Columns: Added ImGuiColumnsFlags_GrowParentContentsSize to internal API to restore old content sizes behavior. (#1444, #125)

imgui.cpp

@@ -10515,7 +10515,8 @@ void ImGui::EndColumns()
 
     window->DC.ColumnsCellMaxY = ImMax(window->DC.ColumnsCellMaxY, window->DC.CursorPos.y);
     window->DC.CursorPos.y = window->DC.ColumnsCellMaxY;
-    window->DC.CursorMaxPos.x = ImMax(window->DC.ColumnsStartMaxPosX, window->DC.ColumnsMaxX);  // Columns don't grow parent
+    if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_GrowParentContentsSize))
+        window->DC.CursorMaxPos.x = ImMax(window->DC.ColumnsStartMaxPosX, window->DC.ColumnsMaxX);  // Restore cursor max pos, as columns don't grow parent
 
     // Draw columns borders and handle resize
     if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoBorder) && !window->SkipItems)

imgui_internal.h

@@ -194,7 +194,8 @@ enum ImGuiColumnsFlags_
     ImGuiColumnsFlags_NoBorder              = 1 << 0,   // Disable column dividers
     ImGuiColumnsFlags_NoResize              = 1 << 1,   // Disable resizing columns when clicking on the dividers
     ImGuiColumnsFlags_NoPreserveWidths      = 1 << 2,   // Disable column width preservation when adjusting columns
-    ImGuiColumnsFlags_NoForceWithinWindow   = 1 << 3    // Disable forcing columns to fit within window
+    ImGuiColumnsFlags_NoForceWithinWindow   = 1 << 3,   // Disable forcing columns to fit within window
+    ImGuiColumnsFlags_GrowParentContentsSize= 1 << 4,   // (WIP) Restore pre-1.51 behavior of extending the parent window contents size but _without affecting the columns width at all_. Will eventually remove.
 };
 
 enum ImGuiSelectableFlagsPrivate_