Merge branch 'viewport' into docking

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui.cpp
#	imgui_demo.cpp

docs/CHANGELOG.txt

@@ -47,6 +47,46 @@ HOW TO UPDATE?
   - Demo: Added "DockSpace" example app showcasing use of explicit dockspace nodes.
 
 
+-----------------------------------------------------------------------
+ VIEWPORT BRANCH (In Progress)
+-----------------------------------------------------------------------
+
+Breaking Changes:
+
+- IMPORTANT: When multi-viewports are enabled (with io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable), 
+  all coordinates/positions will be in your natural OS coordinates space. It means that:
+   - Reference to hard-coded positions such as in SetNextWindowPos(ImVec2(0,0)) are _probably_ not what you want anymore. 
+     Use GetMainViewport()->Pos to offset hard-coded positions, e.g. SetNextWindowPos(GetMainViewport()->Pos).
+   - Likewise io.MousePos and GetMousePos() will use OS coordinates. 
+     If you query mouse positions to interact with non-imgui coordinates you will need to offset them.
+     e.g. subtract GetWindowViewport()->Pos.
+- IO: Moved IME support functions from io.ImeSetInputScreenPosFn, io.ImeWindowHandle to the PlatformIO api.
+- IO: Removed io.DisplayVisibleMin, io.DisplayVisibleMax settings (they were marked obsoleted, used to clip within the (0,0)..(DisplaySize) range).
+
+
+Other changes:
+(FIXME: This need a fuller explanation!)
+
+- Added ImGuiPlatformIO structure and GetPlatformIO().
+  Similarly to ImGuiIO and GetIO(), this structure is the main point of communication for back-ends supporting multi-viewports.
+- Added ImGuiPlatformMonitor to feed OS monitor information in the ImGuiPlatformIO::Monitors.
+- Added GetMainViewport().
+- Added GetWindowViewport(), SetNextWindowViewport().
+- Added GetWindowDpiScale().
+- Added GetOverlayDrawList(ImGuiViewport* viewport). 
+  The no-parameter version of GetOverlayDrawList() return the overlay for the current window's viewport.
+- Added UpdatePlatformWindows(), RenderPlatformWindows(), DestroyPlatformWindows() for usage for application core.
+- Added FindViewportByID(), FindViewportByPlatformHandle() for usage by back-ends.
+- Added ImGuiConfigFlags_ViewportsEnable configuration flag and other viewport options.
+- Added ImGuiBackendFlags_PlatformHasViewports, ImGuiBackendFlags_RendererHasViewports, ImGuiBackendFlags_HasMouseHoveredViewport backend flags.
+- Added io.MainViewport, io.Viewports, io.MouseHoveredViewport (MouseHoveredViewport is optional _even_ for multi-viewport support).
+- Added ImGuiViewport structure, ImGuiViewportFlags flags.
+- Added ImGuiWindowClass and SetNextWindowClass() for passing viewport related hints to the OS/platform back-end.
+- Examples: Renderer: OpenGL2, OpenGL3, DirectX11, DirectX12, Vulkan: Added support for multi-viewports.
+- Examples: Platforms: Win32, GLFW, SDL2: Added support for multi-viewports. 
+  Note that Linux/Mac still have inconsistent support for multi-viewports. If you want to help see https://github.com/ocornut/imgui/issues/2117.
+
+
 -----------------------------------------------------------------------
  VERSION 1.67 (In Progress)
 -----------------------------------------------------------------------
@@ -59,6 +99,7 @@ Breaking Changes:
   undesirable side-effect as the window would have ID zero. In particular it is causing problems in viewport/docking branches.
 
