Function DrawLayoutLine

src/gfx.cpp:506–649

* Drawing routine for drawing a laid out line of text. * @param line String to draw. * @param y The top most position to draw on. * @param left The left most position to draw on. * @param right The right most position to draw on. * @param align The alignment of the string when drawing left-to-right. In the * case a right-to-left language is chosen t

 *         In case of right alignment the left most pixel we have drawn to.
 */
static int DrawLayoutLine(const ParagraphLayouter::Line &line, int y, int left, int right, StringAlignment align, bool underline, bool truncation, TextColour default_colour)
{
	if (line.CountRuns() == 0) return 0;

	int w = line.GetWidth();
	int h = line.GetLeading();

	/*
	 * The following is needed for truncation.
	 * Depending on the text direction, we either remove bits at the rear
	 * or the front. For this we shift the entire area to draw so it fits
	 * within the left/right bounds and the side we do not truncate it on.
	 * Then we determine the truncation location, i.e. glyphs that fall
	 * outside of the range min_x - max_x will not be drawn; they are thus
	 * the truncated glyphs.
	 *
	 * At a later step we insert the dots.
	 */

	int max_w = right - left + 1; // The maximum width.

	int offset_x = 0;  // The offset we need for positioning the glyphs
	int min_x = left;  // The minimum x position to draw normal glyphs on.
	int max_x = right; // The maximum x position to draw normal glyphs on.

	truncation &= max_w < w;         // Whether we need to do truncation.
	int truncation_width = 0; // Width of the ellipsis string.

	std::optional<Layouter> truncation_layout; ///< Layout for truncation ellipsis.
	if (truncation) {
		/*
		 * Assumption may be made that all fonts of a run are of the same size.
		 * In any case, we'll use these dots for the abbreviation, so even if
		 * another size would be chosen it won't have truncated too little for
		 * the truncation dots.
		 */
		truncation_layout.emplace(GetEllipsis(), INT32_MAX, line.GetVisualRun(0).GetFont()->fc->GetSize());
		truncation_width = truncation_layout->GetBounds().width;

		/* Is there enough space even for an ellipsis? */
		if (max_w < truncation_width) return (_current_text_dir == TD_RTL) ? left : right;

		if (_current_text_dir == TD_RTL) {
			min_x += truncation_width;
			offset_x = w - max_w;
		} else {
			max_x -= truncation_width;
		}

		w = max_w;
	}

	/* In case we have a RTL language we swap the alignment. */
	if (!(align & SA_FORCE) && _current_text_dir == TD_RTL && (align & SA_HOR_MASK) != SA_HOR_CENTER) align ^= SA_RIGHT;

	/* right is the right most position to draw on. In this case we want to do
	 * calculations with the width of the string. In comparison right can be
	 * seen as lastof(todraw) and width as lengthof(todraw). They differ by 1.