From 870c822ce26bd866761f6abd71fd9e109b9d9d98 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 10 Aug 2026 11:11:18 -0700
Subject: Chapter 31: Software Drawing, Time, and Graphical Games

Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: Symious <14933944+symious@users.noreply.github.com>
Co-authored-by: Jun Kawasaki <jun784@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
---
 src/main/c/simple_graphics.c | 102 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 src/main/c/simple_graphics.c

(limited to 'src/main/c/simple_graphics.c')

diff --git a/src/main/c/simple_graphics.c b/src/main/c/simple_graphics.c
new file mode 100644
index 00000000..40d66ba9
--- /dev/null
+++ b/src/main/c/simple_graphics.c
@@ -0,0 +1,102 @@
+#define _POSIX_C_SOURCE 200809L
+#include "simple_graphics.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dlfcn.h>
+#include <unistd.h>
+
+#ifdef __CYGWIN__
+#define BACKEND_NAME "simple_minifb.dll"
+#define BACKEND_ABI "x86_64_v2_win64"
+#else
+#define BACKEND_NAME "libsimple_minifb.so"
+#define BACKEND_ABI "x86_64_v2_SystemV"
+#endif
+
+// Executable-relative paths work even when launched outside the checkout.
+// Working-directory paths also cover test executables and chapter/root shells.
+static void *find_backend(void) {
+    char executable[4096], path[8192];
+    ssize_t n=readlink("/proc/self/exe",executable,sizeof(executable)-1);
+    if (n>0 && n<(ssize_t)sizeof(executable)-1) {
+        executable[n]=0;
+        char *slash=strrchr(executable,'/');
+        if (slash) {
+            *slash=0;
+            const char *relative[]={"/" BACKEND_NAME,
+                "/../../release/" BACKEND_ABI "/" BACKEND_NAME,
+                "/../release/" BACKEND_ABI "/" BACKEND_NAME};
+            for (unsigned i=0;i<sizeof(relative)/sizeof(*relative);++i) {
+                snprintf(path,sizeof(path),"%s%s",executable,relative[i]);
+                void *handle=dlopen(path,RTLD_NOW | RTLD_LOCAL);
+                if (handle) return handle;
+            }
+        }
+    }
+    const char *relative[]={"./" BACKEND_NAME,
+        "./build/release/" BACKEND_ABI "/" BACKEND_NAME,
+        "./chapter31/build/release/" BACKEND_ABI "/" BACKEND_NAME};
+    for (unsigned i=0;i<sizeof(relative)/sizeof(*relative);++i) {
+        void *handle=dlopen(relative[i],RTLD_NOW | RTLD_LOCAL);
+        if (handle) return handle;
+    }
+    return NULL;
+}
+
+// No MiniFB headers or link dependency in the default runtime. Cygwin's
+// dlopen also loads native Windows DLLs; both use the x64 Windows C ABI.
+static const struct simple_graphics_api *api;
+static void *library;
+
+static int load_graphics(void) {
+    // Explicitly disabling graphics also makes headless tests deterministic.
+    const char *path = getenv("SIMPLE_MINIFB");
+    if (path && strcmp(path, "off") == 0) {
+        fprintf(stderr, "Simple graphics: disabled (SIMPLE_MINIFB=off).\n");
+        return -1;
+    }
+    if (api) return 0;
+    int explicit_path=path && *path;
+    library = explicit_path ? dlopen(path, RTLD_NOW | RTLD_LOCAL) : find_backend();
+    if (!library) {
+        if (explicit_path)
+            fprintf(stderr, "Simple graphics: cannot load MiniFB backend '%s': %s\n", path, dlerror());
+        else
+            fprintf(stderr, "Simple graphics: MiniFB backend not found beside the executable or in build/release/"
+                    BACKEND_ABI ". Run make graphics, or set SIMPLE_MINIFB to its full path.\n");
+        return -1;
+    }
+    if (!explicit_path) path="automatically discovered backend";
+    const struct simple_graphics_api *(*get_api)(void) =
+        (const struct simple_graphics_api *(*)(void))dlsym(library, "simple_minifb_api");
+    const struct simple_graphics_api *candidate = get_api ? get_api() : NULL;
+    if (!candidate || candidate->version != SIMPLE_GRAPHICS_VERSION ||
+        !candidate->open || !candidate->present || !candidate->poll ||
+        !candidate->mouse_x || !candidate->mouse_y || !candidate->button ||
+        !candidate->key || !candidate->close || !candidate->wait) {
+        fprintf(stderr, "Simple graphics: incompatible MiniFB backend '%s'. Rebuild with make graphics.\n", path);
+        dlclose(library);
+        library = NULL;
+        return -1;
+    }
+    api = candidate;
+    // Keep the library loaded until process exit; its window callbacks may
+    // still be registered. Closing a window releases its native resources.
+    atexit(api->close);
+    return 0;
+}
+
+int32_t simple_gfx_open(const char *title, uint32_t width, uint32_t height) {
+    return load_graphics() ? -1 : api->open(title, width, height);
+}
+int32_t simple_gfx_present(const uint32_t *pixels, uint32_t count) {
+    return api ? api->present(pixels, count) : -1;
+}
+int32_t simple_gfx_poll(int32_t wait) { return api ? api->poll(wait) : -1; }
+int32_t simple_gfx_mouse_x(void) { return api ? api->mouse_x() : 0; }
+int32_t simple_gfx_mouse_y(void) { return api ? api->mouse_y() : 0; }
+int32_t simple_gfx_button(int32_t button) { return api ? api->button(button) : 0; }
+int32_t simple_gfx_key(int32_t key) { return api ? api->key(key) : 0; }
+int32_t simple_gfx_close(void) { if (api) api->close(); return 0; }
+int32_t simple_gfx_wait(int64_t timeout) { return api ? api->wait(timeout) : -1; }
-- 
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