Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui_demo.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.h

Comments, minor tweaks.

Metrics: Fixed crash when viewports are disabled (g.MouseLastHoveredViewport is never set).

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp
#	imgui_widgets.cpp

Tabs: Fixed support for drag and drop ImGuiButtonFlags_PressedOnDragDropHold. (#261) incorrectly missing from the merge from Docking branch.

Internals: Windows hidden with HiddenFramesRegular (but NOT HiddenFramesForResize) preserve their SizeContents, so restoring a auto-resize window after it's been hidden by tabs won't reset its size for a frame. Arguable. Let's see how it goes. (Followup to b48e295)

Contents size is preserved while a window collapsed. Fix auto-resizing window losing their size for one frame when uncollapsed.

Demo: Using Tabs in Style Editor and Simple Layout example. + Adding missing early out in About and Documents examples.

BeginTabBar: Fix to push the expected ID into the ID stack (instead of a hash's hash). (#261)

Demo: Fix collateral damage of 54a60aa

Demo: Fix collateral damage of 54a60aa

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/TODO.txt
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_draw.cpp
#	imgui_internal.h
#	imgui_widgets.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

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.

Added ImGuiWindowFlags_UnsavedDocument window flag to append '*' to title without altering the ID, as a convenience to avoid using the ### operator. (merged from Docking branch)

Using named flags instead of 0 + shallow formatting tweaks from other branches.

Docking: Fix io.ConfigWindowsMoveFromTitleBarOnly for docking branch.

Merge branch 'viewport' into docking + moved io.ConfigFlags ImGuiConfigFlags_DockingNoSplit to io.ConfigDockingNoSplit ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp

Added io.ConfigWindowsMoveFromTitleBarOnly option. Still is ignored by window with no title bars (often popups). This affects clamping window within the visible area: with this option enabled title bars need to be visible. (#899) ...

Tweaked default value of style.DisplayWindowPadding from (20,20) to (19,19) so the default style as a value which is the same as the title bar height.

Renamed io.ConfigResizeWindowsFromEdges to io.ConfigWindowsResizeFromEdges and removed its [Beta] mark. Resizing windows from edge is now enabled by default (io.ConfigWindowsResizeFromEdges=true). Note that it only works _if_ the back-end sets ImGuiBackendFlags_HasMouseCursors, which the standard back-end do.

Tests: Adding imgui-test engine hooks (experimental) to provide missing widget state to the testing system.

Tabs: Fixed crash when using TabItem in a regular (non-docking) tab bar. (#2231)

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Viewport: Win32, GLFW, SDL: Clarified back-ends by using global mouse position direction. GLFW: disabled io.MouseHoveredViewport setting under Mac/Linux. (#1542, #2117) + various comments.

Viewport: Fix handling of PlatformRequestResize/PlatformRequestPos. when OS decoration are enabled via ImGuiConfigFlags_ViewportsDecoration .

Viewport: Fix handling of PlatformRequestResize/PlatformRequestPos. when OS decoration are enabled via ImGuiConfigFlags_ViewportsDecoration .

Docking: Adjusting the docking popup menu position so it tends to stay within the same viewport.