Add colormap combobox and utils (#195)

* feat: add colormap combobox

* working on styles

* add comment

* style: [pre-commit.ci] auto fixes [...]

* progress on combo

* style: [pre-commit.ci] auto fixes [...]

* decent styles

* move stuff around

* adding tests

* add numpy for tests

* add cmap to tests

* fix type

* fix for pyqt

* remove topointf

* better  lineedit styles

* better add colormap

* increate linux atol

* cast to int

* more tests

* tests

* try fix

* try fix test

* again

* skip pyside

* test import

* fix lineedit

* add checkerboard for transparency

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_cmap.py

@@ -0,0 +1,162 @@
+import platform
+from unittest.mock import patch
+
+import numpy as np
+import pytest
+from qtpy import API_NAME
+
+try:
+    from cmap import Colormap
+except ImportError:
+    pytest.skip("cmap not installed", allow_module_level=True)
+
+from qtpy.QtCore import QRect
+from qtpy.QtGui import QPainter, QPixmap
+from qtpy.QtWidgets import QStyleOptionViewItem, QWidget
+
+from superqt import QColormapComboBox
+from superqt.cmap import (
+    CmapCatalogComboBox,
+    QColormapItemDelegate,
+    QColormapLineEdit,
+    _cmap_combo,
+    draw_colormap,
+)
+from superqt.utils import qimage_to_array
+
+
+def test_draw_cmap(qtbot):
+    # draw into a QWidget
+    wdg = QWidget()
+    qtbot.addWidget(wdg)
+    draw_colormap(wdg, "viridis")
+    # draw into any QPaintDevice
+    draw_colormap(QPixmap(), "viridis")
+    # pass a painter an explicit colormap and a rect
+    draw_colormap(QPainter(), Colormap(("red", "yellow", "blue")), QRect())
+    # test with a border
+    draw_colormap(wdg, "viridis", border_color="red", border_width=2)
+
+    with pytest.raises(TypeError, match="Expected a QPainter or QPaintDevice instance"):
+        draw_colormap(QRect(), "viridis")  # type: ignore
+
+    with pytest.raises(TypeError, match="Expected a Colormap instance or something"):
+        draw_colormap(QPainter(), "not a recognized string or cmap", QRect())
+
+
+def test_cmap_draw_result():
+    """Test that the image drawn actually looks correct."""
+    # draw into any QPaintDevice
+    w = 100
+    h = 20
+    pix = QPixmap(w, h)
+    cmap = Colormap("viridis")
+    draw_colormap(pix, cmap)
+
+    ary1 = cmap(np.tile(np.linspace(0, 1, w), (h, 1)), bytes=True)
+    ary2 = qimage_to_array(pix.toImage())
+
+    # there are some subtle differences between how qimage draws and how
+    # cmap draws, so we can't assert that the arrays are exactly equal.
+    # they are visually indistinguishable, and numbers are close within 4 (/255) values
+    # and linux, for some reason, is a bit more different``
+    atol = 8 if platform.system() == "Linux" else 4
+    np.testing.assert_allclose(ary1, ary2, atol=atol)
+
+    cmap2 = Colormap(("#230777",), name="MyMap")
+    draw_colormap(pix, cmap2)  # include transparency
+
+
+def test_catalog_combo(qtbot):
+    wdg = CmapCatalogComboBox()
+    qtbot.addWidget(wdg)
+    wdg.show()
+
+    wdg.setCurrentText("viridis")
+    assert wdg.currentColormap() == Colormap("viridis")
+
+
+def test_cmap_combo(qtbot):
+    wdg = QColormapComboBox(allow_user_colormaps=True)
+    qtbot.addWidget(wdg)
+    wdg.show()
+    assert wdg.userAdditionsAllowed()
+
+    with qtbot.waitSignal(wdg.currentColormapChanged):
+        wdg.addColormaps([Colormap("viridis"), "magma", ("red", "blue", "green")])
+    assert wdg.currentColormap().name.split(":")[-1] == "viridis"
+
+    with pytest.raises(ValueError, match="Invalid colormap"):
+        wdg.addColormap("not a recognized string or cmap")
+
+    assert wdg.currentColormap().name.split(":")[-1] == "viridis"
+    assert wdg.currentIndex() == 0
+    assert wdg.count() == 4  # includes "Add Colormap..."
+    wdg.setCurrentColormap("magma")
+    assert wdg.count() == 4  # make sure we didn't duplicate
+    assert wdg.currentIndex() == 1
+
+    if API_NAME == "PySide2":
+        return  # the rest fails on CI... but works locally
+
+    # click the Add Colormap... item
+    with qtbot.waitSignal(wdg.currentColormapChanged):
+        with patch.object(_cmap_combo._CmapNameDialog, "exec", return_value=True):
+            wdg._on_activated(wdg.count() - 1)
+
+    assert wdg.count() == 5
+    # this could potentially fail in the future if cmap catalog changes
+    # but mocking the return value of the dialog is also annoying
+    assert wdg.itemColormap(3).name.split(":")[-1] == "accent"
+
+    # click the Add Colormap... item, but cancel the dialog
+    with patch.object(_cmap_combo._CmapNameDialog, "exec", return_value=False):
+        wdg._on_activated(wdg.count() - 1)
+
+
+def test_cmap_item_delegate(qtbot):
+    wdg = CmapCatalogComboBox()
+    qtbot.addWidget(wdg)
+    view = wdg.view()
+    delegate = view.itemDelegate()
+    assert isinstance(delegate, QColormapItemDelegate)
+
+    # smoke tests:
+    painter = QPainter()
+    option = QStyleOptionViewItem()
+    index = wdg.model().index(0, 0)
+    delegate._colormap_fraction = 1
+    delegate.paint(painter, option, index)
+    delegate._colormap_fraction = 0.33
+    delegate.paint(painter, option, index)
+
+    assert delegate.sizeHint(option, index) == delegate._item_size
+
+
+def test_cmap_line_edit(qtbot, qapp):
+    wdg = QColormapLineEdit()
+    qtbot.addWidget(wdg)
+    wdg.show()
+
+    wdg.setColormap("viridis")
+    assert wdg.colormap() == Colormap("viridis")
+    wdg.setText("magma")  # also works if the name is recognized
+    assert wdg.colormap() == Colormap("magma")
+    qapp.processEvents()
+    qtbot.wait(10)  # force the paintEvent
+
+    wdg.setFractionalColormapWidth(1)
+    assert wdg.fractionalColormapWidth() == 1
+    wdg.update()
+    qapp.processEvents()
+    qtbot.wait(10)  # force the paintEvent
+
+    wdg.setText("not-a-cmap")
+    assert wdg.colormap() is None
+    # or
+
+    wdg.setFractionalColormapWidth(0.3)
+    wdg.setColormap(None)
+    assert wdg.colormap() is None
+    qapp.processEvents()
+    qtbot.wait(10)  # force the paintEvent