Solves #46.

Introduce a dependency on tinycss2. Then _use_ it via some convenience
parsing finding functions.

Author: samcunliffe

setup.cfg

@@ -30,6 +30,7 @@ install_requires =
     matplotlib
     napari
     numpy
+    tinycss2
 python_requires = >=3.8
 include_package_data = True
 package_dir =
@@ -57,6 +58,7 @@ testing =
     pyqt6
     pytest
     pytest-cov
+    pytest-mock
     pytest-mpl
     pytest-qt
     tox

src/napari_matplotlib/base.py

@@ -12,7 +12,7 @@
 from qtpy.QtGui import QIcon
 from qtpy.QtWidgets import QVBoxLayout, QWidget
 
-from .util import Interval
+from .util import Interval, from_css_get_size_of
 
 # Icons modified from
 # https://github.com/matplotlib/matplotlib/tree/main/lib/matplotlib/mpl-data/images
@@ -52,7 +52,9 @@ def __init__(self, napari_viewer: napari.viewer.Viewer):
 
         self.canvas.figure.patch.set_facecolor("none")
         self.canvas.figure.set_layout_engine("constrained")
-        self.toolbar = NapariNavigationToolbar(self.canvas, self)
+        self.toolbar = NapariNavigationToolbar(
+            self.canvas, self
+        )  # type: ignore[no-untyped-call]
         self._replace_toolbar_icons()
 
         self.setLayout(QVBoxLayout())
@@ -189,6 +191,12 @@ def _replace_toolbar_icons(self) -> None:
 class NapariNavigationToolbar(NavigationToolbar2QT):
     """Custom Toolbar style for Napari."""
 
+    def __init__(self, *args, **kwargs):  # type: ignore[no-untyped-def]
+        super().__init__(*args, **kwargs)
+        self.setIconSize(
+            from_css_get_size_of("QtViewerPushButton", fallback=(28, 28))
+        )
+
     def _update_buttons_checked(self) -> None:
         """Update toggle tool icons when selected/unselected."""
         super()._update_buttons_checked()

src/napari_matplotlib/tests/test_util.py

@@ -1,6 +1,7 @@
 import pytest
+from qtpy.QtCore import QSize
 
-from napari_matplotlib.util import Interval
+from napari_matplotlib.util import Interval, from_css_get_size_of
 
 
 def test_interval():
@@ -13,3 +14,18 @@ def test_interval():
 
     with pytest.raises(ValueError, match="must be an integer"):
         "string" in interval  # type: ignore
+
+
+def test_get_size_from_css(mocker):
+    """Test getting the max-width and max-height from something in css"""
+    test_css = """
+        Flibble {
+            min-width : 0;
+            max-width : 123px;
+            min-height : 0px;
+            max-height : 456px;
+            padding: 0px;
+        }
+        """
+    mocker.patch("napari.qt.get_current_stylesheet").return_value = test_css
+    assert from_css_get_size_of("Flibble", (1, 1)) == QSize(123, 456)

src/napari_matplotlib/util.py

@@ -1,4 +1,8 @@
-from typing import Optional
+from typing import List, Optional, Tuple, Union
+
+import napari.qt
+import tinycss2
+from qtpy.QtCore import QSize
 
 
 class Interval:
@@ -34,3 +38,60 @@ def __contains__(self, val: int) -> bool:
         if self.upper is not None and val > self.upper:
             return False
         return True
+
+
+def _has_id(nodes: List[tinycss2.ast.Node], id_name: str) -> bool:
+    """
+    Is `id_name` in IdentTokens in the list of CSS `nodes`?
+    """
+    return any(
+        [node.type == "ident" and node.value == id_name for node in nodes]
+    )
+
+
+def _get_dimension(
+    nodes: List[tinycss2.ast.Node], id_name: str
+) -> Union[int, None]:
+    """
+    Get the value of the DimensionToken for the IdentToken `id_name`.
+
+    Returns
+    -------
+        None if no IdentToken is found.
+    """
+    cleaned_nodes = [node for node in nodes if node.type != "whitespace"]
+    for name, _, value, _ in zip(*(iter(cleaned_nodes),) * 4):
+        if (
+            name.type == "ident"
+            and value.type == "dimension"
+            and name.value == id_name
+        ):
+            return value.int_value
+    return None
+
+
+def from_css_get_size_of(
+    qt_element_name: str, fallback: Tuple[int, int]
+) -> QSize:
+    """
+    Get the size of `qt_element_name` from napari's current stylesheet.
+
+    TODO: Confirm that the napari.qt.get_current_stylesheet changes with napari
+          theme (docs seem to indicate it should)
+
+    Returns
+    -------
+        QSize of the element if it's found, the `fallback` if it's not found..
+    """
+    rules = tinycss2.parse_stylesheet(
+        napari.qt.get_current_stylesheet(),
+        skip_comments=True,
+        skip_whitespace=True,
+    )
+    w, h = None, None
+    for rule in rules:
+        if _has_id(rule.prelude, qt_element_name):
+            w = _get_dimension(rule.content, "max-width")
+            h = _get_dimension(rule.content, "max-height")
+            return QSize(w, h)
+    return QSize(*fallback)