Tables: added ImGuiTableFlags_HighlightHoveredColumn.

docs/CHANGELOG.txt

@@ -94,6 +94,7 @@ Other changes:
 - Drag and Drop: Fixed submitting a tooltip from drop target location when using AcceptDragDropPayload()
   with ImGuiDragDropFlags_AcceptNoPreviewTooltip and submitting a tooltip manually.
 - TreeNode: Added ImGuiTreeNodeFlags_SpanAllColumns for use in tables. (#3151, #3565, #2451, #2438)
+- Tables: Added ImGuiTableFlags_HighlightHoveredColumn flag, currently highlighting column header.
 - Tables: Fixed an edge-case when no columns are visible + table scrollbar is visible + user
   code is always testing return value of TableSetColumnIndex() to coarse clip. With an active
   clipper it would have asserted. Without a clipper, the scrollbar range would be wrong.

imgui.h

@@ -1216,6 +1216,8 @@ enum ImGuiTableFlags_
     // Sorting
     ImGuiTableFlags_SortMulti                  = 1 << 26,  // Hold shift when clicking headers to sort on multiple column. TableGetSortSpecs() may return specs where (SpecsCount > 1).
     ImGuiTableFlags_SortTristate               = 1 << 27,  // Allow no sorting, disable default sorting. TableGetSortSpecs() may return specs where (SpecsCount == 0).
+    // Miscellaneous
+    ImGuiTableFlags_HighlightHoveredColumn     = 1 << 28,  // Highlight column headers when hovered (may evolve into a fuller highlight)
 
     // [Internal] Combinations and masks
     ImGuiTableFlags_SizingMask_                = ImGuiTableFlags_SizingFixedFit | ImGuiTableFlags_SizingFixedSame | ImGuiTableFlags_SizingStretchProp | ImGuiTableFlags_SizingStretchSame,

imgui_demo.cpp

@@ -3973,10 +3973,10 @@ static void ShowDemoWindowTables()
     ImGui::PushID("Tables");
 
     int open_action = -1;
-    if (ImGui::Button("Open all"))
+    if (ImGui::Button("Expand all"))
         open_action = 1;
     ImGui::SameLine();
-    if (ImGui::Button("Close all"))
+    if (ImGui::Button("Collapse all"))
         open_action = 0;
     ImGui::SameLine();
 
@@ -4262,6 +4262,7 @@ static void ShowDemoWindowTables()
         ImGui::CheckboxFlags("ImGuiTableFlags_Hideable", &flags, ImGuiTableFlags_Hideable);
         ImGui::CheckboxFlags("ImGuiTableFlags_NoBordersInBody", &flags, ImGuiTableFlags_NoBordersInBody);
         ImGui::CheckboxFlags("ImGuiTableFlags_NoBordersInBodyUntilResize", &flags, ImGuiTableFlags_NoBordersInBodyUntilResize); ImGui::SameLine(); HelpMarker("Disable vertical borders in columns Body until hovered for resize (borders will always appear in Headers)");
+        ImGui::CheckboxFlags("ImGuiTableFlags_HighlightHoveredColumn", &flags, ImGuiTableFlags_HighlightHoveredColumn);
         PopStyleCompact();
 
         if (ImGui::BeginTable("table1", 3, flags))
@@ -5299,6 +5300,7 @@ static void ShowDemoWindowTables()
         static ImGuiTableFlags flags = ImGuiTableFlags_Resizable | ImGuiTableFlags_Reorderable | ImGuiTableFlags_Hideable | ImGuiTableFlags_Borders | ImGuiTableFlags_SizingFixedFit | ImGuiTableFlags_NoSavedSettings;
         ImGui::CheckboxFlags("ImGuiTableFlags_ScrollY", &flags, ImGuiTableFlags_ScrollY);
         ImGui::CheckboxFlags("ImGuiTableFlags_SizingFixedFit", &flags, ImGuiTableFlags_SizingFixedFit);
+        ImGui::CheckboxFlags("ImGuiTableFlags_HighlightHoveredColumn", &flags, ImGuiTableFlags_HighlightHoveredColumn);
         for (int n = 0; n < 3; n++)
         {
             char buf[32];
@@ -5519,9 +5521,15 @@ static void ShowDemoWindowTables()
                 ImGui::TreePop();
             }
 
