Function HighlightDragPosition

src/train_gui.cpp:65–88

* Highlight the position where a rail vehicle is dragged over by drawing a light gray background. * @param px The current x position to draw from. * @param max_width The maximum space available to draw. * @param y The vertical centre position to draw from. * @param selection Selected vehicle that is dragged. * @param chain Whether a whole chain is dragged. * @return The wi

 * @return The width of the highlight mark.
 */
static int HighlightDragPosition(int px, int max_width, int y, VehicleID selection, bool chain)
{
	bool rtl = _current_text_dir == TD_RTL;

	assert(selection != VehicleID::Invalid());
	int dragged_width = 0;
	for (Train *t = Train::Get(selection); t != nullptr; t = chain ? t->Next() : (t->HasArticulatedPart() ? t->GetNextArticulatedPart() : nullptr)) {
		dragged_width += t->GetDisplayImageWidth(nullptr);
	}

	int drag_hlight_left = rtl ? std::max(px - dragged_width + 1, 0) : px;
	int drag_hlight_right = rtl ? px : std::min(px + dragged_width, max_width) - 1;
	int drag_hlight_width = std::max(drag_hlight_right - drag_hlight_left + 1, 0);

	if (drag_hlight_width > 0) {
		int height = ScaleSpriteTrad(12);
		int top = y - height / 2;
		Rect r = {drag_hlight_left, top, drag_hlight_right, top + height - 1};
		/* Sprite-scaling is used here as the area is from sprite size */
		GfxFillRect(r.Shrink(ScaleSpriteTrad(1)), GetColourGradient(COLOUR_GREY, SHADE_LIGHTEST));
	}

	return drag_hlight_width;
}

/**
 * Draws an image of a whole train