Add dte -Q option, to allow greater control over terminal queries

The previous (undocumented) `$DTE_FULL_QUERY` environment variable
is now replaced by `dte -Q6` (see the added comment for details).
`dte -Q0` disables queries entirely.

Values 1 through 3 correspond to the 3 existing query levels, but
also result in *all* levels between 1 and the selected value being
emitted at startup (instead of conditionally, based on responses to
earlier queries). Values 4 and 5 are reserved for future use and
anything `>= 6` is treated the same way as 6.

Note: this feature has been left undocumented for now, which implies
it may still receive breaking changes in the future.

src/editor.c

@@ -289,8 +289,8 @@ void ui_start(EditorState *e)
 // Like ui_start(), but to be called only the first time the UI is started.
 // Terminal queries are buffered before ui_resize() is called, so that only
 // a single term_output_flush() is needed (i.e. as opposed to calling
-// ui_start() + term_put_level_1_queries() + term_output_flush()).
-void ui_first_start(EditorState *e, bool emit_all_queries)
+// ui_start() + term_put_initial_queries() + term_output_flush()).
+void ui_first_start(EditorState *e, unsigned int terminal_query_level)
 {
     BUG_ON(e->status != EDITOR_RUNNING);
     Terminal *term = &e->terminal;
@@ -299,7 +299,7 @@ void ui_first_start(EditorState *e, bool emit_all_queries)
     term_use_alt_screen_buffer(term);
     term_enable_private_modes(term);
 
-    term_put_level_1_queries(term, emit_all_queries);
+    term_put_initial_queries(term, terminal_query_level);
     ui_resize(e);
 }
 

src/editor.h

@@ -162,7 +162,7 @@ EditorState *init_editor_state(void) RETURNS_NONNULL;
 void free_editor_state(EditorState *e) NONNULL_ARGS;
 void any_key(Terminal *term, unsigned int esc_timeout) NONNULL_ARGS;
 int main_loop(EditorState *e) NONNULL_ARGS WARN_UNUSED_RESULT;
-void ui_first_start(EditorState *e, bool emit_all_queries) NONNULL_ARGS;
+void ui_first_start(EditorState *e, unsigned int terminal_query_level) NONNULL_ARGS;
 void ui_start(EditorState *e) NONNULL_ARGS;
 void ui_end(EditorState *e) NONNULL_ARGS;
 void ui_resize(EditorState *e) NONNULL_ARGS;

src/main.c

@@ -102,7 +102,7 @@ static ExitCode lint_syntax(const char *filename, SyntaxLoadFlags flags)
     return get_nr_errors() ? EC_DATA_ERROR : EC_OK;
 }
 
-static ExitCode showkey_loop(void)
+static ExitCode showkey_loop(unsigned int terminal_query_level)
 {
     if (!term_mode_init()) {
         return ec_error("tcgetattr", EC_IO_ERROR);
@@ -118,7 +118,7 @@ static ExitCode showkey_loop(void)
     term_input_init(ibuf);
     term_output_init(obuf);
     term_enable_private_modes(&term);
-    term_put_level_1_queries(&term, !!xgetenv("DTE_FULL_QUERY"));
+    term_put_initial_queries(&term, terminal_query_level);
     term_put_literal(obuf, "Press any key combination, or use Ctrl+D to exit\r\n");
     term_output_flush(obuf);
 
@@ -401,14 +401,15 @@ static const char usage[] =
 // NOLINTNEXTLINE(readability-function-size)
 int main(int argc, char *argv[])
 {
-    static const char optstring[] = "hBHKRVS:b:c:t:r:s:";
+    static const char optstring[] = "hBHKRVQ:S:b:c:t:r:s:";
     const char *rc = NULL;
     const char *commands[8];
     const char *tags[8];
     size_t nr_commands = 0;
     size_t nr_tags = 0;
     bool read_rc = true;
     bool load_and_save_history = true;
+    unsigned int terminal_query_level = 1;
     errors_to_stderr(true);
 
     for (int ch; (ch = getopt(argc, argv, optstring)) != -1; ) {
@@ -443,8 +444,14 @@ int main(int argc, char *argv[])
         case 'H':
             load_and_save_history = false;
             break;
+        case 'Q':
+            if (!str_to_uint(optarg, &terminal_query_level)) {
+                fprintf(stderr, "Error: invalid argument for -Q: '%s'\n", optarg);
+                return EC_USAGE_ERROR;
+            }
+            break;
         case 'K':
-            return showkey_loop();
+            return showkey_loop(terminal_query_level);
         case 'V':
             return write_stdout(copyright, sizeof(copyright));
         case 'h':
@@ -550,7 +557,7 @@ int main(int argc, char *argv[])
     }
 
