main: refuse to dump the result into tty

Closes: https://codeberg.org/vyivel/dulcepan/issues/17

meson.build

@@ -1,7 +1,7 @@
 project(
   'dulcepan',
   'c',
-  version: '1.0.1',
+  version: '1.0.2',
   license: 'GPL-3.0-only',
   default_options: [
     'c_std=c11',

src/main.c

@@ -1,6 +1,7 @@
 #include <getopt.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <wayland-client-core.h>
 #include <wayland-client-protocol.h>
 #include <xkbcommon/xkbcommon.h>
@@ -167,8 +168,9 @@ static void help(const char *prog) {
 			"  -o <path>    Specify the output file path.\n"
 			"\n"
 			"If the output file path is not specified, the resuling image will be printed to\n"
-			"the standard output. If the output file format is not specified, it is guessed\n"
-			"from the output file path if it's specified, and assumed to be PNG otherwise.\n"
+			"the standard output, which is expected to not be a terminal. If the output file\n"
+			"format is not specified, it is guessed from the output file path if it's\n"
+			"specified, and assumed to be PNG otherwise.\n"
 			"\n"
 			"Supported formats: png, ppm.\n"
 			"\n"
@@ -210,9 +212,13 @@ int main(int argc, char **argv) {
 		}
 	}
 
-	state.basedir_ctx = sfdo_basedir_ctx_create();
-
-	dp_config_load(&state, config_path);
+	if (state.output_path == NULL && isatty(STDOUT_FILENO)) {
+		fprintf(stderr,
+				"Refusing to run as the standard output is a terminal and there's no output file\n"
+				"path specified.\n\n");
+		help(argv[0]);
+		exit(1);
+	}
 
 	if (state.output_format == DP_FILE_UNKNOWN) {
 		if (state.output_path != NULL) {
@@ -227,6 +233,10 @@ int main(int argc, char **argv) {
 		}
 	}
 
+	state.basedir_ctx = sfdo_basedir_ctx_create();
+
+	dp_config_load(&state, config_path);
+
 	wl_list_init(&state.outputs);
 	wl_list_init(&state.seats);
 

src/output.c

@@ -79,6 +79,12 @@ static void frame_handle_buffer(void *data, struct zwlr_screencopy_frame_v1 *fra
 		wl_buffer_destroy(output->frame_buffer);
 	}
 
+	if ((int32_t)width != output->width || (int32_t)height != output->height) {
+		dp_log_fatal("Output/buffer size mismatch: mode=%" PRIi32 "x%" PRIi32 ", buffer=%" PRIu32
+					 "x%" PRIu32,
+				output->width, output->height, width, height);
+	}
+
 	output->frame_format = format;
 	output->frame_stride = (int)stride;
 	output->frame_buffer = dp_buffer_create(output->state, output->width, output->height,
@@ -156,6 +162,10 @@ static void output_handle_geometry(void *data, struct wl_output *wl_output, int3
 
 static void output_handle_mode(void *data, struct wl_output *wl_output, uint32_t flags,
 		int32_t width, int32_t height, int32_t refresh) {
+	if ((flags & WL_OUTPUT_MODE_CURRENT) == 0) {
+		return;
+	}
+
 	struct dp_output *output = data;
 
 	if (output->has_geom) {
@@ -178,6 +188,7 @@ static void output_handle_done(void *data, struct wl_output *wl_output) {
 
 	assert(output->name != NULL);
 
+	assert(output->width > 0 && output->height > 0);
 	if ((output->transform & WL_OUTPUT_TRANSFORM_90) != 0) {
 		output->transformed_width = output->height;
 		output->transformed_height = output->width;