 Other Changes:
+
 - Added BETA api for Tab Bar/Tabs widgets: (#261, #351)
   - Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
   - Added ImGuiTabBarFlags flags for BeginTabBar().

imgui.cpp

@@ -366,15 +366,13 @@ CODE
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
  (Viewport Branch)
- - 2018/XX/XX (1.XX) - examples: the examples imgui_impl_xxx files have been split to separate platform (Win32, Glfw, SDL2, etc.) from renderer (DX11, OpenGL, Vulkan,  etc.)
-                       when adopting new bindings follow the code in examples/ to know which functions to call.
  - 2018/XX/XX (1.XX) - when multi-viewports are enabled, all positions will be in your natural OS coordinates space. It means that:
                         - reference to hard-coded positions such as in SetNextWindowPos(ImVec2(0,0)) are probably not what you want anymore. 
                           you may use GetMainViewport()->Pos to offset hard-coded positions, e.g. SetNextWindowPos(GetMainViewport()->Pos)
-                        - likewise io.MousePos and GetMousePos() will use OS coordinates coordinates. 
+                        - likewise io.MousePos and GetMousePos() will use OS coordinates. 
                           If you query mouse positions to interact with non-imgui coordinates you will need to offset them, e.g. subtract GetWindowViewport()->Pos.
  - 2018/XX/XX (1.XX) - Moved IME support functions from io.ImeSetInputScreenPosFn, io.ImeWindowHandle to the PlatformIO api.
- - 2018/XX/XX (1.XX) - removed io.DisplayVisibleMin, io.DisplayVisibleMax settings (it was used to clip within the DisplayMin..DisplayMax range, I don't know of anyone using it)
+ - 2018/XX/XX (1.XX) - removed io.DisplayVisibleMin, io.DisplayVisibleMax settings (they were used to clip within the (0,0)..DisplaySize range, I don't know of anyone using it)
 
 
  - 2018/12/10 (1.67) - renamed io.ConfigResizeWindowsFromEdges to io.ConfigWindowsResizeFromEdges as we are doing a large pass on configuration flags.
@@ -1152,9 +1150,20 @@ ImGuiIO::ImGuiIO()
     FontAllowUserScaling = false;
     DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
 
-    // Miscellaneous configuration options
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
+    ConfigDockingNoSplit = false;
     ConfigDockingWithShift = false;
+    ConfigDockingTabBarOnSingleWindows = false;
     ConfigDockingTransparentPayload = false;
+
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    ConfigViewportsNoAutoMerge = false;
+    ConfigViewportsNoTaskBarIcon = false;
+    ConfigViewportsNoDecoration = true;
+    ConfigViewportsNoParent = false;
+
+    // Miscellaneous options
+    MouseDrawCursor = false;
 #ifdef __APPLE__
     ConfigMacOSXBehaviors = true;  // Set Mac OS X style defaults based on __APPLE__ compile time flag
 #else
@@ -5306,7 +5315,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         else if ((flags & ImGuiWindowFlags_Tooltip) != 0 && !window_pos_set_by_api && !window_is_child_tooltip)
             window->Pos = FindBestWindowPosForPopup(window);
 
-        if (window->ViewportAllowPlatformMonitorExtend >= 0 && !window->ViewportOwned)
+        if (window->ViewportAllowPlatformMonitorExtend >= 0 && !window->ViewportOwned && !window->Viewport->PlatformWindowMinimized)
             if (!window->Viewport->GetRect().Contains(window->Rect()))
             {
                 // Late create viewport, based on the assumption that with our calculations, the DPI will be known ahead (same as the DPI of the selection done in UpdateSelectWindowViewport)
@@ -5332,13 +5341,17 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             ImGuiViewportFlags viewport_flags = (window->Viewport->Flags) & ~(ImGuiViewportFlags_TopMost | ImGuiViewportFlags_NoTaskBarIcon | ImGuiViewportFlags_NoDecoration);
             if (flags & ImGuiWindowFlags_Tooltip)
                 viewport_flags |= ImGuiViewportFlags_TopMost;
-            if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsNoTaskBarIcon) != 0 || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
+            if (g.IO.ConfigViewportsNoTaskBarIcon || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
                 viewport_flags |= ImGuiViewportFlags_NoTaskBarIcon;
-            if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsDecoration) == 0 || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
+            if (g.IO.ConfigViewportsNoDecoration || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
                 viewport_flags |= ImGuiViewportFlags_NoDecoration;
 
