Viewport: Reorder flags. Set owned viewport common decoration flags in Begin(). Moved code in UpdateViewportsEndFrame() before we introduce family/class based overrides.

imgui.cpp

@@ -1010,7 +1010,8 @@ static void             UpdateManualResize(ImGuiWindow* window, const ImVec2& si
 // Viewports
 const ImGuiID           IMGUI_VIEWPORT_DEFAULT_ID = 0x11111111; // Using an arbitrary constant instead of e.g. ImHash("ViewportDefault", 0); so it's easier to spot in the debugger. The exact value doesn't matter.
 static ImGuiViewportP*  AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& platform_pos, const ImVec2& size, ImGuiViewportFlags flags);
-static void             UpdateViewports();
+static void             UpdateViewportsNewFrame();
+static void             UpdateViewportsEndFrame();
 static void             UpdateSelectWindowViewport(ImGuiWindow* window);
 static bool             UpdateTryMergeWindowIntoHostViewport(ImGuiWindow* window, ImGuiViewportP* host_viewport);
 static void             SetCurrentViewport(ImGuiWindow* window, ImGuiViewportP* viewport);
@@ -3352,7 +3353,7 @@ void ImGui::NewFrame()
     g.WindowsActiveCount = 0;
     g.ConfigFlagsForFrame = g.IO.ConfigFlags;
 
-    UpdateViewports();
+    UpdateViewportsNewFrame();
 
     // Setup current font, and draw list shared data
     // FIXME-VIEWPORT: the concept of a single ClipRectFullscreen is not ideal!
@@ -3846,24 +3847,8 @@ void ImGui::EndFrame()
         }
     }
 
-    // Update user-facing viewport list
+    // Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
-    g.PlatformIO.MainViewport = g.Viewports[0];
+    UpdateViewportsEndFrame();
-    g.PlatformIO.Viewports.resize(0);
-    for (int i = 0; i < g.Viewports.Size; i++)
-    {
-        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 (viewport->Window && !IsWindowActiveAndVisible(viewport->Window)) // Will be destroyed in UpdatePlatformWindows()
-            continue;
-        if (i > 0)
-            IM_ASSERT(viewport->Window != NULL);
-
-        // Add to user-facing list
-        g.PlatformIO.Viewports.push_back(viewport);
-    }
-    g.Viewports[0]->ClearRequestFlags(); // Clear main viewport flags because UpdatePlatformWindows() won't do it and may not even be called
 
     // Sort the window list so that all child windows are after their parent
     // We cannot do that on FocusWindow() because childs may not exist yet
@@ -5178,16 +5163,26 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 SetCurrentWindow(window);
             }
 
-        // Synchronize viewport --> window in case the platform window has been moved or resized from the OS/WM
         if (window->ViewportOwned)
         {
+            // Synchronize viewport -> window in case the platform window has been moved or resized from the OS/WM
             if (window->Viewport->PlatformRequestMove)
                 window->Pos = window->Viewport->Pos;
             if (window->Viewport->PlatformRequestResize)
                 window->Size = window->SizeFull = window->Viewport->Size;
 
+            // Update common viewport 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)
+                viewport_flags |= ImGuiViewportFlags_NoTaskBarIcon;
+            if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsDecoration) == 0 || (flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
+                viewport_flags |= ImGuiViewportFlags_NoDecoration;
+
             // 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;
+            viewport_flags |= ImGuiViewportFlags_NoRendererClear;
+            window->Viewport->Flags = viewport_flags;
         }
 
         // Clamp position so window stays visible within its viewport or monitor
@@ -7387,8 +7382,7 @@ static ImGuiViewportP* FindViewportHoveredFromPlatformWindowStack(const ImVec2 m
     return best_candidate;
 }
 
-// Called in NewFrame()
+static void ImGui::UpdateViewportsNewFrame()
-static void ImGui::UpdateViewports()
 {
     ImGuiContext& g = *GImGui;
     IM_ASSERT(g.PlatformIO.Viewports.Size <= g.Viewports.Size);
@@ -7540,6 +7534,27 @@ static void ImGui::UpdateViewports()
     IM_ASSERT(g.MouseViewport != NULL);
 }
 
