Docking: docked window honor tab and text colors by storing them. (#2771)

Later to lead into #2700 and #2539
Move tab submission block above in DockNodeUpdateTabBar(), not strictly necessary for this change as is, but useful if needing to apply override for TitleBg* as we'd need a value for node->VisibleWindow earlier than currently set.

imgui.cpp

@@ -2488,6 +2488,11 @@ struct ImGuiStyleVarInfo
     void*           GetVarPtr(ImGuiStyle* style) const { return (void*)((unsigned char*)style + Offset); }
 };
 
+static const ImGuiCol GWindowDockStyleColors[ImGuiWindowDockStyleCol_COUNT] =
+{
+    ImGuiCol_Text, ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive
+};
+
 static const ImGuiStyleVarInfo GStyleVarInfo[] =
 {
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, Alpha) },               // ImGuiStyleVar_Alpha
@@ -4059,7 +4064,7 @@ void ImGui::NewFrame()
 
     // Undocking
     // (needs to be before UpdateMouseMovingWindowNewFrame so the window is already offset and following the mouse on the detaching frame)
-    DockContextUpdateUndocking(&g);
+    DockContextNewFrameUpdateUndocking(&g);
 
     // Find hovered window
     // (needs to be before UpdateMouseMovingWindowNewFrame so we fill g.HoveredWindowUnderMovingWindow on the mouse release frame)
@@ -4123,7 +4128,7 @@ void ImGui::NewFrame()
     ClosePopupsOverWindow(g.NavWindow, false);
 
     // Docking
-    DockContextUpdateDocking(&g);
+    DockContextNewFrameUpdateDocking(&g);
 
     // [DEBUG] Item picker tool - start with DebugStartItemPicker() - useful to visually select an item and break into its call-stack.
     UpdateDebugToolItemPicker();
@@ -11934,10 +11939,10 @@ void ImGui::DestroyPlatformWindows()
 // Typical Docking call flow: (root level is generally public API):
 //-----------------------------------------------------------------------------
 // - NewFrame()                               new dear imgui frame
-//    | DockContextUpdateUndocking()          - process queued undocking requests
+//    | DockContextNewFrameUpdateUndocking()  - process queued undocking requests
 //    | - DockContextProcessUndockWindow()    - process one window undocking request
 //    | - DockContextProcessUndockNode()      - process one whole node undocking request
-//    | DockContextUpdateDocking()            - process queue docking requests, create floating dock nodes
+//    | DockContextNewFrameUpdateUndocking()  - process queue docking requests, create floating dock nodes
 //    | - update g.HoveredDockNode            - [debug] update node hovered by mouse
 //    | - DockContextProcessDock()            - process one docking request
 //    | - DockNodeUpdate()
@@ -12124,8 +12129,8 @@ namespace ImGui
 // - DockContextShutdown()
 // - DockContextClearNodes()
 // - DockContextRebuildNodes()
-// - DockContextUpdateUndocking()
+// - DockContextNewFrameUpdateUndocking()
-// - DockContextUpdateDocking()
+// - DockContextNewFrameUpdateDocking()
 // - DockContextFindNodeByID()
 // - DockContextBindNodeToWindow()
 // - DockContextGenNodeID()
@@ -12184,7 +12189,7 @@ void ImGui::DockContextRebuildNodes(ImGuiContext* ctx)
 }
 
 // Docking context update function, called by NewFrame()
-void ImGui::DockContextUpdateUndocking(ImGuiContext* ctx)
+void ImGui::DockContextNewFrameUpdateUndocking(ImGuiContext* ctx)
 {
     ImGuiContext& g = *ctx;
     ImGuiDockContext* dc  = &ctx->DockContext;
@@ -12228,7 +12233,7 @@ void ImGui::DockContextUpdateUndocking(ImGuiContext* ctx)
 }
 
 // Docking context update function, called by NewFrame()
-void ImGui::DockContextUpdateDocking(ImGuiContext* ctx)
+void ImGui::DockContextNewFrameUpdateDocking(ImGuiContext* ctx)
 {
     ImGuiContext& g = *ctx;
     ImGuiDockContext* dc  = &ctx->DockContext;
@@ -13321,8 +13326,8 @@ static void ImGui::DockNodeUpdate(ImGuiDockNode* node)
         if (g.NavWindow && g.NavWindow->RootWindowDockStop->DockNode && g.NavWindow->RootWindowDockStop->ParentWindow == host_window)
             node->LastFocusedNodeId = g.NavWindow->RootWindowDockStop->DockNode->ID;
 
