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)

imgui.cpp

@@ -2369,7 +2369,6 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     ScrollbarSizes = ImVec2(0.0f, 0.0f);
     ScrollbarX = ScrollbarY = false;
     ViewportOwned = false;
-    ViewportTryMerge = ViewportTrySplit = false;
     Active = WasActive = false;
     WriteAccessed = false;
     Collapsed = false;
@@ -4762,10 +4761,6 @@ static void ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
     if (size_target.x != FLT_MAX && (size_target.x != window->SizeFull.x || size_target.y != window->SizeFull.y))
     {
         window->SizeFull = size_target;
-        if (window->ViewportOwned)
-            window->ViewportTryMerge = true;
-        else
-            window->ViewportTrySplit = true;
         MarkIniSettingsDirty(window);
     }
     if (pos_target.x != FLT_MAX)
@@ -5082,10 +5077,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             {
                 // 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)
                 //ImGuiViewport* old_viewport = window->Viewport;
-                ImGuiViewportFlags viewport_flags = ImGuiViewportFlags_NoFocusOnAppearing;
+                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing);
-                if ((window->Flags & ImGuiWindowFlags_NoMouseInputs) && (window->Flags & ImGuiWindowFlags_NoNavInputs))
-                    viewport_flags |= ImGuiViewportFlags_NoInputs;
-                window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, viewport_flags);
 
                 // FIXME-DPI
                 //IM_ASSERT(old_viewport->DpiScale == window->Viewport->DpiScale); // FIXME-DPI: Something went wrong
@@ -5098,15 +5090,9 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         if (window->ViewportOwned)
         {
             if (window->Viewport->PlatformRequestMove)
-            {
                 window->Pos = window->Viewport->Pos;
-                window->ViewportTryMerge = true;
-            }
             if (window->Viewport->PlatformRequestResize)
-            {
                 window->Size = window->SizeFull = window->Viewport->Size;
-                window->ViewportTryMerge = true;
-            }
 
             // We also tell the back-end that clearing the platform window won't be necessary, as our window is filling the viewport and we have disabled BgAlpha
             window->Viewport->Flags |= ImGuiViewportFlags_NoRendererClear;
@@ -5127,7 +5113,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 {
                     // Fallback for "lost" window (e.g. a monitor disconnected): we move the window back over the main viewport
                     SetWindowPos(window, g.Viewports[0]->Pos + style.DisplayWindowPadding, ImGuiCond_Always);
-                    window->ViewportTryMerge = true;
                 }
                 else
                 {
@@ -7385,11 +7370,22 @@ static void ImGui::UpdateViewports()
     IM_ASSERT(g.MouseViewport != NULL);
 }
 
+// FIXME: We should ideally refactor the system to call this everyframe (we currently don't)
 ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& pos, const ImVec2& size, ImGuiViewportFlags flags)
 {
     ImGuiContext& g = *GImGui;
     IM_ASSERT(id != 0);
 
+    if (window != NULL)
+    {
+        if (g.MovingWindow && g.MovingWindow->RootWindow == window)
+            flags |= ImGuiViewportFlags_NoInputs | ImGuiViewportFlags_NoFocusOnAppearing;
+        if ((window->Flags & ImGuiWindowFlags_NoMouseInputs) && (window->Flags & ImGuiWindowFlags_NoNavInputs))
+            flags |= ImGuiViewportFlags_NoInputs;
+        if (window->Flags & ImGuiWindowFlags_NoFocusOnAppearing)
+            flags |= ImGuiViewportFlags_NoFocusOnAppearing;
+    }
+
     ImGuiViewportP* viewport = (ImGuiViewportP*)FindViewportByID(id);
     if (viewport)
     {
@@ -7407,9 +7403,6 @@ ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const
         viewport->PlatformMonitor = FindPlatformMonitorForRect(viewport->GetRect());
         g.Viewports.push_back(viewport);
 
