Use explicit output ordering (#2103)

Removed output sorting by `priority` in favor of explicit output ordering. Fixes some Wayland initialization bugs.

src/display-console.cc

@@ -50,10 +50,7 @@ void register_output<output_t::CONSOLE>(display_outputs_t &outputs) {
 }
 
 display_output_console::display_output_console(const std::string &name_)
-    : display_output_base(name_) {
-  // lowest priority, it's a fallback
-  priority = 0;
-}
+    : display_output_base(name_) {}
 
 bool display_output_console::detect() {
   if ((out_to_stdout.get(*state) || out_to_stderr.get(*state))

src/display-file.cc

@@ -56,8 +56,6 @@ void register_output<output_t::FILE>(display_outputs_t &outputs) {
 
 display_output_file::display_output_file(const std::string &name_)
     : display_output_base(name_) {
-  // lowest priority, it's a fallback
-  priority = 0;
 }
 
 bool display_output_file::detect() {

src/display-http.cc

@@ -127,7 +127,6 @@ std::string string_replace_all(std::string original, const std::string &oldpart,
 //}  // namespace priv
 
 display_output_http::display_output_http() : display_output_base("http") {
-  priority = 0;
   httpd = NULL;
 }
 

src/display-ncurses.cc

@@ -91,9 +91,7 @@ Colour from_ncurses(int nccolor) {
 }
 
 display_output_ncurses::display_output_ncurses()
-    : display_output_console("ncurses") {
-  priority = 1;
-}
+    : display_output_console("ncurses") {}
 
 bool display_output_ncurses::detect() {
   if (out_to_ncurses.get(*state)) {

src/display-output.cc

@@ -80,22 +80,24 @@ std::vector<conky::display_output_base *> current_display_outputs;
 bool initialize_display_outputs() {
   std::vector<display_output_base *> outputs;
   outputs.reserve(static_cast<size_t>(output_t::OUTPUT_COUNT));
-  register_output<output_t::CONSOLE>(outputs);
-  register_output<output_t::NCURSES>(outputs);
-  register_output<output_t::FILE>(outputs);
-  register_output<output_t::HTTP>(outputs);
-  register_output<output_t::X11>(outputs);
+
+  // Order of registration is important!
+  // - Graphical outputs go before textual (e.g. X11 before NCurses).
+  // - Optional outputs go before non-optional (e.g. Wayland before X11).
+  // - Newer outputs go before older (e.g. NCurses before (hypothetical) Curses).
+  // - Fallbacks go last (in group)
   register_output<output_t::WAYLAND>(outputs);
+  register_output<output_t::X11>(outputs);
+  register_output<output_t::HTTP>(outputs);
+  register_output<output_t::FILE>(outputs);
+  register_output<output_t::NCURSES>(outputs);
+  register_output<output_t::CONSOLE>(outputs);  // global fallback - always works
 
   for (auto out : outputs) { NORM_ERR("FOUND: %s", out->name.c_str()); }
 
-  // Sort display outputs by descending priority, to try graphical ones first.
-  sort(outputs.begin(), outputs.end(), &display_output_base::priority_compare);
-
   int graphical_count = 0;
 
   for (auto output : outputs) {
-    if (output->priority < 0) continue;
     DBGP2("Testing display output '%s'... ", output->name.c_str());
     if (output->detect()) {
       DBGP2("Detected display output '%s'... ", output->name.c_str());

src/display-output.hh

@@ -61,17 +61,11 @@ class display_output_base {
   const std::string name;
   bool is_active = false;
   bool is_graphical = false;
-  int priority = -1;
 
   explicit display_output_base(const std::string &name) : name(name){};
 
   virtual ~display_output_base() {}
 
-  static bool priority_compare(const display_output_base *a,
-                               const display_output_base *b) {
-    return a->priority > b->priority;
-  }
-
   // check if available and enabled in settings
   virtual bool detect() { return false; }
   // connect to DISPLAY and other stuff

src/display-wayland.cc

@@ -243,7 +243,6 @@ void register_output<output_t::WAYLAND>(display_outputs_t &outputs) {
 display_output_wayland::display_output_wayland()
     : display_output_base("wayland") {
   is_graphical = true;
-  priority = 2;
 }
 
 bool display_output_wayland::detect() {

src/display-x11.cc

@@ -226,7 +226,6 @@ void register_output<output_t::X11>(display_outputs_t &outputs) {
 
 display_output_x11::display_output_x11() : display_output_base("x11") {
   is_graphical = true;
-  priority = 2;
 }
 
 bool display_output_x11::detect() {