Viewport: Moved ImGuiWindowFlags_FullViewport to an internal ViewportOwned flag. Renamed AddViewport to AddUpdateViewport. (#Viewport: Shuffled code in Begin to reset size of reappearing popups prior to selecting viewport, to avoid mistakenly using an old size. Moved code out of UpdateSelectWindowViewport() to the section of Begin where positions is being locked down, to avoid code in-between duplicating this. (#1542))

imgui.cpp

@@ -766,7 +766,7 @@ const ImGuiID           IMGUI_VIEWPORT_DEFAULT_ID = 0x11111111; // Using an arbi
 static inline ImRect    GetViewportRect(ImGuiWindow* window) { return window->Viewport->GetRect(); }
 static inline ImVec2    ConvertViewportPosToPlatformPos(const ImVec2& imgui_pos, ImGuiViewport* viewport)    { return imgui_pos - viewport->Pos + viewport->PlatformPos; }
 static inline ImVec2    ConvertPlatformPosToViewportPos(const ImVec2& platform_pos, ImGuiViewport* viewport) { return platform_pos - viewport->PlatformPos + viewport->Pos; }
-static ImGuiViewportP*  AddViewport(ImGuiWindow* window, ImGuiID id, ImGuiViewportFlags flags, const ImVec2& platform_pos, const ImVec2& size);
+static ImGuiViewportP*  AddUpdateViewport(ImGuiWindow* window, ImGuiID id, ImGuiViewportFlags flags, const ImVec2& platform_pos, const ImVec2& size);
 static void             UpdateViewports();
 static void             UpdateSelectWindowViewport(ImGuiWindow* window);
 static void             SetCurrentViewport(ImGuiViewportP* viewport);
@@ -1948,8 +1948,9 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     Scroll = ImVec2(0.0f, 0.0f);
     ScrollTarget = ImVec2(FLT_MAX, FLT_MAX);
     ScrollTargetCenterRatio = ImVec2(0.5f, 0.5f);
-    ScrollbarX = ScrollbarY = false;
     ScrollbarSizes = ImVec2(0.0f, 0.0f);
+    ScrollbarX = ScrollbarY = false;
+    ViewportOwned = false;
     Active = WasActive = false;
     WriteAccessed = false;
     Collapsed = false;
@@ -3313,24 +3314,25 @@ static void ImGui::NewFrameUpdateMovingWindowDropViewport(ImGuiWindow* window)
     ImRect mouse_viewport_rect = g.MousePosViewport->GetRect();
     ImVec2 window_pos_in_mouse_viewport = ConvertPlatformPosToViewportPos(ConvertViewportPosToPlatformPos(window->Pos, window->Viewport), g.MousePosViewport);
     ImRect window_rect_in_mouse_viewport = ImRect(window_pos_in_mouse_viewport, window_pos_in_mouse_viewport + window->Size);
-    if ((g.MousePosViewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) &&  mouse_viewport_rect.Contains(window_rect_in_mouse_viewport))
+    if ((g.MousePosViewport->Flags & ImGuiViewportFlags_CanHostOtherWindows) && mouse_viewport_rect.Contains(window_rect_in_mouse_viewport))
     {
         // Drop on an existing viewport
         ImGuiViewportP* old_viewport = window->Viewport;
         SetWindowViewportTranslateToPreservePlatformPos(window, window->Viewport, g.MousePosViewport);
 
-        // Our current scheme allow any window to land on a viewport, so when that viewport merges, move other windows as well
-        // FIXME-OPT
-        if (window->Flags & ImGuiWindowFlags_FullViewport)
+        // Move child/hosted windows as well (FIXME-OPT)
+        if (window->ViewportOwned)
             for (int n = 0; n < g.Windows.Size; n++)
                 if (g.Windows[n]->Viewport == old_viewport)
                     SetWindowViewportTranslateToPreservePlatformPos(g.Windows[n], old_viewport, g.MousePosViewport);
+        window->ViewportOwned = false;
     }
     else
     {
         // Create/persist new viewport
         ImVec2 platform_pos = ConvertViewportPosToPlatformPos(window->Pos, window->Viewport);
-        ImGuiViewportP* viewport = AddViewport(window, window->ID, 0, platform_pos, window->Size);
+        ImGuiViewportP* viewport = AddUpdateViewport(window, window->ID, 0, platform_pos, window->Size);
+        IM_ASSERT(viewport == window->Viewport);
         SetWindowViewportTranslateToPreservePlatformPos(window, window->Viewport, viewport);
     }
 }
@@ -3476,7 +3478,7 @@ static void ImGui::UpdateViewports()
     ImVec2 main_viewport_platform_pos = ImVec2(0.0f, 0.0f);
     if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
         main_viewport_platform_pos = g.PlatformIO.Platform_GetWindowPos(main_viewport);
-    AddViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, ImGuiViewportFlags_CanHostOtherWindows, main_viewport_platform_pos, g.IO.DisplaySize);
+    AddUpdateViewport(NULL, IMGUI_VIEWPORT_DEFAULT_ID, ImGuiViewportFlags_CanHostOtherWindows, main_viewport_platform_pos, g.IO.DisplaySize);
 
     if (!(g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsEnable))
     {
@@ -4699,7 +4701,7 @@ void ImGui::SetCurrentViewport(ImGuiViewportP* viewport)
         g.PlatformIO.Platform_OnChangedViewport(g.CurrentViewport);
 }
 
