ANSIScrollPane

ANSIScrollPane Class

An ANSIScrollPane object draws a vertical scroll box on a text-mode terminal or X terminal. Applications can use the pane’s instance variables to set the position and height of the scroll thumb, and the border and shadow decorations.

The class provides a handleInput method that allows users to move the scroll thumb independently if the pane is used by itself.

This app draws a scroll pane independently.

int main () {
  ANSIScrollPane new scrollBox;

  scrollBox shadow = 0;
  scrollBox border = 1;

  scrollBox thumbHeight = 3;    // Sets the position and height
  scrollBox thumbStartLine = 1; // of the scroll thumb.

  scrollBox show 2, 2;          // The Up and Down arrow keys 
                                // move the scroll thumb while
                                // the pane is displayed.

  scrollBox cleanup;
}

When used to indicate the position of other panes, applications should set and read the scroll thumb’s using the thumbHeight and thumbStartLine instance variables. If the application wants to use the ANSIScrollPane object to set another pane’s position, it needs to handle the Up and Down cursor motion keys in the app’s handleInput method,

In that case, the app should use the classes’ display method instead of show to display the ANSIScrollPane object, because display doesn’t wait for user input on its own.

There’s no terminal independent way, however, to indicate that the ANSIScrollPane object has the input focus. An app might do this by either setting or omitting the pane’s shadow, but that can occupy an extra line of terminal space.

The class is simplified by keeping the width of the scroll thumb at one column. Apps can draw a wider scroll pane, but that does not affect the scroll thumb’s width.

Instance Variables

viewHeight

An Integer that specifies the height of the scroll channel in character rows.

viewWidth

An Integer that specifies the width of the scroll channel in character columns.

thumbHeight

An Integer that specifies the height of the scroll thumb in character rows.

thumbStartLine

An Integer that specifies the row of the top of the scroll thumb. This should be less than the viewHeight instance variable for the thumb to be visible.

Instance Methods

cleanup (void)

Delete the buffers associated with the pane object.

dimension (Integer width, Integer height)

Set the width and height of the receiver pane. Also adjusts the width of the viewWidth and viewHeight instance variables.

display (Integer x, Integer y)

Draw the pane on the terminal at row and column x,y, and return immediately.

handleInput (void)

Waits for user input from the pane’s ANSITerminalStream object. Pressing Enter or Escape withdraws the pane from the display and returns. Pressing the Up or Down arrow keys moves the scroll thumb.

new (String paneName)

Create a new ANSIScrollPane object, with the name paneName. If more than one name is given in the argument list, create new ANSIScrollPane objects with the arguments’ names.

refresh (void)

Draw the pane on the terminal.

show (Integer x, Integer y)

Draw the pane on the terminal at row and column x,y, and wait for the user’s input.