Global: adds general cache layer

CHANGELOG.md

@@ -90,6 +90,7 @@ Bugfixes:
 * Worked around an iTerm bug where the image logo may be moved out of view. (Logo)
 * Increased the terminal response wait time to 1s to improve compatibility with slower terminals. (General)
 * Fixed the `PublicIp` and `Weather` modules exiting with "can only be used once due to internal limitations" on the round after a failed request when `--dynamic-interval` is used, instead of retrying. (PublicIp / Weather)
+* Fixed the `Display`, `Monitor`, `WM`, `DE`, `Media`, `Player`, `Shell` and `Terminal` modules replaying the first round's result when `--dynamic-interval` is used. The detection results that are cached for the whole run are now dropped between rounds, so these modules detect again on every round. (Display / Monitor / WM / DE / Media / Player / Shell / Terminal)
 * Some internal cleanups and optimizations.
 
 Logos:

CMakeLists.txt

@@ -462,6 +462,7 @@ set(LIBFASTFETCH_SRC
     src/common/impl/time.c
     src/common/impl/edidHelper.c
     src/common/impl/base64.c
+    src/common/impl/FFcache.c
     src/common/impl/FFlist.c
     src/common/impl/FFstrbuf.c
     src/common/impl/path.c
@@ -2197,6 +2198,13 @@ endif()
 ###################
 
 if (BUILD_TESTS)
+    add_executable(fastfetch-test-cache
+        tests/cache.c
+    )
+    target_link_libraries(fastfetch-test-cache
+        PRIVATE libfastfetch
+    )
+
     add_executable(fastfetch-test-strbuf
         tests/strbuf.c
     )

src/common/FFcache.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include "fastfetch.h"
+
+// A cache for a value that is built at most once per generation.
+//
+// The value itself is owned by the entry owner (usually a file scope `static`); the entry only
+// remembers whether that value is still valid and knows how to drop it. `--dynamic-interval`
+// starts a new generation for every round, dropping all the values that have been built so far,
+// so the modules re-detect them instead of replaying the first round's snapshot.
+//
+// An entry registers itself the first time it is used. There is therefore no central list to keep
+// in sync, and a cache cannot be forgotten in it. Do not use this type for state that is carried
+// across calls to derive a rate (cpuusage, diskio, netio, top): that is a baseline rather than a
+// snapshot, and dropping it makes the first sample of a round read as zero.
+//
+// The storage pointed to by `storage` must stay valid for the whole run; only the value behind it
+// is dropped by an invalidation.
+//
+// Not thread safe: entries are only touched from a single thread, on a frame boundary, while the
+// modules are not running.
+typedef struct FFcacheEntry {
+    const char* name;               // For diagnostics.
+    void* storage;                  // Owned by the entry owner. May be nullptr.
+    void (*init)(void* storage);    // Optional. Runs whenever the entry is stale.
+    void (*destroy)(void* storage); // Optional. Must be idempotent, and tolerate a partially initialized storage.
+    bool initialized;
+    bool registered;
+    struct FFcacheEntry* next; // Internal: registry link.
+} FFcacheEntry;
+
+// Returns `entry->storage`, running `init` on it first when the entry is stale. The entry is marked
+// initialized before `init` runs, so a call made from within `init` returns the partially built
+// value instead of recursing.
+[[gnu::nonnull(1)]] void* ffCacheGet(FFcacheEntry* entry);
+
+// Staleness test for entries whose initialization needs arguments that are not part of the cache
+// identity (such as the cover file request of `ffDetectMedia`) and therefore cannot live behind
+// `init(void*)`. Returns true exactly once per generation: the caller must then build the value
+// itself.
+[[gnu::nonnull(1), nodiscard]] bool ffCacheBeginInit(FFcacheEntry* entry);
+
+// Drops the cached value of one entry, so that the next request builds it again. Idempotent, and
+// safe on an entry that has never been used.
+[[gnu::nonnull(1)]] void ffCacheInvalidate(FFcacheEntry* entry);
+
+// Drops every value that has been built so far. Called once per `--dynamic-interval` round.
+void ffCacheInvalidateAll(void);

src/common/impl/FFcache.c

@@ -0,0 +1,53 @@
+#include "common/FFcache.h"
+
+// Entries are file scope statics owned by the cache owner, so they can be linked into a list
+// without any allocation. The list holds every entry that has been used at least once: an entry
+// that was never used has nothing to drop.
+static FFcacheEntry* entries = nullptr;
+
+static void registerEntry(FFcacheEntry* entry) {
+    if (entry->registered) {
+        return;
+    }
+
+    entry->registered = true;
+    entry->next = entries;
+    entries = entry;
+}
+
+void* ffCacheGet(FFcacheEntry* entry) {
+    if (ffCacheBeginInit(entry) && entry->init) {
+        entry->init(entry->storage);
+    }
+
+    return entry->storage;
+}
+
+bool ffCacheBeginInit(FFcacheEntry* entry) {
+    registerEntry(entry);
+
+    if (entry->initialized) {
+        return false;
+    }
+
+    entry->initialized = true;
+    return true;
+}
+
+void ffCacheInvalidate(FFcacheEntry* entry) {
+    if (!entry->initialized) {
+        return;
+    }
+
+    entry->initialized = false;
+
+    if (entry->destroy) {
+        entry->destroy(entry->storage);
+    }
+}
+
+void ffCacheInvalidateAll(void) {
+    for (FFcacheEntry* entry = entries; entry; entry = entry->next) {
+        ffCacheInvalidate(entry);
+    }
+}

src/common/impl/netif.c

@@ -1,22 +1,47 @@
 #include "common/netif.h"
+#include "common/FFcache.h"
 
