Added ShowAboutWindow(), About Window now showing various config/build information.

Merge misc/shallow changes from Docking branch to minimize drift: moved some blocks, added comments.

Viewport: Fixed a bug where tooltips on their first frame didn't find a monitor leading to the "recovery" code to revert it to the main viewport for a frame. (#1542)

When the focused window become inactive don't restore focus to a window with the ImGuiWindowFlags_NoInputs flag. (#2213)

Viewport: Avoid calling platform functions when window is not created (apart from Platform_GetWindowDpiScale, documented as such). Main viewport situation is still ambiguous. (#1542)

Viewport: Misc renaming.

Merge branch 'master' into viewport

Viewport: Better support for toggling ImGuiConfigFlags_ViewportsEnable. (#2196)

Added ImGuiConfigFlags_None, ImGuiBackendFlags_None for good measure.

Viewport: Merging fixes + relying on multiple viewport overlaps. Follow-up to previous attempts are reworking the split/merge mechanisms. (#1542)

Viewport: Fixes moving child menu viewport (fix 379733a).

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Viewport: Fix viewport regression with protruding child window creating their own viewport. (fixes cae4d02, 760c1d95) (#1542)

Viewport: Added support for minimized window which caused problem when ImGuiBackendFlags_HasMouseHoveredViewport was not supported. (#1542) + todo

Viewport: Avoid unnecessary reapplying platform pos/size every frame. (#2205) + Fix GLFW ImGui_ImplGlfw_CreateWindow() from not applying position immediately. Clear LastNameHash properly (bug already fixed in Docking branch)

Viewport: Merging/Extracting to/from main host viewport is now performed based on current state rather than triggers. Windows which don't fit in host window are now consistently in their own viewport. Toward simplifying the UpdateSelectWindowViewport() function. Probably broke something.. (#1542)

Viewport: UpdateTryMergeWindowIntoHostViewport() calls BringWindowToDisplayFront() - possible now that BringWindowToFocusFront() is a different function.

Version 1.67 WIP

Viewport: Stop relying on viewport->CreatedPlatformWindow to create Platform_DestroyWindow and Renderer_DestroyWindow. Explicitly require Platform_GetWindowFocus() to require supporting empty data.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Version 1.66

Nav: Fixed explicit directional input not re-highlighting current nav item if there is a single item in the window and highlight has been previously disabled by the mouse. (#787)

Internals: Using GetOverlayDrawList(ImGuiWindow*) to match syntax of viewport/master branches. Fixed compiling with IMGUI_DEBUG_NAV_RECTS

Removed unnecessary ImGui:: prefixes.

Internals: Added FindWindowByID() helper. (#2190)

Merge branch 'master' into viewport + comments ...

# Conflicts:
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp

Nav: Fixed an assert in certain circumstance (mostly when using popups) when mouse positions stop being valid. (#2168) + adding a else block to make NavCalcPreferredRefPos() more explicit.

Viewport: BeginMainMenuBar(): explicitly set viewport to avoid creating new one when ImGuiConfigFlags_ViewportsNoMerge is set + misc shallow changes.

Made IsWindowFocused() work outside of NewFrame()-EndFrame() and added comments about how ImGuiFocusedFlags_AnyWindow should NOT be used in place of io.WantCaptureMouse. (#2185)

Viewport: Fixed SDL+OpenGL2 example to work with multi-viewports. (#2175)