+// Update user-facing viewport list (g.Viewports -> g.PlatformIO.Viewports after filtering out some)
+static void ImGui::UpdateViewportsEndFrame()
+{
+    ImGuiContext& g = *GImGui;
+    g.PlatformIO.MainViewport = g.Viewports[0];
+    g.PlatformIO.Viewports.resize(0);
+    for (int i = 0; i < g.Viewports.Size; i++)
+    {
+        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 (viewport->Window && !IsWindowActiveAndVisible(viewport->Window))
+            continue;
+        if (i > 0)
+            IM_ASSERT(viewport->Window != NULL);
+        g.PlatformIO.Viewports.push_back(viewport);
+    }
+    g.Viewports[0]->ClearRequestFlags(); // Clear main viewport flags because UpdatePlatformWindows() won't do it and may not even be called
+}
+
 // FIXME: We should ideally refactor the system to call this every frame (we currently don't)
 ImGuiViewportP* ImGui::AddUpdateViewport(ImGuiWindow* window, ImGuiID id, const ImVec2& pos, const ImVec2& size, ImGuiViewportFlags flags)
 {
@@ -7734,19 +7749,6 @@ void ImGui::UpdatePlatformWindows()
         if (viewport->LastFrameActive < g.FrameCount || viewport->Size.x <= 0 || viewport->Size.y <= 0)
             continue;
 
-        // Update common viewport flags for owned viewports
-        if (ImGuiWindow* window = viewport->Window)
-        {
-            ImGuiViewportFlags flags = viewport->Flags & ~(ImGuiViewportFlags_TopMost | ImGuiViewportFlags_NoTaskBarIcon | ImGuiViewportFlags_NoDecoration);
-            if (window->Flags & ImGuiWindowFlags_Tooltip)
-                flags |= ImGuiViewportFlags_TopMost;
-            if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsNoTaskBarIcon) != 0 || (window->Flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
-                flags |= ImGuiViewportFlags_NoTaskBarIcon;
-            if ((g.IO.ConfigFlags & ImGuiConfigFlags_ViewportsDecoration) == 0 || (window->Flags & (ImGuiWindowFlags_ChildMenu | ImGuiWindowFlags_Tooltip | ImGuiWindowFlags_Popup)) != 0)
-                flags |= ImGuiViewportFlags_NoDecoration;
-            viewport->Flags = flags;
-        }
-
         // Create window
         bool is_new_platform_window = (viewport->PlatformWindowCreated == false);
         if (is_new_platform_window)

imgui.h

@@ -989,8 +989,8 @@ enum ImGuiConfigFlags_
     // 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_ViewportsNoMerge       = 1 << 12,  // All floating windows will always create their own viewport and platform window.
+    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_ViewportsDecoration    = 1 << 13,  // 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_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.
 
@@ -2217,11 +2217,11 @@ struct ImGuiPlatformIO
 enum ImGuiViewportFlags_
 {
     ImGuiViewportFlags_None                     = 0,
-    ImGuiViewportFlags_NoDecoration             = 1 << 0,   // Platform Window: Disable platform decorations: title bar, borders, etc.
+    ImGuiViewportFlags_NoDecoration             = 1 << 0,   // Platform Window: Disable platform decorations: title bar, borders, etc. (generally set all windows, but if ImGuiConfigFlags_ViewportsDecoration is set we only set this on popups/tooltips)
-    ImGuiViewportFlags_NoFocusOnAppearing       = 1 << 1,   // Platform Window: Don't take focus when created.
+    ImGuiViewportFlags_NoTaskBarIcon            = 1 << 1,   // Platform Window: Disable platform task bar icon (generally set on popups/tooltips, or all windows if ImGuiConfigFlags_ViewportsNoTaskBarIcon is set)
-    ImGuiViewportFlags_NoInputs                 = 1 << 2,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
+    ImGuiViewportFlags_NoFocusOnAppearing       = 1 << 2,   // Platform Window: Don't take focus when created.
-    ImGuiViewportFlags_NoTaskBarIcon            = 1 << 3,   // Platform Window: Disable platform task bar icon (for popups, menus, or all windows if ImGuiConfigFlags_ViewportsNoTaskBarIcons if set)
+    ImGuiViewportFlags_NoInputs                 = 1 << 3,   // Platform Window: Make mouse pass through so we can drag this window while peaking behind it.
-    ImGuiViewportFlags_NoRendererClear          = 1 << 4,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead.
+    ImGuiViewportFlags_NoRendererClear          = 1 << 4,   // Platform Window: Renderer doesn't need to clear the framebuffer ahead (because we will fill it entirely).
     ImGuiViewportFlags_TopMost                  = 1 << 5    // Platform Window: Display on top (for tooltips only)
 };
 

imgui_internal.h

@@ -665,7 +665,7 @@ struct ImGuiViewportP : public ImGuiViewport
     short               PlatformMonitor;
     bool                PlatformWindowCreated;
     bool                PlatformWindowMinimized;
-    ImGuiWindow*        Window;                   // Set when the viewport is owned by a window
+    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;
     ImDrawDataBuilder   DrawDataBuilder;