Reworked modal/ctrl+tab dimming system to be entirely processed at end of the frame (backported 1dc3af3 from docking)

Author: ocornut

Diff for: imgui.cpp

@@ -946,7 +946,8 @@ static bool             UpdateWindowManualResize(ImGuiWindow* window, const ImVe
 static void             RenderWindowOuterBorders(ImGuiWindow* window);
 static void             RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size);
 static void             RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open);
-static void             EndFrameDrawDimmedBackgrounds();
+static void             RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32 col);
+static void             RenderDimmedBackgrounds();
 
 // Viewports
 static void             UpdateViewportsNewFrame();
@@ -4442,9 +4443,58 @@ void ImGui::PopClipRect()
     window->ClipRect = window->DrawList->_ClipRectStack.back();
 }
 
-static void ImGui::EndFrameDrawDimmedBackgrounds()
+static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32 col)
 {
-    // (This is currently empty, left here to facilitate sync/merge with docking branch)
+    if ((col & IM_COL32_A_MASK) == 0)
+        return;
+
+    ImGuiViewportP* viewport = (ImGuiViewportP*)GetMainViewport();
+    ImRect viewport_rect = viewport->GetMainRect();
+
+    // Draw behind window by moving the draw command at the FRONT of the draw list
+    {
+        ImDrawList* draw_list = window->RootWindow->DrawList;
+        draw_list->AddDrawCmd();
+        draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // Ensure ImDrawCmd are not merged
+        draw_list->AddRectFilled(viewport_rect.Min, viewport_rect.Max, col);
+        ImDrawCmd cmd = draw_list->CmdBuffer.back();
+        IM_ASSERT(cmd.ElemCount == 6);
+        draw_list->CmdBuffer.pop_back();
+        draw_list->CmdBuffer.push_front(cmd);
+    }
+}
+
+static void ImGui::RenderDimmedBackgrounds()
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* modal_window = GetTopMostAndVisiblePopupModal();
+    const bool dim_bg_for_modal = (modal_window != NULL);
+    const bool dim_bg_for_window_list = (g.NavWindowingTargetAnim != NULL && g.NavWindowingTargetAnim->Active);
+    if (!dim_bg_for_modal && !dim_bg_for_window_list)
+        return;
+
+    if (dim_bg_for_modal)
+    {
+        // Draw dimming behind modal
+        RenderDimmedBackgroundBehindWindow(modal_window, GetColorU32(ImGuiCol_ModalWindowDimBg, g.DimBgRatio));
+    }
+    else if (dim_bg_for_window_list)
+    {
+        // Draw dimming behind CTRL+Tab target window
+        RenderDimmedBackgroundBehindWindow(g.NavWindowingTargetAnim, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
+
+        // Draw border around CTRL+Tab target window
+        ImGuiWindow* window = g.NavWindowingTargetAnim;
+        ImGuiViewport* viewport = GetMainViewport();
+        float distance = g.FontSize;
+        ImRect bb = window->Rect();
+        bb.Expand(distance);
+        if (bb.GetWidth() >= viewport->Size.x && bb.GetHeight() >= viewport->Size.y)
+            bb.Expand(-distance - 1.0f); // If a window fits the entire viewport, adjust its highlight inward
+        window->DrawList->PushClipRect(viewport->Pos, viewport->Pos + viewport->Size);
+        window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha), window->WindowRounding, 0, 3.0f);
+        window->DrawList->PopClipRect();
+    }
 }
 
 // This is normally called by Render(). You may want to call it directly if you want to avoid calling Render() but the gain will be very minimal.
@@ -4502,9 +4552,6 @@ void ImGui::EndFrame()
     // Initiate moving window + handle left-click and right-click focus
     UpdateMouseMovingWindowEndFrame();
 
-    // Draw modal/window whitening backgrounds
-    EndFrameDrawDimmedBackgrounds();
-
     // Sort the window list so that all child windows are after their parent
     // We cannot do that on FocusWindow() because children may not exist yet
     g.WindowsTempSortBuffer.resize(0);
@@ -4574,6 +4621,10 @@ void ImGui::Render()
         if (windows_to_render_top_most[n] && IsWindowActiveAndVisible(windows_to_render_top_most[n])) // NavWindowingTarget is always temporarily displayed as the top-most window
             AddRootWindowToDrawData(windows_to_render_top_most[n]);
 
