Combos: Changed the combo popup to use a different id to also using a context menu with the default item id. (#4167)

Docs: Improvements to description of using colored glyphes/emojis. (#4169, #3369) + Add Fonts to Metrics. Removed IMGUI_HAS_TABLE markers.

Nav: Fixed single frame CTRL+Tab from properly enabling the  menu layer of target window if it doesn't have other active layers.

Backends: GLFW: Adding bound check in KeyCallback because GLFW appears to send -1 on some setups. [#4124]

InputText: Fixed CTRL+Arrow or OSX double-click leaking the presence of spaces when ImGuiInputTextFlags_Password is used. (#4155, #4156) [@michael-swan]

Tweak computation of io.Framerate so it is less biased toward high-values in the first 120 frames. (#4138)

Merged 13 commits.

+ GC pass on that data.

Squashed 3 commits.

(e.g. ImVec2, ImVector) leading to a 10-20% increase of performances with MSVC "default" Debug settings.

Refactor focusable/tabbalbe item registration toward allowing to handle it prior to clipping (not yet the case) (#343, #4079)

Now performed in ItemAdd(). It can't be trivially moved above clipping effectively because it would require us to scroll to be useful, meaning we'd be better off locking the bounding box a frame earlier. Still wip.
As-is this commit has no value for end-user, but it's a reengineering that moves us closer to the solution. + Internals: moved internal flags.

Nav: Fixed Tabbing initial activation from skipping the first item if it is tabbable through. (#787)

Internals: ItemFlags is a shared resource as advertised. Fix Begin/PushItemFlags/End sequence (mostly for consistency)

TestEngine: fixed wrong flags passed to ItemInfo queries. Was luckily/misleadingly not causing issues as the test-engine flags we tested were upper bits not colliding with the other type.

Moved those flags higher as well. (unrelated to the fix itself)

Fixes for MSVC static analyzers (wider range of versions). (#3938, #4073) + warning fix (#4089) + comments.

Fixes for PVS Studio and MSVC static analyzers. Using a macro to suppress single-use MSVC false positives. (#3938, #4073)

Fixes for Visual Studio 2019 static analyzers. (#3938, #4073) + two minor edge case were invalid scalar input (e.g. a sign only) would return buffer as modified.

When defining ImTextureID to a type such as Texture*, the const-qualifier here stops us from using the texture ID. const Texture* is not valid to be pushed as a texture ID anymore.

Nav, InputText: Fixed accidental menu toggling while typing non-ascii characters using AltGR. (#370)

Nav: clear activeid on menu toggle (so pressing Alt leaving an InputText will steal ActiveID. Previously wouldn't not, but ButtonBehavior() hover logic would not show Menu layer item as hovered when ActiveId != 0). (#787)

(Adjacent to #370)

(no expected side-effects, maybe consistency, but those NavLastIds[] values would likely have been 0 already)

Backends: DirectX9: explicitely setting up more graphics states to increase compatibility with unusual non-default states. (#4063)

Added D3DRS_FILLMODE, D3DRS_ZWRITEENABLE, D3DRS_RANGEFOGENABLE, D3DRS_SPECULARENABLE, D3DRS_STENCILENABLE, D3DRS_CLIPPING. Reordered some to match order in DX9 headers.