-            if (ImGui::TreeNodeEx("Other:", ImGuiTreeNodeFlags_DefaultOpen))
+            if (ImGui::TreeNodeEx("Headers:", ImGuiTreeNodeFlags_DefaultOpen))
             {
                 ImGui::Checkbox("show_headers", &show_headers);
+                ImGui::CheckboxFlags("ImGuiTableFlags_HighlightHoveredColumn", &flags, ImGuiTableFlags_HighlightHoveredColumn);
+                ImGui::TreePop();
+            }
+
+            if (ImGui::TreeNodeEx("Other:", ImGuiTreeNodeFlags_DefaultOpen))
+            {
                 ImGui::Checkbox("show_wrapped_text", &show_wrapped_text);
 
                 ImGui::DragFloat2("##OuterSize", &outer_size_value.x);

imgui_internal.h

@@ -2669,6 +2669,7 @@ struct ImGuiTableCellData
 };
 
 // Per-instance data that needs preserving across frames (seemingly most others do not need to be preserved aside from debug needs. Does that means they could be moved to ImGuiTableTempData?)
+// sizeof() ~ 24 bytes
 struct ImGuiTableInstanceData
 {
     ImGuiID                     TableInstanceID;
@@ -2754,6 +2755,7 @@ struct IMGUI_API ImGuiTable
     ImGuiTableColumnIdx         DeclColumnsCount;           // Count calls to TableSetupColumn()
     ImGuiTableColumnIdx         HoveredColumnBody;          // Index of column whose visible region is being hovered. Important: == ColumnsCount when hovering empty region after the right-most column!
     ImGuiTableColumnIdx         HoveredColumnBorder;        // Index of column whose right-border is being hovered (for resizing).
+    ImGuiTableColumnIdx         HighlightColumnHeader;      // Index of column which should be highlighted.
     ImGuiTableColumnIdx         AutoFitSingleColumn;        // Index of single column requesting auto-fit.
     ImGuiTableColumnIdx         ResizedColumn;              // Index of column being resized. Reset when InstanceCurrent==0.
     ImGuiTableColumnIdx         LastResizedColumn;          // Index of column being resized from previous frame.
@@ -2786,6 +2788,8 @@ struct IMGUI_API ImGuiTable
     bool                        IsResetDisplayOrderRequest;
     bool                        IsUnfrozenRows;             // Set when we got past the frozen row.
     bool                        IsDefaultSizingPolicy;      // Set if user didn't explicitly set a sizing policy in BeginTable()
+    bool                        IsActiveIdAliveBeforeTable;
+    bool                        IsActiveIdInTable;
     bool                        HasScrollbarYCurr;          // Whether ANY instance of this table had a vertical scrollbar during the current frame.
     bool                        HasScrollbarYPrev;          // Whether ANY instance of this table had a vertical scrollbar during the previous.
     bool                        MemoryCompacted;

imgui_tables.cpp

@@ -346,7 +346,8 @@ bool    ImGui::BeginTableEx(const char* name, ImGuiID id, int columns_count, ImG
     flags = TableFixFlags(flags, outer_window);
 
     // Initialize
-    const int instance_no = (table->LastFrameActive != g.FrameCount) ? 0 : table->InstanceCurrent + 1;
+    const int previous_frame_active = table->LastFrameActive;
+    const int instance_no = (previous_frame_active != g.FrameCount) ? 0 : table->InstanceCurrent + 1;
     table->ID = id;
     table->Flags = flags;
     table->LastFrameActive = g.FrameCount;
@@ -478,6 +479,8 @@ bool    ImGui::BeginTableEx(const char* name, ImGuiID id, int columns_count, ImG
     table->FreezeColumnsRequest = table->FreezeColumnsCount = 0;
     table->IsUnfrozenRows = true;
     table->DeclColumnsCount = 0;
+    if (previous_frame_active + 1 < g.FrameCount)
+        table->IsActiveIdInTable = false;
 
