Method DrawGraph

src/graph_gui.cpp:369–627

* Actually draw the graph. * @param r the rectangle of the data field of the graph */

	 * @param r the rectangle of the data field of the graph
	 */
	void DrawGraph(Rect r) const
	{
		uint x, y;               ///< Reused whenever x and y coordinates are needed.
		ValuesInterval interval; ///< Interval that contains all of the graph data.
		int x_axis_offset;       ///< Distance from the top of the graph to the x axis.

		/* the colours and cost array of GraphDrawer must accommodate
		 * both values for cargo and companies. So if any are higher, quit */
		static_assert(GRAPH_MAX_DATASETS >= (int)NUM_CARGO && GRAPH_MAX_DATASETS >= (int)MAX_COMPANIES);
		assert(this->num_vert_lines > 0);

		bool rtl = _current_text_dir == TD_RTL;

		/* Rect r will be adjusted to contain just the graph, with labels being
		 * placed outside the area. */
		r.top    += ScaleGUITrad(5) + GetCharacterHeight(FS_SMALL) / 2;
		r.bottom -= (this->draw_dates ? 2 : 1) * GetCharacterHeight(FS_SMALL) + ScaleGUITrad(4);
		r.left   += ScaleGUITrad(rtl ? 5 : 9);
		r.right  -= ScaleGUITrad(rtl ? 9 : 5);

		/* Initial number of horizontal lines. */
		int num_hori_lines = 160 / ScaleGUITrad(MIN_GRID_PIXEL_SIZE);
		/* For the rest of the height, the number of horizontal lines will increase more slowly. */
		int resize = (r.bottom - r.top - 160) / (2 * ScaleGUITrad(MIN_GRID_PIXEL_SIZE));
		if (resize > 0) num_hori_lines += resize;

		interval = GetValuesInterval(num_hori_lines);

		int label_width = GetYLabelWidth(interval, num_hori_lines);

		if (rtl) {
			r.right -= label_width;
		} else {
			r.left += label_width;
		}

		int x_sep = (r.right - r.left) / this->num_vert_lines;
		int y_sep = (r.bottom - r.top) / num_hori_lines;

		/* Redetermine right and bottom edge of graph to fit with the integer
		 * separation values. */
		if (rtl) {
			r.left = r.right - x_sep * this->num_vert_lines;
		} else {
			r.right = r.left + x_sep * this->num_vert_lines;
		}
		r.bottom = r.top + y_sep * num_hori_lines;

		OverflowSafeInt64 interval_size = interval.highest + abs(interval.lowest);
		/* Where to draw the X axis. Use floating point to avoid overflowing and results of zero. */
		x_axis_offset = (int)((r.bottom - r.top) * (double)interval.highest / (double)interval_size);

		/* Draw the background of the graph itself. */
		GfxFillRect(r.left, r.top, r.right, r.bottom, GRAPH_BASE_COLOUR);

		/* Draw the grid lines. */
		int gridline_width = WidgetDimensions::scaled.bevel.top;
		PixelColour grid_colour = GRAPH_GRID_COLOUR;