Icon support for all columns in Winforms Table

changes/4164.feature.md

@@ -0,0 +1 @@
+Allows the WinForms Table widget to display icons in all columns. Previously, icons were only supported in the first column. Changes to the tests have also been made to test the new structure.

winforms/src/toga_winforms/widgets/table.py

@@ -1,3 +1,12 @@
+from ctypes import (
+    POINTER,
+    WINFUNCTYPE,
+    Structure as c_Structure,
+    c_size_t,
+    cast,
+    windll,
+)
+from ctypes.wintypes import HWND, INT, LPARAM, LPWSTR, UINT, WPARAM
 from warnings import warn
 
 import System.Windows.Forms as WinForms
@@ -6,6 +15,89 @@
 
 from .base import Widget
 
+################################################
+# C classes used with Windows shell functions.
+################################################
+LRESULT = LPARAM  # LPARAM is essentially equivalent to LRESULT
+UINT_PTR = c_size_t
+DWORD_PTR = c_size_t
+
+
+class LVITEMW(c_Structure):
+    _fields_ = [
+        ("uiMask", UINT),
+        ("iItem", INT),
+        ("iSubItem", INT),
+        ("state", UINT),
+        ("stateMask", UINT),
+        ("pszText", LPWSTR),
+        ("cchTextMax", INT),
+        ("iImage", INT),
+        ("lParam", LPARAM),
+        ("iIndent", INT),
+        ("iGroupId", INT),
+        ("cColumns", UINT),
+        ("puColumns", POINTER(UINT)),
+        ("piColFmt", INT),
+        ("iGroup", INT),
+    ]
+
+
+class NMHDR(c_Structure):
+    _fields_ = [
+        ("hwndFrom", HWND),
+        ("idFrom", UINT_PTR),
+        ("code", UINT),
+    ]
+
+
+class NMLVDISPINFOW(c_Structure):
+    _fields_ = [
+        ("hdr", NMHDR),
+        ("item", LVITEMW),
+    ]
+
+
+SUBCLASSPROC = WINFUNCTYPE(
+    # Return type:
+    LRESULT,
+    # Argument types:
+    HWND,
+    UINT,
+    WPARAM,
+    LPARAM,
+    UINT_PTR,
+    DWORD_PTR,
+)
+
+################################################
+# Windows shell functions.
+################################################
+PostMessageW = windll.user32.PostMessageW
+
+DefSubclassProc = windll.comctl32.DefSubclassProc
+SetWindowSubclass = windll.comctl32.SetWindowSubclass
+RemoveWindowSubclass = windll.comctl32.RemoveWindowSubclass
+
+################################################
+# Windows message hex codes.
+################################################
+LVIF_TEXT = 0x0001
+LVIF_IMAGE = 0x0002
+LVIF_STATE = 0x0008
+
+LVM_GETEXTENDEDLISTVIEWSTYLE = 0x1037
+LVM_SETEXTENDEDLISTVIEWSTYLE = 0x1036
+
+LVN_GETDISPINFOW = 0xFFFFFF4F
+
+LVS_EX_SUBITEMIMAGES = 0x2
+
+WM_NCDESTROY = 0x0082
+WM_REFLECT_NOTIFY = 0x204E
+
+################################################
+
 
 class Table(Widget):
     # The following methods are overridden in DetailedList.
@@ -25,9 +117,18 @@ def _multiple_select(self):
     def _data(self):
         return self.interface.data
 
+    def __del__(self):
+        self.native.Dispose()
+
     def create(self):
+        self.pfn_subclass = SUBCLASSPROC(self._subclass_proc)
         self.native = WinForms.ListView()
+        self._set_subclass()
+
+        self.native.HandleCreated += WeakrefCallable(self.handle_created)
+
         self.native.View = WinForms.View.Details
+        self._enable_multi_icon_style()
         self._cache = []
         self._first_item = 0
         self._pending_resize = True
@@ -67,6 +168,57 @@ def create(self):
         )
         self.add_action_events()
 
+    def _enable_multi_icon_style(self):
+        list_view_handle = int(self.native.Handle.ToString())
+
+        old_style = PostMessageW(list_view_handle, LVM_GETEXTENDEDLISTVIEWSTYLE, 0, 0)
+        new_style = old_style | LVS_EX_SUBITEMIMAGES
+
+        PostMessageW(list_view_handle, LVM_SETEXTENDEDLISTVIEWSTYLE, 0, new_style)
+
+    def handle_created(self, sender, e):
+        self._set_subclass()
+
+    def _set_subclass(self):
+        SetWindowSubclass(int(self.native.Handle.ToString()), self.pfn_subclass, 0, 0)
+
+    def _subclass_proc(
+        self,
+        hWnd: int,
+        uMsg: int,
+        wParam: int,
+        lParam: int,
+        uIdSubclass: int,
+        dwRefData: int,
+    ) -> LRESULT:
+        # Remove the window subclass in the way recommended by Raymond Chen here:
+        # https://devblogs.microsoft.com/oldnewthing/20031111-00/?p=41883
+        if uMsg == WM_NCDESTROY:
+            RemoveWindowSubclass(hWnd, self.pfn_subclass, uIdSubclass)
+
+        if uMsg == WM_REFLECT_NOTIFY:
+            phdr = cast(lParam, POINTER(NMHDR)).contents
+            code = phdr.code
+            if hex(code) == hex(LVN_GETDISPINFOW):
+                disp_info = cast(lParam, POINTER(NMLVDISPINFOW)).contents
+                self._set_subitem_icon(disp_info.item)
+
+        # Call the original window procedure
+        return DefSubclassProc(HWND(hWnd), UINT(uMsg), LPARAM(wParam), LPARAM(lParam))
+
+    def _set_subitem_icon(self, lvitem: LVITEMW):
+        row_index = lvitem.iItem
+        column_index = lvitem.iSubItem
+
+        _, icon_indices = self._toga_retrieve_virtual_item(row_index)
+
+        # Add the icon property if it doesn't exist.
+        if lvitem.uiMask == (LVIF_TEXT | LVIF_STATE):
+            lvitem.uiMask = LVIF_TEXT | LVIF_STATE | LVIF_IMAGE
+
+        if lvitem.uiMask & LVIF_IMAGE != 0 and icon_indices[column_index] > -1:
+            lvitem.iImage = icon_indices[column_index]
+
     def add_action_events(self):
         self.native.MouseDoubleClick += WeakrefCallable(self.winforms_double_click)
 
