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>

examples/Makefile

@@ -437,7 +437,8 @@ TEXTURES = \
     textures/textures_sprite_explosion \
     textures/textures_bunnymark \
     textures/textures_blend_modes \
-    textures/textures_draw_tiled
+    textures/textures_draw_tiled \
+    textures/textures_poly
 
 TEXT = \
     text/text_raylib_fonts \

examples/textures/textures_poly.c

@@ -0,0 +1,95 @@
+/*******************************************************************************************
+*
+*   raylib [shapes] example - Draw Textured Polygon
+*
+*   This example has been created using raylib 99.98 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Copyright (c) 2014 Ramon Santamaria (@raysan5)
+*   Copyright (c) 2021 Chris Camacho (codifies - bedroomcoders.co.uk)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include "raymath.h"
+
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    int numPnts = 11;  // 10 points and back to the start
+
+    Vector2 tPnts[] = {
+        (Vector2){.75,  0},
+        (Vector2){.25,  0},
+        (Vector2){0,    .5},
+        (Vector2){0,    .75},
+        (Vector2){.25,  1},
+        (Vector2){.375, .875},
+        (Vector2){.625, .875},
+        (Vector2){.75,  1},
+        (Vector2){1,    .75},
+        (Vector2){1,    .5},
+        (Vector2){.75,  0}  // close the poly
+    };
+
+    Vector2 pnts[numPnts];
+
+    // create the poly coords from the UV's
+    // you don't have to do this you can specify
+    // them however you want
+    for (int i=0; i < numPnts; i++)
+    {
+        pnts[i].x = (tPnts[i].x - 0.5) * 256.0;
+        pnts[i].y = (tPnts[i].y - 0.5) * 256.0;
+    }
+
+    InitWindow(screenWidth, screenHeight, "raylib [textures] example - Textured Polygon");
+
+    Texture tex = LoadTexture("resources/cat.png");
+
+    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+    float ang = 0;
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        // Update your variables here
+        //----------------------------------------------------------------------------------
+        ang++;
+        
+        Vector2 dPnts[numPnts];
+        for (int i = 0; i < numPnts; i++)
+        {
+            dPnts[i] = Vector2Rotate(pnts[i], ang);
+        }
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            DrawText("Textured Polygon", 20, 20, 20, DARKGRAY);
+            
+            DrawTexturePoly(tex, screenWidth/2, screenHeight/2,
+                                dPnts, tPnts, numPnts, WHITE);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+    
+    UnloadTexture(tex);
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}

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)
 {