Tables: TableHeader() uses provided row min header rather than incremental one to allow multi-item multi-line in header cells. Demo TableHeader() - will caveat, comments.

imgui_demo.cpp

@@ -3940,6 +3940,54 @@ static void ShowDemoWindowTables()
         ImGui::TreePop();
     }
 
+    // Demonstrate using TableHeader() calls instead of TableAutoHeaders()
+    // FIXME-TABLE: Currently this doesn't get us feature-parity with TableAutoHeaders(), e.g. missing context menu.  Tables API needs some work! 
+    if (open_action != -1)
+        ImGui::SetNextItemOpen(open_action != 0);
+    if (ImGui::TreeNode("Custom headers"))
+    {
+        const int COLUMNS_COUNT = 3;
+        if (ImGui::BeginTable("##table1", COLUMNS_COUNT, ImGuiTableFlags_Borders | ImGuiTableFlags_Reorderable))
+        {
+            ImGui::TableSetupColumn("Apricot");
+            ImGui::TableSetupColumn("Banana");
+            ImGui::TableSetupColumn("Cherry");
+
+            // Dummy entire-column selection storage
+            // FIXME: It would be nice to actually demonstrate full-featured selection using those checkbox.
+            static bool column_selected[3] = {};
+
+            // Instead of calling TableAutoHeaders() we'll submit custom headers ourselves
+            ImGui::TableNextRow(ImGuiTableRowFlags_Headers);
+            for (int column = 0; column < COLUMNS_COUNT; column++)
+            {
+                ImGui::TableSetColumnIndex(column);
+                const char* column_name = ImGui::TableGetColumnName(column); // Retrieve name passed to TableSetupColumn()
+                ImGui::PushID(column);
+                ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(0, 0));
+                ImGui::Checkbox("##checkall", &column_selected[column]);
+                ImGui::PopStyleVar();
+                ImGui::SameLine(0.0f, ImGui::GetStyle().ItemInnerSpacing.x);
+                ImGui::TableHeader(column_name);
+                ImGui::PopID();
+            }
+
+            for (int row = 0; row < 5; row++)
+            {
+                ImGui::TableNextRow();
+                for (int column = 0; column < 3; column++)
+                {
+                    char buf[32];
+                    sprintf(buf, "Cell %d,%d", row, column);
+                    ImGui::TableSetColumnIndex(column);
+                    ImGui::Selectable(buf, column_selected[column]);
+                }
+            }
+            ImGui::EndTable();
+        }
+        ImGui::TreePop();
+    }
+
     static const char* template_items_names[] =
     {
         "Banana", "Apple", "Cherry", "Watermelon", "Grapefruit", "Strawberry", "Mango",

imgui_internal.h

@@ -1898,6 +1898,7 @@ struct ImGuiTable
     ImS16                       InstanceInteracted;         // Mark which instance (generally 0) of the same ID is being interacted with
     float                       RowPosY1;
     float                       RowPosY2;
+    float                       RowMinHeight;               // Height submitted to TableNextRow()
     float                       RowTextBaseline;
     ImGuiTableRowFlags          RowFlags : 16;              // Current row flags, see ImGuiTableRowFlags_
     ImGuiTableRowFlags          LastRowFlags : 16;

imgui_tables.cpp

@@ -1419,7 +1419,7 @@ void    ImGui::TableSetupColumn(const char* label, ImGuiTableColumnFlags flags,
 }
 
 // Starts into the first cell of a new row
-void    ImGui::TableNextRow(ImGuiTableRowFlags row_flags, float min_row_height)
+void    ImGui::TableNextRow(ImGuiTableRowFlags row_flags, float row_min_height)
 {
     ImGuiContext& g = *GImGui;
     ImGuiTable* table = g.CurrentTable;
@@ -1431,12 +1431,13 @@ void    ImGui::TableNextRow(ImGuiTableRowFlags row_flags, float min_row_height)
 
     table->LastRowFlags = table->RowFlags;
     table->RowFlags = row_flags;
+    table->RowMinHeight = row_min_height;
     TableBeginRow(table);
 
     // We honor min_row_height requested by user, but cannot guarantee per-row maximum height,
     // because that would essentially require a unique clipping rectangle per-cell.
     table->RowPosY2 += table->CellPaddingY * 2.0f;
-    table->RowPosY2 = ImMax(table->RowPosY2, table->RowPosY1 + min_row_height);
+    table->RowPosY2 = ImMax(table->RowPosY2, table->RowPosY1 + row_min_height);
 
     TableBeginCell(table, 0);
 }
@@ -1937,6 +1938,7 @@ void    ImGui::TableAutoHeaders()
 
 // Emit a column header (text + optional sort order)
 // We cpu-clip text here so that all columns headers can be merged into a same draw call.
+// Note that because of how we cpu-clip and display sorting indicators, you _cannot_ use SameLine() after a TableHeader()
 // FIXME-TABLE: Should hold a selection state.
 // FIXME-TABLE: Style confusion between CellPadding.y and FramePadding.y
 void    ImGui::TableHeader(const char* label)
@@ -1961,7 +1963,7 @@ void    ImGui::TableHeader(const char* label)
 
     // If we already got a row height, there's use that.
     ImRect cell_r = TableGetCellRect();
-    float label_height = ImMax(label_size.y, cell_r.GetHeight() - g.Style.CellPadding.y * 2.0f);
+    float label_height = ImMax(label_size.y, table->RowMinHeight - g.Style.CellPadding.y * 2.0f);
 
     //GetForegroundDrawList()->AddRect(cell_r.Min, cell_r.Max, IM_COL32(255, 0, 0, 255)); // [DEBUG]
     ImRect work_r = cell_r;