-    // We need to draw a background at the root level if requested by ImGuiDockNodeFlags_PassthruCentralNode, but we will only know the correct pos/size after
+    // We need to draw a background at the root level if requested by ImGuiDockNodeFlags_PassthruCentralNode, but we will only know the correct pos/size
-    // processing the resizing splitters. So we are using the DrawList channel splitting facility to submit drawing primitives out of order!
+    // _after_ processing the resizing splitters. So we are using the DrawList channel splitting facility to submit drawing primitives out of order!
     const bool render_dockspace_bg = node->IsRootNode() && host_window && (node_flags & ImGuiDockNodeFlags_PassthruCentralNode) != 0;
     if (render_dockspace_bg)
     {
@@ -13561,6 +13566,17 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
     ImVec2 window_menu_button_pos;
     DockNodeCalcTabBarLayout(node, &title_bar_rect, &tab_bar_rect, &window_menu_button_pos);
 
+    // Submit new tabs and apply NavWindow focus back to the tab bar. They will be added as Unsorted and sorted below based on relative DockOrder value.
+    const int tabs_count_old = tab_bar->Tabs.Size;
+    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
+    {
+        ImGuiWindow* window = node->Windows[window_n];
+        if (g.NavWindow && g.NavWindow->RootWindowDockStop == window)
+            tab_bar->SelectedTabId = window->ID;
+        if (TabBarFindTabByID(tab_bar, window->ID) == NULL)
+            TabBarAddTab(tab_bar, ImGuiTabItemFlags_Unsorted, window);
+    }
+
     // Title bar
     if (is_focused)
         node->LastFrameFocused = g.FrameCount;
@@ -13576,17 +13592,6 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
             focus_tab_id = tab_bar->SelectedTabId;
     }
 
-    // Submit new tabs and apply NavWindow focus back to the tab bar. They will be added as Unsorted and sorted below based on relative DockOrder value.
-    const int tabs_count_old = tab_bar->Tabs.Size;
-    for (int window_n = 0; window_n < node->Windows.Size; window_n++)
-    {
-        ImGuiWindow* window = node->Windows[window_n];
-        if (g.NavWindow && g.NavWindow->RootWindowDockStop == window)
-            tab_bar->SelectedTabId = window->ID;
-        if (TabBarFindTabByID(tab_bar, window->ID) == NULL)
-            TabBarAddTab(tab_bar, ImGuiTabItemFlags_Unsorted, window);
-    }
-
     // If multiple tabs are appearing on the same frame, sort them based on their persistent DockOrder value
     int tabs_unsorted_start = tab_bar->Tabs.Size;
     for (int tab_n = tab_bar->Tabs.Size - 1; tab_n >= 0 && (tab_bar->Tabs[tab_n].Flags & ImGuiTabItemFlags_Unsorted); tab_n--)
@@ -13618,6 +13623,11 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
     BeginTabBarEx(tab_bar, tab_bar_rect, tab_bar_flags, node);
     //host_window->DrawList->AddRect(tab_bar_rect.Min, tab_bar_rect.Max, IM_COL32(255,0,255,255));
 
+    // Backup style colors
+    ImVec4 backup_style_cols[ImGuiWindowDockStyleCol_COUNT];
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        backup_style_cols[color_n] = g.Style.Colors[GWindowDockStyleColors[color_n]];
+
     // Submit actual tabs
     node->VisibleWindow = NULL;
     for (int window_n = 0; window_n < node->Windows.Size; window_n++)
@@ -13634,6 +13644,10 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
             if (tab_bar->Flags & ImGuiTabBarFlags_NoCloseWithMiddleMouseButton)
                 tab_item_flags |= ImGuiTabItemFlags_NoCloseWithMiddleMouseButton;
 