     set_view(window_get_first_view(window));
-    ui_first_start(e, !!xgetenv("DTE_FULL_QUERY"));
+    ui_first_start(e, terminal_query_level);
 
     for (size_t i = 0; i < nr_commands; i++) {
         handle_normal_command(e, commands[i], false);

src/terminal/output.c

@@ -195,21 +195,36 @@ void term_put_str(TermOutputBuffer *obuf, const char *str)
  * • https://vt100.net/docs/vt510-rm/DA1.html
  * • ECMA-48 §8.3.24
  */
-void term_put_level_1_queries(Terminal *term, bool emit_all)
+void term_put_initial_queries(Terminal *term, unsigned int level)
 {
+    if (level < 1) {
+        return;
+    }
+
     LOG_INFO("sending level 1 queries to terminal");
+    term_put_literal(&term->obuf, "\033[c"); // ECMA-48 DA (AKA "DA1")
 
-    // ECMA-48 DA (Device Attributes; referred to as "DA1" in other contexts)
-    term_put_literal(&term->obuf, "\033[c");
+    if (level < 2) {
+        return;
+    }
 
+    // Level 6 or greater means emit all query levels and also emit even
+    // conditional queries, i.e. those that are usually omitted when the
+    // corresponding feature flag was already set by term_init()
+    bool emit_all = (level >= 6);
     if (emit_all) {
-        LOG_INFO("emit_all set; unconditionally sending all queries");
-        term_put_level_2_queries(term, true);
-        term_put_level_3_queries(term, true);
-        // Set QUERY flags in Terminal::features, so that handle_query_reply()
-        // doesn't send level 2/3 queries again
-        term->features |= TFLAG_QUERY_L2 | TFLAG_QUERY_L3;
+        LOG_INFO("query level set to %u; unconditionally sending all queries", level);
     }
+
+    term_put_level_2_queries(term, emit_all);
+    term->features |= TFLAG_QUERY_L2;
+
+    if (level < 3) {
+        return;
+    }
+
+    term_put_level_3_queries(term, emit_all);
+    term->features |= TFLAG_QUERY_L3;
 }
 
 /*

src/terminal/output.h

@@ -53,7 +53,7 @@ void term_put_byte(TermOutputBuffer *obuf, char ch);
 void term_put_bytes(TermOutputBuffer *obuf, const char *str, size_t count);
 TermSetBytesMethod term_set_bytes(Terminal *term, char ch, size_t count);
 void term_put_str(TermOutputBuffer *obuf, const char *str);
-void term_put_level_1_queries(Terminal *term, bool emit_all);
+void term_put_initial_queries(Terminal *term, unsigned int level);
 void term_put_level_2_queries(Terminal *term, bool emit_all);
 void term_put_level_3_queries(Terminal *term, bool emit_all);
 void term_use_alt_screen_buffer(Terminal *term);

test/terminal.c

@@ -1681,14 +1681,14 @@ static void test_term_put_level_1_queries(TestContext *ctx)
     EXPECT_UINT_EQ(term.features, (C256 | BCE | TITLE | OSC52));
     EXPECT_EQ(obuf->count, 0);
 
-    // Basic level 1 queries (with emit_all=false)
+    // Basic level 1 queries
     static const char level1[] = "\033[c";
-    term_put_level_1_queries(&term, false);
+    term_put_initial_queries(&term, 1);
     EXPECT_MEMEQ(obuf->buf, obuf->count, level1, sizeof(level1) - 1);
 
     // All queries (forced by emit_all=true)
     static const char full[] =
-        // term_put_level_1_queries()
+        // term_put_initial_queries()
         "\033[c"
         // term_put_level_2_queries()
         "\033[>c"
@@ -1720,7 +1720,7 @@ static void test_term_put_level_1_queries(TestContext *ctx)
     ;
 
     obuf->count = 0;
-    term_put_level_1_queries(&term, true);
+    term_put_initial_queries(&term, 6);
     EXPECT_MEMEQ(obuf->buf, obuf->count, full, sizeof(full) - 1);
 
     EXPECT_EQ(obuf->scroll_x, 0);