Tables: internal tidying up, calculate WidthAuto in first loop of layout + TableSetupColumn() with unspecified stretch weight leaves it at -1.0f (unset) rather than overrding default. Amend 3b3503e.

Both changes are intended to have no side-effects. Committed separately from upcoming commit for easier future bissecting.
Small demo fix.

imgui.h

@@ -664,7 +664,7 @@ namespace ImGui
     // - 1. Call BeginTable()
     // - 2. Optionally call TableSetupColumn() to submit column name/flags/defaults
     // - 3. Optionally call TableSetupScrollFreeze() to request scroll freezing of columns/rows
-    // - 4. Optionally call TableHeadersRow() to submit a header row (names will be pulled from data submitted to TableSetupColumns)
+    // - 4. Optionally call TableHeadersRow() to submit a header row. Names will be pulled from data provided TableSetupColumn() calls)
     // - 5. Populate contents
     //    - In most situations you can use TableNextRow() + TableSetColumnIndex(N) to start appending into a column.
     //    - If you are using tables as a sort of grid, where every columns is holding the same type of contents,

imgui_demo.cpp

@@ -4080,15 +4080,15 @@ static void ShowDemoWindowTables()
         static int column_count = 3;
 
         PushStyleCompact();
-        ImGui::SetNextItemWidth(TEXT_BASE_WIDTH * 22);
+        ImGui::PushItemWidth(TEXT_BASE_WIDTH * 30);
         ImGui::Combo("Contents", &contents_type, "Short Text\0Long Text\0Button\0Fill Button\0InputText\0");
         if (contents_type == CT_FillButton)
         {
             ImGui::SameLine();
             HelpMarker("Be mindful that using right-alignment (e.g. size.x = -FLT_MIN) creates a feedback loop where contents width can feed into auto-column width can feed into contents width.");
         }
-        ImGui::SetNextItemWidth(TEXT_BASE_WIDTH * 22);
         ImGui::DragInt("Columns", &column_count, 0.1f, 1, 64, "%d", ImGuiSliderFlags_AlwaysClamp);
+        ImGui::PopItemWidth();
         ImGui::CheckboxFlags("ImGuiTableFlags_BordersInnerH", &flags, ImGuiTableFlags_BordersInnerH);
         ImGui::CheckboxFlags("ImGuiTableFlags_BordersOuterH", &flags, ImGuiTableFlags_BordersOuterH);
         ImGui::CheckboxFlags("ImGuiTableFlags_BordersInnerV", &flags, ImGuiTableFlags_BordersInnerV);
@@ -4181,13 +4181,14 @@ static void ShowDemoWindowTables()
         static float inner_width = 1000.0f;
         PushStyleCompact();
         ImGui::PushID("flags3");
+        ImGui::PushItemWidth(TEXT_BASE_WIDTH * 30);
         ImGui::CheckboxFlags("ImGuiTableFlags_ScrollX", &flags3, ImGuiTableFlags_ScrollX);
         if (ImGui::CheckboxFlags("ImGuiTableFlags_SizingPolicyStretch", &flags3, ImGuiTableFlags_SizingPolicyStretch))
             flags3 &= ~ImGuiTableFlags_SizingPolicyFixed;      // Can't specify both sizing polices so we clear the other
         if (ImGui::CheckboxFlags("ImGuiTableFlags_SizingPolicyFixed", &flags3, ImGuiTableFlags_SizingPolicyFixed))
             flags3 &= ~ImGuiTableFlags_SizingPolicyStretch;    // Can't specify both sizing polices so we clear the other
-        ImGui::SetNextItemWidth(TEXT_BASE_WIDTH * 10.0f);
         ImGui::DragFloat("inner_width", &inner_width, 1.0f, 0.0f, FLT_MAX, "%.1f");
+        ImGui::PopItemWidth();
         ImGui::PopID();
         PopStyleCompact();
         if (ImGui::BeginTable("##table3", 7, flags3 | ImGuiTableFlags_SizingPolicyStretch | ImGuiTableFlags_ContextMenuInBody, outer_size, inner_width))
@@ -4853,8 +4854,8 @@ static void ShowDemoWindowTables()
             ImGui::TableSetupColumn("ID",           ImGuiTableColumnFlags_DefaultSort | ImGuiTableColumnFlags_WidthFixed | ImGuiTableColumnFlags_NoHide, -1.0f, MyItemColumnID_ID);
             ImGui::TableSetupColumn("Name",         ImGuiTableColumnFlags_WidthFixed, -1.0f, MyItemColumnID_Name);
             ImGui::TableSetupColumn("Action",       ImGuiTableColumnFlags_NoSort | ImGuiTableColumnFlags_WidthFixed, -1.0f, MyItemColumnID_Action);
-            ImGui::TableSetupColumn("Quantity",     ImGuiTableColumnFlags_PreferSortDescending, 1.0f, MyItemColumnID_Quantity);
-            ImGui::TableSetupColumn("Description",  ImGuiTableColumnFlags_WidthStretch, 1.0f, MyItemColumnID_Description);
+            ImGui::TableSetupColumn("Quantity",     ImGuiTableColumnFlags_PreferSortDescending, -1.0f, MyItemColumnID_Quantity);
+            ImGui::TableSetupColumn("Description",  ImGuiTableColumnFlags_WidthStretch, -1.0f, MyItemColumnID_Description);
             ImGui::TableSetupColumn("Hidden",       ImGuiTableColumnFlags_DefaultHide | ImGuiTableColumnFlags_NoSort);
             ImGui::TableSetupScrollFreeze(freeze_cols, freeze_rows);
 

imgui_tables.cpp

@@ -644,7 +644,7 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     table->EnabledMaskByDisplayOrder = 0x00;
     table->MinColumnWidth = ImMax(1.0f, g.Style.FramePadding.x * 1.0f); // g.Style.ColumnsMinSpacing; // FIXME-TABLE
 
