added in basic ellipse algorithm

src/display.cpp

@@ -1275,7 +1275,7 @@ void display::draw_tile(int x, int y, SDL_Surface* unit_image_override,
 			}
 		}
 
-		if((grid_ || show_unit_colour) && srcrect.w >= 1) {
+		if(grid_ && srcrect.w >= 1) {
 			SDL_Rect rect = dstrect;
 			if(j == ypos || j == yend-1) {
 				SDL_FillRect(dst,&rect,grid_colour);
@@ -1289,6 +1289,10 @@ void display::draw_tile(int x, int y, SDL_Surface* unit_image_override,
 		}
 	}
 
+	if(show_unit_colour) {
+		draw_ellipse(dst,grid_colour,xpos,ypos,zoom_,zoom_);
+	}
+
 	if(game_config::debug && debugHighlights_.count(gamemap::location(x,y))) {
 		const scoped_sdl_surface cross(image::get_image(game_config::cross_image));
 		if(cross != NULL)
@@ -2205,6 +2209,7 @@ void display::draw_unit(int x, int y, SDL_Surface* image,
                         bool reverse, bool upside_down,
                         double alpha, Pixel blendto, double submerged)
 {
+	std::cerr << "drawing unit submerged at " << submerged << "\n";
 	//the alpha value to use for submerged units
 	static const double unit_submerged_alpha = 0.2;
 
@@ -2224,7 +2229,7 @@ void display::draw_unit(int x, int y, SDL_Surface* image,
 	surface_lock srclock(image);
 	const Pixel* src = srclock.pixels();
 
-	const int height = image->h; //*(1.0 - submerged);
+	const int height = image->h;
 	const int submerge_height = y + image->h*(1.0 - submerged);
 
 	const int endy = (y + height) < h ? (y + height) : h;

src/sdl_utils.cpp

@@ -12,6 +12,7 @@
 */
 
 #include <algorithm>
+#include <cmath>
 #include <iostream>
 
 #include "game.hpp"
@@ -27,6 +28,32 @@ int sdl_add_ref(SDL_Surface* surface)
 		return 0;
 }
 
+void draw_ellipse(SDL_Surface* surf, short colour, int xloc, int yloc, int width, int height, const SDL_Rect& clip)
+{
+	const double centerx = xloc + double(width)*0.5;
+	const double centery = yloc + double(height)*0.5;
+	const double r = double(width)*0.5;
+
+	int last_y = 0;
+	for(int xit = xloc; xit != xloc+width; ++xit) {
+		//r^2 = x^2 + y^2
+		//y^2 = r^2 - x^2
+		const double x = double(xit) - centerx;
+		const int y = int(sqrt(r*r - x*x));
+
+		const int direction = y > last_y ? 1 : -1;
+		for(int i = last_y; i != y+direction; i += direction) {
+			const int yit = yloc+height/2-y;
+			if(xit >= 0 && yit >= 0 && xit < surf->w && yit < surf->h) {
+				SDL_Rect rect = {xit,yit,1,1};
+				SDL_FillRect(surf,&rect,colour);
+			}
+		}
+
+		last_y = y;
+	}
+}
+
 SDL_Surface* clone_surface(SDL_Surface* surface)
 {
 	if(surface == NULL)

src/sdl_utils.hpp

@@ -41,6 +41,8 @@ int sdl_add_ref(SDL_Surface* surface);
 
 typedef util::scoped_resource<SDL_Surface*,free_sdl_surface> scoped_sdl_surface;
 
+void draw_ellipse(SDL_Surface* surf, short colour, int xloc, int yloc, int width, int height);
+
 SDL_Surface* clone_surface(SDL_Surface* surface);
 SDL_Surface* scale_surface(SDL_Surface* surface, int w, int h);