Viewport: Added ImGuiConfigFlags_ViewportsDecoration to re-enable platform decoration (#1542)

Docking: Kept ImGuiDockNodeFlags_PassthruDockspace and removed ImGuiDockNodeFlags_PassthruInEmptyNodes, ImGuiDockNodeFlags_RenderWindowBg. Doesn't include ImGuiDockNodeFlags_NoDockingInCentralNode. (#2109)

BeginTabItem: Fixed missing parameter name in .h file messing up with cimgui generator. (#2115)

Docking: Added ImGuiDockNodeFlags_PassthruDockspace mode (subdivided in three flags: ImGuiDockNodeFlags_NoDockingInCentralNode, ImGuiDockNodeFlags_PassthruInEmptyNodes, ImGuiDockNodeFlags_RenderWindowBg). Added internal facility for register a rectangular hit-test hole in window. Updated DockSpace demo accordingly. (#2109)

Docking: Added ImGuiDockNodeFlags_NoOuterBorder, tweaked DockSpace demo to remove window border. Made docking splitter use the same standard setting as resizing from edges. (#2109)

Docking: Renamed "DocRoot/DocumentRoot" to "CentralNode", more self explanatory. Moved Splitter update higher up in DockNodeUpdate() + minor misc tweak. (#2109)

Docking: Added ImGuiDockNodeFlags_NoDockingInsideDocRootNode flag. Honoring ImGuiDockNodeFlags_NoSplit in child node is already split (so we can use DockBuilder and then lock the layout). Added those options to the demo. (#2109)

Docking: Fixed DockSpace() child window displaying a scrollbar behind the node backgrounds. Rename ImGuiCol_DockingBg to ImGuiCol_DockingEmptyBg. Added ImGuiDockNode::IsLeaftNode(). (#2109)

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Docking: Renamed io.ConfigDockingWithKeyMode to io.ConfigDockingWithShift.

Drag and Drop: Added GetDragDropPayload() to peek directly into the payload (if any) from anywhere. (#143)

Docking: Fixes for C++03 compilers.

Docking: Demo: Displaying a message if master docking flag is disabled. + DockSpace() early out + comments.

Style: Added style.TabRounding setting.

Fix missing IMGUI_API and mismatching namespace internal's CreateNewWindowSettings (#2105)

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h
#	imgui.cpp

Renamed SetScrollHere() to SetScrollHereY(). Kept redirection function (will obsolete).

BeginChild(): Fixed BeginChild(const char*, ...) variation erroneously not applying the ID stack to the provided string to uniquely identify the child window. This was undoing an intentional change introduced in 1.50 and broken in 1.60. (#1698, #894, #713) + reworked the Begin/BeginChild comments in imgui.h.

Docking: Added DockBuilderForkNode() primitive for usage for user code to fork/copy entire layouts. This will probably need to be added to as I find ways to migrate patterns from user code to the library. Added IMGUI_DEBUG_DOCKING_INI helper to facilitate debugging. (+1 squashed commits)

Docking: Minor renaming. DockContextAddNode() uses 0 as marker for automatic ID selection + TODO update and moved docking entries to docs/TODO.txt

Docking: Renamed SetNextWindowDock() to SetNextWindowDockId(). Added GetWindowDockId().

Docking: Reworked SetNextWindowUserType() as SetNextWindowDockFamily(), allowing multiple scene to be tagged with their scene id and not receive tabs from other scene + persistent storage for family id to allow for docking tree fork/remap.

ImVector: Fixed a oddly unqualified return type in the assignment operator (I assume C++ handles it nicely as this never warned anywhere, but it is completely unintentional).

Docking: Renamed ImGuiDockSpaceFlags to ImGuiDockNodeFlags. Clarified in comments/demos that DockSpace creates a Node. Renamed IsExplicitRoot to IsDockSpace. Assert against explicitly calling DockSpace twice in a frame.

Fixed bad merge (a82be53) where we lost the version number in Docking branch + moved Docking related API together for now.

Docking: Changed DockSpace() signature to take an ID, as ID will frequently be used by other API it makes more sense to let the user compute it.

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui_demo.cpp
#	imgui_internal.h

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_vulkan.cpp