-ImGuiViewportP* ImGui::AddViewport(ImGuiWindow* window, ImGuiID id, ImGuiViewportFlags flags, const ImVec2& platform_pos, const ImVec2& size)
+ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, ImGuiViewportFlags flags, const ImVec2& platform_pos, const ImVec2& size)
 {
     ImGuiContext& g = *GImGui;
     IM_ASSERT(id != 0);
@@ -4733,6 +4735,9 @@ ImGuiViewportP* ImGui::AddViewport(ImGuiWindow* window, ImGuiID id, ImGuiViewpor
     viewport->PlatformPos = platform_pos;
     viewport->LastFrameActive = g.FrameCount;
 
+    if (window != NULL)
+        window->ViewportOwned = true;
+
     // Request an initial DpiScale before the OS platform window creation
     // This is so we can select an appropriate font size on the first frame of our window lifetime
     if (g.PlatformIO.Platform_GetWindowDpiScale)
@@ -6070,7 +6075,7 @@ static ImVec2 CalcSizeAutoFit(ImGuiWindow* window, const ImVec2& size_contents)
     else
     {
         // When the window cannot fit all contents (either because of constraints, either because screen is too small): we are growing the size on the other axis to compensate for expected scrollbar. FIXME: Might turn bigger than ViewportSize-WindowPadding.
-        ImVec2 viewport_size = (window->Flags & ImGuiWindowFlags_FullViewport) ? ImVec2(FLT_MAX, FLT_MAX) : window->Viewport->Size;
+        ImVec2 viewport_size = window->ViewportOwned ? ImVec2(FLT_MAX, FLT_MAX) : window->Viewport->Size;
         size_auto_fit = ImClamp(size_contents, style.WindowMinSize, ImMax(style.WindowMinSize, viewport_size - g.Style.DisplaySafeAreaPadding));
         ImVec2 size_auto_fit_after_constraint = CalcSizeAfterConstraint(window, size_auto_fit);
         if (size_auto_fit_after_constraint.x < size_contents.x && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar))
@@ -6156,6 +6161,7 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindowFlags flags = window->Flags;
+    window->ViewportOwned = false;
 
     // Restore main viewport if multi-viewport is not supported by the back-end
     ImGuiViewportP* main_viewport = g.Viewports[0];
@@ -6186,8 +6192,7 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
         window->Viewport = FindViewportByID(window->ViewportId);
         if (window->Viewport == NULL && window->ViewportPlatformPos.x != FLT_MAX && window->ViewportPlatformPos.y != FLT_MAX)
         {
-            ImGuiViewportP* viewport = AddViewport(window, window->ID, ImGuiViewportFlags_NoDecoration, window->ViewportPlatformPos, window->Size);
-            window->Flags |= ImGuiWindowFlags_FullViewport;
+            ImGuiViewportP* viewport = AddUpdateViewport(window, window->ID, ImGuiViewportFlags_NoDecoration, window->ViewportPlatformPos, window->Size);
             window->Viewport = viewport;
             created_viewport = true;
         }
@@ -6213,8 +6218,7 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
             // Calculate mouse position in OS/platform coordinates, create a Viewport at this position.
             ImVec2 platform_pos = ConvertViewportPosToPlatformPos(g.IO.MousePos - g.ActiveIdClickOffset, g.MousePosViewport);
             ImGuiViewportFlags viewport_flags = ImGuiViewportFlags_NoDecoration | ImGuiViewportFlags_NoFocusOnAppearing | ImGuiViewportFlags_NoInputs;
-            ImGuiViewportP* viewport = AddViewport(window, window->ID, viewport_flags, platform_pos, window->Size);
-            window->Flags |= ImGuiWindowFlags_FullViewport;
+            ImGuiViewportP* viewport = AddUpdateViewport(window, window->ID, viewport_flags, platform_pos, window->Size);
             window->Viewport = viewport;
             created_viewport = true;
         }
@@ -6239,14 +6243,14 @@ static void ImGui::UpdateSelectWindowViewport(ImGuiWindow* window)
         if (!window->Viewport->PlatformRequestResize)
             window->Viewport->Size = window->Size;
         window->Viewport->PlatformPos = ConvertViewportPosToPlatformPos(window->Pos, window->Viewport);
-        window->Flags |= ImGuiWindowFlags_FullViewport;
+        window->ViewportOwned = true;
     }
 
     // If the OS window has a title bar, hide our imgui title bar
-    if ((window->Flags & ImGuiWindowFlags_FullViewport) && !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration))
+    if (window->ViewportOwned && !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration))
         window->Flags |= ImGuiWindowFlags_NoTitleBar;
 
