private void updatedStructureSize() {

		if (updatingSize) {
			return;
		}
		if (!sizeTextField.isShowing()) {
			return;
		}

		if (!model.isSizeEditable()) {
			return;
		}

		if (sizeTextField.getTextEntryStatus() != CHANGED) {
			return;
		}

		int size = decodeUnsignedIntEntry(sizeTextField, "structure size", true);
		if (size < 0) {
			return;
		}

		updatingSize = true;
		try {
			if (size < model.getLength()) {
				// Decreasing structure length.
				// Verify that user really wants this.
				String question = "The size field was changed to " + size + " bytes.\n" +
					"Do you really want to truncate " + model.getCompositeName() + "?";
				String title = "Truncate " + model.getTypeName() + " In Editor?";
				int response =
					OptionDialog.showYesNoDialogWithNoAsDefaultButton(this, title, question);
				if (response != OptionDialog.YES_OPTION) {
					compositeInfoChanged();
					return;
				}
			}
			((StructureEditorModel) model).setStructureSize(size);
		}
		finally {
			updatingSize = false;
		}
		compositeInfoChanged();
	}
Sets the currently displayed structure packing value (maximum component alignment)
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/compositeeditor/CompEditorPanel.java