Draft: Liquid Glass Adaptation on UIScrollView

changes/4275.feature.md

@@ -0,0 +1 @@
+On iOS 18-, system effects are applied to the title bar when a ScrollContainer is the content of the window and reaches the titlebar area; on iOS 26+, system effects are consistently applied to the title bar when a ScrollContainer simply reaches the top of the window container layout.

cocoa/src/toga_cocoa/widgets/scrollcontainer.py

@@ -37,7 +37,7 @@ def refreshContent(self):
     # This cannot be covered in CI because the function used to emit
     # a scrolling event is unreliable.
     @objc_method
-    def wantsForwardedScrollEventsForAxis_(self, axis: int) -> None:  # pragma: no cover
+    def wantsForwardedScrollEventsForAxis_(self, axis: int) -> bool:  # pragma: no cover
         return True
 
 

examples/scrollcontainer/pyproject.toml

@@ -45,6 +45,7 @@ requires = [
     "../../iOS",
     "std-nslog>=1.0.0",
 ]
+info."UIDesignRequiresCompatibility" = true
 
 [tool.briefcase.app.scrollcontainer.android]
 requires = [

examples/scrollcontainer/scrollcontainer/app.py

@@ -19,8 +19,6 @@ class ScrollContainerApp(toga.App):
     TOGGLE_CHUNK = 10
 
     def startup(self):
-        main_box = toga.Box(direction=COLUMN)
-
         self.hswitch = toga.Switch(
             "Horizontal",
             value=False,
@@ -46,10 +44,6 @@ def startup(self):
             value=False,
             on_change=lambda widget: self.update_content(),
         )
-        main_box.add(
-            toga.Box(children=[self.hswitch, self.vswitch]),
-            toga.Box(children=[self.wide_switch, self.tall_switch, self.nested_switch]),
-        )
 
         self.inner_box = toga.Box(
             direction=COLUMN, margin=10, background_color="yellow"
@@ -59,16 +53,22 @@ def startup(self):
             vertical=self.vswitch.value,
             on_scroll=self.on_scroll,
             flex=1,
-            margin=10,
             background_color="pink",
         )
+        self.button = toga.Button("Toggle Controls", on_press=self.on_control_press)
         self.update_content()
 
         self.scroller.content = self.inner_box
-        main_box.add(self.scroller)
+
+        self.main_box = toga.Box(direction=COLUMN, margin_bottom=10)
+        self.main_box.add(self.scroller)
+        self.main_box.add(
+            toga.Box(children=[self.hswitch, self.vswitch]),
+            toga.Box(children=[self.wide_switch, self.tall_switch, self.nested_switch]),
+        )
 
         self.main_window = toga.MainWindow(size=(400, 700))
-        self.main_window.content = main_box
+        self.main_window.content = self.main_box
         self.main_window.show()
 
         self.commands.add(
@@ -102,6 +102,20 @@ def startup(self):
             ),
         )
 
+    def on_control_press(self, widget):
+        if self.main_window.content != self.scroller:
+            self.main_box.clear()
+            self.main_window.content = self.scroller
+        else:
+            self.main_window.content = self.main_box
+            self.main_box.add(self.scroller)
+            self.main_box.add(
+                toga.Box(children=[self.hswitch, self.vswitch]),
+                toga.Box(
+                    children=[self.wide_switch, self.tall_switch, self.nested_switch]
+                ),
+            )
+
     def handle_hscrolling(self, widget):
         self.scroller.horizontal = self.hswitch.value
 
@@ -110,14 +124,17 @@ def handle_vscrolling(self, widget):
 
     def update_content(self):
         self.inner_box.clear()
+        self.inner_box.add(self.button)
 
         width = 10 if self.wide_switch.value else 2
         height = 30 if self.tall_switch.value else 2
         for x in range(height):
             label_text = f"Label {x}"
             if self.nested_switch.value:
                 self.inner_box.add(
-                    toga.ScrollContainer(content=Item(width, label_text)),
+                    toga.ScrollContainer(
+                        content=Item(width, label_text), vertical=False
+                    ),
                 )
             else:
                 self.inner_box.add(Item(width, label_text))

iOS/src/toga_iOS/container.py

@@ -112,6 +112,11 @@ def __init__(
         self.bottom_inset = 0
         self.right_inset = 0
 
+        self.top_unset = False
+        self.left_unset = False
+        self.bottom_unset = False
+        self.right_unset = False
+
     def __del__(self):
         # Mark the contained native object as explicitly None so that the
         # constraints know the object has been deleted.