-        if (window && (window->Flags & ImGuiWindowFlags_NoFocusOnAppearing))
-            flags |= ImGuiViewportFlags_NoFocusOnAppearing;
-
         // We normally setup for all viewports in NewFrame() but here need to handle the mid-frame creation of a new viewport.
         // We need to extend the fullscreen clip rect so the OverlayDrawList clip is correct for that the first frame
         g.DrawListSharedData.ClipRectFullscreen.z = ImMax(g.DrawListSharedData.ClipRectFullscreen.z, viewport->Pos.x + viewport->Size.x);
@@ -7447,12 +7440,9 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
         return;
     }
 
-    // Merge into host viewports (after moving, resizing)
+    // Merge into host viewport
-    if (window->ViewportOwned && window->ViewportTryMerge && g.ActiveId == 0)
+    if (window->ViewportOwned && g.ActiveId == 0)
-    {
         UpdateTryMergeWindowIntoHostViewport(window, g.Viewports[0]);
-        window->ViewportTryMerge = false;
-    }
     window->ViewportOwned = false;
 
     // Appearing popups reset their viewport so they can inherit again
@@ -7492,23 +7482,15 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
     {
         window->Viewport = g.MouseViewport;
     }
-    else if (g.MovingWindow && g.MovingWindow->RootWindow == window && IsMousePosValid())
-    {
-        // Transition to our own viewport when leaving our host boundaries + set the NoInputs flag (will be cleared in UpdateMouseMovingWindow() when releasing mouse)
-        // If we are already in our own viewport, if need to set the NoInputs flag.
-        // If we have no viewport (which happens when detaching a docked node) immediately create one.
-        // We test for 'window->Viewport->Window == window' instead of 'window->ViewportOwned' because ViewportOwned is not valid during this function.
-        bool has_viewport = (window->Viewport != NULL);
-        bool own_viewport = has_viewport && (window->Viewport->Window == window);
-        bool leave_host_viewport = has_viewport && !own_viewport && !window->Viewport->GetRect().Contains(window->Rect());
-        bool move_from_own_viewport = has_viewport && own_viewport && !(window->Viewport->Flags & ImGuiViewportFlags_NoInputs);
-        if (!has_viewport || leave_host_viewport || move_from_own_viewport)
-            window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_NoFocusOnAppearing | ImGuiViewportFlags_NoInputs);
-    }
     else if (GetWindowAlwaysWantOwnViewport(window))
     {
         window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
     }
+    else if (g.MovingWindow && g.MovingWindow->RootWindow == window && IsMousePosValid())
+    {
+        if (window->Viewport != NULL && window->Viewport->Window == window)
+            window->Viewport = AddUpdateViewport(window, window->ID, window->Pos, window->Size, ImGuiViewportFlags_None);
+    }
 
     // Mark window as allowed to protrude outside of its viewport and into the current monitor
     // We need to take account of the possibility that mouse may become invalid.
@@ -7522,14 +7504,14 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
         else
             window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
     }
-    if (window->ViewportTrySplit && window->ViewportAllowPlatformMonitorExtend < 0)
-        window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
-    window->ViewportTrySplit = false;
 
     // Fallback to default viewport
     if (window->Viewport == NULL)
         window->Viewport = main_viewport;
 
+    if (window->ViewportAllowPlatformMonitorExtend < 0)
+        window->ViewportAllowPlatformMonitorExtend = window->Viewport->PlatformMonitor;
+
     // Update flags
     window->ViewportOwned = (window == window->Viewport->Window);
 

imgui_internal.h

@@ -1074,8 +1074,6 @@ struct IMGUI_API ImGuiWindow
     ImVec2                  ScrollbarSizes;                     // Size taken by scrollbars on each axis
     bool                    ScrollbarX, ScrollbarY;
     bool                    ViewportOwned;
-    bool                    ViewportTryMerge;                   // Request attempt to merge into a host viewport and destroy our owned viewport
-    bool                    ViewportTrySplit;                   // Request attempt to split out of a host viewport and create our owned viewport
     bool                    Active;                             // Set to true on Begin(), unless Collapsed
     bool                    WasActive;
     bool                    WriteAccessed;                      // Set to true when any widget access the current window