Method SetZoomLevel

src/smallmap_gui.cpp:1208–1250

* Initialize or change the zoom level. * @param change Way to change the zoom level. * @param zoom_pt Position to keep fixed while zooming. * @pre \c *zoom_pt should contain a point in the smallmap display when zooming in or out. */

	 * @pre \c *zoom_pt should contain a point in the smallmap display when zooming in or out.
	 */
	void SetZoomLevel(ZoomLevelChange change, const Point *zoom_pt)
	{
		static const int zoomlevels[] = {1, 2, 4, 6, 8}; // Available zoom levels. Bigger number means more zoom-out (further away).
		static const int MIN_ZOOM_INDEX = 0;
		static const int MAX_ZOOM_INDEX = lengthof(zoomlevels) - 1;

		int new_index, cur_index, sub;
		Point tile;
		switch (change) {
			case ZLC_INITIALIZE:
				cur_index = - 1; // Definitely different from new_index.
				new_index = MIN_ZOOM_INDEX;
				tile.x = tile.y = 0;
				break;

			case ZLC_ZOOM_IN:
			case ZLC_ZOOM_OUT:
				for (cur_index = MIN_ZOOM_INDEX; cur_index <= MAX_ZOOM_INDEX; cur_index++) {
					if (this->zoom == zoomlevels[cur_index]) break;
				}
				assert(cur_index <= MAX_ZOOM_INDEX);

				tile = this->PixelToTile(zoom_pt->x, zoom_pt->y, &sub);
				new_index = Clamp(cur_index + ((change == ZLC_ZOOM_IN) ? -1 : 1), MIN_ZOOM_INDEX, MAX_ZOOM_INDEX);
				break;

			default: NOT_REACHED();
		}

		if (new_index != cur_index) {
			this->zoom = zoomlevels[new_index];
			if (cur_index >= 0) {
				Point new_tile = this->PixelToTile(zoom_pt->x, zoom_pt->y, &sub);
				this->SetNewScroll(this->scroll_x + (tile.x - new_tile.x) * TILE_SIZE,
						this->scroll_y + (tile.y - new_tile.y) * TILE_SIZE, sub);
			} else if (this->map_type == SMT_LINKSTATS) {
				this->overlay->SetDirty();
			}
			this->SetWidgetDisabledState(WID_SM_ZOOM_IN,  this->zoom == zoomlevels[MIN_ZOOM_INDEX]);
			this->SetWidgetDisabledState(WID_SM_ZOOM_OUT, this->zoom == zoomlevels[MAX_ZOOM_INDEX]);
			this->SetDirty();
		}
	}

	/**
	 * Set the link graph overlay cargo mask from the legend.