             // We can overwrite viewport flags using ImGuiWindowClass (advanced users)
-            window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId ? window->WindowClass.ParentViewportId : IMGUI_VIEWPORT_DEFAULT_ID;
+            // We don't default to the main viewport because.
+            if (window->WindowClass.ParentViewportId)
+                window->Viewport->ParentViewportId = window->WindowClass.ParentViewportId;
+            else
+                window->Viewport->ParentViewportId = g.IO.ConfigViewportsNoParent ? 0 : IMGUI_VIEWPORT_DEFAULT_ID;
             if (window->WindowClass.ViewportFlagsOverrideMask)
                 viewport_flags = (viewport_flags & ~window->WindowClass.ViewportFlagsOverrideMask) | (window->WindowClass.ViewportFlagsOverrideValue & window->WindowClass.ViewportFlagsOverrideMask);
 
@@ -5634,6 +5647,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             {
                 window->Viewport->PlatformRequestClose = false;
                 g.NavWindowingToggleLayer = false; // Assume user mapped PlatformRequestClose on ALT-F4 so we disable ALT for menu toggle. False positive not an issue.
+                //IMGUI_DEBUG_LOG("Window '%s' PlatformRequestClose\n", window->Name);
                 *p_open = false;
             }
         }
@@ -7561,7 +7575,7 @@ static bool ImGui::GetWindowAlwaysWantOwnViewport(ImGuiWindow* window)
 {
     // Tooltips and menus are not automatically forced into their own viewport when the NoMerge flag is set, however the multiplication of viewports makes them more likely to protude and create their own.
     ImGuiContext& g = *GImGui;
-    if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsNoMerge) && (g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
+    if (g.IO.ConfigViewportsNoAutoMerge && (g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
         if (!window->DockIsActive)
             if ((window->Flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip)) == 0)
                 return true;
@@ -7638,14 +7652,25 @@ static void ImGui::UpdateViewportsNewFrame()
     ImGuiContext& g = *GImGui;
     IM_ASSERT(g.PlatformIO.Viewports.Size <= g.Viewports.Size);
 
-    // Update main viewport with current platform position and size
+    // Update Minimized status (we need it first in order to decide if we'll apply Pos/Size of the main viewport)
+    for (int n = 0; n < g.Viewports.Size; n++)
+    {
+        ImGuiViewportP* viewport = g.Viewports[n];
+        const bool platform_funcs_available = (n == 0 || viewport->PlatformWindowCreated);
+        if ((g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
+            if (g.PlatformIO.Platform_GetWindowMinimized && platform_funcs_available)
+                viewport->PlatformWindowMinimized = g.PlatformIO.Platform_GetWindowMinimized(viewport);
+    }
+
+    // Create/update main viewport with current platform position and size
     ImGuiViewportP* main_viewport = g.Viewports[0];
     IM_ASSERT(main_viewport->ID == IMGUI_VIEWPORT_DEFAULT_ID);
     IM_ASSERT(main_viewport->Window == NULL);
     ImVec2 main_viewport_platform_pos = ImVec2(0.0f, 0.0f);
-    if ((g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
+    ImVec2 main_viewport_platform_size = g.IO.DisplaySize;
-        main_viewport_platform_pos = g.PlatformIO.Platform_GetWindowPos(main_viewport);
+    if (g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable)
-    AddUpdateViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, main_viewport_platform_pos, g.IO.DisplaySize, ImGuiViewportFlags_CanHostOtherWindows);
+        main_viewport_platform_pos = main_viewport->PlatformWindowMinimized ? main_viewport->Pos : g.PlatformIO.Platform_GetWindowPos(main_viewport);
+    AddUpdateViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, main_viewport_platform_pos, main_viewport_platform_size, ImGuiViewportFlags_CanHostOtherWindows);
 