+    // Draw modal/window whitening backgrounds
+    if (first_render_of_frame)
+        RenderDimmedBackgrounds();
+
     // Setup ImDrawData structures for end-user
     g.IO.MetricsRenderVertices = g.IO.MetricsRenderIndices = 0;
     for (int n = 0; n < g.Viewports.Size; n++)
@@ -6248,24 +6299,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->DrawList->PushTextureID(g.Font->ContainerAtlas->TexID);
         PushClipRect(host_rect.Min, host_rect.Max, false);
 
-        // Draw modal window background (darkens what is behind them, all viewports)
-        const bool dim_bg_for_modal = (flags & ImGuiWindowFlags_Modal) && window == GetTopMostPopupModal() && window->HiddenFramesCannotSkipItems <= 0;
-        const bool dim_bg_for_window_list = g.NavWindowingTargetAnim && (window == g.NavWindowingTargetAnim->RootWindow);
-        if (dim_bg_for_modal || dim_bg_for_window_list)
-        {
-            const ImU32 dim_bg_col = GetColorU32(dim_bg_for_modal ? ImGuiCol_ModalWindowDimBg : ImGuiCol_NavWindowingDimBg, g.DimBgRatio);
-            window->DrawList->AddRectFilled(viewport_rect.Min, viewport_rect.Max, dim_bg_col);
-        }
-
-        // Draw navigation selection/windowing rectangle background
-        if (dim_bg_for_window_list && window == g.NavWindowingTargetAnim)
-        {
-            ImRect bb = window->Rect();
-            bb.Expand(g.FontSize);
-            if (!bb.Contains(viewport_rect)) // Avoid drawing if the window covers all the viewport anyway
-                window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha * 0.25f), g.Style.WindowRounding);
-        }
-
         // Child windows can render their decoration (bg color, border, scrollbars, etc.) within their parent to save a draw call (since 1.71)
         // When using overlapping child windows, this will break the assumption that child z-order is mapped to submission order.
         // FIXME: User code may rely on explicit sorting of overlapping child window and would need to disable this somehow. Please get in contact if you are affected (github #4493)
@@ -6293,20 +6326,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 window->DrawList = &window->DrawListInst;
         }
 
-        // Draw navigation selection/windowing rectangle border
-        if (g.NavWindowingTargetAnim == window)
-        {
-            float rounding = ImMax(window->WindowRounding, g.Style.WindowRounding);
-            ImRect bb = window->Rect();
-            bb.Expand(g.FontSize);
-            if (bb.Contains(viewport_rect)) // If a window fits the entire viewport, adjust its highlight inward
-            {
-                bb.Expand(-g.FontSize - 1.0f);
-                rounding = window->WindowRounding;
-            }
-            window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_NavWindowingHighlight, g.NavWindowingHighlightAlpha), rounding, 0, 3.0f);
-        }
-
         // UPDATE RECTANGLES (2- THOSE AFFECTED BY SCROLLING)
 
         // Work rectangle.
@@ -8363,6 +8382,16 @@ ImGuiWindow* ImGui::GetTopMostPopupModal()
     return NULL;
 }
 
+ImGuiWindow* ImGui::GetTopMostAndVisiblePopupModal()
+{
+    ImGuiContext& g = *GImGui;
+    for (int n = g.OpenPopupStack.Size - 1; n >= 0; n--)
+        if (ImGuiWindow* popup = g.OpenPopupStack.Data[n].Window)
+            if ((popup->Flags & ImGuiWindowFlags_Modal) && IsWindowActiveAndVisible(popup))
+                return popup;
+    return NULL;
+}
+
 void ImGui::OpenPopup(const char* str_id, ImGuiPopupFlags popup_flags)
 {
     ImGuiContext& g = *GImGui;

Diff for: imgui.h

@@ -64,7 +64,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.86 WIP"
-#define IMGUI_VERSION_NUM           18513
+#define IMGUI_VERSION_NUM           18514
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 #define IMGUI_HAS_TABLE
 

Diff for: imgui_internal.h

@@ -2539,6 +2539,7 @@ namespace ImGui
     IMGUI_API void          BeginTooltipEx(ImGuiTooltipFlags tooltip_flags, ImGuiWindowFlags extra_window_flags);
     IMGUI_API ImRect        GetPopupAllowedExtentRect(ImGuiWindow* window);
     IMGUI_API ImGuiWindow*  GetTopMostPopupModal();
+    IMGUI_API ImGuiWindow*  GetTopMostAndVisiblePopupModal();
     IMGUI_API ImVec2        FindBestWindowPosForPopup(ImGuiWindow* window);
     IMGUI_API ImVec2        FindBestWindowPosForPopupEx(const ImVec2& ref_pos, const ImVec2& size, ImGuiDir* last_dir, const ImRect& r_outer, const ImRect& r_avoid, ImGuiPopupPositionPolicy policy);