+            // Apply stored style overrides for the window
+            for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+                g.Style.Colors[GWindowDockStyleColors[color_n]] = ColorConvertU32ToFloat4(window->DockStyle.Colors[color_n]);
+
             bool tab_open = true;
             TabItemEx(tab_bar, window->Name, window->HasCloseButton ? &tab_open : NULL, tab_item_flags, window);
             if (!tab_open)
@@ -13651,6 +13665,10 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
         }
     }
 
+    // Restore style colors
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        g.Style.Colors[GWindowDockStyleColors[color_n]] = backup_style_cols[color_n];
+
     // Notify root of visible window (used to display title in OS task bar)
     if (node->VisibleWindow)
         if (is_focused || root_node->VisibleWindow == NULL)
@@ -13999,7 +14017,6 @@ static void ImGui::DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDock
         overlay_draw_lists[overlay_draw_lists_count++] = GetForegroundDrawList(root_payload->Viewport);
 
     // Draw main preview rectangle
-    const ImU32 overlay_col_tabs = GetColorU32(ImGuiCol_TabActive);
     const ImU32 overlay_col_main = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.60f : 0.40f);
     const ImU32 overlay_col_drop = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 0.90f : 0.70f);
     const ImU32 overlay_col_drop_hovered = GetColorU32(ImGuiCol_DockingPreview, is_transparent_payload ? 1.20f : 1.00f);
@@ -14054,6 +14071,9 @@ static void ImGui::DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDock
             ImVec2 tab_size = TabItemCalcSize(payload_window->Name, payload_window->HasCloseButton);
             ImRect tab_bb(tab_pos.x, tab_pos.y, tab_pos.x + tab_size.x, tab_pos.y + tab_size.y);
             tab_pos.x += tab_size.x + g.Style.ItemInnerSpacing.x;
+            const ImU32 overlay_col_text = GetColorU32(payload_window->DockStyle.Colors[ImGuiWindowDockStyleCol_Text]);
+            const ImU32 overlay_col_tabs = GetColorU32(payload_window->DockStyle.Colors[ImGuiWindowDockStyleCol_TabActive]);
+            PushStyleColor(ImGuiCol_Text, overlay_col_text);
             for (int overlay_n = 0; overlay_n < overlay_draw_lists_count; overlay_n++)
             {
                 ImGuiTabItemFlags tab_flags = ImGuiTabItemFlags_Preview | ((payload_window->Flags & ImGuiWindowFlags_UnsavedDocument) ? ImGuiTabItemFlags_UnsavedDocument : 0);
@@ -14064,6 +14084,7 @@ static void ImGui::DockNodePreviewDockRender(ImGuiWindow* host_window, ImGuiDock
                 if (!tab_bar_rect.Contains(tab_bb))
                     overlay_draw_lists[overlay_n]->PopClipRect();
             }
+            PopStyleColor();
         }
     }
 
@@ -15142,7 +15163,7 @@ void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
     // Note how we are testing for LastFrameAlive and NOT LastFrameActive. A DockSpace node can be maintained alive while being inactive with ImGuiDockNodeFlags_KeepAliveOnly.
     if (node->LastFrameAlive < g.FrameCount)
     {
-        // If the window has been orphaned, transition the docknode to an implicit node processed in DockContextUpdateDocking()
+        // If the window has been orphaned, transition the docknode to an implicit node processed in DockContextNewFrameUpdateDocking()
         ImGuiDockNode* root_node = DockNodeGetRootNode(node);
         if (root_node->LastFrameAlive < g.FrameCount)
         {
@@ -15156,6 +15177,10 @@ void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
         return;
     }
 
+    // Store style overrides
+    for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+        window->DockStyle.Colors[color_n] = ColorConvertFloat4ToU32(g.Style.Colors[GWindowDockStyleColors[color_n]]);
+
     // Fast path return. It is common for windows to hold on a persistent DockId but be the only visible window,
     // and never create neither a host window neither a tab bar.
     // FIXME-DOCK: replace ->HostWindow NULL compare with something more explicit (~was initially intended as a first frame test)
@@ -15227,6 +15252,10 @@ void ImGui::BeginDockableDragDropSource(ImGuiWindow* window)
     {
         SetDragDropPayload(IMGUI_PAYLOAD_TYPE_WINDOW, &window, sizeof(window));
         EndDragDropSource();
+
+        // Store style overrides
+        for (int color_n = 0; color_n < ImGuiWindowDockStyleCol_COUNT; color_n++)
+            window->DockStyle.Colors[color_n] = ColorConvertFloat4ToU32(g.Style.Colors[GWindowDockStyleColors[color_n]]);
     }
 }
 

imgui_internal.h

@@ -1247,6 +1247,26 @@ struct ImGuiDockNode
     ImRect                  Rect() const            { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
 };
 