-#ifndef _WIN32
-    #include <net/if.h>
-    #include <netinet/in.h>
-#endif
+#include <string.h>
+
+// netio, localip and dns resolve the default route on every round, and it can change while a
+// `--dynamic-interval` run is going on: a laptop switching from Wi-Fi to Ethernet, a VPN coming up.
+static FFNetifDefaultRouteResult defaultRouteV4;
+static FFNetifDefaultRouteResult defaultRouteV6;
+
+static void resetDefaultRoute(void* storage) {
+    // The impls only write the fields they found, so without this a round that finds no default
+    // route would keep reporting the interface of the previous one.
+    memset(storage, 0, sizeof(FFNetifDefaultRouteResult));
+}
+
+static void initDefaultRouteV4(void* storage) {
+    FFNetifDefaultRouteResult* result = storage;
+    result->status = ffNetifGetDefaultRouteImplV4(result) ? FF_NETIF_OK : FF_NETIF_INVALID;
+}
+
+static void initDefaultRouteV6(void* storage) {
+    FFNetifDefaultRouteResult* result = storage;
+    result->status = ffNetifGetDefaultRouteImplV6(result) ? FF_NETIF_OK : FF_NETIF_INVALID;
+}
+
+static FFcacheEntry ffCacheEntryDefaultRouteV4 = {
+    .name = "default route V4",
+    .storage = &defaultRouteV4,
+    .init = initDefaultRouteV4,
+    .destroy = resetDefaultRoute,
+};
+
+static FFcacheEntry ffCacheEntryDefaultRouteV6 = {
+    .name = "default route V6",
+    .storage = &defaultRouteV6,
+    .init = initDefaultRouteV6,
+    .destroy = resetDefaultRoute,
+};
 
 const FFNetifDefaultRouteResult* ffNetifGetDefaultRouteV4(void) {
-    static FFNetifDefaultRouteResult result;
-    if (result.status == FF_NETIF_UNINITIALIZED) {
-        result.status = ffNetifGetDefaultRouteImplV4(&result) ? FF_NETIF_OK : FF_NETIF_INVALID;
-    }
-    return &result;
+    return ffCacheGet(&ffCacheEntryDefaultRouteV4);
 }
 
 const FFNetifDefaultRouteResult* ffNetifGetDefaultRouteV6(void) {
-    static FFNetifDefaultRouteResult result;
-    if (result.status == FF_NETIF_UNINITIALIZED) {
-        result.status = ffNetifGetDefaultRouteImplV6(&result) ? FF_NETIF_OK : FF_NETIF_INVALID;
-    }
-    return &result;
+    return ffCacheGet(&ffCacheEntryDefaultRouteV6);
 }

src/detection/displayserver/displayserver.c

@@ -1,4 +1,5 @@
 #include "displayserver.h"
+#include "common/FFcache.h"
 
 FFDisplayResult* ffdsAppendDisplay(
     FFDisplayServerResult* result,
@@ -50,18 +51,45 @@ FFDisplayResult* ffdsAppendDisplay(
 
 void ffConnectDisplayServerImpl(FFDisplayServerResult* ds);
 
-const FFDisplayServerResult* ffConnectDisplayServer() {
-    static FFDisplayServerResult result;
-    static bool initialized = false;
-    if (!initialized) {
-        initialized = true;
-        ffStrbufInit(&result.wmProcessName);
-        ffStrbufInit(&result.wmPrettyName);
-        ffStrbufInit(&result.wmProtocolName);
-        ffStrbufInit(&result.deProcessName);
-        ffStrbufInit(&result.dePrettyName);
-        ffListInit(&result.displays);
-        ffConnectDisplayServerImpl(&result);
-    }
-    return &result;
+static FFDisplayServerResult result;
+
+static void initDisplayServerResult(void* storage) {
+    FFDisplayServerResult* ds = storage;
+
+    ffStrbufInit(&ds->wmProcessName);
+    ffStrbufInit(&ds->wmPrettyName);
+    ffStrbufInit(&ds->wmProtocolName);
+    ffStrbufInit(&ds->deProcessName);
+    ffStrbufInit(&ds->dePrettyName);
+    ffListInit(&ds->displays);
+
+    ffConnectDisplayServerImpl(ds);
+}
+
+static void destroyDisplayServerResult(void* storage) {
+    FFDisplayServerResult* ds = storage;
+
+    ffStrbufDestroy(&ds->wmProcessName);
+    ffStrbufDestroy(&ds->wmPrettyName);
+    ffStrbufDestroy(&ds->wmProtocolName);
+    ffStrbufDestroy(&ds->deProcessName);
+    ffStrbufDestroy(&ds->dePrettyName);
+
+    // Every display owns its name and serial, which are lost if the list is dropped as a whole
+    FF_LIST_FOR_EACH (FFDisplayResult, display, ds->displays) {
+        ffStrbufDestroy(&display->name);
+        ffStrbufDestroy(&display->serial);
+    }
+    ffListDestroy(&ds->displays);
+}
+
+static FFcacheEntry ffCacheEntryDisplayServer = {
+    .name = "displayServer",
+    .storage = &result,
+    .init = initDisplayServerResult,
+    .destroy = destroyDisplayServerResult,
+};
+
+const FFDisplayServerResult* ffConnectDisplayServer() {
+    return ffCacheGet(&ffCacheEntryDisplayServer);
 }

src/detection/gtk_qt/gtk.c

@@ -1,7 +1,7 @@
 #include "fastfetch.h"
 #include "common/properties.h"
-#include "common/thread.h"
 #include "common/settings.h"
+#include "common/FFcache.h"
 #include "detection/gtk_qt/gtk_qt.h"
 #include "detection/displayserver/displayserver.h"
 
@@ -11,29 +11,42 @@ static inline bool allPropertiesSet(FFGTKResult* result) {
         result->font.length > 0;
 }
 
-static inline void applyGTKSettings(FFGTKResult* result, const char* themeName, const char* iconsName, const char* fontName, const char* cursorTheme, int cursorSize, const char* wallpaper) {
+// The values read from the desktop settings daemons, shared by the GTK2/3/4 results. They are
+// owned copies on purpose: `settings.c` hands out strings it leaks deliberately (see the
+// "Leaks value.chars" notes there), so borrowing them past a `--dynamic-interval` round would
+// leak one set per round. Copying them also lets `destroy` release them.
+typedef struct FFGTKSettings {
+    FFstrbuf theme;
+    FFstrbuf icons;
+    FFstrbuf font;
+    FFstrbuf cursor;
+    FFstrbuf wallpaper;
+    int32_t cursorSize;
+} FFGTKSettings;
+
+static inline void applyGTKSettings(FFGTKResult* result, const FFGTKSettings* settings) {
     if (result->theme.length == 0) {
-        ffStrbufAppendS(&result->theme, themeName);
+        ffStrbufAppend(&result->theme, &settings->theme);
     }
 
     if (result->icons.length == 0) {
-        ffStrbufAppendS(&result->icons, iconsName);
+        ffStrbufAppend(&result->icons, &settings->icons);
     }
 
     if (result->font.length == 0) {
-        ffStrbufAppendS(&result->font, fontName);
+        ffStrbufAppend(&result->font, &settings->font);
     }
 
     if (result->cursor.length == 0) {
-        ffStrbufAppendS(&result->cursor, cursorTheme);
+        ffStrbufAppend(&result->cursor, &settings->cursor);
     }
 
