[examples] Add textures_cellular_automata (#5395)

* [examples] Add `textures_cellular_automata`

* Comparison always true. Fixed

* Tabs to spaces

Author: JordSant

examples/textures/textures_cellular_automata.c

@@ -0,0 +1,212 @@
+/*******************************************************************************************
+*
+*   raylib [textures] example - one-dimensional elementary cellular automata
+*
+*   Example complexity rating: [★★☆☆] 2/4
+*
+*   Example originally created with raylib 5.6, last time updated with raylib 5.6
+*
+*   Example contributed by Jordi Santonja (@JordSant) 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) 2025 Jordi Santonja (@JordSant)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+// Initialization constants
+//--------------------------------------------------------------------------------------
+const int screenWidth = 800;
+const int screenHeight = 450;
+const int imageWidth = 800;
+const int imageHeight = 800/2;
+
+// Rule button sizes and positions
+const int drawRuleStartX       = 585;
+const int drawRuleStartY       = 10;
+const int drawRuleSpacing      = 15;
+const int drawRuleGroupSpacing = 50;
+const int drawRuleSize         = 14;
+const int drawRuleInnerSize    = 10;
+
+// Preset button sizes
+const int presetsSizeX = 42;
+const int presetsSizeY = 22;
+
+const int linesUpdatedPerFrame = 4;
+
+//----------------------------------------------------------------------------------
+// Functions
+//----------------------------------------------------------------------------------
+void ComputeLine(Image *image, int line, int rule)
+{
+    // Compute next line pixels. Boundaries are not computed, always 0
+    for (int i = 1; i < imageWidth - 1; i++)
+    {
+        // Get, from the previous line, the 3 pixels states as a binary value
+        const int prevValue = ((GetImageColor(*image, i - 1, line - 1).r < 5)? 4 : 0) +     // Left pixel
+                              ((GetImageColor(*image, i,     line - 1).r < 5)? 2 : 0) +     // Center pixel
+                              ((GetImageColor(*image, i + 1, line - 1).r < 5)? 1 : 0);      // Right pixel
+        // Get next value from rule bitmask
+        const bool currValue = (rule & (1 << prevValue));
+        // Update pixel color
+        ImageDrawPixel(image, i, line, (currValue)? BLACK : RAYWHITE);
+    }
+}
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    InitWindow(screenWidth, screenHeight, "raylib [textures] example - elementary cellular automata");
+
+    // Image that contains the cellular automaton
+    Image image = GenImageColor(imageWidth, imageHeight, RAYWHITE);
+    // The top central pixel set as black
+    ImageDrawPixel(&image, imageWidth/2, 0, BLACK);
+
+    Texture2D texture = LoadTextureFromImage(image);
+
+    // Some interesting rules
+    const int presetValues[] = { 18, 30, 60, 86, 102, 124, 126, 150, 182, 225 };
+    const int presetsCount = sizeof(presetValues)/sizeof(presetValues[0]);
+
+    // Variables
+    int rule = 30;  // Starting rule
+    int line = 1;   // Line to compute, starting from line 1. One point in line 0 is already set
+
+    SetTargetFPS(60);
+    //---------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        // Handle mouse
+        const Vector2 mouse = GetMousePosition();
+        int mouseInCell = -1;   // -1: outside any button; 0-7: rule cells; 8+: preset cells
+
+        // Check mouse on rule cells
+        for (int i = 0; i < 8; i++)
+        {
+            const int cellX = drawRuleStartX - drawRuleGroupSpacing*i + drawRuleSpacing;
+            const int cellY = drawRuleStartY + drawRuleSpacing;
+            if ((mouse.x >= cellX) && (mouse.x <= cellX + drawRuleSize) &&
+                (mouse.y >= cellY) && (mouse.y <= cellY + drawRuleSize))
+            {
+                mouseInCell = i;    // 0-7: rule cells
+                break;
+            }
+        }
+
+        // Check mouse on preset cells
+        if (mouseInCell < 0)
+        {
+            for (int i = 0; i < presetsCount; i++)
+            {
