Version 1.69, comments, typos

Fix typos. (#2413)

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.

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.

InputText: Renamed some local variables to clarify code. Should be a no-op functionality wise. TODO items.

Menus: Tweaked horizontal overlap between parent and child menu (to help convey relative depth) from using style.ItemSpacing.x to style.ItemInnerSpacing.x, the later being expected to be smaller. (#1086)

Removed trailing spaces from text files. (#2038, #2299)

ImDrawList: Fixed AddCircle(), AddCircleFilled() angle step being off, which was visible when drawing a "circle" with a small number of segments (e.g. an hexagon). (#2287) [@baktery] ...

+ Demo tweaks

TODO update + internals: changed order or ImGuiLayoutType enums to allow using them for indexing.

Merge branch 'atlas_fixes'

FAQ entry, moved ImTextureId, Gallery links.

ImFontAtlas: Rewrote stb_truetype based builder. ...

- Atlas width is now properly based on total surface rather than glyph count (unless overridden with TexDesiredWidth).
- Fixed atlas builder so missing glyphs won't influence the atlas texture width. (#2233)
- Fixed atlas builder so duplicate glyphs (when merging fonts) won't be included in the rasterized atlas.

ImFontGlyphRangesBuilder: Using 32-bits fields for storage instead of 8-bit ones, comments, todo.

Demo: Log: Comments. Using clipper. Not linking with rand() anymore.

Fixed using SetNextWindowPos() on a child window (which wasn't really documented) position the cursor as expected in the parent window, so there is no mismatch between the layout in parent and the position of the child window. Demo tweak and adding some child window stuff

Added BETA api for Tab Bar/Tabs widgets. (#261, #351) (merged this feature from the from Docking branch so it can be used earlier as as standalone feature) ...

- Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
- Added ImGuiTabBarFlags flags for BeginTabBar().
- Added ImGuiTabItemFlags flags for BeginTabItem().
- Style: Added ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive colors.
- Demo: Added Layout->Tabs demo code.
- Demo: Added "Documents" example app showcasing possible use for tabs.

Version 1.67 WIP + todo notes

Refactor: Moved README, ChangeLog, TODO files to docs/ folder + update Changelog. (#2036)