Graphics.java

/**
 * Protected method that fixes coordinates of a line using Cohen-Sutherland algorithm,
 * then calls drawLineBresenham () method to draw the line with corrected coordinates
 *
 * @param startX x coordinate of start point
 * @param startY y coordinate of start point
 * @param endX x coordinate of end point
 * @param endY y coordinate of end point
 * @param color color of painted line
 */
protected void drawLine (int startX, int startY, int endX, int endY, G_Color color) {
	int codeStart, codeEnd;
	boolean accept;

	codeStart = generateCode (startX, startY);
	codeEnd = generateCode (endX, endY);
	accept = false;

	while (true) {
		if ((codeStart == 0) && (codeEnd == 0)) {
			accept = true;
			break;
		} else if ((codeStart & codeEnd) != 0) {
			break;
		} else {
			boolean codeWhich;
			int workX, workY, codeWork;

			// if start code isn't 0 -> true, we're working with start point
			// if start code is 0 -> false, we're working with end point
			codeWhich = (codeStart != 0);

			if (codeWhich) {
				codeWork = codeStart;
				workX = startX;
				workY = startY;
			} else {
				codeWork = codeEnd;
				workX = endX;
				workY = endY;
			}

			if ((codeWork & 1) != 0) {
				workY = ((endY - startY) / (endX - startX)) * (Form.leftX - workX) + workY;
				workX = Form.leftX;
			} else if ((codeWork & 2) != 0) {
				workY = ((endY - startY) / (endX - startX)) * (Form.rightX - workX) + workY;
				workX = Form.rightX;
			} else if ((codeWork & 4) != 0) {
				workX = ((endX - startX) / (endY - startX)) * (Form.bottomY - workY) + workX;
				workY = Form.bottomY;
			} else if ((codeWork & 8) != 0) {
				workX = ((endX - startX) / (endY - startX)) * (Form.topY - workY) + workX;
				workY = Form.topY;
			}

			if (codeWork == codeStart) {
				startX = workX;
				startY = workY;
				codeStart = generateCode (startX, startY);
			} else {
				endX = workX;
				endY = workY;
				codeEnd = generateCode (endX, endY);
			}
		}
	}

	if (accept) {
		drawLineBresenham (startX, startY, endX, endY, color);
	}
}

/**
 * Generates code required for clipping for given point
 * 1 = left
 * 2 = right
 * 4 = bottom
 * 8 = top
 *
 * @param x x coordinate of given point
 * @param y y coordinate of given point
 * @return calculated code
 */
private int generateCode (int x, int y) {
	int code = 0;

	if (x < Form.leftX) {
		code += 1;
	} else if (x > Form.rightX) {
		code += 2;
	}

	if (y > Form.bottomY) {
		code += 4;
	} else if (y < Form.topY) {
		code += 8;
	}

	return (code);
}