-    if (result->cursorSize.length == 0 && cursorSize > 0) {
-        ffStrbufAppendF(&result->cursorSize, "%i", cursorSize);
+    if (result->cursorSize.length == 0 && settings->cursorSize > 0) {
+        ffStrbufAppendSInt(&result->cursorSize, settings->cursorSize);
     }
 
     if (result->wallpaper.length == 0) {
-        ffStrbufAppendS(&result->wallpaper, wallpaper);
+        ffStrbufAppend(&result->wallpaper, &settings->wallpaper);
     }
 }
 
@@ -43,22 +56,23 @@ static bool testXfconfWallpaperPropKey([[maybe_unused]] void* data, const char*
     return count == 0;
 }
 
-static void detectGTKFromSettings(FFGTKResult* result) {
-    static const char* themeName = nullptr;
-    static const char* iconsName = nullptr;
-    static const char* fontName = nullptr;
-    static const char* cursorTheme = nullptr;
-    static int cursorSize = 0;
-    static const char* wallpaper = nullptr;
+static FFGTKSettings gtkSettings;
 
-    static bool init = false;
+static void initGTKSettings(void* storage) {
+    FFGTKSettings* settings = storage;
 
-    if (init) {
-        applyGTKSettings(result, themeName, iconsName, fontName, cursorTheme, cursorSize, wallpaper);
-        return;
-    }
+    ffStrbufInit(&settings->theme);
+    ffStrbufInit(&settings->icons);
+    ffStrbufInit(&settings->font);
+    ffStrbufInit(&settings->cursor);
+    ffStrbufInit(&settings->wallpaper);
 
-    init = true;
+    const char* themeName = nullptr;
+    const char* iconsName = nullptr;
+    const char* fontName = nullptr;
+    const char* cursorTheme = nullptr;
+    int cursorSize = 0;
+    const char* wallpaper = nullptr;
 
     const FFDisplayServerResult* wmde = ffConnectDisplayServer();
 
@@ -98,14 +112,14 @@ static void detectGTKFromSettings(FFGTKResult* result) {
             wallpaper = ffSettingsGetGnome("/org/gnome/desktop/background/picture-uri", "org.gnome.desktop.background", nullptr, "picture-uri", FF_VARIANT_TYPE_STRING).strValue;
         } else if (
             ffStrbufIgnCaseEqualS(&wmde->dePrettyName, FF_DE_PRETTY_ENLIGHTENMENT)) {
-            ffEnlightenmentSettings settings = {};
-            if (ffSettingsGetEnlightenmentProperty(&settings)) {
-                themeName = settings.theme;
-                iconsName = settings.icon_theme;
-                fontName = settings.font;
-                cursorTheme = settings.use_e_cursor ? "Enlightenment" : "Application";
-                cursorSize = settings.cursor_size;
-                wallpaper = settings.desktop_default_background;
+            ffEnlightenmentSettings enlightenmentSettings = {};
+            if (ffSettingsGetEnlightenmentProperty(&enlightenmentSettings)) {
+                themeName = enlightenmentSettings.theme;
+                iconsName = enlightenmentSettings.icon_theme;
+                fontName = enlightenmentSettings.font;
+                cursorTheme = enlightenmentSettings.use_e_cursor ? "Enlightenment" : "Application";
+                cursorSize = enlightenmentSettings.cursor_size;
+                wallpaper = enlightenmentSettings.desktop_default_background;
             }
         }
     } else {
@@ -121,9 +135,34 @@ static void detectGTKFromSettings(FFGTKResult* result) {
         cursorSize = ffSettingsGetDConf("/org/gnome/desktop/interface/cursor-size", FF_VARIANT_TYPE_INT).intValue;
     }
 
-    applyGTKSettings(result, themeName, iconsName, fontName, cursorTheme, cursorSize, wallpaper);
+    // The strings above are owned by `settings.c`, which leaks them on purpose, so copy them into
+    // the cache instead of borrowing them: this runs again on every `--dynamic-interval` round.
+    ffStrbufSetS(&settings->theme, themeName);
+    ffStrbufSetS(&settings->icons, iconsName);
+    ffStrbufSetS(&settings->font, fontName);
+    ffStrbufSetS(&settings->cursor, cursorTheme);
+    ffStrbufSetS(&settings->wallpaper, wallpaper);
+    settings->cursorSize = cursorSize;
 }
 
+static void destroyGTKSettings(void* storage) {
+    FFGTKSettings* settings = storage;
+
+    ffStrbufDestroy(&settings->theme);
+    ffStrbufDestroy(&settings->icons);
+    ffStrbufDestroy(&settings->font);
+    ffStrbufDestroy(&settings->cursor);
+    ffStrbufDestroy(&settings->wallpaper);
+    settings->cursorSize = 0;
+}
+
+static FFcacheEntry ffCacheEntryGTKSettings = {
+    .name = "gtk-settings",
+    .storage = &gtkSettings,
+    .init = initGTKSettings,
+    .destroy = destroyGTKSettings,
+};
+
 static void detectGTKFromConfigFile(const char* filename, FFGTKResult* result) {
     ffParsePropFileValues(filename, 5, (FFpropquery[]) { { "gtk-theme-name =", &result->theme }, { "gtk-icon-theme-name =", &result->icons }, { "gtk-font-name =", &result->font }, { "gtk-cursor-theme-name =", &result->cursor }, { "gtk-cursor-theme-size =", &result->cursorSize } });
 }
@@ -172,7 +211,7 @@ static void detectGTKFromConfigDir(FFstrbuf* configDir, const char* version, FFG
 static void detectGTK(const char* version, FFGTKResult* result) {
     // Mate, Cinnamon, GNOME, Unity, Budgie use dconf to save theme config
     // On other DEs, this will do nothing
-    detectGTKFromSettings(result);
+    applyGTKSettings(result, ffCacheGet(&ffCacheEntryGTKSettings));
     if (allPropertiesSet(result)) {
         return;
     }
@@ -189,20 +228,51 @@ static void detectGTK(const char* version, FFGTKResult* result) {
     }
 }
 