     // Using opaque colors facilitate overlapping lines of the grid, otherwise we'd need to improve TableDrawBorders()
     table->BorderColorStrong = GetColorU32(ImGuiCol_TableBorderStrong);
@@ -974,8 +977,7 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     ImGuiTableInstanceData* table_instance = TableGetInstanceData(table, table->InstanceCurrent);
     table_instance->HoveredRowLast = table_instance->HoveredRowNext;
     table_instance->HoveredRowNext = -1;
-    table->HoveredColumnBody = -1;
-    table->HoveredColumnBorder = -1;
+    table->HoveredColumnBody = table->HoveredColumnBorder = -1;
     const ImRect mouse_hit_rect(table->OuterRect.Min.x, table->OuterRect.Min.y, table->OuterRect.Max.x, ImMax(table->OuterRect.Max.y, table->OuterRect.Min.y + table_instance->LastOuterHeight));
     const ImGuiID backup_active_id = g.ActiveId;
     g.ActiveId = 0;
@@ -1122,13 +1124,13 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     // because of using _WidthAuto/_WidthStretch). This will hide the resizing option from the context menu.
     const float unused_x1 = ImMax(table->WorkRect.Min.x, table->Columns[table->RightMostEnabledColumn].ClipRect.Max.x);
     if (is_hovering_table && table->HoveredColumnBody == -1)
-    {
         if (g.IO.MousePos.x >= unused_x1)
             table->HoveredColumnBody = (ImGuiTableColumnIdx)table->ColumnsCount;
-    }
     if (has_resizable == false && (table->Flags & ImGuiTableFlags_Resizable))
         table->Flags &= ~ImGuiTableFlags_Resizable;
 
+    table->IsActiveIdAliveBeforeTable = (g.ActiveIdIsAlive != 0);
+
     // [Part 8] Lock actual OuterRect/WorkRect right-most position.
     // This is done late to handle the case of fixed-columns tables not claiming more widths that they need.
     // Because of this we are careful with uses of WorkRect and InnerClipRect before this point.
@@ -1161,6 +1163,14 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     table->IsLayoutLocked = true;
     table->IsUsingHeaders = false;
 
+    // Highlight header
+    table->HighlightColumnHeader = -1;
+    if (table->IsContextPopupOpen && table->ContextPopupColumn != -1 && table->InstanceInteracted == table->InstanceCurrent)
+        table->HighlightColumnHeader = table->ContextPopupColumn;
+    else if ((table->Flags & ImGuiTableFlags_HighlightHoveredColumn) && table->HoveredColumnBody != -1 && table->HoveredColumnBody != table->ColumnsCount && table->HoveredColumnBorder == -1)
+        if (g.ActiveId == 0 || (table->IsActiveIdInTable || g.DragDropActive))
+            table->HighlightColumnHeader = table->HoveredColumnBody;
+
     // [Part 11] Context menu
     if (TableBeginContextMenuPopup(table))
     {
@@ -1382,6 +1392,8 @@ void    ImGui::EndTable()
         table->ResizedColumnNextWidth = new_width;
     }
 
+    table->IsActiveIdInTable = (g.ActiveIdIsAlive != 0 && table->IsActiveIdAliveBeforeTable == false);
+
     // Pop from id stack
     IM_ASSERT_USER_ERROR(inner_window->IDStack.back() == table_instance->TableInstanceID, "Mismatching PushID/PopID!");
     IM_ASSERT_USER_ERROR(outer_window->DC.ItemWidthStack.Size >= temp_data->HostBackupItemWidthStackSize, "Too many PopItemWidth!");
@@ -2301,6 +2313,7 @@ void ImGui::TableUpdateColumnsWeightFromWidth(ImGuiTable* table)
 // - TablePopBackgroundChannel() [Internal]
 // - TableSetupDrawChannels() [Internal]
 // - TableMergeDrawChannels() [Internal]
+// - TableGetColumnBorderCol() [Internal]
 // - TableDrawBorders() [Internal]
 //-------------------------------------------------------------------------
 
@@ -2584,6 +2597,18 @@ void ImGui::TableMergeDrawChannels(ImGuiTable* table)
     }
 }
 