-    if (window->Flags & ImGuiWindowFlags_FullViewport)
+    if (window->ViewportOwned)
     {
         // We currently have window fully covering a viewport and we disable WindowBg alpha, so clearing is not necessary
         window->Viewport->Flags |= ImGuiViewportFlags_NoRendererClear;
@@ -6386,7 +6390,7 @@ static void ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
     }
     if (pos_target.x != FLT_MAX)
     {
-        if (window->Flags & ImGuiWindowFlags_FullViewport)
+        if (window->ViewportOwned)
             window->Viewport->PlatformPos = ConvertViewportPosToPlatformPos(ImFloor(pos_target), window->Viewport);
         else
             window->Pos = window->PosFloat = ImFloor(pos_target);
@@ -6557,7 +6561,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
         // Lock window rounding, border size and padding for the frame (so that altering them doesn't cause inconsistencies)
         window->WindowRounding = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildRounding : ((flags & ImGuiWindowFlags_Popup) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupRounding : style.WindowRounding;
-        if (window->Flags & ImGuiWindowFlags_FullViewport)
+        if (window->ViewportOwned)
             window->WindowRounding = 0.0f;
         window->WindowBorderSize = (flags & ImGuiWindowFlags_ChildWindow) ? style.ChildBorderSize : ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupBorderSize : style.WindowBorderSize;
         window->WindowPadding = style.WindowPadding;
@@ -6683,7 +6687,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Clamp position so window stays visible within its viewport
         // Ignore zero-sized display explicitly to avoid losing positions if a window manager reports zero-sized window when initializing or minimizing.
         ImRect viewport_rect(GetViewportRect(window));
-        if (!window_pos_set_by_api && !(flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_FullViewport)) && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0)
+        if (!window_pos_set_by_api && !(flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Tooltip)) && !window->ViewportOwned && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0)
             if (viewport_rect.GetWidth() > 0 && viewport_rect.GetHeight() > 0.0f)
             {
                 ImVec2 padding = ImMax(style.DisplayWindowPadding, style.DisplaySafeAreaPadding);
@@ -6724,12 +6728,11 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
         // When a window is marked as owning its viewport, we immediately update the viewport after a resize
         window->ViewportPlatformPos = window->Viewport->PlatformPos;
-        if (flags & ImGuiWindowFlags_FullViewport)
-            if (window->Size.x != window->Viewport->Size.x || window->Size.y != window->Viewport->Size.y)
-            {
-                window->Viewport->Size = window->SizeFull;
-                viewport_rect = GetViewportRect(window);
-            }
+        if (window->ViewportOwned && (window->Size.x != window->Viewport->Size.x || window->Size.y != window->Viewport->Size.y))
+        {
+            window->Viewport->Size = window->SizeFull;
+            viewport_rect = GetViewportRect(window);
+        }
 
         // DRAWING
 
@@ -6780,7 +6783,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             ImU32 bg_col = GetColorU32(GetWindowBgColorIdxFromFlags(flags));
             if (g.NextWindowData.BgAlphaCond != 0)
                 bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(g.NextWindowData.BgAlphaVal) << IM_COL32_A_SHIFT);
-            if (window->Flags & ImGuiWindowFlags_FullViewport)
+            if (window->ViewportOwned)
                 bg_col = (bg_col | IM_COL32_A_MASK);
             window->DrawList->AddRectFilled(window->Pos+ImVec2(0,window->TitleBarHeight()), window->Pos+window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? ImDrawCornerFlags_All : ImDrawCornerFlags_Bot);
 

imgui.h

@@ -593,8 +593,7 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_Tooltip                = 1 << 25,  // Don't use! For internal use by BeginTooltip()
     ImGuiWindowFlags_Popup                  = 1 << 26,  // Don't use! For internal use by BeginPopup()
     ImGuiWindowFlags_Modal                  = 1 << 27,  // Don't use! For internal use by BeginPopupModal()
-    ImGuiWindowFlags_ChildMenu              = 1 << 28,  // Don't use! For internal use by BeginMenu()
-    ImGuiWindowFlags_FullViewport           = 1 << 29   // Don't use! For internal use by Begin() and viewports.
+    ImGuiWindowFlags_ChildMenu              = 1 << 28   // Don't use! For internal use by BeginMenu()
 };
 
 // Flags for ImGui::InputText()

imgui_internal.h

@@ -955,8 +955,9 @@ struct IMGUI_API ImGuiWindow
     ImVec2                  Scroll;
     ImVec2                  ScrollTarget;                       // target scroll position. stored as cursor position with scrolling canceled out, so the highest point is always 0.0f. (FLT_MAX for no change)
     ImVec2                  ScrollTargetCenterRatio;            // 0.0f = scroll so that target position is at top, 0.5f = scroll so that target position is centered
-    bool                    ScrollbarX, ScrollbarY;
     ImVec2                  ScrollbarSizes;
+    bool                    ScrollbarX, ScrollbarY;
+    bool                    ViewportOwned;
     bool                    Active;                             // Set to true on Begin(), unless Collapsed
     bool                    WasActive;
     bool                    WriteAccessed;                      // Set to true when any widget access the current window