linux-capture: Fix xcomp capturing random windows

There are two situations where xcomposite window capture will capture
random windows: on first creation, and when going to the properties when
the current window is invalid. The first happens because for whatever
reason someone decided to just make it capture the first top-level
window if there is no set value. The second happens because the
properties widget cannot find the value it's looking for and defaults to
the first one when the properties are opened, thus selecting and
capturing the first window in the list (which is probably something we
should fix in the properties view at some point but I don't want to dive
into code that's even *more* cursed than xcomposite code right now)

I think that this was a major oversight and that whoever wrote it
however many countless years ago did not realize that this is something
that maybe users don't want to have happen.

So instead, this diff makes it so that on first creation, it creates a
value that says "[Select a window to capture]" that keeps the capture
inactive until a user actually chooses a window rather than the
top-level window. It also makes it so that if the user has a window that
is no longer valid, it will keep that window in the list and as the
currently selected value, which prevents it from automatically selecting
the first window in the list when properties are opened.

(Have I mentioned xcomposite is cursed? Trying to debug xcomposite code
in a debugger freezes my window compositor and forces me to do a hard
restart of my entire computer, so I was forced to use printf debugging.
Absolute nightmare-inducing code in here.)

plugins/linux-capture/data/locale/en-US.ini

@@ -11,3 +11,5 @@ CropRight="Crop Right"
 CropBottom="Crop Bottom"
 IncludeXBorder="Include X Border"
 ExcludeAlpha="Use alpha-less texture format (Mesa workaround)"
+SelectAWindow="[Select a window to capture]"
+UnknownWindow="[Unknown window]"

plugins/linux-capture/xcomposite-input.c

@@ -320,17 +320,14 @@ xcb_window_t xcomp_find_window(xcb_connection_t *conn, Display *disp,
 	char *wcls = NULL;
 	DARRAY(xcb_window_t) tlw = {0};
 
-	tlw.da = xcomp_top_level_windows(conn);
 	if (!str || strlen(str) == 0) {
-		if (tlw.num > 0)
-			ret = *(xcb_window_t *)darray_item(sizeof(xcb_window_t),
-							   &tlw.da, 0);
 		goto cleanup;
 	}
 
 	ret = convert_encoded_window_id(str, &wname, &wcls);
 
 	// first try to find a match by the window-id
+	tlw.da = xcomp_top_level_windows(conn);
 	if (da_find(tlw, &ret, 0) != DARRAY_INVALID) {
 		goto cleanup;
 	}
@@ -783,9 +780,9 @@ static inline bool compare_ids(const char *id1, const char *id2)
 	return id1 && id2 && strcmp(id1, id2) == 0;
 }
 
-static obs_properties_t *xcompcap_props(void *unused)
+static obs_properties_t *xcompcap_props(void *data)
 {
-	UNUSED_PARAMETER(unused);
+	struct xcompcap *s = (struct xcompcap *)data;
 
 	obs_properties_t *props = obs_properties_create();
 	obs_property_t *prop;
@@ -796,7 +793,47 @@ static obs_properties_t *xcompcap_props(void *unused)
 				       OBS_COMBO_FORMAT_STRING);
 
 	DARRAY(struct WindowInfo) window_strings = {0};
+	bool had_window_saved = false;
+
+	if (s) {
+		had_window_saved = s->windowName && *s->windowName;
+		if (had_window_saved) {
+			char *wname;
+			char *wcls;
+
+			convert_encoded_window_id(s->windowName, &wname, &wcls);
+			bfree(wcls);
+
+			struct dstr name = {0};
+			struct dstr desc = {0};
+			struct dstr name_lower = {0};
+
+			dstr_copy(&name,
+				  wname ? wname
+					: obs_module_text("UnknownWindow"));
+			bfree(wname);
+
+			dstr_copy(&desc, s->windowName);
+			dstr_copy_dstr(&name_lower, &name);
+			dstr_to_lower(&name_lower);
+
+			da_push_back(
+				window_strings,
+				(&(struct WindowInfo){name_lower, name, desc}));
+		} else {
+			struct dstr select_window_str;
+			dstr_init_copy(&select_window_str,
+				       obs_module_text("SelectAWindow"));
+			da_push_back(window_strings,
+				     (&(struct WindowInfo){{0},
+							   select_window_str,
+							   {0}}));
+		}
+	}
+
 	struct darray windows = xcomp_top_level_windows(conn);
+	bool window_found = false;
+
 	for (size_t w = 0; w < windows.num; w++) {
 		xcb_window_t win = *(xcb_window_t *)darray_item(
 			sizeof(xcb_window_t), &windows, w);
@@ -813,27 +850,41 @@ static obs_properties_t *xcompcap_props(void *unused)
 		dstr_init_copy_dstr(&name_lower, &name);
 		dstr_to_lower(&name_lower);
 
-		da_push_back(window_strings,
-			     (&(struct WindowInfo){name_lower, name, desc}));
+		if (!had_window_saved ||
+		    (s && !compare_ids(desc.array, s->windowName)))
+			da_push_back(
+				window_strings,
+				(&(struct WindowInfo){name_lower, name, desc}));
+		else {
+			window_found = true;
+			dstr_free(&name);
+			dstr_free(&name_lower);
+			dstr_free(&desc);
+		}
 	}
 	darray_free(&windows);
 
-	qsort(window_strings.array, window_strings.num,
-	      sizeof(struct WindowInfo), cmp_wi);
+	if (window_strings.num > 2)
+		qsort(window_strings.array + 1, window_strings.num - 1,
+		      sizeof(struct WindowInfo), cmp_wi);
 
 	for (size_t i = 0; i < window_strings.num; i++) {
-		struct WindowInfo *s = (struct WindowInfo *)darray_item(
+		struct WindowInfo *w = (struct WindowInfo *)darray_item(
 			sizeof(struct WindowInfo), &window_strings.da, i);
 
-		obs_property_list_add_string(prop, s->name.array,
-					     s->desc.array);
+		obs_property_list_add_string(prop, w->name.array,
+					     w->desc.array);
 
-		dstr_free(&s->name_lower);
-		dstr_free(&s->name);
-		dstr_free(&s->desc);
+		dstr_free(&w->name_lower);
+		dstr_free(&w->name);
+		dstr_free(&w->desc);
 	}
 	da_free(window_strings);
 
+	if (!had_window_saved || !window_found) {
+		obs_property_list_item_disable(prop, 0, true);
+	}
+
 	prop = obs_properties_add_int(props, "cut_top",
 				      obs_module_text("CropTop"), 0, 4096, 1);
 	obs_property_int_set_suffix(prop, " px");