<*PRAGMA LL*>

An HVBar must be a child of an HVSplit. When the user pushes a mouse button over the bar, the cursor changes shape and the outline of the bar is highlighted. The highlight follows the cursor as long as the button is down. When the button comes up, the bar calls HVSplit.Adjust to move the bar to the currently highlighted position. If the user tries to move the bar outside the range of positions that are consistent with the size constraints of the children of the parent HVSplit, the highlighted bar will not follow the cursor. If the user chords while dragging, then adjusting mode is cancelled.

The bar has methods that you can override that are called each time the bar is moved, or continuously during adjustment.

In order for the bar to highlight correctly, some ancestor of the HVSplit on which it is installed must be a HighlightVBT. Since Trestle.Install automatically inserts a HighlightVBT over top-level windows, you usually don't have to worry about this.

INTERFACE HVBar;

IMPORT VBT, PaintOp, Pixmap, TextureVBT;

TYPE
  T <: Public;
  Public = TextureVBT.T OBJECT METHODS
    <* LL = VBT.mu *>
    pre(READONLY cd: VBT.MouseRec);
    post(READONLY cd: VBT.MouseRec);
    during(n: INTEGER);
    <* LL <= VBT.mu *>
    init(size: REAL := DefaultSize;
      op: PaintOp.T := PaintOp.BgFg;
      txt: Pixmap.T := Pixmap.Gray): T
  END;

The argument size gives the number of millimeters that the bar will occupy in the parent HVSplit.

An adjusting bar b calls b.pre(cd) when it begins adjusting in response to a mouse click cd. It calls b.during(k) each time the mouse moves during dragging, where k is the coordinate that the lo (i.e., west or north) edge of the bar would move to if dragging were stopped at that instant. Finally, the bar calls b.post(cd) when it stops adjusting in response to an upclick or chord cd. The HVSplit will be adjusted (but not redisplayed) before b.post(cd) is called.

The default pre and during methods highlight the position the bar would move to if dragging were stopped. The default post method removes the highlighting.

CONST
  DefaultSize = 2.5;

PROCEDURE New(
    size := DefaultSize;
    op := PaintOp.BgFg;
    txt := Pixmap.Gray): T; <* LL.sup <= VBT.mu *>

New(...) is equivalent to NEW(T).init(...).

END HVBar.