Columns: Improved honoring alignment with various values of ItemSpacing.x and WindowPadding.x. (#125, #2666)

Columns: Made the right-most edge reaches up to the clipping rectangle (removing WindowPadding.x*0.5 worth of asymmetrical/extraneous padding). (#125, #2666) ...

+ Moved a few things in BeginColumns().

Columns: Fix support for BeginColumns() with a count of 1 (not that this isn't available via the old Columns() api). Tweaked Demo to facilitate testing for it.

Debug Tools: Added DebugStartItemPicker() in imgui_internal.h to facilitate binding this anywhere in user's tool. Adedd highlight. Added IMGUI_DEBUG_TOOL_ITEM_PICKER_EX to break in ItemAdd().

Revert "Columns: Improved honoring left-most and right-most alignment with various values of ItemSpacing.x and WindowPadding.x. In particular, the right-most edge now reaches up to the clipping rectangle while ensuring that the right-most column clipping width matches others. (#125, #2666)" ...

This reverts commit 6c16ba6.

Columns: Improved honoring left-most and right-most alignment with various values of ItemSpacing.x and WindowPadding.x. In particular, the right-most edge now reaches up to the clipping rectangle while ensuring that the right-most column clipping width matches others. (#125, #2666)

Columns: Fixed a regression from 1.71 where the right-side of the contents rectangle within each column would wrongly use a WindowPadding.x instead of ItemSpacing.x like it always did. (#125, #2666)

Misc: Made Button(), ColorButton() not trigger an "edited" event leading to IsItemDeactivatedAfterEdit() returning true. This also effectively make ColorEdit4() not incorrect trigger IsItemDeactivatedAfterEdit() when clicking the color button to open the picker popup. (#1875) ...

Demo: Added Button with repeater and InputFloat with +/- button to the status query test demo.

Internals: Refactor: Moved all Columns code from imgui.cpp to imgui_widgets.cpp (#125) ...

Also moved NextColumn between BeginColumn and NextColumn which makes it easier to work on that code.

Fixed old SetWindowFontScale() api value from not being inherited by child window. Added comments about the right way to scale your UI (load a font at the right side, rebuild atlas, scale style). ...

+ Added missing IMGUI_API marker to the EmptyString storage used by ImGuiTextBuffer. (#2672)

Debug, Metrics: Added "Tools->Item Picker" tool which allow clicking on a widget to break in the debugger within the item code. The tool calls IM_DEBUG_BREAK() which can be redefined in imconfig.h if needed.

Style: Added style.ColorButtonButton (left/right, defaults to ImGuiDir_Right) to move the color button of ColorEdit3/ColorEdit4 functions to either side of the inputs.

Removed TreeAdvanceToLabelPos() which is rarely used and only does SetCursorPosX(GetCursorPosX() + GetTreeNodeToLabelSpacing()). Kept redirection function (will obsolete). (#581, #324)

TabBar: Fixed unfocused tab bar separator color (was using ImGuiCol_Tab, should use ImGuiCol_TabUnfocusedActive).

Fixed unnecessary test in UpdateMouseWheel() (thanks PVS). ...

TreeNodeBehavior: avoid computing bg_col for non-framed non-active tree nodes.
Comments, binaries update, minor typos.

Moved ImGuiColumnsFlags erroneously forward declared in imgui.h + demo bit.

Settings: Minor optimization to reduce calls in SettingsHandlerWindow_WriteAll.

Renamed ImFontAtlas::CustomRect to ImFontAtlasCustomRect. Keep redirection typedef (will obsolete).

Prefixed internal structs exposed in imgui.h with a fully qualified name to facilitate auto-generation with cimgui.

Combo: Hide arrow when there's not enough space even for the square button. ...

+ Various todo items.

fonts/binary_to_compress: display error message when failing to open file + misc comments.

Window: Mouse wheel scrolling while hovering a child window is automatically forwarded to parent window if ScrollMax is zero on the scrolling axis. Also still case if ImGuiWindowFlags_NoScrollWithMouse is set (not new), but previously the forwarding ...

would be disabled if ImGuiWindowFlags_NoScrollbar was set on the child window, which is not the case any more (amend #1502, #1380).

Scrollbar: Avoid overlapping the opposite side when window (often a child window) is forcibly too small.

Misc: Added IMGUI_DISABLE_METRICS_WINDOW imconfig.h setting to explicitly compile out ShowMetricsWindow(). + Internals: Minor renaming.

Added SetScrollXHere, SetScrollFromPosX: Changelog, demo, comments (#1580).

Added 'SetScrollHereX' and 'SetScrollFromPosX' (#1580)

Internals: Checkbox: Added undocumented mixed/indeterminate/tristate support via ImGuiItemFlags_MixedValue. (#2644)

Child windows inherit Hidden frames setting from parent more accurately, so HiddenFramesCannotSkipItems is honored by child windows.

Internals: Moved CalcListClipping close to ImGuiListClipper code (no-op)

Internals: ImGuiListClipper using absolute coordinate (instead of relative one). Minor no-op tweaks + ImDrawListSplitter assert