Enforce configurable height and pixel limits for tablet documents

tests/test_checked_documents.py

@@ -54,7 +54,7 @@ class CheckedDocumentTests(unittest.TestCase):
                                           overwrite=overwrite, output_mode='checks')
 
     def test_splits_on_labels_and_resets_geometry_at_each_part(self):
-        self.assertEqual(MAX_HEIGHT_PX, 32000)
+        self.assertEqual(MAX_HEIGHT_PX, 33000)
         self.assertEqual(self.generate(), 'success')
         parts = copy_documents(self.output)
         self.assertEqual([part.name for part in parts], ['Part1', 'Part2'])
@@ -75,6 +75,30 @@ class CheckedDocumentTests(unittest.TestCase):
         self.assertTrue((self.output / 'Concat.pdf').is_file())
         self.assertFalse((self.output / 'Part1').exists())
 
+    def test_pixel_limit_splits_documents_at_exact_boundary(self):
+        with patch.object(checks, 'MAX_PIXELS', 6000):
+            self.assertEqual(self.generate(), 'success')
+        parts = copy_documents(self.output)
+        self.assertEqual([read_json(p / 'bnote.json')['height'] for p in parts], [60, 40, 60])
+
+    def test_pixel_limit_accounts_for_width_growth_and_preserves_previous_copy(self):
+        original = self.compose
+        def wider(base, label, *args, **kwargs):
+            image, header = original(base, label, *args, **kwargs)
+            if label == 'Ex 2':
+                image = image.resize((200, image.height))
+            return image, header
+        with patch.object(self, 'compose', side_effect=wider), patch.object(checks, 'MAX_PIXELS', 12000):
+            self.assertEqual(self.generate(), 'success')
+        parts = copy_documents(self.output)
+        self.assertEqual([read_json(p / 'bnote.json')['width'] for p in parts], [100, 200, 100])
+        sentinel = self.output / 'sentinel'
+        sentinel.write_text('previous')
+        with patch.object(checks, 'MAX_PIXELS', 5999):
+            with self.assertRaisesRegex(CliError, 'Copie01.*Ex 1'):
+                self.generate(overwrite=True)
+        self.assertEqual(sentinel.read_text(), 'previous')
+
     def test_single_oversized_answer_and_save_failure_preserve_previous_copy(self):
         self.generate()
         sentinel = self.output / 'sentinel'