     g.CurrentViewport = NULL;
     g.MouseViewport = NULL;
@@ -7680,9 +7705,6 @@ static void ImGui::UpdateViewportsNewFrame()
         const bool platform_funcs_available = (n == 0 || viewport->PlatformWindowCreated);
         if ((g.ConfigFlagsForFrame & ImGuiConfigFlags_ViewportsEnable))
         {
-            if (g.PlatformIO.Platform_GetWindowMinimized && platform_funcs_available)
-                viewport->PlatformWindowMinimized = g.PlatformIO.Platform_GetWindowMinimized(viewport);
-
             // Update Position and Size (from Platform Window to ImGui) if requested. 
             // We do it early in the frame instead of waiting for UpdatePlatformWindows() to avoid a frame of lag when moving/resizing using OS facilities.
             if (!viewport->PlatformWindowMinimized && platform_funcs_available)
@@ -7796,7 +7818,8 @@ static void ImGui::UpdateViewportsEndFrame()
         ImGuiViewportP* viewport = g.Viewports[i];
         viewport->LastPos = viewport->Pos;
         if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0.0f || viewport->Size.y <= 0.0f)
-            continue;
+            if (i > 0) // Always include main viewport in the list
+                continue;
         if (viewport->Window && !IsWindowActiveAndVisible(viewport->Window))
             continue;
         if (i > 0)
@@ -13565,7 +13588,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         static void NodeViewport(ImGuiViewportP* viewport)
         {
             ImGui::SetNextTreeNodeOpen(true, ImGuiCond_Once);
-            if (ImGui::TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->Window ? viewport->Window->Name : "N/A"))
+            if (ImGui::TreeNode((void*)(intptr_t)viewport->ID, "Viewport #%d, ID: 0x%08X, Parent: 0x%08X, Window: \"%s\"", viewport->Idx, viewport->ID, viewport->ParentViewportId, viewport->Window ? viewport->Window->Name : "N/A"))
             {
                 ImGuiWindowFlags flags = viewport->Flags;
                 ImGui::BulletText("Pos: (%.0f,%.0f), Size: (%.0f,%.0f), Monitor: %d, DpiScale: %.0f%%", viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y, viewport->PlatformMonitor, viewport->DpiScale * 100.0f);

imgui.h

@@ -1025,11 +1025,8 @@ enum ImGuiConfigFlags_
     // [BETA] Viewports
     // When using viewports it is recommended that your default value for ImGuiCol_WindowBg is opaque (Alpha=1.0) so transition to a viewport won't be noticeable.
     ImGuiConfigFlags_ViewportsEnable        = 1 << 10,  // Viewport enable flags (require both ImGuiConfigFlags_PlatformHasViewports + ImGuiConfigFlags_RendererHasViewports set by the respective back-ends)
-    ImGuiConfigFlags_ViewportsNoTaskBarIcon = 1 << 11,  // Disable task bars icons for all secondary viewports (will set ImGuiViewportFlags_NoTaskBarIcon on them)
+    ImGuiConfigFlags_DpiEnableScaleViewports= 1 << 14,  // [BETA: Don't use] FIXME-DPI: Reposition and resize imgui windows when the DpiScale of a viewport changed (mostly useful for the main viewport hosting other window). Note that resizing the main window itself is up to your application.
-    ImGuiConfigFlags_ViewportsDecoration    = 1 << 12,  // FIXME [Broken] Enable platform decoration for all secondary viewports (will not set ImGuiViewportFlags_NoDecoration on them). This currently doesn't behave well in Windows because 1) By default the new window animation get in the way of our transitions, 2) It enable a minimum window size which tends to breaks resizing. You can workaround the later by setting style.WindowMinSize to a bigger value.
+    ImGuiConfigFlags_DpiEnableScaleFonts    = 1 << 15,  // [BETA: Don't use] FIXME-DPI: Request bitmap-scaled fonts to match DpiScale. This is a very low-quality workaround. The correct way to handle DPI is _currently_ to replace the atlas and/or fonts in the Platform_OnChangedViewport callback, but this is all early work in progress.
-    ImGuiConfigFlags_ViewportsNoMerge       = 1 << 13,  // All floating windows will always create their own viewport and platform window.
-    ImGuiConfigFlags_DpiEnableScaleViewports= 1 << 14,  // FIXME-DPI: Reposition and resize imgui windows when the DpiScale of a viewport changed (mostly useful for the main viewport hosting other window). Note that resizing the main window itself is up to your application.
-    ImGuiConfigFlags_DpiEnableScaleFonts    = 1 << 15,  // FIXME-DPI: Request bitmap-scaled fonts to match DpiScale. This is a very low-quality workaround. The correct way to handle DPI is _currently_ to replace the atlas and/or fonts in the Platform_OnChangedViewport callback, but this is all early work in progress.
 