@@ -80,14 +232,17 @@ def winforms_retrieve_virtual_item(self, sender, e):
         # Because ListView is in VirtualMode, it's necessary implement
         # VirtualItemsSelectionRangeChanged event to create ListViewItem
         # when it's needed
+        e.Item, _ = self._toga_retrieve_virtual_item(e.ItemIndex)
+
+    def _toga_retrieve_virtual_item(self, item_index):
         if (
             self._cache
-            and e.ItemIndex >= self._first_item
-            and e.ItemIndex < self._first_item + len(self._cache)
+            and item_index >= self._first_item
+            and item_index < self._first_item + len(self._cache)
         ):
-            e.Item = self._cache[e.ItemIndex - self._first_item]
+            return self._cache[item_index - self._first_item]
         else:
-            e.Item = self._new_item(e.ItemIndex)
+            return self._new_item(item_index)
 
     def winforms_cache_virtual_items(self, sender, e):
         if (
@@ -194,28 +349,26 @@ def _resize_columns(self):
     def change_source(self, source):
         self.update_data()
 
+    def _icon_index(self, row, column) -> int:
+        icon = column.icon(row)
+        return -1 if icon is None else self._image_index(icon._impl)
+
     def _new_item(self, index):
-        item = self._data[index]
+        row = self._data[index]
 
         missing_value = self.interface.missing_value
         lvi = WinForms.ListViewItem(
-            [column.text(item, missing_value) for column in self._columns],
+            [column.text(row, missing_value) for column in self._columns],
         )
-        if any(column.widget(item) is not None for column in self._columns):
+        if any(column.widget(row) is not None for column in self._columns):
             warn(
                 "Winforms does not support the use of widgets in cells",
                 stacklevel=1,
             )
 
-        # If the table has accessors, populate the icons for the table.
-        if self._columns:
-            # TODO: ListView only has built-in support for one icon per row. One
-            # possible workaround is in https://stackoverflow.com/a/46128593.
-            icon = self._columns[0].icon(item)
-            if icon is not None:
-                lvi.ImageIndex = self._image_index(icon._impl)
+        icon_indices = tuple(self._icon_index(row, column) for column in self._columns)
 
-        return lvi
+        return (lvi, icon_indices)
 
     def _image_index(self, icon):
         images = self.native.SmallImageList.Images

winforms/tests_backend/widgets/table.py

@@ -30,25 +30,26 @@ def assert_cell_content(self, row, col, value=None, icon=None, widget=None):
             pytest.skip("This backend doesn't support widgets in Tables")
         else:
             lvi = self.native.Items[row]
+
+            _, icon_indices = self.impl._toga_retrieve_virtual_item(row)
+            icon_index = icon_indices[col]
+
             assert lvi.SubItems[col].Text == value
-            if col == 0:
-                if icon is None:
-                    assert lvi.ImageIndex == -1
-                    assert lvi.ImageKey == ""
-                else:
-                    imagelist = self.native.SmallImageList
-                    size = imagelist.ImageSize
-                    assert size.Width == size.Height == 16
-
-                    # The image is resized and copied, so we need to compare the actual
-                    # pixels.
-                    actual = imagelist.Images[lvi.ImageIndex]
-                    expected = Bitmap(icon._impl.bitmap, size)
-                    for x in range(size.Width):
-                        for y in range(size.Height):
-                            assert actual.GetPixel(x, y) == expected.GetPixel(x, y)
-            else:
-                assert icon is None
+            assert lvi.ImageIndex == -1
+            assert lvi.ImageKey == ""
+
+            if icon is not None:
+                imagelist = self.native.SmallImageList
+                size = imagelist.ImageSize
+                assert size.Width == size.Height == 16
+
+                # The image is resized and copied, so we need to compare the actual
+                # pixels.
+                actual = imagelist.Images[icon_index]
+                expected = Bitmap(icon._impl.bitmap, size)
+                for x in range(size.Width):
+                    for y in range(size.Height):
+                        assert actual.GetPixel(x, y) == expected.GetPixel(x, y)
 
     @property
     def max_scroll_position(self):