Add DrawTexturedPoly and example (#1677)

* adds DrawTexturedPoly with example

* the actual example ... ahem

* moved DrawTexturePoly to textures function and example
NB function name changed to fit with other DrawTextureXXX functions
(no "d" )

Co-authored-by: codifies <you@example.com>

src/raylib.h

@@ -1260,6 +1260,7 @@ RLAPI void DrawTextureQuad(Texture2D texture, Vector2 tiling, Vector2 offset, Re
 RLAPI void DrawTextureTiled(Texture2D texture, Rectangle source, Rectangle dest, Vector2 origin, float rotation, float scale, Color tint);  // Draw part of a texture (defined by a rectangle) with rotation and scale tiled into dest.
 RLAPI void DrawTexturePro(Texture2D texture, Rectangle source, Rectangle dest, Vector2 origin, float rotation, Color tint);       // Draw a part of a texture defined by a rectangle with 'pro' parameters
 RLAPI void DrawTextureNPatch(Texture2D texture, NPatchInfo nPatchInfo, Rectangle dest, Vector2 origin, float rotation, Color tint);  // Draws a texture (or part of it) that stretches or shrinks nicely
+RLAPI void DrawTexturePoly(Texture t, float x, float y, Vector2 *points, Vector2 *tPnts, int numPoints, Color colour); // Draw a textured polygon
 
 // Color/pixel related functions
 RLAPI Color Fade(Color color, float alpha);                                 // Returns color with alpha applied, alpha goes from 0.0f to 1.0f

src/textures.c

@@ -3510,6 +3510,48 @@ void DrawTextureNPatch(Texture2D texture, NPatchInfo nPatchInfo, Rectangle dest,
     }
 }
 
+// t            texture to use
+// x,y          position to draw the poly (centre)
+// points       points of the poly (relative to 0,0)
+// tPnts        uv coordinates
+// numPoints    number of points in the poly
+// colour       the tint of the poly
+//
+// NB centre (0,0) must have straight line path to all points
+// without crossing perimeter, points must be in anticlockwise
+// order
+void DrawTexturePoly(Texture t, float x, float y,
+                        Vector2 *points, Vector2 *tPnts,
+                        int numPoints, Color colour)
+{
+    rlEnableTexture(t.id);
+
+    // for some reason texturing doesn't work on trianglesso make a 
+    // degenerate QUAD, DrawTriangleFan does this too why ?
+    rlCheckRenderBatchLimit((numPoints-1)*4);
+    rlBegin(RL_QUADS);
+    rlColor4ub(colour.r, colour.g, colour.b, colour.a);
+
+    for (int i = 0; i < numPoints-1; i++)
+    {
+        rlTexCoord2f(0.5, 0.5);
+        rlVertex2f(x, y);
+
+        rlTexCoord2f(tPnts[i].x, tPnts[i].y);
+        rlVertex2f(points[i].x + x, points[i].y + y);
+
+        rlTexCoord2f(tPnts[i + 1].x, tPnts[i + 1].y);
+        rlVertex2f(points[i + 1].x + x, points[i + 1].y + y);
+
+        rlTexCoord2f(tPnts[i + 1].x, tPnts[i + 1].y);
+        rlVertex2f(points[i + 1].x + x, points[i + 1].y + y);
+    }
+    rlEnd();
+    rlDisableTexture();
+
+}
+
+
 // Returns color with alpha applied, alpha goes from 0.0f to 1.0f
 Color Fade(Color color, float alpha)
 {