     // User storage (to allow your back-end/engine to communicate to code that may be shared between multiple projects. Those flags are not used by core ImGui)
     ImGuiConfigFlags_IsSRGB                 = 1 << 20,  // Application is SRGB-aware.
@@ -1300,12 +1297,20 @@ struct ImGuiIO
     ImFont*     FontDefault;                    // = NULL           // Font to use on NewFrame(). Use NULL to uses Fonts->Fonts[0].
     ImVec2      DisplayFramebufferScale;        // = (1.0f,1.0f)    // For hi-dpi/retina display or other situations where window coordinates are different from framebuffer coordinates. User storage only, presently not used by ImGui.
 
-    // Miscellaneous configuration options
+    // Docking options (when ImGuiConfigFlags_DockingEnable is set)
-    bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by back-end implementations.
     bool        ConfigDockingNoSplit;           // = false          // Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.
     bool        ConfigDockingWithShift;         // = false          // Enable docking with holding Shift key (reduce visual noise, allows dropping in wider space)
     bool        ConfigDockingTabBarOnSingleWindows; // = false      // [BETA] Make every single floating window display within a docking node.
     bool        ConfigDockingTransparentPayload;// = false          // [BETA] Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport can be synced. Best used with ImGuiConfigFlags_ViewportsNoMerge.
+    
+    // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
+    bool        ConfigViewportsNoAutoMerge;     // = false;         // Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it.
+    bool        ConfigViewportsNoTaskBarIcon;   // = false          // Set default OS task bar icon enable flag for secondary viewports. When a viewport doesn't want a task bar icon, ImGuiViewportFlags_NoTaskBarIcon will be set on it.
+    bool        ConfigViewportsNoDecoration;    // = true           // [BETA] Set default OS window decoration enable  flags for secondary viewports. When a viewport doesn't want window decorations, ImGuiViewportFlags_NoDecoration will be set on it. Enabling decoration can create subsequent issues at OS levels (e.g. minimum window size).
+    bool        ConfigViewportsNoParent;        // = false          // Set default OS parenting for secondary viewports. By default, viewports are marked with ParentViewportId = <main_viewport>, expecting the platform back-end to setup a parent/child relationship between the OS windows (some back-end may ignore this). Set to true if you want the default to be 0, then all viewports will be top-level OS windows.
+
+    // Miscellaneous options
+    bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by back-end implementations.
     bool        ConfigMacOSXBehaviors;          // = defined(__APPLE__) // OS X style: Text editing cursor movement using Alt instead of Ctrl, Shortcuts using Cmd/Super instead of Ctrl, Line/Text Start and End using Cmd+Arrows instead of Home/End, Double click selects by word instead of selecting whole text, Multi-selection in lists uses Cmd/Super instead of Ctrl (was called io.OptMacOSXBehaviors prior to 1.63)
     bool        ConfigInputTextCursorBlink;     // = true           // Set to false to disable blinking cursor, for users who consider it distracting. (was called: io.OptCursorBlink prior to 1.63)
     bool        ConfigWindowsResizeFromEdges;   // = true           // Enable resizing of windows from their edges and from the lower-left corner. This requires (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors) because it needs mouse cursor feedback. (This used to be the a per-window ImGuiWindowFlags_ResizeFromAnySide flag)

imgui_demo.cpp

@@ -339,22 +339,35 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::SameLine(); ShowHelpMarker("Instruct back-end to not alter mouse cursor shape and visibility.");
 
