About: Added build/system info relating to Viewport branch.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_win32.cpp
#	imgui.h

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

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

Separator: Fixed Separator() outputting an extraneous empty line when captured into clipboard/text/file.

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)

Comments

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.

Viewport: imgui_impl_sdl2: Added support for PlatformIO Platform_SetWindowAlpha.

Examples: DX12: Fixed compilation of imgui_impl_dx12.cpp in viewport branch. Multi-viewport is still not functional.

Viewport: Comments.

Merge branch 'master' into viewport

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

Added ImGuiConfigFlags_None, ImGuiBackendFlags_None for good measure.

imgui.h: Comments

imgui.h: Moved ImGuiListClipper

mgui.h: Moved ImGuiInputTextCallbackData,, ImGuiSizeCallbackData, ImGuiPayload structures so they are not in the "Helpers" section.

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

Viewport: Comment to suggest making WindowBg opaque when viewports are enabled.

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)

Examples: SDL: changed the signature of ImGui_ImplSDL2_ProcessEvent() to use a const SDL_Event*. (#2187)

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.