al_draw_filled_polygon_with_holes - Man Page

#include <allegro5/allegro_primitives.h>

void al_draw_filled_polygon_with_holes(const float *vertices,
   const int *vertex_counts, ALLEGRO_COLOR color)

Draws a filled simple polygon with zero or more other simple polygons subtracted from it - the holes. The holes cannot touch or intersect with the outline of the filled polygon.

• vertices - Interleaved array of (x, y) vertex coordinates for each of the polygons, including holes.
• vertex_counts - Number of vertices for each polygon. The number of vertices in the filled polygon is given by vertex_counts[0] and must be at least three. Subsequent elements indicate the number of vertices in each hole. The array must be terminated with an element with value zero.
• color - Color of the filled polygon

When the y-axis is facing downwards (the usual) the filled polygon coordinates must be ordered anti-clockwise. All hole vertices must use the opposite order (clockwise with y down). All hole vertices must be inside the main polygon and no hole may overlap the main polygon.

For example:

float vertices[] = {
      0,   0, // filled polygon, upper left corner
      0, 100, // filled polygon, lower left corner
    100, 100, // filled polygon, lower right corner
    100,   0, // filled polygon, upper right corner
     10,  10, // hole, upper left
     90,  10, // hole, upper right
     90,  90  // hole, lower right
};
int vertex_counts[] = {
   4, // number of vertices for filled polygon
   3, // number of vertices for hole
   0  // terminator
};

There are 7 vertices: four for an outer square from (0, 0) to (100, 100) in anti-clockwise order, and three more for an inner triangle in clockwise order. The outer main polygon uses vertices 0 to 3 (inclusive) and the hole uses vertices 4 to 6 (inclusive).

5.1.0

al_draw_filled_polygon(3), al_draw_filled_polygon_with_holes(3), al_triangulate_polygon(3)

al_draw_filled_polygon(3), al_triangulate_polygon(3).