Tables: Clarify internal calculations of row height so that TableGetCellRect() include expected paddings. Add demo code. Comments.

Remove misleading commented-out flags for now.

imgui.h

@@ -1081,10 +1081,6 @@ enum ImGuiTableColumnFlags_
     // [Internal] Combinations and masks
     ImGuiTableColumnFlags_WidthMask_                = ImGuiTableColumnFlags_WidthFixed | ImGuiTableColumnFlags_WidthStretch | ImGuiTableColumnFlags_WidthAlwaysAutoResize,
     ImGuiTableColumnFlags_NoDirectResize_           = 1 << 20   // [Internal] Disable user resizing this column directly (it may however we resized indirectly from its left edge)
-    //ImGuiTableColumnFlags_AlignLeft               = 1 << 14,
-    //ImGuiTableColumnFlags_AlignCenter             = 1 << 15,
-    //ImGuiTableColumnFlags_AlignRight              = 1 << 16,
-    //ImGuiTableColumnFlags_AlignMask_              = ImGuiTableColumnFlags_AlignLeft | ImGuiTableColumnFlags_AlignCenter | ImGuiTableColumnFlags_AlignRight
 };
 
 // Flags for ImGui::TableNextRow()

imgui_demo.cpp

@@ -3842,6 +3842,27 @@ static void ShowDemoWindowTables()
         ImGui::TreePop();
     }
 
+    if (open_action != -1)
+        ImGui::SetNextItemOpen(open_action != 0);
+    if (ImGui::TreeNode("Row height"))
+    {
+        HelpMarker("You can pass a 'min_row_height' to TableNextRow().\n\nRows are padded with 'style.CellPadding.y' on top and bottom, so effectively the minimum row height will always be >= 'style.CellPadding.y * 2.0f'.\n\nWe cannot honor a _maximum_ row height as that would requires a unique clipping rectangle per row.");
+        if (ImGui::BeginTable("##2ways", 2, ImGuiTableFlags_Borders))
+        {
+            float min_row_height = ImGui::GetFontSize() + ImGui::GetStyle().CellPadding.y * 2.0f;
+            ImGui::TableNextRow(ImGuiTableRowFlags_None, min_row_height);
+            ImGui::Text("min_row_height = %.2f", min_row_height);
+            for (int row = 0; row < 10; row++)
+            {
+                min_row_height = (float)(int)(ImGui::GetFontSize() * 0.30f * row);
+                ImGui::TableNextRow(ImGuiTableRowFlags_None, min_row_height);
+                ImGui::Text("min_row_height = %.2f", min_row_height);
+            }
+            ImGui::EndTable();
+        }
+        ImGui::TreePop();
+    }
+
     static const char* template_items_names[] =
     {
         "Banana", "Apple", "Cherry", "Watermelon", "Grapefruit", "Strawberry", "Mango",

imgui_tables.cpp

@@ -724,9 +724,9 @@ void    ImGui::TableUpdateLayout(ImGuiTable* table)
             // FIXME-TABLE: This align based on the whole column width, not per-cell, and therefore isn't useful in many cases.
             // (To be able to honor this we might be able to store a log of cells width, per row, for visible rows, but nav/programmatic scroll would have visible artifacts.)
             //if (column->Flags & ImGuiTableColumnFlags_AlignRight)
-            //    column->StartXRows = ImMax(column->StartXRows, column->MaxX - column->WidthContent[0]);
+            //    column->StartXRows = ImMax(column->StartXRows, column->MaxX - column->ContentWidthRowsUnfrozen);
             //else if (column->Flags & ImGuiTableColumnFlags_AlignCenter)
-            //    column->StartXRows = ImLerp(column->StartXRows, ImMax(column->StartXRows, column->MaxX - column->WidthContent[0]), 0.5f);
+            //    column->StartXRows = ImLerp(column->StartXRows, ImMax(column->StartXRows, column->MaxX - column->ContentWidthRowsUnfrozen), 0.5f);
 
             // Reset content width variables
             const float initial_max_pos_x = column->MinX + table->CellPaddingX1;
@@ -1401,8 +1401,10 @@ void    ImGui::TableNextRow(ImGuiTableRowFlags row_flags, float min_row_height)
     table->RowFlags = row_flags;
     TableBeginRow(table);
 
-    // We honor min_height requested by user, but cannot guarantee per-row maximum height as that would essentially require a unique clipping rectangle per-cell.
+    // We honor min_row_height requested by user, but cannot guarantee per-row maximum height,
-    table->RowPosY2 += min_row_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);
 
     TableBeginCell(table, 0);
 }
@@ -1447,8 +1449,6 @@ void    ImGui::TableEndRow(ImGuiTable* table)
 
     TableEndCell(table);
 
-    table->RowPosY2 += table->CellPaddingY;
-
     // Position cursor at the bottom of our row so it can be used for e.g. clipping calculation.
     // However it is likely that the next call to TableBeginCell() will reposition the cursor to take account of vertical padding.
     window->DC.CursorPos.y = table->RowPosY2;
@@ -1605,7 +1605,7 @@ void    ImGui::TableEndCell(ImGuiTable* table)
     else
         p_max_pos_x = table->IsFreezeRowsPassed ? &column->ContentMaxPosRowsUnfrozen : &column->ContentMaxPosRowsFrozen;
     *p_max_pos_x = ImMax(*p_max_pos_x, window->DC.CursorMaxPos.x);
-    table->RowPosY2 = ImMax(table->RowPosY2, window->DC.CursorMaxPos.y);
+    table->RowPosY2 = ImMax(table->RowPosY2, window->DC.CursorMaxPos.y + table->CellPaddingY);
 
     // Propagate text baseline for the entire row
     // FIXME-TABLE: Here we propagate text baseline from the last line of the cell.. instead of the first one.
@@ -1682,6 +1682,9 @@ bool    ImGui::TableSetColumnIndex(int column_idx)
     return (table->VisibleMaskByIndex & ((ImU64)1 << column_idx)) != 0;
 }
 
+// Return the cell rectangle based on currently known height.
+// Important: we generally don't know our row height until the end of the row, so Max.y will be incorrect in many situations.
+// The only case where this is correct is if we provided a min_row_height to TableNextRow() and don't go below it.
 ImRect  ImGui::TableGetCellRect()
 {
     ImGuiContext& g = *GImGui;
@@ -1805,7 +1808,7 @@ void    ImGui::TableAutoHeaders()
     ImGuiTable* table = g.CurrentTable;
     IM_ASSERT(table != NULL && "Need to call TableAutoHeaders() after BeginTable()!");
 
-    TableNextRow(ImGuiTableRowFlags_Headers, GetTextLineHeight());
+    TableNextRow(ImGuiTableRowFlags_Headers, GetTextLineHeight() + g.Style.CellPadding.y * 2.0f);
     if (window->SkipItems)
         return;
 
@@ -1909,6 +1912,7 @@ void    ImGui::TableHeader(const char* label)
 
     float row_height = GetTextLineHeight();
     ImRect cell_r = TableGetCellRect();
+    //GetForegroundDrawList()->AddRect(cell_r.Min, cell_r.Max, IM_COL32(255, 0, 0, 255)); // [DEBUG]
     ImRect work_r = cell_r;
     work_r.Min.x = window->DC.CursorPos.x;
     work_r.Max.y = work_r.Min.y + row_height;