InputText: Moving some code in anticipation of supporting hint display with password. This commit is aimed at having no visible side effect. (#2400)

Fixed IsItemDeactivated()/IsItemDeactivatedAfterEdit() from not correctly returning true when tabbing out of a focusable widget (Input/Slider/Drag) in most situations. (#2215, #1875) ...

+ Minor renaming of a local variable in widget code.

Internal: Tabbing/Focus: Tidying up old code, moved some state to context instead of window. Storing new data will allow us to fix the bug mentioned in #2215 (probably in next commit).

MenuItem, Selectable: Fixed disabled widget interfering with navigation (fix c2db7f63 in 1.67).

Internal: Tabbing: Tweaks to FocusableItemRegister and using the standard mechanism to allow/block Tab being interpreting by tabbing instead of InputText() widget.

Internal: Text: Extracted TextUnformatted into TextEx over which we can freely atter the signature. Clarified current large text behavior of TextUnformatted with explicit ImGuiTextFlags_NoWidthForLargeClippedText flag (always set).

Text: Fixed large Text/TextUnformatted call not declaring its size when starting below the lower point of the current clipping rectangle. Somehow this bug has been there since v1.0! It was hardly noticeable but would affect the scrolling range, which in turn would affect some scrolling request functions when called during the opening frame of a window.

Renamed GetOverlayDrawList() to GetForegroundDrawList() for consistency. Kept redirection function (will obsolete). (#2391) ...

Demo: Using GetBackgroundDrawList() and GetForegroundDrawList() in "Custom Rendering" demo.

ColorPicker: Fix assertion when running in a collapsed window and dragging its title bar (#2389)

InputInt, InputScalar: +/- buttons now respects the natural type limits instead of overflowing or underflowing the value.

DragScalar, InputScalar, SliderScalar: Added support for u8/s8/u16/s16 data types. We are reusing function instances for larger types to reduce code size. (#643, #320, #708, #1011)

Internal: InputText: Tweaks to make PVS static analyzer relax a little with its false positive.

Renamed ColorEdit/ColorPicker's ImGuiColorEditFlags_RGB/_HSV/_HEX flags to respectively ImGuiColorEditFlags_DisplayRGB/_DisplayHSV/_DisplayHex. This is anticipation of adding new flags to ColorEdit/ColorPicker functions which would make those ambiguous. (#2384) [@haldean]

add _Show prefix to color flags that control inputs, rename __InputsMask to __ShowMask ...

This is anticipation of changing __InputsMask to control the format of
input colors, and adding _InputRGB and _InputHSV to change how input
colors are interpreted.

Plot: Fixed error in 5e3a1de (#2387)

Plot: Fixed divide-by-zero in PlotLines() when passing a count of 1. (#2387) [@Lectem]

InputText: Fixed various display corruption related to swapping the underlying buffer while a input widget is active (both for writable and read-only paths). Often they would manifest when manipulating the scrollbar of a multi-line input text.

Internal: InputText: Minor changes (intended to have side-effect but clarify next commit, however there is rarely such a thing as zero side effect in InputText land!)

InputText; Disabled rendering selection when inactive (it kinda work but I'm not sure this is desirable especially for single-line input, was not intended to be active).

InputText: Fixed deactivated but-last-active InputText instance holding on displaying the last active version of the text and not reflecting change in the source. Fix/amend 2e9a175. [+test]

Log/Capture: Fixed LogXXX functions 'auto_open_depth' parameter being treated as an absolute tree depth instead of a relative one. Fixed CollapsingHeader trailing ascii representation being "#" instead of "##". Minor tidying up the of code.

TabBar: Added extra mis-usage error recovery. Past the assert, common mis-usage don't lead to hard crashes any more, facilitating integration with scripting languages. (#1651)

TabBar: Fixed a crash when using BeginTabBar() recursively (didn't affect docking). (#2371) ...

Added ImPool::Contains() helper.

Internal: InputText: Tweaks (including a large indentation change, compare ignoring space) to make next commit more digestible.

Internal: InputText: refactor the flow to easily decorrelate rendering of selection vs cursor, which would allow us to render selection on inactive items, and generally makes the code clearer. + Some renaming.

Internal: InputText: Made clipboard copy/cut use its own temporary buffer (like paste) so we can guarantee that TempBuffer if not altered and can be preserved. Renamed TempBufferA to TextA to celebrate this.

Internal: InputText: Renamed is_editable to !is_readonly, Hopefully more explicit. Renamed internal member. Shuffled some code. Added comments, assert (_will_ trigger on !readonly > readonly edge, old bug).

InputText: Fixed an edge case crash that would happen if another widget sharing the same ID is being swapped with an InputText that has yet to be activated.

Internal: InputText: Refactor to clarify access pattern to the InputTextState (we are now accessing via a pointer which can be NULL, shortened its name while we are at it) + added an assert to track an issue that existed already before.

Internal: InputText: Comments. Renamed internal member. Renamed ImGuiStb->ImStb.