config: add a debug environment variable

This is where we keep temporary, short living, private debug options.

Adding and removing command line and config file options are
troublesome, and we don't want people adding these to their config
files.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/config.c

@@ -8,6 +8,7 @@
 #include <limits.h>
 #include <math.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -615,6 +616,72 @@ char *locate_auxiliary_file(const char *scope, const char *path, const char *inc
 	return ret;
 }
 
+struct debug_options_entry {
+	const char *name;
+	const char **choices;
+	size_t offset;
+};
+
+static const struct debug_options_entry debug_options_entries[] = {
+
+};
+
+void parse_debug_option_single(char *setting, struct debug_options *debug_options) {
+	char *equal = strchr(setting, '=');
+	size_t name_len = equal ? (size_t)(equal - setting) : strlen(setting);
+	for (size_t i = 0; i < ARR_SIZE(debug_options_entries); i++) {
+		if (strncmp(setting, debug_options_entries[i].name, name_len) != 0) {
+			continue;
+		}
+		if (debug_options_entries[i].name[name_len] != '\0') {
+			continue;
+		}
+		auto value = (int *)((void *)debug_options + debug_options_entries[i].offset);
+		if (equal) {
+			const char *const arg = equal + 1;
+			if (debug_options_entries[i].choices != NULL) {
+				for (size_t j = 0; debug_options_entries[i].choices[j]; j++) {
+					if (strcmp(arg, debug_options_entries[i].choices[j]) ==
+					    0) {
+						*value = (int)j;
+						return;
+					}
+				}
+			}
+			if (!parse_int(arg, value)) {
+				log_error("Invalid value for debug option %s: %s, it "
+				          "will be ignored.",
+				          debug_options_entries[i].name, arg);
+			}
+		} else if (debug_options_entries[i].choices == NULL) {
+			*value = 1;
+		} else {
+			log_error(
+			    "Missing value for debug option %s, it will be ignored.", setting);
+		}
+		return;
+	}
+	log_error("Invalid debug option: %s", setting);
+}
+
+/// Parse debug options from environment variable `PICOM_DEBUG`.
+void parse_debug_options(struct debug_options *debug_options) {
+	const char *debug = getenv("PICOM_DEBUG");
+	const struct debug_options default_debug_options = {};
+
+	*debug_options = default_debug_options;
+	if (!debug) {
+		return;
+	}
+
+	scoped_charp debug_copy = strdup(debug);
+	char *tmp, *needle = strtok_r(debug_copy, ";", &tmp);
+	while (needle) {
+		parse_debug_option_single(needle, debug_options);
+		needle = strtok_r(NULL, ";", &tmp);
+	}
+}
+
 /**
  * Parse a list of window shader rules.
  */
@@ -817,5 +884,6 @@ char *parse_config(options_t *opt, const char *config_file, bool *shadow_enable,
 	(void)hasneg;
 	(void)winopt_mask;
 #endif
+	parse_debug_options(&opt->debug_options);
 	return ret;
 }

src/config.h

@@ -73,6 +73,11 @@ enum blur_method {
 
 typedef struct _c2_lptr c2_lptr_t;
 
+/// Internal, private options for debugging and development use.
+struct debug_options {
+
+};
+
 /// Structure representing all options.
 typedef struct options {
 	// === Debugging ===
@@ -262,6 +267,8 @@ typedef struct options {
 	c2_lptr_t *transparent_clipping_blacklist;
 
 	bool dithered_present;
+
+	struct debug_options debug_options;
 } options_t;
 
 extern const char *const BACKEND_STRS[NUM_BKEND + 1];