Nav: Minor tidying up. (#787)

Internals: ImRect: Added IsInverted() helper.

ImRect: added IsInverted() helper.

Nav: TreeNode: Added ImGuiTreeNodeFlags_NavCloseFromChild flag, allow closing a TreeNode() from any of child. The explicit flag is not great, perhaps allowing some form of inheritance would help. (#787, #1079)

Nav: When focusing a parent window while closing a popup, hide its highlight for one frame to avoid potential double highlight and flicker with the common pattern of menu items leading to the opening other windows. (#787)

Nav: Fixed Selectable/MenuItem Nav Highlight from using rounding when outer highlight stays square. (#787)

Merge branch 'master' into navigation

Internals: Renamed CloseInactivePopups() to a better ClosePopupsOverWindow(). Exposed in imgui_internal.h

Nav: SetFocusID() clears NavInitRequest for consistency (repro would a same frame interaction / race condition). (#787)

Internals: Nav: Extracted code into IsWindowNavFocusable(). (#787)

Nav: Child window is restored on focus when returning to layer 0 or refocusing. This is a little experimental and potentially error-prone right now. (#787, vaguely relate to ~#727) Ideally we should maintain a non-sorted last-focused list that include childs windows.

Merge branch 'master' into context

Nav: Added proper version of ImGuiWindowFlags_NavFlattened that handles scrolling nicely. Marked as private as I'm not happy with the name. (#787)

Nav: Internals: Renamed RootNavWindow to NavRootWindow (#787)

Nav: Refactor NavMoveResult** flags into ImGuiNavMoveResult structure as we are going to want two instances of it. (#787) (+1 squashed commits) ...

+ store window inside result.

Internals: Nav: Renamed ImGuiNavForward enum (#787)

Nav: Comments, added enum to clarify NavForward code. (#787)

Merge branch 'master' into navigation

Nav: Cleaning up + using ImGuiInputSource source enum instead of a silly bool. (#787)

Nav: Keyboard: Added CTRL+TAB (and CTRL+Shift+TAB) style window selection. (#787)

Internals: ImRect::Contains(ImRect&) include boundaries (whereas Contains(ImVec2) should not).

Nav: Mouse clicking on a window (to select/move) disables hides nav highlight. (#787) + comments

Merge branch 'master' into context

Nav: Internals: Moved some enums and functions to internals, renamed ImGuiNavReadMode to ImGuiInputReadMode as well. (#787)

Merge branch 'master' into navigation ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp

Added SetNextWindowBgAlpha() helper. (#1567) particularly helpul with the marking of the old 5-parameters version of Begin() as obsolete.

Internals: Exposed SetCurrentFont() in imgui_internal.h

Internals: Moved unnecessary MovingWindowMoveId field.

Merge branch 'master' into navigation

Reorganized context handling to be more explicit, ...

- YOU NOW NEED TO CALL ImGui::CreateContext() AT THE BEGINNING OF YOUR APP, AND CALL ImGui::DestroyContext() AT THE END.
- removed Shutdown() function, as DestroyContext() serve this purpose.
- you may pass a ImFontAtlas* pointer to CreateContext() to share a font atlas between contexts. Otherwhise CreateContext() will create its own font atlas instance.
- removed allocator parameters from CreateContext(), they are now setup with SetAllocatorFunctions(), and shared by all contexts.
- removed the default global context and font atlas instance, which were confusing for users of DLL reloading and users of multiple contexts
(#1565, #586, #992, #1007, #1558)