REDESIGNED: example: shapes_kaleidoscope, store lines #5361

This redesign stores lines in Update and draws stored lines in Draw, instead of previous approach of drawing directly to framebuffer with no cleaning. This approach allows some interesting features like line draw replay or reversing.

examples/shapes/shapes_kaleidoscope.c

@@ -11,13 +11,26 @@
 *   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) 2025 Hugo ARNAL (@hugoarnal)
+*   Copyright (c) 2025 Hugo ARNAL (@hugoarnal) and Ramon Santamaria (@raysan5)
 *
 ********************************************************************************************/
 
 #include "raylib.h"
+
 #include "raymath.h"
 
+#define MAX_DRAW_LINES  8192
+
+// Line data type
+typedef struct {
+    Vector2 start;
+    Vector2 end;
+} Line;
+
+// Lines array as a global static variable to be stored
+// in heap and avoid potential stack overflow (on Web platform)
+static Line lines[MAX_DRAW_LINES] = { 0 };
+
 //------------------------------------------------------------------------------------
 // Program main entry point
 //------------------------------------------------------------------------------------
@@ -30,22 +43,24 @@ int main(void)
 
     InitWindow(screenWidth, screenHeight, "raylib [shapes] example - kaleidoscope");
 
+    // Line drawing properties
     int symmetry = 6;
     float angle = 360.0f/(float)symmetry;
     float thickness = 3.0f;
+    Vector2 mousePos = { 0 };
     Vector2 prevMousePos = { 0 };
-
+    Vector2 scaleVector = { 1.0f, -1.0f };
-    SetTargetFPS(60);
-    ClearBackground(BLACK);
-
     Vector2 offset = { (float)screenWidth/2.0f, (float)screenHeight/2.0f };
+    
     Camera2D camera = { 0 };
     camera.target = (Vector2){ 0 };
     camera.offset = offset;
     camera.rotation = 0.0f;
     camera.zoom = 1.0f;
     
-    Vector2 scaleVector = { 1.0f, -1.0f };
+    int lineCounter = 0;
+
+    SetTargetFPS(20);
     //--------------------------------------------------------------------------------------
 
     // Main game loop
@@ -53,38 +68,58 @@ int main(void)
     {
         // Update
         //----------------------------------------------------------------------------------
-        Vector2 mousePos = GetMousePosition();
+        prevMousePos = mousePos;
+        mousePos = GetMousePosition();
+        
         Vector2 lineStart = Vector2Subtract(mousePos, offset);
         Vector2 lineEnd = Vector2Subtract(prevMousePos, offset);
+        
+        if (IsMouseButtonDown(MOUSE_LEFT_BUTTON))
+        {
+            for (int s = 0; (s < symmetry) && (lineCounter < (MAX_DRAW_LINES - 1)); s++)
+            {
+                lineStart = Vector2Rotate(lineStart, angle*DEG2RAD);
+                lineEnd = Vector2Rotate(lineEnd, angle*DEG2RAD);
+
+                // Store mouse line
+                lines[lineCounter].start = lineStart;
+                lines[lineCounter].end = lineEnd;
+
+                // Store reflective line
+                lines[lineCounter + 1].start = Vector2Multiply(lineStart, scaleVector);
+                lines[lineCounter + 1].end = Vector2Multiply(lineEnd, scaleVector);
+                
+                lineCounter += 2;
+            }
+        }
         //----------------------------------------------------------------------------------
 
         // Draw
         //----------------------------------------------------------------------------------
         BeginDrawing();
+        
+            ClearBackground(RAYWHITE);
+    
             BeginMode2D(camera);
-                if (IsMouseButtonDown(MOUSE_LEFT_BUTTON)) {
+                for (int s = 0; s < symmetry; s++)
-                    for (int i = 0; i < symmetry; i++) {
+                {
-                        lineStart = Vector2Rotate(lineStart, angle*DEG2RAD);
+                    for (int i = 0; i < lineCounter; i += 2)
-                        lineEnd = Vector2Rotate(lineEnd, angle*DEG2RAD);
+                    {
-
+                        DrawLineEx(lines[i].start, lines[i].end, thickness, BLACK);
-                        DrawLineEx(lineStart, lineEnd, thickness, WHITE);
+                        DrawLineEx(lines[i + 1].start, lines[i + 1].end, thickness, BLACK);
-
-                        Vector2 reflectLineStart = Vector2Multiply(lineStart, scaleVector);
-                        Vector2 reflectLineEnd = Vector2Multiply(lineEnd, scaleVector);
-
-                        DrawLineEx(reflectLineStart, reflectLineEnd, thickness, WHITE);
                     }
                 }
-
-                prevMousePos = mousePos;
             EndMode2D();
+            
+            DrawText(TextFormat("LINES: %i/%i", lineCounter, MAX_DRAW_LINES), 10, screenHeight - 30, 20, MAROON);
+            DrawFPS(10, 10);
+            
         EndDrawing();
         //----------------------------------------------------------------------------------
     }
 
     // De-Initialization
     //--------------------------------------------------------------------------------------
-
     CloseWindow();        // Close window and OpenGL context
     //--------------------------------------------------------------------------------------