-#define FF_DETECT_GTK_IMPL(version)   \
-    static FFGTKResult result;        \
-    static bool init = false;         \
-    if (init)                         \
-        return &result;               \
-    init = true;                      \
-    ffStrbufInit(&result.theme);      \
-    ffStrbufInit(&result.icons);      \
-    ffStrbufInit(&result.font);       \
-    ffStrbufInit(&result.cursor);     \
-    ffStrbufInit(&result.cursorSize); \
-    ffStrbufInit(&result.wallpaper);  \
-    detectGTK(#version, &result);     \
-    return &result;
+static void initGTKResult(const char* version, FFGTKResult* result) {
+    ffStrbufInit(&result->theme);
+    ffStrbufInit(&result->icons);
+    ffStrbufInit(&result->font);
+    ffStrbufInit(&result->cursor);
+    ffStrbufInit(&result->cursorSize);
+    ffStrbufInit(&result->wallpaper);
+    detectGTK(version, result);
+}
+
+static void destroyGTKResult(void* storage) {
+    FFGTKResult* result = storage;
+
+    ffStrbufDestroy(&result->theme);
+    ffStrbufDestroy(&result->icons);
+    ffStrbufDestroy(&result->font);
+    ffStrbufDestroy(&result->cursor);
+    ffStrbufDestroy(&result->cursorSize);
+    ffStrbufDestroy(&result->wallpaper);
+}
+
+static void initGTK2Result(void* storage) {
+    initGTKResult("2", storage);
+}
+
+static void initGTK3Result(void* storage) {
+    initGTKResult("3", storage);
+}
+
+static void initGTK4Result(void* storage) {
+    initGTKResult("4", storage);
+}
+
+// Each version gets its own result and its own entry, so a refresh drops all three (each one is
+// then rebuilt on demand, in the same lazy order as a single-shot run). They share the single
+// `gtk-settings` entry above, which keeps a round at one settings query instead of three.
+#define FF_DETECT_GTK_IMPL(version)       \
+    static FFGTKResult result;            \
+    static FFcacheEntry entry = {         \
+        .name = "gtk" #version,           \
+        .storage = &result,               \
+        .init = initGTK##version##Result, \
+        .destroy = destroyGTKResult,      \
+    };                                    \
+    return ffCacheGet(&entry);
 
 const FFGTKResult* ffDetectGTK2(void) {
     FF_DETECT_GTK_IMPL(2)
@@ -216,4 +286,4 @@ const FFGTKResult* ffDetectGTK4(void) {
     FF_DETECT_GTK_IMPL(4)
 }
 
-#undef FF_CALCULATE_GTK_IMPL
+#undef FF_DETECT_GTK_IMPL

src/detection/gtk_qt/qt.c

@@ -1,7 +1,7 @@
 #include "fastfetch.h"
 #include "common/properties.h"
-#include "common/thread.h"
 #include "common/strutil.h"
+#include "common/FFcache.h"
 #include "detection/gtk_qt/gtk_qt.h"
 #include "detection/displayserver/displayserver.h"
 
@@ -172,38 +172,53 @@ static void detectKvantum(FFQtResult* result) {
                                                                });
 }
 
-const FFQtResult* ffDetectQt(void) {
-    static FFQtResult result;
+static FFQtResult result;
 
-    static bool init = false;
-    if (init) {
-        return &result;
-    }
-    init = true;
+static void initQtResult(void* storage) {
+    FFQtResult* qt = storage;
 
-    ffStrbufInit(&result.widgetStyle);
-    ffStrbufInit(&result.colorScheme);
-    ffStrbufInit(&result.icons);
-    ffStrbufInit(&result.font);
-    ffStrbufInit(&result.wallpaper);
+    ffStrbufInit(&qt->widgetStyle);
+    ffStrbufInit(&qt->colorScheme);
+    ffStrbufInit(&qt->icons);
+    ffStrbufInit(&qt->font);
+    ffStrbufInit(&qt->wallpaper);
 
     const FFDisplayServerResult* wmde = ffConnectDisplayServer();
 
     if (ffStrbufIgnCaseEqualS(&wmde->dePrettyName, FF_DE_PRETTY_PLASMA)) {
-        detectPlasma(&result);
+        detectPlasma(qt);
     } else if (ffStrbufIgnCaseEqualS(&wmde->dePrettyName, FF_DE_PRETTY_LXQT)) {
-        detectLXQt(&result);
+        detectLXQt(qt);
     } else {
         const char* qPlatformTheme = getenv("QT_QPA_PLATFORMTHEME");
         if (qPlatformTheme && (ffStrEquals(qPlatformTheme, "qt5ct") || ffStrEquals(qPlatformTheme, "qt6ct"))) {
-            detectQtCt(qPlatformTheme[2], &result);
+            detectQtCt(qPlatformTheme[2], qt);
         }
     }
 
-    if (ffStrbufEqualS(&result.widgetStyle, "kvantum") || ffStrbufEqualS(&result.widgetStyle, "kvantum-dark")) {
-        ffStrbufClear(&result.widgetStyle);
-        detectKvantum(&result);
+    if (ffStrbufEqualS(&qt->widgetStyle, "kvantum") || ffStrbufEqualS(&qt->widgetStyle, "kvantum-dark")) {
+        ffStrbufClear(&qt->widgetStyle);
+        detectKvantum(qt);
     }
-
-    return &result;
+}
+
+static void destroyQtResult(void* storage) {
+    FFQtResult* qt = storage;
+
+    ffStrbufDestroy(&qt->widgetStyle);
+    ffStrbufDestroy(&qt->colorScheme);
+    ffStrbufDestroy(&qt->icons);
+    ffStrbufDestroy(&qt->font);
+    ffStrbufDestroy(&qt->wallpaper);
+}
+
+static FFcacheEntry ffCacheEntryQt = {
+    .name = "qt",
+    .storage = &result,
+    .init = initQtResult,
+    .destroy = destroyQtResult,
+};
+
+const FFQtResult* ffDetectQt(void) {
+    return ffCacheGet(&ffCacheEntryQt);
 }

src/detection/media/media.c

@@ -1,19 +1,53 @@
 #include "media.h"
+#include "common/FFcache.h"
 #include "common/io.h"
 
 void ffDetectMediaImpl(FFMediaResult* media, bool saveCover);
 
 static FFMediaResult result;
 
