Fix: Adjust scrolling interval of credits to account for text line height

src/misc_gui.cpp

@@ -497,7 +497,7 @@ struct AboutWindow : public Window {
 	int line_height;                         ///< The height of a single line
 	static const int num_visible_lines = 19; ///< The number of lines visible simultaneously
 
-	static const uint TIMER_INTERVAL = 150;  ///< Scrolling interval in ms
+	static const uint TIMER_INTERVAL = 2100; ///< Scrolling interval, scaled by line text line height. This value chosen to maintain parity: 2100 / FONT_HEIGHT_NORMAL = 150ms
 	GUITimer timer;
 
 	AboutWindow() : Window(&_about_desc)
@@ -505,7 +505,6 @@ struct AboutWindow : public Window {
 		this->InitNested(WN_GAME_OPTIONS_ABOUT);
 
 		this->text_position = this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->pos_y + this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->current_y;
-		this->timer.SetInterval(TIMER_INTERVAL);
 	}
 
 	void SetStringParameters(int widget) const override
@@ -528,6 +527,10 @@ struct AboutWindow : public Window {
 			d.width = std::max(d.width, GetStringBoundingBox(_credits[i]).width);
 		}
 		*size = maxdim(*size, d);
+
+		/* Set scroll interval based on required speed. To keep scrolling smooth,
+		 * the interval is adjusted rather than the distance moved. */
+		this->timer.SetInterval(TIMER_INTERVAL / FONT_HEIGHT_NORMAL);
 	}
 
 	void DrawWidget(const Rect &r, int widget) const override