From 5f5fe249f8cfbf2c1977ebfe4e55839eb9159507 Mon Sep 17 00:00:00 2001
From: Dimitri Lozeve <dimitri@lozeve.com>
Date: Fri, 26 Feb 2021 20:16:17 +0100
Subject: [PATCH] Make inotify optional

If it fails, display a warning and allow manual reloading only. Also
add more logging for inotify-related stuff.
---
 src/main.c     | 50 +++++++++++++++++++++++++++++++-------------------
 src/renderer.c | 22 ++++++++++++++--------
 2 files changed, 45 insertions(+), 27 deletions(-)

diff --git a/src/main.c b/src/main.c
index 1fb9985..d49d518 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,8 +1,8 @@
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>
+#include <fcntl.h>
 #include <stdlib.h>
 #include <sys/inotify.h>
-#include <fcntl.h>
 
 #include "log.h"
 #include "renderer.h"
@@ -22,32 +22,44 @@ int main(int argc, char *argv[]) {
   /* Create inotify instance */
   state.inotify_fd = inotify_init();
   if (state.inotify_fd == -1) {
-    log_error("Cannot initialize inotify");
+    log_warn("[inotify] Cannot initialize inotify");
     perror("inotify_init");
-    return EXIT_FAILURE;
+  } else {
+    /* Set the inotify file descriptor to be non-blocking */
+    if (!fcntl(state.inotify_fd, F_SETFL, O_NONBLOCK)) {
+      log_debug("[inotify] Initialized successfully");
+    }
   }
-  /* Set the inotify file descriptor to be non-blocking */
-  fcntl(state.inotify_fd, F_SETFL, O_NONBLOCK);
 
   state.screen_shader.filename = argv[1];
-  state.screen_shader.wd =
-      inotify_add_watch(state.inotify_fd, state.screen_shader.filename, IN_MODIFY);
-  if (state.screen_shader.wd == -1) {
-    log_error("Cannot watch file %s", state.screen_shader.filename);
-    perror("inotify_add_watch");
-    return EXIT_FAILURE;
-  }
   log_debug("Screen shader file: %s", state.screen_shader.filename);
+
+  if (state.inotify_fd != -1) {
+    state.screen_shader.wd = inotify_add_watch(
+        state.inotify_fd, state.screen_shader.filename, IN_MODIFY);
+    if (state.screen_shader.wd == -1) {
+      log_warn("[inotify] Cannot watch file %s", state.screen_shader.filename);
+      perror("inotify_add_watch");
+    } else {
+      log_debug("[inotify] Watching file %s", state.screen_shader.filename);
+    }
+  }
+
   if (argc >= 3) {
     state.buffer_shader.filename = argv[2];
-    state.buffer_shader.wd =
-        inotify_add_watch(state.inotify_fd, state.buffer_shader.filename, IN_MODIFY);
-    if (state.buffer_shader.wd == -1) {
-      log_error("Cannot watch file %s", state.buffer_shader.filename);
-      perror("inotify_add_watch");
-      return EXIT_FAILURE;
-    }
     log_debug("Buffer shader file: %s", state.buffer_shader.filename);
+
+    if (state.inotify_fd != -1) {
+      state.buffer_shader.wd = inotify_add_watch(
+          state.inotify_fd, state.buffer_shader.filename, IN_MODIFY);
+      if (state.buffer_shader.wd == -1) {
+        log_warn("[inotify] Cannot watch file %s",
+                 state.buffer_shader.filename);
+        perror("inotify_add_watch");
+      } else {
+        log_debug("[inotify] Watching file %s", state.buffer_shader.filename);
+      }
+    }
   }
 
   state.window = initialize_window(WINDOW_WIDTH, WINDOW_HEIGHT);
diff --git a/src/renderer.c b/src/renderer.c
index a96994d..439569c 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -194,14 +194,20 @@ void capture_screenshot() {
  */
 void process_input(struct renderer_state *state) {
   bool should_reload = false;
-  char buf[BUF_LEN] = {0};
-  int num_read = read(state->inotify_fd, buf, BUF_LEN);
-  if (num_read == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
-    // No event, do nothing
-  } else if (num_read <= 0) {
-    log_error("Could not read inotify state");
-  } else {
-    should_reload = true;
+
+  // Skip inotify checking if it's not available
+  if (state->inotify_fd != -1 &&
+      (state->screen_shader.wd != -1 || state->buffer_shader.wd != -1)) {
+    char buf[BUF_LEN] = {0};
+    int num_read = read(state->inotify_fd, buf, BUF_LEN);
+    if (num_read == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
+      // No event, do nothing
+    } else if (num_read <= 0) {
+      log_error("[inotify] Could not read inotify state");
+    } else {
+      log_debug("[inotify] File changed on disk, reloading shaders");
+      should_reload = true;
+    }
   }
 
   if (glfwGetKey(state->window, GLFW_KEY_ESCAPE) == GLFW_PRESS) {