feat: Allow adjusting user interface font size via hotkeys

Primary - plus/keypad plus = increase font size
Primary - minus/keypad minus = decrease font size
Primary - 0/keypad 0 = reset font size

Fixes #11343

8 files changed, 114 insertions, 18 deletions

diff --git a/gajim/common/setting_values.py b/gajim/common/setting_values.py
index d4ff0022f..1bba3453c 100644
--- a/gajim/common/setting_values.py
+++ b/gajim/common/setting_values.py
@@ -12,6 +12,7 @@
 # You should have received a copy of the GNU General Public License
 # along with Gajim. If not, see <http://www.gnu.org/licenses/>.
 
+from typing import Any
 from typing import Literal
 from typing import TypedDict
 
@@ -125,6 +126,10 @@ IntSettings = Literal[
     'preview_size',
 ]
 
+FloatSettings = Literal[
+    'app_font_size',
+]
+
 StringSettings = Literal[
     'action_on_close',
     'additional_uri_schemes',
@@ -159,10 +164,10 @@ StringSettings = Literal[
     'video_size',
 ]
 
-AllSettings = Literal[BoolSettings, IntSettings, StringSettings]
-AllSettingsT = str | int | bool | list[str]
+AllSettings = Literal[BoolSettings, IntSettings, FloatSettings, StringSettings]
+AllSettingsT = str | int | float | bool | list[str]
 
-APP_SETTINGS = {
+APP_SETTINGS: dict[str, str | int | float | bool | list[Any]] = {
     'additional_uri_schemes': '',
     'allow_open_file_uris': False,
     'always_english_wikipedia': False,
@@ -277,6 +282,7 @@ APP_SETTINGS = {
     'use_speller': True,
     'use_stun_server': False,
     'use_urgency_hint': True,
+    'app_font_size': 1.0,
     'video_framerate': '',
     'video_input_device': 'autovideosrc',
     'video_see_self': True,
diff --git a/gajim/common/settings.py b/gajim/common/settings.py
index d4324d9f5..063860184 100644
--- a/gajim/common/settings.py
+++ b/gajim/common/settings.py
@@ -52,6 +52,7 @@ from gajim.common.setting_values import BoolContactSettings
 from gajim.common.setting_values import BoolGroupChatSettings
 from gajim.common.setting_values import BoolSettings
 from gajim.common.setting_values import DEFAULT_SOUNDEVENT_SETTINGS
+from gajim.common.setting_values import FloatSettings
 from gajim.common.setting_values import HAS_ACCOUNT_DEFAULT
 from gajim.common.setting_values import HAS_APP_DEFAULT
 from gajim.common.setting_values import INITAL_WORKSPACE
@@ -239,6 +240,9 @@ class Settings:
         if IS_PORTABLE:
             APP_SETTINGS['use_keyring'] = False
 
+        if sys.platform == 'win32':
+            APP_SETTINGS['app_font_size'] = 1.125
+
     def _load_app_overrides(self) -> None:
         if not OVERRIDES_PATH.exists():
             return
@@ -628,6 +632,10 @@ class Settings:
     def get_app_setting(self, setting: IntSettings) -> int:
         ...
 
+    @overload
+    def get_app_setting(self, setting: FloatSettings) -> float:
+        ...
+
     def get_app_setting(self, setting: str) -> AllSettingsT:
         if setting not in APP_SETTINGS:
             raise ValueError(f'Invalid app setting: {setting}')
@@ -659,6 +667,12 @@ class Settings:
 
