Tables: fixed an issue where ideal size reported to parent container wouldn't correctly take account of inner scrollbar. (#7651)

docs/CHANGELOG.txt

@@ -49,6 +49,9 @@ Other changes:
   grab scrolls by one page, holding mouse button repeats scrolling. (#7328, #150)
 - Scrollbar: fixed miscalculation of vertical scrollbar visibility when required
   solely by the presence of an horizontal scrollbar. (#1574)
+- Tables: fixed an issue where ideal size reported to parent container wouldn't
+  correctly take account of inner scrollbar, affecting potential auto-resize of
+  parent container. (#7651)
 - Tables: fixed a bug where after disabling the ScrollY flag for a table,
   previous scrollbar width would be accounted for. (#5920)
 - Combo: simplified Combo() API uses a list clipper (due to its api it wasn't

imgui_tables.cpp

@@ -1491,10 +1491,13 @@ void    ImGui::EndTable()
     }
     else if (temp_data->UserOuterSize.x <= 0.0f)
     {
+        // Some references for this: #7651 + tests "table_reported_size", "table_reported_size_outer" equivalent Y block
+        // - Checking for ImGuiTableFlags_ScrollX/ScrollY flag makes us a frame ahead when disabling those flags.
+        // - FIXME-TABLE: Would make sense to pre-compute expected scrollbar visibility/sizes to generally save a frame of feedback.
         const float inner_content_max_x = table->OuterRect.Min.x + table->ColumnsAutoFitWidth; // Slightly misleading name but used for code symmetry with inner_content_max_y
-        const float decoration_size = table->TempData->AngledHeadersExtraWidth + ((table->Flags & ImGuiTableFlags_ScrollX) ? inner_window->ScrollbarSizes.x : 0.0f);
+        const float decoration_size = table->TempData->AngledHeadersExtraWidth + ((table->Flags & ImGuiTableFlags_ScrollY) ? inner_window->ScrollbarSizes.x : 0.0f);
         outer_window->DC.IdealMaxPos.x = ImMax(outer_window->DC.IdealMaxPos.x, inner_content_max_x + decoration_size - temp_data->UserOuterSize.x);
-        outer_window->DC.CursorMaxPos.x = ImMax(backup_outer_max_pos.x, ImMin(table->OuterRect.Max.x, inner_content_max_x));
+        outer_window->DC.CursorMaxPos.x = ImMax(backup_outer_max_pos.x, ImMin(table->OuterRect.Max.x, inner_content_max_x + decoration_size));
     }
     else
     {
@@ -1502,9 +1505,9 @@ void    ImGui::EndTable()
     }
     if (temp_data->UserOuterSize.y <= 0.0f)
     {
-        const float decoration_size = (table->Flags & ImGuiTableFlags_ScrollY) ? inner_window->ScrollbarSizes.y : 0.0f;
+        const float decoration_size = (table->Flags & ImGuiTableFlags_ScrollX) ? inner_window->ScrollbarSizes.y : 0.0f;
         outer_window->DC.IdealMaxPos.y = ImMax(outer_window->DC.IdealMaxPos.y, inner_content_max_y + decoration_size - temp_data->UserOuterSize.y);
-        outer_window->DC.CursorMaxPos.y = ImMax(backup_outer_max_pos.y, ImMin(table->OuterRect.Max.y, inner_content_max_y));
+        outer_window->DC.CursorMaxPos.y = ImMax(backup_outer_max_pos.y, ImMin(table->OuterRect.Max.y, inner_content_max_y + decoration_size));
     }
     else
     {