[examples] Add shapes_polygon_lines (#6023)

Add an example to demonstrate/observe DrawPolyLinesEx() behavior.

Author: MatthewRoush

examples/shapes/shapes_polygon_lines.c

@@ -0,0 +1,118 @@
+/*******************************************************************************************
+*
+*   raylib [shapes] example - polygon lines
+*
+*   Example complexity rating: [★★☆☆] 2/4
+*
+*   Example originally created with raylib 6.1, last time updated with raylib 6.1
+*
+*   Example contributed by Matthew Roush (@MatthewRoush) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2026 Matthew Roush (@MatthewRoush)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - polygon lines");
+
+    int thick = 2;
+    float rotation = 0.0f;
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        if (IsKeyPressed(KEY_UP))   thick = thick + 1;
+        if (IsKeyPressed(KEY_DOWN)) thick = thick - 1;
+
+        thick = (thick < 1) ? 1 : (thick > 60) ? 60 : thick;
+
+        rotation += (360.0f/10.0f)*GetFrameTime();
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            DrawText(TextFormat("thick = %d", thick), 10, 280, 20, LIME);
+
+            // The square and circle outlines in the top left should match
+            // The fist pair of outlines are drawn using `DrawRectangleLinesEx()` and `DrawCircleLinesEx()`
+            // The second pair are drawn using `DrawPolyLinesEx()` with parameters that should visually match the first pair
+
+            DrawText("These should look identical!", 10, 10, 20, MAROON);
+
+            // Outline pair 1
+            DrawRectangle(10, 40, 50, 50, LIGHTGRAY);
+            DrawRectangleLinesEx((Rectangle){ 10, 40, 50, 50 }, (float)thick, RED);
+
+            DrawCircle(95, 65, 25, LIGHTGRAY);
+            DrawCircleLinesEx((Vector2){ 95, 65 }, 25, (float)thick, RED);
+
+            DrawText("DrawRectangleLinesEx() and DrawCircleLinesEx()", 130, 60, 10, BLACK);
+
+            // Outline pair 2
+            DrawPoly((Vector2){ 35, 125 }, 4, 35.355f, 45, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 35, 125 }, 4, 35.355f, 45, (float)thick, RED);
+
+            DrawPoly((Vector2){ 95, 125 }, 36, 25, 0, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 95, 125 }, 36, 25, 0, (float)thick, RED);
+
+            DrawText("DrawPolyLinesEx()", 130, 120, 10, BLACK);
+
+            // Some other shapes, all of these outlines should have the same looking thickness
+            DrawPoly((Vector2){ 290, 220 }, 3, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 290, 220 }, 3, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 430, 220 }, 4, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 430, 220 }, 4, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 570, 220 }, 5, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 570, 220 }, 5, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 710, 220 }, 6, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 710, 220 }, 6, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 290, 360 }, 7, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 290, 360 }, 7, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 430, 360 }, 8, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 430, 360 }, 8, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 570, 360 }, 9, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 570, 360 }, 9, 60, rotation, (float)thick, BLUE);
+
+            DrawPoly((Vector2){ 710, 360 }, 10, 60, rotation, LIGHTGRAY);
+            DrawPolyLinesEx((Vector2){ 710, 360 }, 10, 60, rotation, (float)thick, BLUE);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}