+ * Update the viewport location from a mouse drag within the overview's box
+ *
+ * @param mousex
+ * x location of mouse
+ * @param mousey
+ * y location of mouse
+ * @param hiddenSeqs
+ * the alignment's hidden sequences
+ * @param hiddenCols
+ * the alignment's hidden columns
+ */
+ public abstract void adjustViewportFromMouse(int mousex, int mousey,
+ HiddenSequences hiddenSeqs, HiddenColumns hiddenCols);
+
+ /**
+ * Initialise dragging from the mouse - must be called on initial mouse click
+ * before using adjustViewportFromMouse in drag operations
+ *
+ * @param mousex
+ * x location of mouse
+ * @param mousey
+ * y location of mouse
+ * @param hiddenSeqs
+ * the alignment's hidden sequences
+ * @param hiddenCols
+ * the alignment's hidden columns
+ */
+ public abstract void setDragPoint(int x, int y,
+ HiddenSequences hiddenSeqs, HiddenColumns hiddenCols);
+
+ /*
+ * Move the viewport so that the top left corner of the overview's box
+ * is at the mouse position (leftx, topy)
+ */
+ protected abstract void updateViewportFromTopLeft(int leftx, int topy,
+ HiddenSequences hiddenSeqs, HiddenColumns hiddenCols);
+
+ /**