     @overload
     def set_app_setting(self,
+                        setting: FloatSettings,
+                        value: float | None) -> None:
+        ...
+
+    @overload
+    def set_app_setting(self,
                         setting: Literal['workspace_order'],
                         value: list[str]) -> None:
         ...
diff --git a/gajim/data/gui/shortcuts_window.ui b/gajim/data/gui/shortcuts_window.ui
index 1c24e5be6..b032bcc19 100644
--- a/gajim/data/gui/shortcuts_window.ui
+++ b/gajim/data/gui/shortcuts_window.ui
@@ -65,6 +65,34 @@
         <child>
           <object class="GtkShortcutsGroup">
             <property name="visible">1</property>
+            <property name="title" translatable="yes">User Interface</property>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;primary&gt;plus</property>
+                <property name="title" translatable="yes">Increase User Interface Font Size</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;primary&gt;minus</property>
+                <property name="title" translatable="yes">Decrease User Interface Font Size</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
+                <property name="accelerator">&lt;primary&gt;0</property>
+                <property name="title" translatable="yes">Reset User Interface Font Size</property>
+              </object>
+            </child>
+          </object>
+        </child>
+
+        <child>
+          <object class="GtkShortcutsGroup">
+            <property name="visible">1</property>
             <property name="title" translatable="yes">Message composition</property>
             <child>
               <object class="GtkShortcutsShortcut">
diff --git a/gajim/data/other/shortcuts.json b/gajim/data/other/shortcuts.json
index 27e14db7b..4f26e891f 100644
--- a/gajim/data/other/shortcuts.json
+++ b/gajim/data/other/shortcuts.json
@@ -38,6 +38,9 @@
     "win.switch-workspace-7": ["<Primary>7", "<Primary>KP_7"],
     "win.switch-workspace-8": ["<Primary>8", "<Primary>KP_8"],
     "win.switch-workspace-9": ["<Primary>9", "<Primary>KP_9"],
+    "win.increase-app-font-size": ["<Primary>plus", "<Primary>KP_Add"],
+    "win.decrease-app-font-size": ["<Primary>minus", "<Primary>KP_Subtract"],
+    "win.reset-app-font-size": ["<Primary>0", "<Primary>KP_0"],
     "win.toggle-chat-list": ["<Primary>R"],
     "win.scroll-view-up": ["<Shift>Page_Up"],
     "win.scroll-view-down": ["<Shift>Page_Down"]
diff --git a/gajim/gtk/const.py b/gajim/gtk/const.py
index 107a910df..085eb449e 100644
--- a/gajim/gtk/const.py
+++ b/gajim/gtk/const.py
@@ -270,6 +270,9 @@ MAIN_WIN_ACTIONS = [
     ('switch-workspace-7', None, True),
     ('switch-workspace-8', None, True),
     ('switch-workspace-9', None, True),
+    ('increase-app-font-size', None, True),
+    ('decrease-app-font-size', None, True),
+    ('reset-app-font-size', None, True),
     ('toggle-chat-list', None, True),
     ('add-workspace', 's', True),
     ('edit-workspace', 's', True),
diff --git a/gajim/gtk/css_config.py b/gajim/gtk/css_config.py
index a683510ae..4f246250c 100644
--- a/gajim/gtk/css_config.py
+++ b/gajim/gtk/css_config.py
@@ -108,6 +108,13 @@ class CSSConfig:
             self._dynamic_provider,
             CSSPriority.APPLICATION)
 
+        # Font size provider for GUI font size
+        self._app_font_size_provider = Gtk.CssProvider()
+        Gtk.StyleContext.add_provider_for_screen(
+            screen,
+            self._app_font_size_provider,
+            CSSPriority.PRE_APPLICATION)
+
         # Cache of recently requested values
         self._cache: dict[str, str | Pango.FontDescription | None] = {}
 
@@ -128,8 +135,7 @@ class CSSConfig:
             self._provider,
             CSSPriority.USER_THEME)
 
-        if sys.platform == 'win32':
-            self._apply_windows_font_size()
+        self.apply_app_font_size()
 
     @property
     def prefer_dark(self) -> bool:
@@ -197,20 +203,14 @@ class CSSConfig:
         except Exception:
             log.exception('Error loading application css')
 
