Internal: Minor tidying/reordering of sections within ImGuiContext / window DC.

Internal: Scrollbar: Further sane simplification (using InnerMainRect instead of duplicating calculations).

Internal: Scrollbar: Extracted scrollbar code for other uses (eg. table v2 scrolling without using a child window).

Separator: Revert 1.70 "Declare its thickness (1.0f) to the layout" change (c5d83d8a). It's not incorrect but it breaks existing some layout patterns. Will return back to it when we expose Separator flags.

Internal: Refactored Separator into SeparatorEx(), exposed ImGuiSeparatorFlags_SpanAllColumns in imgui_internal.h and support without. (#759) + misc comments

Columns: Fixed Separator from creating an extraneous draw command. Fixed Selectable with SpanAllColumns flag from creating an extraneous draw command. (#125)

Version 1.71 WIP + fixed minor typo

Version 1.70

Selectable: With ImGuiSelectableFlags_AllowDoubleClick doesn't return true on the mouse button releas efollowing the double-click. Only first mouse release + second mouse down (double-click) returns true. Likewise for internal ButtonBehavior() with both _PressedOnClickRelease | _PressedOnDoubleClick. (#2503)

Internals: Rename GetContentRegionMaxScreen() -> GetWorkRectMax(). At this point this is mostly useful to facilitate merge of other branches.

Tidying up BeginMenu() code + comments.

Popups: Closing a popup restores the focused/nav window in place at the time of the popup opening, instead of restoring the window that was in the window stack at the time of the OpenPopup call. (#2517) ...

Among other things, this allows opening a popup while no window are focused, and pressing Escape to clear the focus again.

Internals: Added DataTypeApplyOp, DataTypeApplyOpFromText to imgui_internal.h

Internals: Renaming. Renamed ImGuiPopupRef to ImGuiPopupData for consistency and added constructor.

Internals: Exposed ImGuiDataTypeInfo, DataTypeGetInfo(), DataTypeFormatString(). Comments.

Separator: Declare its thickness (1.0f) to the layout, making items around separator more symmetrical.

Nav: Fixed Drag/Slider functions going into text input mode when keyboard CTRL is held while pressing NavActivate.

Internals: TempInputText: Tidying up DragScalar / SliderScalar / TempInputTextScalar.

Internals: TempInputText: Rename InputScalarAsWidgetReplacement() -> TempInputTextScalar(), ScalarAsInputTextId -> TempInputTextId, small tidying up in affected functions.

Internals: Using more explicit PushOverrideID() helper + renamed equivalent internal tree helper.

MenuItem, BeginMenu: Fix undesirable tall frames in horizontal layout context, which would be visible when trying to use rounded selectable/menus. ...

PushStyleVar: Added comments in the assert message.
Minor tweaks.

Misc comments, internal renaming, added disable indentation option to Columns demo section.

Internals: ImHashStr() default parameter.

Added SetNextItemWidth() helper to avoid using PushItemWidth/PopItemWidth() for single items.

Added commentary about ContentRegion functions. Added internal GetContentRegionMaxScreen() to facilitate internal code at the moment.

Internals: Moved CalcItemSize next to CalcItemWidth, added comments to clarify their respective intent. Should have no side effect.

Combo, Slider: Improve rendering in situation when there's there's very little space available.

Internals: Columns: Tweaks, renaming. Metrics: Show rectangles for child windows. ...

Renamed SameLine() first parameter.

Metrics: Added "Show windows rectangles" tool to visualize the different rectangles.

Internals: Columns: Some renaming, extracted code into GetColumnsID().