             ImGui::CheckboxFlags("io.ConfigFlags: DockingEnable", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_DockingEnable);
-            ImGui::SameLine(); ShowHelpMarker("Use SHIFT to dock window into another (or without SHIFT if io.ConfigDockingWithShift == false)");
+            ImGui::SameLine(); ShowHelpMarker(io.ConfigDockingWithShift ? "[beta] Use SHIFT to dock window into each others." : "[beta] Drag from title bar to dock windows into each others.");
+            if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)
+            {
+                ImGui::Indent();
+                ImGui::Checkbox("io.ConfigDockingNoSplit", &io.ConfigDockingNoSplit);
+                ImGui::SameLine(); ShowHelpMarker("Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.");
+                ImGui::Checkbox("io.ConfigDockingWithShift", &io.ConfigDockingWithShift);
+                ImGui::SameLine(); ShowHelpMarker("Enable docking when holding Shift only (allows to drop in wider space, reduce visual noise)");
+                ImGui::Checkbox("io.ConfigDockingTabBarOnSingleWindows", &io.ConfigDockingTabBarOnSingleWindows);
+                ImGui::SameLine(); ShowHelpMarker("Create a docking node and tab-bar on single floating windows.");
+                ImGui::Unindent();
+            }
 
             ImGui::CheckboxFlags("io.ConfigFlags: ViewportsEnable", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsEnable);
-            ImGui::CheckboxFlags("io.ConfigFlags: ViewportsNoTaskBarIcon", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsNoTaskBarIcon);
+            ImGui::SameLine(); ShowHelpMarker("[beta] Enable beta multi-viewports support. See ImGuiPlatformIO for details.");
-            ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the task bar icon state right away).");
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
-            ImGui::CheckboxFlags("io.ConfigFlags: ViewportsDecoration", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsDecoration);
+            {
-            ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the decoration right away).");
+                ImGui::Indent();
-            ImGui::CheckboxFlags("io.ConfigFlags: ViewportsNoMerge", (unsigned int *)&io.ConfigFlags, ImGuiConfigFlags_ViewportsNoMerge);
+                ImGui::Checkbox("io.ConfigViewportsNoAutoMerge", &io.ConfigViewportsNoAutoMerge);
-            ImGui::SameLine(); ShowHelpMarker("All floating windows will always create their own viewport and platform window.");
+                ImGui::SameLine(); ShowHelpMarker("Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it.");
+                ImGui::Checkbox("io.ConfigViewportsNoTaskBarIcon", &io.ConfigViewportsNoTaskBarIcon);
+                ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the task bar icon state right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoDecoration", &io.ConfigViewportsNoDecoration);
+                ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the decoration right away).");
+                ImGui::Checkbox("io.ConfigViewportsNoParent", &io.ConfigViewportsNoParent);
+                ImGui::SameLine(); ShowHelpMarker("Toggling this at runtime is normally unsupported (most platform back-ends won't refresh the parenting right away).");
+                ImGui::Unindent();
+            }
 
