Internals: Merged some changes to facilitate 1D->2D transition for some elements, and merging the stack layout PR (#846)

Internals: Renaming of non-user facing parts from ValueChanged to Edited terminology. (#2034, #820, #956, #1875)

Internals: Wired a ImGuiItemStatusFlags_ValueChanged into ItemStatusFlags, for an hypothetical IsItemValueChanged() function. (#2034)

Rearrange header comments to find enums easily + fixed inconsistent sorting.

Internals: InputText: Renaming. Comments.

InputText: Renamed ImGuiTextEditCallback to ImGuiInputTextCallback, ImGuiTextEditCallbackData to ImGuiInputTextCallbackData for consistency. Kept redirection types (will obsolete).

InputText: Added support for buffer size/capacity changes via the ImGuiInputTextFlags_CallbackResize flag. (#2006, #1443, #1008).

InputText: Internal renaming of some fields + final copy uses edit_state.CurLenA+1 instead of buf_size.

Internals: Moved code out of SliderBehaviorT to reduce code bloat and also because caller may have use for the grab_bb for styling purposes.

Internals: Added ImTextCountUtf8BytesFromChar() helper.

Fixed assertion when transitioning from an active ID to another within a group, affecting ColorPicker (broken in 1.62). Made ActiveIdIsAlive track the actual ID to avoid incorrect polling in BeginGroup/EndGroup when the ID changes within the group. (#2023, #820, #956, #1875).

Selectable: Added ImGuiSelectableFlags_Disabled flag in the public API. (#211)

TODO + added missing _None enum for some internals flags.

Internals: Extracted RenderMouseCursor() out of EndFrame(). Moved to imgui_draw.cpp along with RenderArrowPointingAt(). Comments. (#2013)

Internals: Minor renaming for consistency.

Fixed PushID() from keeping alive the new ID Stack top value (if a previously active widget shared the ID it would be erroneously kept alive) (drag and drop demo could soft-lock the UI until pressing Escape!)

Drag and Drop: Payload stays available and under the mouse if the source stops being submitted, however the tooltip is replaced by "..." + moved FrameScopeActive = false at the bottom of EndFrame() for safety. (#1725)

Made assertion more clear when trying to call Begin() outside of the NewFrame()..EndFrame() scope. (#1987)

Internals: Changed signature of ShadeVerts functions to remove pointers. (#1286, #1700, #1986)

Internals: Changed SplitterBehavior() signature to be consistent with other similar signatures. (#319).

Internals: Extracted part of Begin into UpdateWindowParentAndRootLinks(). Useful to call to keep state updated immediately (namely useful for docking) + small tidying up of imgui_internal.h

Internals: Child windows that are clipped or part of a collapsed parent are not marked as collapsed anymore, but just a separate hidden marker set. We distinguish hiding for size measurement vs hiding for other reasons. Cleaned a little the end of Begin.

Nav: Tweaked CTRL+TAB to hide visual noise on fast switch + fading out screen dimming and highlight to make the experience less harsh

Internals: SplitterBehavior() added hover_visibility_delay parameter which is helpful to reduce visual noise. (#319)

Made it possible to move a window by dragging from the Collapse button (past the drag threshold). Extracted some code out to a CollapseButton() function.

Internals: Renamed one of the arrow functions so their name don't collide.

Changed ImGui::GetTime() return value from float to double to avoid accumulating floating point imprecisions over time.

Comments, exposed a few things in imgui_internal.h for consistency, added ImQsort wrapper.

IsItemHovered(): Added ImGuiHoveredFlags_AllowWhenDisabled flag to query hovered status on disabled items. (#1940, #211) ...

+ shallow changelog tweaks

Internals: Extracted StartMouseMovingWindow so we can add code to turn an arbitrary widget into a window mover (will be useful to make the Collapse button a window mover past a mouse drag threshold) + added a couple of _None flags.