindowClass. Renamed CompatibleWithClassZero to DockingAllowUnclassed. (#2109)

Renamed extra_flags to flags in InputXXX parameters.

Happy new year! & comments

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.h

Removed IMGUI_HAS_TABS from Docking branch, it's not defined anywhere anymore.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Viewport: Corrected/clarified comments. Moved RenderPlatformWindowsDefault() next to UpdatePlatformWindow(). Removed unnecessary flag check.

IO: Realigned all fields, very minor comments change. This is nearly a no-op if you don't ignore Spaces.

IO: Added BackendPlatformUserData, BackendRendererUserData, BackendLanguageUserData void* for storage use by back-ends. (#2004 + for cimgui)

Various user-facing comments

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp

Internals: Popup related comments. Renamed the misleading internal ClosePopup() function. Added bool* test to BeginPopupModal in demo.

Viewport, DPI: Now using DpiScale from the ImGuiPlatformMonitor array instead of calling Platform_GetWindowDpiScale() before the platform window creation. Might even tentatively see if things work out without Platform_GetWindowDpiScale. (#1676)

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui_demo.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.h

Comments, minor tweaks.

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp
#	imgui_widgets.cpp

Demo: Using Tabs in Style Editor and Simple Layout example. + Adding missing early out in About and Documents examples.

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/TODO.txt
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_draw.cpp
#	imgui_internal.h
#	imgui_widgets.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Added BETA api for Tab Bar/Tabs widgets. (#261, #351) (merged this feature from the from Docking branch so it can be used earlier as as standalone feature) ...

- Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
- Added ImGuiTabBarFlags flags for BeginTabBar().
- Added ImGuiTabItemFlags flags for BeginTabItem().
- Style: Added ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive colors.
- Demo: Added Layout->Tabs demo code.
- Demo: Added "Documents" example app showcasing possible use for tabs.