+// List of colors that are stored at the time of Begin() into Docked Windows.
+// We currently store the packed colors in a simple array window->DockStyle.Colors[].
+// A better solution may involve appending into a log of colors in ImGuiContext + store offsets into those arrays in ImGuiWindow,
+// but it would be more complex as we'd need to double-buffer both as e.g. drop target may refer to window from last frame.
+enum ImGuiWindowDockStyleCol
+{
+    ImGuiWindowDockStyleCol_Text,
+    ImGuiWindowDockStyleCol_Tab,
+    ImGuiWindowDockStyleCol_TabHovered,
+    ImGuiWindowDockStyleCol_TabActive,
+    ImGuiWindowDockStyleCol_TabUnfocused,
+    ImGuiWindowDockStyleCol_TabUnfocusedActive,
+    ImGuiWindowDockStyleCol_COUNT
+};
+
+struct ImGuiWindowDockStyle
+{
+    ImU32 Colors[ImGuiWindowDockStyleCol_COUNT];
+};
+
 struct ImGuiDockContext
 {
     ImGuiStorage                    Nodes;          // Map ID -> ImGuiDockNode*: Active nodes
@@ -1970,15 +1990,16 @@ struct IMGUI_API ImGuiWindow
     bool                    MemoryCompacted;                    // Set when window extraneous data have been garbage collected
 
     // Docking
+    bool                    DockIsActive        :1;             // When docking artifacts are actually visible. When this is set, DockNode is guaranteed to be != NULL. ~~ (DockNode != NULL) && (DockNode->Windows.Size > 1).
+    bool                    DockTabIsVisible    :1;             // Is our window visible this frame? ~~ is the corresponding tab selected?
+    bool                    DockTabWantClose    :1;
+    short                   DockOrder;                          // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
+    ImGuiWindowDockStyle    DockStyle;
     ImGuiDockNode*          DockNode;                           // Which node are we docked into. Important: Prefer testing DockIsActive in many cases as this will still be set when the dock node is hidden.
     ImGuiDockNode*          DockNodeAsHost;                     // Which node are we owning (for parent windows)
     ImGuiID                 DockId;                             // Backup of last valid DockNode->ID, so single window remember their dock node id even when they are not bound any more
     ImGuiItemStatusFlags    DockTabItemStatusFlags;
     ImRect                  DockTabItemRect;
-    short                   DockOrder;                          // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.
-    bool                    DockIsActive        :1;             // When docking artifacts are actually visible. When this is set, DockNode is guaranteed to be != NULL. ~~ (DockNode != NULL) && (DockNode->Windows.Size > 1).
-    bool                    DockTabIsVisible    :1;             // Is our window visible this frame? ~~ is the corresponding tab selected?
-    bool                    DockTabWantClose    :1;
 
 public:
     ImGuiWindow(ImGuiContext* context, const char* name);
@@ -2504,8 +2525,8 @@ namespace ImGui
     IMGUI_API void          DockContextShutdown(ImGuiContext* ctx);
     IMGUI_API void          DockContextClearNodes(ImGuiContext* ctx, ImGuiID root_id, bool clear_settings_refs); // Use root_id==0 to clear all
     IMGUI_API void          DockContextRebuildNodes(ImGuiContext* ctx);
-    IMGUI_API void          DockContextUpdateUndocking(ImGuiContext* ctx);
+    IMGUI_API void          DockContextNewFrameUpdateUndocking(ImGuiContext* ctx);
-    IMGUI_API void          DockContextUpdateDocking(ImGuiContext* ctx);
+    IMGUI_API void          DockContextNewFrameUpdateDocking(ImGuiContext* ctx);
     IMGUI_API ImGuiID       DockContextGenNodeID(ImGuiContext* ctx);
     IMGUI_API void          DockContextQueueDock(ImGuiContext* ctx, ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, float split_ratio, bool split_outer);
     IMGUI_API void          DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window);