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st/theme: Reuse stylesheets if possible

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The following happens when processing an `@import()` rule:

 1. `_st_theme_resolve_url()` to resolve file
 2. `insert_stylesheet()` to track file/sheet
   a. take ownership of file/sheet (ref)
   b. use file as key in `stylesheets_by_file` hash table
   c. use file as value in `files_by_stylesheet` hash table
 3. release reference to file

This leads to a refcount error when importing a file that
was already parsed before:

 1. file start with refcount 1
 2. `insert_stylesheet()`
   a. increases refcount to 2
   b. inserting into `stylesheets_by_file` *decreases* the
      passed-in key if the key already exists
   c. `files_by_stylesheet` now tracks a file with recount 1
 3. releases the last reference to file

The file object tracked in `files_by_stylesheet` is now invalid,
and accessing it results in a crash.

Avoid this issue by reusing existing stylesheets, so we don't insert
a stylesheet that's already tracked.

As a side-effect, this also saves us from re-parsing the same file
unnecessarily.

Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7306
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3619>
This commit is contained in:
Florian Müllner 2025-01-29 02:46:44 +01:00 committed by Marge Bot
parent e5b81e19f5
commit 829d2fd469
1 changed files with 26 additions and 6 deletions
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32
src/st/st-theme.c
View File

@ -244,6 +244,27 @@ insert_stylesheet (StTheme *theme,
g_hash_table_insert (theme->files_by_stylesheet, stylesheet, file);
}
static CRStyleSheet *
resolve_stylesheet (StTheme *theme,
GFile *file,
GError **error)
{
CRStyleSheet *sheet;
sheet = g_hash_table_lookup (theme->stylesheets_by_file, file);
if (sheet)
{
cr_stylesheet_ref (sheet);
return sheet;
}
sheet = parse_stylesheet (file, error);
if (sheet)
insert_stylesheet (theme, file, sheet);
return sheet;
}
/**
* st_theme_load_stylesheet:
* @theme: a #StTheme
@ -261,13 +282,12 @@ st_theme_load_stylesheet (StTheme *theme,
{
CRStyleSheet *stylesheet;
stylesheet = parse_stylesheet (file, error);
stylesheet = resolve_stylesheet (theme, file, error);
if (!stylesheet)
return FALSE;
stylesheet->app_data = GUINT_TO_POINTER (TRUE);
insert_stylesheet (theme, file, stylesheet);
cr_stylesheet_ref (stylesheet);
theme->custom_stylesheets = g_slist_prepend (theme->custom_stylesheets, stylesheet);
g_signal_emit (theme, signals[STYLESHEETS_CHANGED], 0);
@ -884,6 +904,7 @@ add_matched_properties (StTheme *a_this,
if (import_rule->sheet == NULL)
{
CRStyleSheet *sheet = NULL;
GFile *file = NULL;
if (import_rule->url->stryng && import_rule->url->stryng->str)
@ -891,13 +912,12 @@ add_matched_properties (StTheme *a_this,
file = _st_theme_resolve_url (a_this,
a_nodesheet,
import_rule->url->stryng->str);
import_rule->sheet = parse_stylesheet (file, NULL);
sheet = resolve_stylesheet (a_this, file, NULL);
}
if (import_rule->sheet)
if (sheet)
{
insert_stylesheet (a_this, file, import_rule->sheet);
/* refcount of stylesheets starts off at zero, so we don't need to unref! */
import_rule->sheet = sheet;
}
else
{