+// The cover file of this run, if there is one. It is tracked here rather than in `result` because
+// the cached result is dropped between `--dynamic-interval` rounds, while the file has to stay on
+// disk for the whole run: the `kitty-direct` logo type lets the terminal open it by path, and the
+// logo is replayed from the line cache on every round.
+static FFstrbuf coverFile;
+static bool coverFileRegistered = false;
+
 static void removeMediaCoverFile(void) {
-    if (result.cover.length > 0) {
-        ffRemoveFile(result.cover.chars);
-        ffStrbufDestroy(&result.cover);
+    if (coverFile.length > 0) {
+        ffRemoveFile(coverFile.chars);
+        ffStrbufDestroy(&coverFile);
     }
 }
 
+static void destroyMediaResult(void* storage) {
+    FFMediaResult* media = storage;
+
+    ffStrbufDestroy(&media->error);
+    ffStrbufDestroy(&media->playerId);
+    ffStrbufDestroy(&media->player);
+    ffStrbufDestroy(&media->song);
+    ffStrbufDestroy(&media->artist);
+    ffStrbufDestroy(&media->album);
+    ffStrbufDestroy(&media->url);
+    ffStrbufDestroy(&media->status);
+    ffStrbufDestroy(&media->cover);
+    media->length = 0;
+    media->position = 0;
+    media->removeCoverAfterUse = false;
+}
+
+// `saveCover` asks for a side effect and is not part of the cache identity, so the entry cannot be
+// initialized through `init(void*)`: the first caller of a generation decides, and the callers that
+// follow reuse its result, as they did when the result was cached for the whole run.
+static FFcacheEntry ffCacheEntryMedia = {
+    .name = "media",
+    .storage = &result,
+    .destroy = destroyMediaResult,
+};
+
 const FFMediaResult* ffDetectMedia(bool saveCover) {
-    if (result.error.chars == nullptr) {
+    if (ffCacheBeginInit(&ffCacheEntryMedia)) {
         ffStrbufInit(&result.error);
         ffStrbufInit(&result.playerId);
         ffStrbufInit(&result.player);
@@ -37,7 +71,11 @@ const FFMediaResult* ffDetectMedia(bool saveCover) {
         ffStrbufTrimRightSpace(&result.player);
 
         if (saveCover && result.removeCoverAfterUse) {
-            atexit(removeMediaCoverFile);
+            ffStrbufSet(&coverFile, &result.cover);
+            if (!coverFileRegistered) {
+                coverFileRegistered = true;
+                atexit(removeMediaCoverFile);
+            }
         }
     }
 

src/detection/os/os.c

@@ -1,21 +1,48 @@
 #include "os.h"
+#include "common/FFcache.h"
 
 void ffDetectOSImpl(FFOSResult* os);
 
-const FFOSResult* ffDetectOS(void) {
-    static FFOSResult result;
-    if (result.name.chars == nullptr) {
-        ffStrbufInit(&result.name);
-        ffStrbufInit(&result.prettyName);
-        ffStrbufInit(&result.id);
-        ffStrbufInit(&result.version);
-        ffStrbufInit(&result.versionID);
-        ffStrbufInit(&result.codename);
-        ffStrbufInit(&result.buildID);
-        ffStrbufInit(&result.idLike);
-        ffStrbufInit(&result.variant);
-        ffStrbufInit(&result.variantID);
-        ffDetectOSImpl(&result);
-    }
-    return &result;
+static FFOSResult result;
+
+static void initOSResult(void* storage) {
+    FFOSResult* os = storage;
+
+    ffStrbufInit(&os->name);
+    ffStrbufInit(&os->prettyName);
+    ffStrbufInit(&os->id);
+    ffStrbufInit(&os->version);
+    ffStrbufInit(&os->versionID);
+    ffStrbufInit(&os->codename);
+    ffStrbufInit(&os->buildID);
+    ffStrbufInit(&os->idLike);
+    ffStrbufInit(&os->variant);
+    ffStrbufInit(&os->variantID);
+    ffDetectOSImpl(os);
+}
+
+static void destroyOSResult(void* storage) {
+    FFOSResult* os = storage;
+
+    ffStrbufDestroy(&os->name);
+    ffStrbufDestroy(&os->prettyName);
+    ffStrbufDestroy(&os->id);
+    ffStrbufDestroy(&os->version);
+    ffStrbufDestroy(&os->versionID);
+    ffStrbufDestroy(&os->codename);
+    ffStrbufDestroy(&os->buildID);
+    ffStrbufDestroy(&os->idLike);
+    ffStrbufDestroy(&os->variant);
+    ffStrbufDestroy(&os->variantID);
+}
+
+static FFcacheEntry ffCacheEntryOS = {
+    .name = "os",
+    .storage = &result,
+    .init = initOSResult,
+    .destroy = destroyOSResult,
+};
+
+const FFOSResult* ffDetectOS(void) {
+    return ffCacheGet(&ffCacheEntryOS);
 }

src/detection/terminalshell/terminalshell_linux.c

@@ -1,4 +1,5 @@
 #include "terminalshell.h"
+#include "common/FFcache.h"
 #include "common/io.h"
 #include "common/parsing.h"
 #include "common/processing.h"
@@ -376,22 +377,43 @@ static void setTerminalInfoDetails(FFTerminalResult* result) {
     #define FF_EXE_PATH_LEN 260
 #endif
 
-const FFShellResult* ffDetectShell() {
-    static FFShellResult result;
-    static bool init = false;
-    if (init) {
-        return &result;
-    }
-    init = true;
+static FFShellResult shellResult;
 
