Function CanvasSetOrigin

micropolis-activity/src/tk/tkcanvas.c:3461–3520

(canvasPtr, xOrigin, yOrigin)

	result = Tcl_VarEval(canvasPtr->interp, canvasPtr->yScrollCmd, args,
	    (char *) NULL);
	if (result != TCL_OK) {
	    TkBindError(canvasPtr->interp);
	}
	Tcl_ResetResult(canvasPtr->interp);
    }
}


/*
 *--------------------------------------------------------------
 *
 * CanvasSetOrigin --
 *
 *	This procedure is invoked to change the mapping between
 *	canvas coordinates and screen coordinates in the canvas
 *	window.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The canvas will be redisplayed to reflect the change in
 *	view.  In addition, scrollbars will be updated if there
 *	are any.
 *
 *--------------------------------------------------------------
 */

static void
CanvasSetOrigin(canvasPtr, xOrigin, yOrigin)
    register Tk_Canvas *canvasPtr;	/* Information about canvas. */
    int xOrigin;			/* New X origin for canvas (canvas
					 * x-coord corresponding to left edge
					 * of canvas window). */
    int yOrigin;			/* New Y origin for canvas (canvas
					 * y-coord corresponding to top edge
					 * of canvas window). */
{
    /*
     * Adjust the origin if necessary to keep as much as possible of the
     * canvas in the view.
     */

    if ((canvasPtr->confine) && (canvasPtr->regionString != NULL)) {
	int windowWidth, windowHeight, canvasWidth, canvasHeight;

	windowWidth = Tk_Width(canvasPtr->tkwin);
	windowHeight = Tk_Height(canvasPtr->tkwin);
	canvasWidth = canvasPtr->scrollX2 - canvasPtr->scrollX1;
	canvasHeight = canvasPtr->scrollY2 - canvasPtr->scrollY1;
	if (canvasWidth < windowWidth) {
	    xOrigin = (canvasPtr->scrollX1) - (windowWidth-canvasWidth)/2;
	} else if (xOrigin < canvasPtr->scrollX1) {
	    xOrigin = canvasPtr->scrollX1;
	} else if (xOrigin > (canvasPtr->scrollX2 - windowWidth)) {
	    xOrigin = canvasPtr->scrollX2 - windowWidth;
	}
	if (canvasHeight < windowHeight) {