+                const int cellX = 4 + (presetsSizeX + 2)*(i/2);
+                const int cellY = 2 + (presetsSizeY + 2)*(i%2);
+                if ((mouse.x >= cellX) && (mouse.x <= cellX + presetsSizeX) &&
+                    (mouse.y >= cellY) && (mouse.y <= cellY + presetsSizeY))
+                {
+                    mouseInCell = i + 8;    // 8+: preset cells
+                    break;
+                }
+            }
+        }
+
+        if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && (mouseInCell >= 0))
+        {
+            // Rule changed both by selecting a preset or toggling a bit
+            if (mouseInCell < 8)
+                rule ^= (1 << mouseInCell);
+            else
+                rule = presetValues[mouseInCell - 8];
+
+            // Reset image
+            ImageClearBackground(&image, RAYWHITE);
+            ImageDrawPixel(&image, imageWidth/2, 0, BLACK);
+            line = 1;
+        }
+
+        // Compute next lines
+        //----------------------------------------------------------------------------------
+        if (line < imageHeight)
+        {
+            for (int i = 0; (i < linesUpdatedPerFrame) && (line + i < imageHeight); i++)
+                ComputeLine(&image, line + i, rule);
+            line += linesUpdatedPerFrame;
+
+            UpdateTexture(texture, image.data);
+        }
+
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+            ClearBackground(RAYWHITE);
+
+            // Draw cellular automaton texture
+            DrawTexture(texture, 0, screenHeight - imageHeight, WHITE);
+
+            // Draw preset values
+            for (int i = 0; i < presetsCount; i++)
+            {
+                DrawText(TextFormat("%i", presetValues[i]), 8 + (presetsSizeX + 2)*(i/2), 4 + (presetsSizeY + 2)*(i%2), 20, GRAY);
+                DrawRectangleLines(4 + (presetsSizeX + 2)*(i/2), 2 + (presetsSizeY + 2)*(i%2), presetsSizeX, presetsSizeY, BLUE);
+
+                // If the mouse is on this preset, highlight it
+                if (mouseInCell == i + 8)
+                    DrawRectangleLinesEx((Rectangle) { 2 + (presetsSizeX + 2.0f)*(i/2),
+                                                       (presetsSizeY + 2.0f)*(i%2),
+                                                       presetsSizeX + 4.0f, presetsSizeY + 4.0f }, 3, RED);
+            }
+
+            // Draw rule bits
+            for (int i = 0; i < 8; i++)
+            {
+                // The three input bits
+                for (int j = 0; j < 3; j++)
+                {
+                    DrawRectangleLines(drawRuleStartX - drawRuleGroupSpacing*i + drawRuleSpacing*j, drawRuleStartY, drawRuleSize, drawRuleSize, GRAY);
+                    if (i & (4 >> j))
+                        DrawRectangle(drawRuleStartX + 2 - drawRuleGroupSpacing*i + drawRuleSpacing*j, drawRuleStartY + 2, drawRuleInnerSize, drawRuleInnerSize, BLACK);
+                }
+
+                // The output bit
+                DrawRectangleLines(drawRuleStartX - drawRuleGroupSpacing*i + drawRuleSpacing, drawRuleStartY + drawRuleSpacing, drawRuleSize, drawRuleSize, BLUE);
+                if (rule & (1 << i))
+                    DrawRectangle(drawRuleStartX + 2 - drawRuleGroupSpacing*i + drawRuleSpacing, drawRuleStartY + 2 + drawRuleSpacing, drawRuleInnerSize, drawRuleInnerSize, BLACK);
+
+                // If the mouse is on this rule bit, highlight it
+                if (mouseInCell == i)
+                    DrawRectangleLinesEx((Rectangle){ drawRuleStartX - drawRuleGroupSpacing*i + drawRuleSpacing - 2.0f,
+                                                      drawRuleStartY + drawRuleSpacing - 2.0f,
+                                                      drawRuleSize + 4.0f, drawRuleSize + 4.0f }, 3, RED);
+            }
+
+            DrawText(TextFormat("RULE: %i", rule), drawRuleStartX + drawRuleSpacing*4, drawRuleStartY + 1, 30, GRAY);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    UnloadImage(image);
+    UnloadTexture(texture);
+
+    CloseWindow();              // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}
+