-    ffStrbufInit(&result.processName);
-    ffStrbufInitA(&result.exe, FF_EXE_PATH_LEN);
-    result.exeName = result.exe.chars;
-    ffStrbufInit(&result.exePath);
-    ffStrbufInit(&result.version);
-    result.pid = 0;
-    result.ppid = 0;
-    result.tty = -1;
+static void destroyShellResult(void* storage) {
+    FFShellResult* result = storage;
+
+    ffStrbufDestroy(&result->processName);
+    ffStrbufDestroy(&result->exe);
+    result->exeName = result->exe.chars; // `exeName` points into `exe`, which is empty again
+    ffStrbufDestroy(&result->exePath);
+    ffStrbufDestroy(&result->prettyName);
+    ffStrbufDestroy(&result->version);
+    result->pid = 0;
+    result->ppid = 0;
+    result->tty = -1;
+}
+
+static FFcacheEntry ffCacheEntryShell = {
+    .name = "shell",
+    .storage = &shellResult,
+    .destroy = destroyShellResult,
+};
+
+const FFShellResult* ffDetectShell() {
+    FFShellResult* result = &shellResult;
+
+    if (!ffCacheBeginInit(&ffCacheEntryShell)) {
+        return result;
+    }
+
+    ffStrbufInit(&result->processName);
+    ffStrbufInitA(&result->exe, FF_EXE_PATH_LEN);
+    result->exeName = result->exe.chars;
+    ffStrbufInit(&result->exePath);
+    ffStrbufInit(&result->version);
+    result->pid = 0;
+    result->ppid = 0;
+    result->tty = -1;
 
     pid_t ppid = getppid();
 
@@ -401,49 +423,70 @@ const FFShellResult* ffDetectShell() {
         ffProcessGetBasicInfoLinux(ppid, &_, &ppid, nullptr);
     }
 
-    ppid = getShellInfo(&result, ppid);
-    getUserShellFromEnv(&result);
+    ppid = getShellInfo(result, ppid);
+    getUserShellFromEnv(result);
 
-    if (result.processName.length > 0) {
-        setShellInfoDetails(&result);
+    if (result->processName.length > 0) {
+        setShellInfoDetails(result);
         if (instance.config.general.detectVersion) {
-            fftsGetShellVersion(result.exePath.length > 0 ? &result.exePath : &result.exe, result.exeName, &result.version);
+            fftsGetShellVersion(result->exePath.length > 0 ? &result->exePath : &result->exe, result->exeName, &result->version);
         }
     }
 
-    return &result;
+    return result;
 }
 
-const FFTerminalResult* ffDetectTerminal() {
-    static FFTerminalResult result;
-    static bool init = false;
-    if (init) {
-        return &result;
-    }
-    init = true;
+static FFTerminalResult terminalResult;
 
-    ffStrbufInit(&result.processName);
-    ffStrbufInitA(&result.exe, FF_EXE_PATH_LEN);
-    result.exeName = result.exe.chars;
-    ffStrbufInit(&result.exePath);
-    ffStrbufInit(&result.version);
-    ffStrbufInitS(&result.tty, ttyname(STDOUT_FILENO));
-    result.pid = 0;
-    result.ppid = 0;
+static void destroyTerminalResult(void* storage) {
+    FFTerminalResult* result = storage;
+
+    ffStrbufDestroy(&result->processName);
+    ffStrbufDestroy(&result->exe);
+    result->exeName = result->exe.chars; // `exeName` points into `exe`, which is empty again
+    ffStrbufDestroy(&result->exePath);
+    ffStrbufDestroy(&result->prettyName);
+    ffStrbufDestroy(&result->version);
+    ffStrbufDestroy(&result->tty);
+    result->pid = 0;
+    result->ppid = 0;
+}
+
+static FFcacheEntry ffCacheEntryTerminal = {
+    .name = "terminal",
+    .storage = &terminalResult,
+    .destroy = destroyTerminalResult,
+};
+
+const FFTerminalResult* ffDetectTerminal() {
+    FFTerminalResult* result = &terminalResult;
+
+    if (!ffCacheBeginInit(&ffCacheEntryTerminal)) {
+        return result;
+    }
+
+    ffStrbufInit(&result->processName);
+    ffStrbufInitA(&result->exe, FF_EXE_PATH_LEN);
+    result->exeName = result->exe.chars;
+    ffStrbufInit(&result->exePath);
+    ffStrbufInit(&result->version);
+    ffStrbufInitS(&result->tty, ttyname(STDOUT_FILENO));
+    result->pid = 0;
+    result->ppid = 0;
 
     pid_t ppid = (pid_t) ffDetectShell()->ppid;
 
     if (ppid) {
-        ppid = getTerminalInfo(&result, ppid);
+        ppid = getTerminalInfo(result, ppid);
     }
-    getTerminalFromEnv(&result);
+    getTerminalFromEnv(result);
 
-    if (result.processName.length > 0) {
-        setTerminalInfoDetails(&result);
+    if (result->processName.length > 0) {
+        setTerminalInfoDetails(result);
         if (instance.config.general.detectVersion) {
-            fftsGetTerminalVersion(&result.processName, result.exePath.length > 0 ? &result.exePath : &result.exe, &result.version);
+            fftsGetTerminalVersion(&result->processName, result->exePath.length > 0 ? &result->exePath : &result->exe, &result->version);
         }
     }
 
-    return &result;
+    return result;
 }

src/detection/terminalshell/terminalshell_windows.c

@@ -1,4 +1,5 @@
 #include "terminalshell.h"
+#include "common/FFcache.h"
 #include "common/io.h"
 #include "common/processing.h"
 #include "common/thread.h"
@@ -293,27 +294,48 @@ static void setTerminalInfoDetails(FFTerminalResult* result) {
     }
 }
 
-const FFShellResult* ffDetectShell(void) {
-    static FFShellResult result;
-    static bool init = false;
-    if (init) {
-        return &result;
-    }
-    init = true;
+static FFShellResult shellResult;
 
