Viewport, Platform: Fixed IME positioning for multi-viewport. Moved API from ImGuiIO to ImGuiPlatformIO. Because it is extremely unlikely to people redefined this API manually the moving-forward-breakage is ok. (#1542) ...

SDL2 ime support under Win32 never worked properly because of SDL interferences.

Viewport: Clamp windows within monitors + fallback rescue window when it is out of sight (e.g. removed monitor, changed resolution) + Win32: declare primary monitor at the beginning of the list. (#1542)

Viewports: Todos, Tooltips/menus not automatically forced into their own viewport when the NoMerge flag is set (however the multiplication of viewports makes them more likely to protude and create their own). Win32: try to make primary monitor the first tin the list. (#1542)

Viewport: Added ImGuiConfigFlags_ViewportsNoMerge flag (to enforce a platform window for all floating windows) + minor tidying up and addition of non-functional wip code.

Viewport: Fixed initial popup positioning not using the monitor area properly. (#1542)

Viewport, Platform: Added work area in ImGuiPlatformMonitor. Renamed fields. (#1542)

Viewport: Switched to using unified platform-absolute mouse coordinates, which simplify lots of problems and simplify/reduce tricky conversions, makes ImVec2 less ambiguous. Fixed various viewport/windowing/popups/synchronization bugs. Settings on host-viewport are stored as relative (made settings decently compatible between viewport enable/disabled settings). Merged ImGuiViewport::Pos and ::PlatformPos. Tweaked thumbnails. Better, smaller code. (#1542)

Viewport: WIP for Tooltips, Popups, Menus to create their own viewport. Resizing a window allows it to leave the main viewport. (#1542)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp
#	imgui.cpp
#	imgui_internal.h

Fixed DisplaySafeAreaPadding not affecting popups/tooltips/menus at it should have (partly broken in 2e5577f).

BeginMainMenuBar: Followup to 1e41bad9. Removed public window flag. DisplaySafeAreaPadding defaults to (3,3) instead of (4.4). Comments, tab to spaces, Changelog. (#1439)

Added DisplaySafeAreaPadding to MainMenuBar height and fixed starting x position. Fixes main menu bar problems with TVs. (#1439)

Fixed default proportional item width lagging by one frame on resize + miscellaneous minor tweaks.

Viewport: Fixed manual mouse resize to handle mouse viewport change, which will allow resizing a window while it changes viewport. Releasing manual resize may merge a window. Added ConvertViewportPosToViewportPos() helper. Renamed NewFrameUpdateMovingWindowDropViewport() to UpdateTryMergeWindowIntoHostViewport() and removed the now-unnecessary half of the function. + renaming (#1542)

Viewport: Tweaked selection of g.MouseRefViewport, in particular aimed at fixing browsing child-menus while holding mouse buttons with menus in multiple viewports. (#1542)

Viewport: Comments, tweaks, renaming. Removed unnecessary stuff. Fixed zealous Clang warning. (#1542)

Viewport: Render: Fix draw list build code to allow child windows to be in a different viewports (which will happen with e.g. extruding menus). (#1542)

Viewport: Shuffled code in Begin to reset size of reappearing popups prior to selecting viewport, to avoid mistakenly using an old size. Moved code out of UpdateSelectWindowViewport() to the section of Begin where positions is being locked down, to avoid code in-between duplicating this. (#1542)

Viewport: Moved ImGuiWindowFlags_FullViewport to an internal ViewportOwned flag. Renamed AddViewport to AddUpdateViewport. (#Viewport: Shuffled code in Begin to reset size of reappearing popups prior to selecting viewport, to avoid mistakenly using an old size. Moved code out of UpdateSelectWindowViewport() to the section of Begin where positions is being locked down, to avoid code in-between duplicating this. (#1542))

Viewport: Remove old code that never worked (testing wrong flag type, always false) + shuffled a few things in Begin() to clarify dependencies. Fixed viewport change on Begin/Begin/End/End patterns. (#1542)

Fix typos KeyDown => KeysDown

Documentation bits. Misc comments.

Viewport, Platform, DPI: Back-end store per-monitor DPI information in ImGuiPlatformMonitor. (#1542, #1676)

Viewport: Fix to allow changing/animated window name to be reflected in the OS e.g. task bar, so named documents can appear properly. (#1542)

Viewport: Fixed DPI changing viewport from interfering with moving another window (disabling code) + metrics crash fix on closed viewport window + Windows 10 call to SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) for DPI, with no noticeable improvements. (#1542, #1676)

Viewport: Virtual mouse position are patched immediately when viewports are moved in the virtual space, avoiding interaction glitchs on a resizing frame. (#1542)

Viewport: Debug/metrics tweaks + renaming comments

Fix minor error in doc ...

Not a big deal.

Viewport, Platform: Added ImGuiViewportFlags_TopMost that will be used by tooltip window (without it, clicking and holding the window emitting the tooltip would move the tooltip to the back) + GLFW backend fixes for non-win32 platforms. (#1542)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h