-            ImGui::Checkbox("io.ConfigDockingNoSplit", &io.ConfigDockingNoSplit);
-            ImGui::SameLine(); ShowHelpMarker("Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.");
-            ImGui::Checkbox("io.ConfigDockingWithShift", &io.ConfigDockingWithShift);
-            ImGui::SameLine(); ShowHelpMarker("Enable docking when holding Shift only (allows to drop in wider space, reduce visual noise)");
-            ImGui::Checkbox("io.ConfigDockingTabBarOnSingleWindows", &io.ConfigDockingTabBarOnSingleWindows);
-            ImGui::SameLine(); ShowHelpMarker("Associate a docking node and tab-bar to sinle floating windows.");
             ImGui::Checkbox("io.ConfigInputTextCursorBlink", &io.ConfigInputTextCursorBlink);
             ImGui::SameLine(); ShowHelpMarker("Set to false to disable blinking cursor, for users who consider it distracting");
             ImGui::Checkbox("io.ConfigWindowsResizeFromEdges", &io.ConfigWindowsResizeFromEdges);
@@ -2706,15 +2719,21 @@ void ImGui::ShowAboutWindow(bool* p_open)
         if (io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange)      ImGui::Text(" NoMouseCursorChange");
         if (io.ConfigFlags & ImGuiConfigFlags_DockingEnable)            ImGui::Text(" DockingEnable");
         if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)          ImGui::Text(" ViewportsEnable");
-        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsNoTaskBarIcon)   ImGui::Text(" ViewportsNoTaskBarIcon");
-        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsNoMerge)         ImGui::Text(" ViewportsNoMerge");
-        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsDecoration)      ImGui::Text(" ViewportsDecoration");
         if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)  ImGui::Text(" DpiEnableScaleViewports");
         if (io.ConfigFlags & ImGuiConfigFlags_DpiEnableScaleFonts)      ImGui::Text(" DpiEnableScaleFonts");
         if (io.MouseDrawCursor)                                         ImGui::Text("io.MouseDrawCursor");
+        if (io.ConfigViewportsNoAutoMerge)                              ImGui::Text("io.ConfigViewportsNoAutoMerge");
+        if (io.ConfigViewportsNoTaskBarIcon)                            ImGui::Text("io.ConfigViewportsNoTaskBarIcon");
+        if (io.ConfigViewportsNoDecoration)                             ImGui::Text("io.ConfigViewportsNoDecoration");
+        if (io.ConfigViewportsNoParent)                                 ImGui::Text("io.ConfigViewportsNoParent");
         if (io.ConfigDockingNoSplit)                                    ImGui::Text("io.ConfigDockingNoSplit");
         if (io.ConfigDockingWithShift)                                  ImGui::Text("io.ConfigDockingWithShift");
+        if (io.ConfigDockingTabBarOnSingleWindows)                      ImGui::Text("io.ConfigDockingTabBarOnSingleWindows");
         if (io.ConfigDockingTransparentPayload)                         ImGui::Text("io.ConfigDockingTransparentPayload");
+        if (io.ConfigViewportsNoAutoMerge)                              ImGui::Text("io.ConfigViewportsNoAutoMerge");
+        if (io.ConfigViewportsNoTaskBarIcon)                            ImGui::Text("io.ConfigViewportsNoTaskBarIcon");
+        if (io.ConfigViewportsNoDecoration)                             ImGui::Text("io.ConfigViewportsNoDecoration");
+        if (io.ConfigViewportsNoParent)                                 ImGui::Text("io.ConfigViewportsNoParent");
         if (io.ConfigMacOSXBehaviors)                                   ImGui::Text("io.ConfigMacOSXBehaviors");
         if (io.ConfigInputTextCursorBlink)                              ImGui::Text("io.ConfigInputTextCursorBlink");
         if (io.ConfigWindowsResizeFromEdges)                            ImGui::Text("io.ConfigWindowsResizeFromEdges");

imgui_internal.h

@@ -682,7 +682,7 @@ struct ImGuiViewportP : public ImGuiViewport
     float               LastAlpha;
     short               PlatformMonitor;
     bool                PlatformWindowCreated;
-    bool                PlatformWindowMinimized;
+    bool                PlatformWindowMinimized;  // When minimized we tend to avoid using the viewport pos/size for clipping window or testing if they are contained in the viewport
     ImGuiWindow*        Window;                   // Set when the viewport is owned by a window (and ImGuiViewportFlags_CanHostOtherWindows is NOT set)
     ImDrawList*         OverlayDrawList;          // For convenience, a draw list we can render to that's always rendered last (we use it to draw software mouse cursor when io.MouseDrawCursor is set)
     ImDrawData          DrawDataP;