-    ffStrbufInit(&result.processName);
-    ffStrbufInitA(&result.exe, MAX_PATH);
-    result.exeName = "";
-    ffStrbufInit(&result.exePath);
-    ffStrbufInit(&result.prettyName);
-    ffStrbufInit(&result.version);
-    result.pid = 0;
-    result.ppid = 0;
-    result.tty = -1;
+static void destroyShellResult(void* storage) {
+    FFShellResult* result = storage;
+
+    ffStrbufDestroy(&result->processName);
+    ffStrbufDestroy(&result->exe);
+    result->exeName = ""; // The `exe` buffer is empty again, so nothing points into it
+    ffStrbufDestroy(&result->exePath);
+    ffStrbufDestroy(&result->prettyName);
+    ffStrbufDestroy(&result->version);
+    result->pid = 0;
+    result->ppid = 0;
+    result->tty = -1;
+}
+
+static FFcacheEntry ffCacheEntryShell = {
+    .name = "shell",
+    .storage = &shellResult,
+    .destroy = destroyShellResult,
+};
+
+const FFShellResult* ffDetectShell(void) {
+    FFShellResult* result = &shellResult;
+
+    if (!ffCacheBeginInit(&ffCacheEntryShell)) {
+        return result;
+    }
+
+    ffStrbufInit(&result->processName);
+    ffStrbufInitA(&result->exe, MAX_PATH);
+    result->exeName = "";
+    ffStrbufInit(&result->exePath);
+    ffStrbufInit(&result->prettyName);
+    ffStrbufInit(&result->version);
+    result->pid = 0;
+    result->ppid = 0;
+    result->tty = -1;
 
     uint32_t ppid;
     if (!ffProcessGetInfoWindows(0, &ppid, nullptr, nullptr, nullptr, nullptr, nullptr)) {
-        return &result;
+        return result;
     }
 
     const char* ignoreParent = getenv("FFTS_IGNORE_PARENT");
@@ -321,60 +343,81 @@ const FFShellResult* ffDetectShell(void) {
         ffProcessGetInfoWindows(ppid, &ppid, nullptr, nullptr, nullptr, nullptr, nullptr);
     }
 
-    ppid = getShellInfo(&result, ppid);
+    ppid = getShellInfo(result, ppid);
 
-    if (result.processName.length > 0) {
-        setShellInfoDetails(&result);
+    if (result->processName.length > 0) {
+        setShellInfoDetails(result);
         char tmp[MAX_PATH];
-        strcpy(tmp, result.exeName);
+        strcpy(tmp, result->exeName);
         char* ext = strrchr(tmp, '.');
         if (ext) {
             *ext = '\0';
         }
         if (instance.config.general.detectVersion) {
-            fftsGetShellVersion(result.exePath.length > 0 ? &result.exePath : &result.exe, tmp, &result.version);
+            fftsGetShellVersion(result->exePath.length > 0 ? &result->exePath : &result->exe, tmp, &result->version);
         }
     }
 
-    return &result;
+    return result;
 }
 
-const FFTerminalResult* ffDetectTerminal(void) {
-    static FFTerminalResult result;
-    static bool init = false;
-    if (init) {
-        return &result;
-    }
-    init = true;
+static FFTerminalResult terminalResult;
 
-    ffStrbufInit(&result.processName);
-    ffStrbufInitA(&result.exe, MAX_PATH);
-    result.exeName = "";
-    ffStrbufInit(&result.exePath);
-    ffStrbufInit(&result.prettyName);
-    ffStrbufInit(&result.version);
-    ffStrbufInit(&result.tty);
-    result.pid = 0;
-    result.ppid = 0;
+static void destroyTerminalResult(void* storage) {
+    FFTerminalResult* result = storage;
+
+    ffStrbufDestroy(&result->processName);
+    ffStrbufDestroy(&result->exe);
+    result->exeName = ""; // The `exe` buffer is empty again, so nothing points into it
+    ffStrbufDestroy(&result->exePath);
+    ffStrbufDestroy(&result->prettyName);
+    ffStrbufDestroy(&result->version);
+    ffStrbufDestroy(&result->tty);
+    result->pid = 0;
+    result->ppid = 0;
+}
+
+static FFcacheEntry ffCacheEntryTerminal = {
+    .name = "terminal",
+    .storage = &terminalResult,
+    .destroy = destroyTerminalResult,
+};
+
+const FFTerminalResult* ffDetectTerminal(void) {
+    FFTerminalResult* result = &terminalResult;
+
+    if (!ffCacheBeginInit(&ffCacheEntryTerminal)) {
+        return result;
+    }
+
+    ffStrbufInit(&result->processName);
+    ffStrbufInitA(&result->exe, MAX_PATH);
+    result->exeName = "";
+    ffStrbufInit(&result->exePath);
+    ffStrbufInit(&result->prettyName);
+    ffStrbufInit(&result->version);
+    ffStrbufInit(&result->tty);
+    result->pid = 0;
+    result->ppid = 0;
 
     uint32_t ppid = ffDetectShell()->ppid;
     if (ppid) {
-        getTerminalInfo(&result, ppid);
+        getTerminalInfo(result, ppid);
     }
 
-    if (result.processName.length == 0) {
-        getTerminalFromEnv(&result);
+    if (result->processName.length == 0) {
+        getTerminalFromEnv(result);
     }
-    if (result.processName.length == 0) {
-        detectDefaultTerminal(&result);
+    if (result->processName.length == 0) {
+        detectDefaultTerminal(result);
     }
 
-    if (result.processName.length > 0) {
-        setTerminalInfoDetails(&result);
+    if (result->processName.length > 0) {
+        setTerminalInfoDetails(result);
         if (instance.config.general.detectVersion) {
-            fftsGetTerminalVersion(&result.processName, result.exePath.length > 0 ? &result.exePath : &result.exe, &result.version);
+            fftsGetTerminalVersion(&result->processName, result->exePath.length > 0 ? &result->exePath : &result->exe, &result->version);
         }
     }
 