+static ImU32 TableGetColumnBorderCol(ImGuiTable* table, int order_n, int column_n)
+{
+    const bool is_hovered = (table->HoveredColumnBorder == column_n);
+    const bool is_resized = (table->ResizedColumn == column_n) && (table->InstanceInteracted == table->InstanceCurrent);
+    const bool is_frozen_separator = (table->FreezeColumnsCount == order_n + 1);
+    if (is_resized || is_hovered)
+        return ImGui::GetColorU32(is_resized ? ImGuiCol_SeparatorActive : ImGuiCol_SeparatorHovered);
+    if (is_frozen_separator || (table->Flags & (ImGuiTableFlags_NoBordersInBody | ImGuiTableFlags_NoBordersInBodyUntilResize)))
+        return table->BorderColorStrong;
+    return table->BorderColorLight;
+}
+
 // FIXME-TABLE: This is a mess, need to redesign how we render borders (as some are also done in TableEndRow)
 void ImGui::TableDrawBorders(ImGuiTable* table)
 {
@@ -2626,21 +2651,9 @@ void ImGui::TableDrawBorders(ImGuiTable* table)
 
             // Draw in outer window so right-most column won't be clipped
             // Always draw full height border when being resized/hovered, or on the delimitation of frozen column scrolling.
-            ImU32 col;
-            float draw_y2;
-            if (is_hovered || is_resized || is_frozen_separator)
-            {
-                draw_y2 = draw_y2_body;
-                col = is_resized ? GetColorU32(ImGuiCol_SeparatorActive) : is_hovered ? GetColorU32(ImGuiCol_SeparatorHovered) : table->BorderColorStrong;
-            }
-            else
-            {
-                draw_y2 = (table->Flags & (ImGuiTableFlags_NoBordersInBody | ImGuiTableFlags_NoBordersInBodyUntilResize)) ? draw_y2_head : draw_y2_body;
-                col = (table->Flags & (ImGuiTableFlags_NoBordersInBody | ImGuiTableFlags_NoBordersInBodyUntilResize)) ? table->BorderColorStrong : table->BorderColorLight;
-            }
-
+            float draw_y2 = (is_hovered || is_resized || is_frozen_separator || (table->Flags & (ImGuiTableFlags_NoBordersInBody | ImGuiTableFlags_NoBordersInBodyUntilResize)) == 0) ? draw_y2_body : draw_y2_head;
             if (draw_y2 > draw_y1)
-                inner_drawlist->AddLine(ImVec2(column->MaxX, draw_y1), ImVec2(column->MaxX, draw_y2), col, border_size);
+                inner_drawlist->AddLine(ImVec2(column->MaxX, draw_y1), ImVec2(column->MaxX, draw_y2), TableGetColumnBorderCol(table, order_n, column_n), border_size);
         }
     }
 
@@ -2994,7 +3007,6 @@ void ImGui::TableHeader(const char* label)
     column->ContentMaxXHeadersIdeal = ImMax(column->ContentMaxXHeadersIdeal, max_pos_x);
 
     // Keep header highlighted when context menu is open.
-    const bool selected = (table->IsContextPopupOpen && table->ContextPopupColumn == column_n && table->InstanceInteracted == table->InstanceCurrent);
     ImGuiID id = window->GetID(label);
     ImRect bb(cell_r.Min.x, cell_r.Min.y, cell_r.Max.x, ImMax(cell_r.Max.y, cell_r.Min.y + label_height + g.Style.CellPadding.y * 2.0f));
     ItemSize(ImVec2(0.0f, label_height)); // Don't declare unclipped width, it'll be fed ContentMaxPosHeadersIdeal
@@ -3005,9 +3017,10 @@ void ImGui::TableHeader(const char* label)
     //GetForegroundDrawList()->AddRect(bb.Min, bb.Max, IM_COL32(255, 0, 0, 255)); // [DEBUG]
 
     // Using AllowOverlap mode because we cover the whole cell, and we want user to be able to submit subsequent items.
+    const bool highlight = (table->HighlightColumnHeader == column_n);
     bool hovered, held;
     bool pressed = ButtonBehavior(bb, id, &hovered, &held, ImGuiButtonFlags_AllowOverlap);
-    if (held || hovered || selected)
+    if (held || hovered || highlight)
     {
         const ImU32 col = GetColorU32(held ? ImGuiCol_HeaderActive : hovered ? ImGuiCol_HeaderHovered : ImGuiCol_Header);
         //RenderFrame(bb.Min, bb.Max, col, false, 0.0f);