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tests/concrete/test_form_field_geometry.py

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+"""
+Regression tests for form field label geometry (spec S15).
+
+Text renders with a baseline anchor, so drawing the label at the field's origin
+put its glyphs above that origin - outside the box the field claims through size
+and in_object. Stacked fields therefore had each label overprinting the input box
+of the field before it.
+"""
+
+import numpy as np
+import pytest
+from PIL import Image, ImageDraw
+
+from pyWebLayout.abstract.functional import Form, FormField, FormFieldType
+from pyWebLayout.concrete.functional import FormFieldText
+from pyWebLayout.concrete.page import Page
+from pyWebLayout.layout.document_layouter import form_layouter
+from pyWebLayout.style import Font
+from pyWebLayout.style.page_style import PageStyle
+
+
+ORIGIN = (10, 40)
+FIELD_HEIGHT = 24
+
+
+@pytest.fixture
+def font():
+    return Font(font_size=12, colour=(0, 0, 0))
+
+
+@pytest.fixture
+def canvas():
+    image = Image.new("RGB", (300, 200), (255, 255, 255))
+    return image, ImageDraw.Draw(image)
+
+
+def make_field(font, draw, label="Email Address"):
+    field = FormField(name="email", field_type=FormFieldType.TEXT, label=label)
+    renderable = FormFieldText(field, font, draw, field_height=FIELD_HEIGHT)
+    renderable.set_origin(np.array(list(ORIGIN)))
+    return renderable
+
+
+def ink_rows(image, x_range, y_range):
+    pixels = image.convert("RGB").load()
+    return [y for y in y_range
+            if any(sum(pixels[x, y]) < 400 for x in x_range)]
+
+
+class TestLabelStaysInsideTheFieldBox:
+
+    def test_label_ink_is_below_the_origin(self, font, canvas):
+        image, draw = canvas
+        renderable = make_field(font, draw)
+        renderable.render()
+
+        rows = ink_rows(image, range(ORIGIN[0], ORIGIN[0] + 140),
+                        range(0, ORIGIN[1]))
+        assert not rows, \
+            f"label drew above its own origin, at rows {rows}"
+
+    def test_label_and_box_do_not_overlap(self, font, canvas):
+        image, draw = canvas
+        renderable = make_field(font, draw)
+        renderable.render()
+
+        ascent, descent = font.font.getmetrics()
+        label_bottom = ORIGIN[1] + ascent + descent
+        box_top = renderable.field_area_offset + ORIGIN[1]
+
+        assert box_top >= label_bottom, \
+            "the input box must start below the label's descenders"
+
+    def test_reported_height_covers_everything_drawn(self, font, canvas):
+        image, draw = canvas
+        renderable = make_field(font, draw)
+        renderable.render()
+
+        top, bottom = ORIGIN[1], ORIGIN[1] + int(renderable.size[1])
+        rows = ink_rows(image, range(ORIGIN[0], ORIGIN[0] + 200), range(0, 200))
+        assert min(rows) >= top, "ink above the field's declared box"
+        assert max(rows) < bottom, "ink below the field's declared box"
+
+
+class TestStackedFieldsDoNotCollide:
+
+    def test_form_layout_leaves_labels_clear(self, font):
+        page = Page(size=(300, 400), style=PageStyle())
+        form = Form("signup")
+        for name in ["Username", "Email Address", "Password"]:
+            form.add_field(FormField(name=name.lower().replace(" ", "_"),
+                                     field_type=FormFieldType.TEXT, label=name))
+
+        ok, ids = form_layouter(form, page, font)
+        assert ok and len(ids) == 3
+
+        fields = [c for c in page.children if isinstance(c, FormFieldText)]
+        assert len(fields) == 3
+
+        for earlier, later in zip(fields, fields[1:]):
+            earlier_bottom = earlier.origin[1] + earlier.size[1]
+            assert later.origin[1] >= earlier_bottom, \
+                "fields overlap: a label would print over the preceding input box"
+
+    def test_rendered_form_has_no_ink_collisions(self, font):
+        """Every field's ink stays within its own declared bounds."""
+        page = Page(size=(300, 400), style=PageStyle())
+        form = Form("signup")
+        for name in ["Username", "Email Address"]:
+            form.add_field(FormField(name=name.lower(), field_type=FormFieldType.TEXT,
+                                     label=name))
+        form_layouter(form, page, font)
+        image = page.render()
+
+        fields = [c for c in page.children if isinstance(c, FormFieldText)]
+        for field in fields:
+            top = int(field.origin[1])
+            bottom = top + int(field.size[1])
+            rows = ink_rows(image, range(int(field.origin[0]),
+                                         int(field.origin[0] + field.size[0])),
+                            range(max(0, top - 6), top))
+            assert not rows, f"ink found just above a field at y={top}"
+
+
+class TestClickTargetsFollowTheLayout:
+
+    def test_click_in_the_input_area_focuses(self, font, canvas):
+        _, draw = canvas
+        renderable = make_field(font, draw)
+
+        inside = (5, renderable.field_area_offset + FIELD_HEIGHT // 2)
+        assert renderable.handle_click(inside) is True
+        assert renderable._focused is True
+
+    def test_click_on_the_label_does_not_focus(self, font, canvas):
+        _, draw = canvas
+        renderable = make_field(font, draw)
+
+        on_label = (5, 2)
+        assert renderable.handle_click(on_label) is False