Is there a way to place SplitContainerControl's splitter at a percentual position of the control size, that keeps even if its container is resized? Or, on the other hand, set the size of the panels to a percentual value?
If the SplitContainerControl.FixedPanel property is set to the SplitFixedPanel.None
value, the panels' widths (or heights) are changed proportionally when the container is being resized.
Thus, just do not use fixed panels within SplitContainerControl:
splitContainerControl1.FixedPanel = DevExpress.XtraEditors.SplitFixedPanel.None;
splitContainerControl1.SplitterPosition = splitContainerControl1.Width / 3;