iOS/src/toga_iOS/libs/__init__.py

@@ -5,3 +5,4 @@
 from .mapkit import *  # NOQA
 from .uikit import *  # NOQA
 from .webkit import *  # NOQA
+from .liquidglass import *  # noqa: F401, F403

iOS/src/toga_iOS/libs/core_foundation.py

@@ -0,0 +1,28 @@
+from ctypes import c_bool, c_char_p, c_uint32, c_void_p, cdll, util
+
+cf = cdll.LoadLibrary(util.find_library("CoreFoundation"))
+
+kCFStringEncodingUTF8 = 134217984
+
+CFBundleRef = c_void_p
+CFURLRef = c_void_p
+CFStringRef = c_void_p
+
+
+cf.CFBundleGetMainBundle.restype = CFBundleRef
+cf.CFBundleGetMainBundle.argtypes = []
+
+cf.CFBundleCopyBundleURL.restype = CFURLRef
+cf.CFBundleCopyBundleURL.argtypes = [CFBundleRef]
+
+cf.CFBundleCopyInfoDictionaryForURL.restype = c_void_p
+cf.CFBundleCopyInfoDictionaryForURL.argtypes = [CFURLRef]
+
+cf.CFDictionaryGetValue.restype = c_void_p
+cf.CFDictionaryGetValue.argtypes = [c_void_p, c_void_p]
+
+cf.CFStringCreateWithCString.restype = CFStringRef
+cf.CFStringCreateWithCString.argtypes = [c_void_p, c_char_p, c_uint32]
+
+cf.CFBooleanGetValue.restype = c_bool
+cf.CFBooleanGetValue.argtypes = [c_void_p]

iOS/src/toga_iOS/libs/liquidglass.py

@@ -0,0 +1,29 @@
+from platform import ios_ver
+
+from .core_foundation import cf, kCFStringEncodingUTF8
+from .sdk_version import get_sdk_version
+
+bundle = cf.CFBundleGetMainBundle()
+url = cf.CFBundleCopyBundleURL(bundle)
+info_dict = cf.CFBundleCopyInfoDictionaryForURL(url)
+key_cf = cf.CFStringCreateWithCString(
+    None, b"UIDesignRequiresCompatibility", kCFStringEncodingUTF8
+)
+value_cf = cf.CFDictionaryGetValue(info_dict, key_cf)
+if value_cf is None:
+    value_py = None
+else:
+    value_py = bool(cf.CFBooleanGetValue(value_cf))
+supports_liquid_glass = False
+if value_py is True:
+    supports_liquid_glass = False
+elif value_py is False:
+    supports_liquid_glass = True
+else:
+    supports_liquid_glass = int(get_sdk_version().split(".")[0]) >= 26
+
+supports_liquid_glass = (
+    supports_liquid_glass and int(ios_ver().release.split(".")[0]) >= 26
+)
+
+__all__ = ["supports_liquid_glass"]

iOS/src/toga_iOS/libs/sdk_version.py

@@ -0,0 +1,87 @@
+import ctypes
+
+MH_MAGIC = 0xFEEDFACE
+MH_MAGIC_64 = 0xFEEDFACF
+
+LC_BUILD_VERSION = 0x32
+
+
+class MachHeader32(ctypes.Structure):
+    _fields_ = [
+        ("magic", ctypes.c_uint32),
+        ("cputype", ctypes.c_uint32),
+        ("cpusubtype", ctypes.c_uint32),
+        ("filetype", ctypes.c_uint32),
+        ("ncmds", ctypes.c_uint32),
+        ("sizeofcmds", ctypes.c_uint32),
+        ("flags", ctypes.c_uint32),
+    ]
+
+
+class MachHeader64(ctypes.Structure):
+    _fields_ = [
+        ("magic", ctypes.c_uint32),
+        ("cputype", ctypes.c_uint32),
+        ("cpusubtype", ctypes.c_uint32),
+        ("filetype", ctypes.c_uint32),
+        ("ncmds", ctypes.c_uint32),
+        ("sizeofcmds", ctypes.c_uint32),
+        ("flags", ctypes.c_uint32),
+        ("reserved", ctypes.c_uint32),
+    ]
+
+
+class LoadCommand(ctypes.Structure):
+    _fields_ = [
+        ("cmd", ctypes.c_uint32),
+        ("cmdsize", ctypes.c_uint32),
+    ]
+
+
+class BuildVersionCommand(ctypes.Structure):
+    _fields_ = [
+        ("cmd", ctypes.c_uint32),
+        ("cmdsize", ctypes.c_uint32),
+        ("platform", ctypes.c_uint32),
+        ("minos", ctypes.c_uint32),
+        ("sdk", ctypes.c_uint32),
+        ("ntools", ctypes.c_uint32),
+    ]
+
+
+libc = ctypes.CDLL(None)
+_dyld_get_image_header = libc._dyld_get_image_header
+_dyld_get_image_header.restype = ctypes.c_void_p
+_dyld_get_image_header.argtypes = [ctypes.c_uint32]
+
+
+def decode_version(v):
+    return f"{v >> 16}.{(v >> 8) & 0xFF}.{v & 0xFF}"
+
+
+def get_sdk_version():
+    mh_ptr = _dyld_get_image_header(0)
+    magic = ctypes.c_uint32.from_address(mh_ptr).value
+
+    if magic == MH_MAGIC_64:
+        header = MachHeader64.from_address(mh_ptr)
+        cmd_ptr = mh_ptr + ctypes.sizeof(MachHeader64)
+    elif magic == MH_MAGIC:
+        header = MachHeader32.from_address(mh_ptr)
+        cmd_ptr = mh_ptr + ctypes.sizeof(MachHeader32)
+    else:
+        return None
+
+    for _ in range(header.ncmds):
+        lc = LoadCommand.from_address(cmd_ptr)
+
+        if lc.cmd == LC_BUILD_VERSION:
+            cmd = BuildVersionCommand.from_address(cmd_ptr)
+            return decode_version(cmd.sdk)
+
+        cmd_ptr += lc.cmdsize
+
+    return None
+
+
+__all__ = ["get_sdk_version"]