-    // [Part 1] Apply/lock Enabled and Order states.
+    // [Part 1] Apply/lock Enabled and Order states. Calculate auto/ideal width for columns. 
     // Process columns in their visible orders as we are building the Prev/Next indices.
     int last_visible_column_idx = -1;
     bool want_auto_fit = false;
@@ -687,29 +687,33 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
         if (start_auto_fit)
             column->AutoFitQueue = column->CannotSkipItemsQueue = (1 << 3) - 1; // Fit for three frames
 
-        if (column->AutoFitQueue != 0x00)
-            want_auto_fit = true;
-
         ImU64 index_mask = (ImU64)1 << column_n;
         ImU64 display_order_mask = (ImU64)1 << column->DisplayOrder;
-        if (column->IsEnabled)
-        {
-            // Mark as enabled and link to previous/next enabled column
-            column->PrevEnabledColumn = (ImGuiTableColumnIdx)last_visible_column_idx;
-            column->NextEnabledColumn = -1;
-            if (last_visible_column_idx != -1)
-                table->Columns[last_visible_column_idx].NextEnabledColumn = (ImGuiTableColumnIdx)column_n;
-            column->IndexWithinEnabledSet = table->ColumnsEnabledCount;
-            table->ColumnsEnabledCount++;
-            table->EnabledMaskByIndex |= index_mask;
-            table->EnabledMaskByDisplayOrder |= display_order_mask;
-            last_visible_column_idx = column_n;
-        }
-        else
+        if (!column->IsEnabled)
         {
             column->IndexWithinEnabledSet = -1;
+            continue;
         }
+
+        // Mark as enabled and link to previous/next enabled column
+        column->PrevEnabledColumn = (ImGuiTableColumnIdx)last_visible_column_idx;
+        column->NextEnabledColumn = -1;
+        if (last_visible_column_idx != -1)
+            table->Columns[last_visible_column_idx].NextEnabledColumn = (ImGuiTableColumnIdx)column_n;
+        column->IndexWithinEnabledSet = table->ColumnsEnabledCount;
+        table->ColumnsEnabledCount++;
+        table->EnabledMaskByIndex |= index_mask;
+        table->EnabledMaskByDisplayOrder |= display_order_mask;
+        last_visible_column_idx = column_n;
         IM_ASSERT(column->IndexWithinEnabledSet <= column->DisplayOrder);
+
+        // Calculate ideal/auto column width (that's the width required for all contents to be visible without clipping)
+        // Combine width from regular rows + width from headers unless requested not to.
+        if (!column->IsPreserveWidthAuto)
+            column->WidthAuto = TableGetColumnWidthAuto(table, column);
+
+        if (column->AutoFitQueue != 0x00)
+            want_auto_fit = true;
     }
     if ((table->Flags & ImGuiTableFlags_Sortable) && table->SortSpecsCount == 0 && !(table->Flags & ImGuiTableFlags_SortTristate))
         table->IsSortSpecsDirty = true;
@@ -724,7 +728,7 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     if (want_auto_fit)
         table->IsSettingsDirty = true;
 
-    // [Part 3] Fix column flags. Calculate ideal width for columns. Count how many fixed/stretch columns we have and sum of weights.
+    // [Part 3] Fix column flags. Count how many fixed/stretch columns we have and sum of weights.
     int count_fixed = 0;                    // Number of columns that have fixed sizing policy (not stretched sizing policy) (this is NOT the opposite of count_resizable!)
     int count_resizable = 0;                // Number of columns the user can resize (this is NOT the opposite of count_fixed!)
     float sum_weights_stretched = 0.0f;     // Sum of all weights for weighted columns.
@@ -741,11 +745,6 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
         if ((column->Flags & ImGuiTableColumnFlags_NoResize) == 0)
             count_resizable++;
 
-        // Calculate ideal/auto column width (that's the width required for all contents to be visible without clipping)
-        // Combine width from regular rows + width from headers unless requested not to.
-        if (!column->IsPreserveWidthAuto)
-            column->WidthAuto = TableGetColumnWidthAuto(table, column);
-
         if (column->Flags & (ImGuiTableColumnFlags_WidthFixed | ImGuiTableColumnFlags_WidthAuto))
         {
             // Non-resizable columns keep their requested width
@@ -1313,7 +1312,7 @@ void ImGui::TableSetupColumn(const char* label, ImGuiTableColumnFlags flags, flo
         if ((flags & ImGuiTableColumnFlags_WidthFixed) && init_width_or_weight > 0.0f)
             column->WidthRequest = init_width_or_weight;
         if (flags & ImGuiTableColumnFlags_WidthStretch)
-            column->StretchWeight = (init_width_or_weight > 0.0f) ? init_width_or_weight : 1.0f;
+            column->StretchWeight = (init_width_or_weight > 0.0f) ? init_width_or_weight : -1.0f;
 
         // Disable auto-fit if an explicit width/weight has been specified
         if (init_width_or_weight > 0.0f)