-    return &result;
+    return result;
 }

src/fastfetch.c

@@ -2,6 +2,7 @@
 #include "common/ffdata.h"
 #include "detection/version/version.h"
 #include "logo/logo.h"
+#include "common/FFcache.h"
 #include "common/commandoption.h"
 #include "common/genconfig.h"
 #include "common/init.h"
@@ -815,6 +816,7 @@ static void run(FFdata* data) {
             ffTimeSleep(instance.state.dynamicInterval);
             fputs("\e[H", stdout); // Move cursor to the top left corner to overwrite the previous output
             instance.state.keysHeight = 0; // Reset keysHeight so `ffLogoPrintRemaining` will recalculate it
+            ffCacheInvalidateAll(); // Drop the detection results cached for the previous round, so that this round re-detects them
         } else {
             break;
         }

tests/cache.c

@@ -0,0 +1,120 @@
+#include "common/FFcache.h"
+#include "common/textModifier.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdnoreturn.h>
+
+typedef struct TestStorage {
+    int value;
+    int initCalls;
+    int destroyCalls;
+} TestStorage;
+
+static TestStorage storageA, storageB, storageC, storageD, storageUnused;
+
+static void initStorage(void* storage) {
+    TestStorage* test = storage;
+    ++test->initCalls;
+    test->value = 42;
+}
+
+static void destroyStorage(void* storage) {
+    TestStorage* test = storage;
+    ++test->destroyCalls;
+    test->value = -1;
+}
+
+static FFcacheEntry entryA = { .name = "A", .storage = &storageA, .init = initStorage, .destroy = destroyStorage };
+static FFcacheEntry entryB = { .name = "B", .storage = &storageB, .init = initStorage, .destroy = destroyStorage };
+static FFcacheEntry entryC = { .name = "C", .storage = &storageC, .init = initStorage, .destroy = destroyStorage };
+static FFcacheEntry entryD = { .name = "D", .storage = &storageD };
+static FFcacheEntry entryNoStorage = { .name = "no storage" };
+static FFcacheEntry entryUnused = { .name = "unused", .storage = &storageUnused, .init = initStorage, .destroy = destroyStorage };
+
+noreturn static void testFailed(const char* expression, int lineNo) {
+    fprintf(stderr, FASTFETCH_TEXT_MODIFIER_ERROR "[%d] %s\n" FASTFETCH_TEXT_MODIFIER_RESET, lineNo, expression);
+    exit(1);
+}
+
+noreturn static void testFailedInt(int expected, int actual, const char* what, int lineNo) {
+    fprintf(stderr, FASTFETCH_TEXT_MODIFIER_ERROR "[%d] %s: expected %d, got %d\n" FASTFETCH_TEXT_MODIFIER_RESET, lineNo, what, expected, actual);
+    exit(1);
+}
+
+#define VERIFY(expression) \
+    if (!(expression)) testFailed(#expression, __LINE__)
+
+#define VERIFY_INT(expected, actual, what) \
+    if ((expected) != (actual)) testFailedInt((expected), (actual), (what), __LINE__)
+
+int main(void) {
+    // A stale entry is built on the first get, and only then
+    VERIFY(ffCacheGet(&entryA) == &storageA);
+    VERIFY_INT(1, storageA.initCalls, "A init calls after the first get");
+    VERIFY_INT(42, storageA.value, "A value after the first get");
+
+    VERIFY(ffCacheGet(&entryA) == &storageA);
+    VERIFY_INT(1, storageA.initCalls, "A init calls after the second get");
+
+    // Nothing happens to the entry that has not been used yet
+    VERIFY_INT(0, storageUnused.initCalls, "unused init calls");
+
+    // Invalidating drops the value and rearms the entry, and doing it twice is a no-op
+    ffCacheInvalidate(&entryA);
+    VERIFY_INT(1, storageA.destroyCalls, "A destroy calls after invalidating");
+    ffCacheInvalidate(&entryA);
+    VERIFY_INT(1, storageA.destroyCalls, "A destroy calls after invalidating twice");
+
+    VERIFY(ffCacheGet(&entryA) == &storageA);
+    VERIFY_INT(2, storageA.initCalls, "A init calls after rebuilding");
+    VERIFY_INT(42, storageA.value, "A value after rebuilding");
+
+    // An entry that has never been used has nothing to drop
+    ffCacheInvalidate(&entryC);
+    VERIFY_INT(0, storageC.destroyCalls, "C destroy calls after invalidating an unused entry");
+    VERIFY(ffCacheGet(&entryC) == &storageC);
+    VERIFY_INT(1, storageC.initCalls, "C init calls");
+
+    // An entry without an initializer tracks staleness on its own
+    VERIFY(ffCacheGet(&entryD) == &storageD);
+    VERIFY(!ffCacheBeginInit(&entryD));
+    ffCacheInvalidate(&entryD);
+    VERIFY(ffCacheBeginInit(&entryD));
+    VERIFY(!ffCacheBeginInit(&entryD));
+
+    // An entry without storage and without callbacks is tolerated
+    VERIFY(ffCacheGet(&entryNoStorage) == nullptr);
+    ffCacheInvalidate(&entryNoStorage);
+    VERIFY(ffCacheGet(&entryNoStorage) == nullptr);
+
+    // An entry whose owner builds the value itself (which is what `ffCacheBeginInit` is for) is only
+    // marked, never built by the cache; and it must survive a `destroy` on a storage that the owner
+    // never filled in
+    VERIFY(ffCacheBeginInit(&entryB));
+    VERIFY_INT(0, storageB.initCalls, "B init calls (the owner builds the value itself)");
+
+    // Invalidating everything drops exactly the entries that have been used so far
+    ffCacheInvalidateAll();
+    VERIFY_INT(2, storageA.destroyCalls, "A destroy calls after invalidating all");
+    VERIFY_INT(1, storageC.destroyCalls, "C destroy calls after invalidating all");
+    VERIFY_INT(0, storageD.destroyCalls, "D destroy calls"); // D has no callback
+    VERIFY_INT(1, storageB.destroyCalls, "B destroy calls after invalidating a value that was never built");
+    VERIFY_INT(0, entryB.initialized, "B must be stale again after invalidating all");
+    VERIFY_INT(0, storageUnused.initCalls, "unused init calls after invalidating all");
+
+    // Rebuilding after invalidating all
+    VERIFY(ffCacheGet(&entryA) == &storageA);
+    VERIFY_INT(3, storageA.initCalls, "A init calls after invalidating all");
+    VERIFY_INT(42, storageA.value, "A value after invalidating all");
+
+    // An entry joins the registry when it is first used, not when it is created
+    VERIFY(ffCacheGet(&entryUnused) == &storageUnused);
+    VERIFY_INT(1, storageUnused.initCalls, "unused init calls after its first get");
+    ffCacheInvalidateAll();
+    VERIFY_INT(1, storageUnused.destroyCalls, "unused destroy calls after invalidating all");
+    VERIFY_INT(3, storageA.destroyCalls, "A destroy calls after the second invalidating all");
+
+    // Success
+    puts("\033[32mAll tests passed!" FASTFETCH_TEXT_MODIFIER_RESET);
+}