line function works from 2nd quadrant to 4th quadrant

graphics.c

@@ -19,7 +19,8 @@ void render(Canvas* c){
 
 	for(int i=0; i < c->y; i++){
 		for(int j=0; j < c->x; j++){
-			putchar(c->data[i*(c->x)+j]);	
+			putchar(c->data[i*(c->x)+j]);
+			putchar(' ');
 		}
 		putchar('\n');
 	}
@@ -39,23 +40,25 @@ void dot(Canvas* c, uint x, uint y){
 void line(Canvas* c, uint start_x, uint start_y, uint end_x, uint end_y){
 #ifndef abs
 #define abs(x) ((x<0)?(-x):(x))
-
-	
 	int dx = abs(end_x - start_x);
 	int dy = abs(end_y - start_y);
 
 	int direction_x = start_x < end_x ? 1 : -1;
 	int direction_y = start_y < end_y ? 1 : -1;
 
-	printf("dx:%i dy:%i direction:%i,%i", dx, dy, direction_x, direction_y);
+	printf("dx:%i dy:%i direction:%i,%i  \n", dx, dy, direction_x, direction_y);
 
-	if(dx>dy){
-		for(int i=0; i<dx; i++){
-			dot(c, start_x+i*direction_x, start_y+(dy/(i+1))*direction_y);
+	if(dx>=dy){
+		float small = direction_y * (float)dy/(float)dx;
+		
+		for(int i=0; i<dx+1; i++){
+			dot(c, start_x + i*direction_x, start_y + i*small);
 		}
 	}else{
-		for(int i=0; i<dy; i++){
-			dot(c, start_x+(dx/(i+1))*direction_x, start_y+i*direction_y);
+		float small = direction_x * (float)dx/(float)dy;
+		
+		for(int i=0; i<dy+1; i++){
+			dot(c, start_x + i*small, start_y + i*direction_y);
 		}
 	}
 
@@ -66,16 +69,25 @@ void line(Canvas* c, uint start_x, uint start_y, uint end_x, uint end_y){
 
 int main(){
 	char data[] =
-		"---"
-		"---"
-		"---";
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------"
+		"----------";
 
-	Canvas a = {3, 3, data};
+	Canvas a = {10, 10, data};
 
-	//line(&a, 0, 0, 3, 3);
+	//line(&a, 1, 1, 8, 8);
+	line(&a, 8, 8, 1, 1);
+	//line(&a, 5, 5, 8, 8);
 
 	dot(&a, 0, 0);
-	dot(&a, 2, 2);
+	dot(&a, 9, 9);
 
 	render(&a);