iOS/src/toga_iOS/widgets/base.py

@@ -3,6 +3,8 @@
 from toga_iOS.colors import native_color
 from toga_iOS.constraints import Constraints
 
+from ..libs import supports_liquid_glass
+
 
 class Widget:
     def __init__(self, interface):
@@ -22,6 +24,14 @@ def __init__(self, interface):
         # #3104 for details.
         self._default_background_color = self.native.backgroundColor
 
+    @property
+    def scroll_vertical(self):
+        return False
+
+    @property
+    def scroll_horizontal(self):
+        return False
+
     @abstractmethod
     def create(self): ...
 
@@ -78,7 +88,28 @@ def set_tab_index(self, tab_index):
     # APPLICATOR
 
     def set_bounds(self, x, y, width, height):
-        # print("SET BOUNDS", self, x, y, width, height, self.container.top_offset)
+        # print("SET BOUNDS", self, x, y, width, height, self.container.top_inset)
+        if supports_liquid_glass or self.container.content == self:
+            if self.scroll_vertical and self.container.top_unset and y == 0:
+                y -= self.container.top_inset
+                height += self.container.top_inset
+            # Right now, the below lines are irrelevant and lead to coverage issues,
+            # as we only have a title bar to bleed over.  When constructs such as
+            # if (
+            #     self.scroll_vertical
+            #     and self.container.bottom_unset
+            #     and y + height == self.container.height
+            # ):
+            #     height += self.container.bottom_inset
+            # if self.scroll_horizontal and self.container.left_unset and x == 0:
+            #     x -= self.container.left_inset
+            #     width += self.container.left_inset
+            # if (
+            #     self.scroll_horizontal
+            #     and self.container.right_unset
+            #     and x + width == self.container.width
+            # ):
+            #     width += self.container.right_inset
         self.constraints.update(x, y, width, height)
 
     def set_text_align(self, alignment):

iOS/src/toga_iOS/widgets/scrollcontainer.py

@@ -90,6 +90,7 @@ def get_vertical(self):
 
     def set_vertical(self, value):
         self._allow_vertical = value
+        self.native.alwaysBounceVertical = value
         # If the scroll container has content, we need to force a refresh
         # to let the scroll container know how large its content is.
         if self.interface.content:
@@ -102,8 +103,17 @@ def set_vertical(self, value):
     def get_horizontal(self):
         return self._allow_horizontal
 
+    @property
+    def scroll_vertical(self):
+        return self._allow_vertical
+
+    @property
+    def scroll_horizontal(self):
+        return self._allow_horizontal
+
     def set_horizontal(self, value):
         self._allow_horizontal = value
+        self.native.alwaysBounceHorizontal = value
         # If the scroll container has content, we need to force a refresh
         # to let the scroll container know how large its content is.
         if self.interface.content:

iOS/src/toga_iOS/window.py

@@ -267,6 +267,8 @@ def create_container(self):
             on_refresh=self.content_refreshed,
             on_native_layout=self.content_native_layout,
         )
+        # Widgets can extend into the top space with safe blurring.
+        self.container.top_unset = True
 
     def content_native_layout(self, container):
         # Instead of manually computing the geometry at the top,