-    @staticmethod
-    def _apply_windows_font_size() -> None:
-        css = '''
-        * {
-            font-size: 1.125rem;
-        }
+    def apply_app_font_size(self) -> None:
+        app_font_size = app.settings.get('app_font_size')
+        css = f'''
+        * {{
+            font-size: {app_font_size}rem;
+        }}
         '''
-        provider = Gtk.CssProvider()
-        provider.load_from_data(bytes(css.encode('utf-8')))
-        screen = Gdk.Screen.get_default()
-        assert screen is not None
-        Gtk.StyleContext.add_provider_for_screen(screen,
-                                                 provider,
-                                                 CSSPriority.PRE_APPLICATION)
+        self._app_font_size_provider.load_from_data(bytes(css.encode('utf-8')))
 
     @staticmethod
     def _pango_to_css_weight(number: int) -> int:
diff --git a/gajim/gtk/main.py b/gajim/gtk/main.py
index 21b33eedd..7e9d7991a 100644
--- a/gajim/gtk/main.py
+++ b/gajim/gtk/main.py
@@ -416,6 +416,9 @@ class MainWindow(Gtk.ApplicationWindow, EventHelper):
             ('switch-workspace-7', self._on_action),
             ('switch-workspace-8', self._on_action),
             ('switch-workspace-9', self._on_action),
+            ('increase-app-font-size', self._on_app_font_size_action),
+            ('decrease-app-font-size', self._on_app_font_size_action),
+            ('reset-app-font-size', self._on_app_font_size_action),
             ('toggle-chat-list', self._on_action),
             ('preview-download', self._on_preview_action),
             ('preview-open', self._on_preview_action),
@@ -505,6 +508,34 @@ class MainWindow(Gtk.ApplicationWindow, EventHelper):
 
         return None
 
+    def _on_app_font_size_action(
+            self,
+            action: Gio.SimpleAction,
+            _param: GLib.Variant
+            ) -> None:
+
+        action_name = action.get_name()
+        if action_name == 'reset-app-font-size':
+            app.settings.set_app_setting('app_font_size', None)
+            app.css_config.apply_app_font_size()
+            return
+
+        app_font_size = app.settings.get('app_font_size')
+        new_app_font_size = app_font_size
+        if action_name == 'increase-app-font-size':
+            new_app_font_size = app_font_size + 0.125
+        elif action_name == 'decrease-app-font-size':
+            new_app_font_size = app_font_size - 0.125
+
+        # Clamp font size
+        new_app_font_size = max(min(1.5, new_app_font_size), 1.0)
+
+        if new_app_font_size == app_font_size:
+            return
+
+        app.settings.set_app_setting('app_font_size', new_app_font_size)
+        app.css_config.apply_app_font_size()
+
     def _on_preview_action(self,
                            action: Gio.SimpleAction,
                            param: GLib.Variant
diff --git a/gajim/gtk/preferences.py b/gajim/gtk/preferences.py
index 6264ecb56..86b86bbd5 100644
--- a/gajim/gtk/preferences.py
+++ b/gajim/gtk/preferences.py
@@ -643,6 +643,13 @@ class Themes(PreferenceBox):
         }
 
         settings = [
+            Setting(SettingKind.SPIN,
+                    _('User Interface Font Size'),
+                    SettingType.CONFIG,
+                    'app_font_size',
+                    props={'range_': (1.0, 1.5, 0.125)},
+                    callback=self._on_app_font_size_changed),
+
             Setting(SettingKind.POPOVER,
                     _('Dark Theme'),
                     SettingType.CONFIG,
@@ -664,6 +671,10 @@ class Themes(PreferenceBox):
         PreferenceBox.__init__(self, settings)
 
     @staticmethod
+    def _on_app_font_size_changed(_value: float, *args: Any) -> None:
+        app.css_config.apply_app_font_size()
+
+    @staticmethod
     def _get_theme_items() -> list[str]:
         theme_items = ['default']
         theme_items.extend(app.css_config.themes)